"Science, Faculty of"@en . "Zoology, Department of"@en . "DSpace"@en . "UBCV"@en . "Drent, Rudolf Herman"@en . "2012-01-26T20:49:38Z"@en . "1961"@en . "Master of Arts - MA"@en . "University of British Columbia"@en . "The Pigeon Guillemot (Cepphus grylle columba), a member of the Auk family, was studied by the writer at Mandarte Island, British Columbia, in the summers of 1959 and 1960. Banding and the keeping of nest records had commenced at this colony in 1957, so that on many questions four years' data are available. Colour-banded adults and banded immatures of known age, were basic to the study. Behaviour, and social structure of the colony, are described on the basis of these banded birds. Incubation temperatures and rhythm were investigated with thermocouples. Feeding, growth of the chick in weight from hatching to nest departure, and the advent of thermoregulation, are treated. Placed in an appendix are statistics on egg and chick mortality up to the point of nest departure."@en . "https://circle.library.ubc.ca/rest/handle/2429/40299?expand=metadata"@en . "BREEDING BIOLOGY OP THE PIGEON GUILLEMOT (Aves: Cepphus) by RUDOLF HERMAN DRENT B.A., University of B r i t i s h Columbia, 1958 A thesis submitted in p a r t i a l f u l f i l m e n t of , the requirement for the degree of Master of Arts in the Department of Zoology We accept t h i s thesis as conforming to the required standard The University of B r i t i s h Columbia A p r i l , 1961 In presenting t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. . I f u r t h e r agree that permission f o r extensive copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head of my Department or by h i s representatives. It i s understood that copying or p u b l i c a t i o n o f . t h i s t h e s i s f o r f i n a n c i a l gain s h a l l not be allowed without,my written permission. Department of The U n i v e r s i t y of B r i t i s h Columbia, Vancouver 8, Canada. 4 ABSTRACT The Pigeon Guillemot (Cepphus g r y l l e columba), a member of the Auk family, was studied by the writer at Mandarte Island, B r i t i s h Columbia,, in the summers of 1959 and i 9 6 0 . Banding and the keeping of nest records had commenced at t h i s colony in 1957, so that on many questions four years 1 data are avai l a b l e . Colour-banded adults and banded immatures of known age, were basic to the study. Behaviour, and s o c i a l structure of the colony, are described on the basis of these banded birds . Incubation temperatures and rhythm were investigated with thermo-couples. Feeding, growth of the chick i n weight from hatching to nest -departure, and the advent of thermo-regulation, are treated. Placed i n an appendix are s t a t i s -t i c s on egg and chick mortality up to the point of nest departure. LIST OP ILLUSTRATIONS To f o l l o w page MAPS 1. Haro S t r a i t , east portion,,showing l o c a t i o n of study\u00E2\u0080\u00A2area 4 2. Mandarte I s l a n d , showing d i s t r i b u t i o n of\" guillemot nests . 9 FIGURES A l l f i g u r e s deal w i t h the Pigeon Guillemot, Cepphus g r y l l e columba, so i t has seemed' unnecessary to s p e c i f y - t h i s in,each case. A l l photographs were taken i n i 9 6 0 , and a l l but F i g s . 46-47 on Mandarte I s l a n d . 1. Mandarte I s l a n d , NE .facing \u00E2\u0080\u00A2 shore . . . . . . . 5 2 . Mandarte I s l a n d , SW.facing shore 5 3 . Mandarte I s l a n d , general view of north end . . 10 _/4. Mandarte I s l a n d , view of t y p i c a l beach \u00E2\u0080\u00A2 t e r r a i n on SW f a c i n g \u00E2\u0080\u00A2 shore 10 , 5 . Mandarte I s l a n d , view .-of \u00E2\u0080\u00A2 'north b l i n d ' area . . 10 , 6 . Diagram of'General phenology i n breeding of Pigeon Guillemot 11 ,7.a&b D a i l y rhythm, long p e r i o d counts -17-18 . 8 . p a l l y rhythm,. morning averages 19 9-11. Hunch-whistling, a ..threat d i s p l a y . 27 12-13. Intruder i n c i d e n t , i l l u s t r a t i n g u u s e of' hunch-whistle 28 14. - Chuckle-waggle, an appeasement d i s p l a y . . . . 29 15. B i l l - d i p p i n g , an i n d i c a t i o n of an x i e t y . . . . 29 16-17. The scream,- the alarm c a l l 32 FIGURE To follow page ;l8-21. B i l l i n g , a ceremony between members of a p a i r 36-37 22-23. C i r c l i n g , a copulation- preliminary 47 2 4 . Copulation . . . . . . . . 48 25. Male jabbing at termination of copulation . . 48 26-34. Sequence i l l u s t r a t i n g intruder incident followed by copulation 49 35. Copulation rate 55 36. Diagram of nests and perch-sites at the 1 north b l i n d 70 37. Attendance.at colony: diagram of north b l i n d records . \" 72 38. Diagram of main guillemot nest types on Mandarte Island . 89 39. Typical 'type 1' guillemot nest 90 40. Close-up of guillemot eggs in'the nest . . . 90 41. View i l l u s t r a t i n g \u00E2\u0080\u00A2 t h e method of taking incubation temperatures 90 42&43. Two views of a.'type 2' guillemot nest . . . 90 .44. Another\u00E2\u0080\u00A2'type 2' guillemot nest . . . . . . . 90 '45. A 'type 3' guillemot nest 90 46. Beach debris at Imrie I s l e t , guillemot nesting t e r r a i n 90 47. A guillemot nest i n the beach debris of F i g . 46 . 90 48. Diagram of egg-laying at Mandarte 1957-1960 . 91 49. Correlation. of laying date in the same nests 1959 and i960 ' 101 50. Brood-patch temperature in the Pigeon Guillemot through incubation 143 51. Incubation temperature during laying: sample trace , 1 ^ FIGURE , To f o l l o w page 52. Sample temperature record during steady i n c u b a t i o n . . 144 53. diagram of i n c u b a t i n g rhythm during .daylight 152 54. D e t a i l s of i n c u b a t i n g rhythm, two sample morning records 157 55. Diagram of feeding r a t e : f i s h d e l i v e r i e s to nests w i t h chicks 185 56. Growth of Pigeon Guillemot from hatching .to nest .departure 188 57. Newly-hatched gu i l l e m o t chicks w i t h eggs f o r comparison . \u00E2\u0080\u00A2 . 190 58. Another day-old c h i c k 190 59. Twelve-day o l d c h i c k 190 6 0 . Twenty-eight day o l d c h i c k 190 61 . T h i r t y - f o u r - d a y o l d c h i c k , r e a d y ; t o leave the nest 190 62. Body temperature of chicks through the n e s t l i n g p e r i o d 197 LIST OF TABLES TABLE Page 1. Egg-laying in the Pigeon Guillemot: analysis of four seasons on Mandarte Island, B.C. . . 93 2. Laying dates i n i n d i v i d u a l nests 99 3. Mandarte Island data on clutch size 102 4. Laying Interval i n the Tystie '. 105 5. Repeat laying i n the Pigeon Guillemot . . . . 108 6. Period from laying of eggs u n t i l chick-is _ free of s h e l l I l l 7. Incubation periods i n Auks 116 8. Temperature of the fully-developed brood-patch compared to body temperature . . . . . 119 9. Nest temperatures i n the Pigeon Guillemot . . 137 10. Cooling of the egg during overnight absence of the parent . . . . . . . . . . . . . . . . 140 11. Brood-patch temperatures in\"the'Pigeon Guillemot 142 12. Cloacal temperature i n the adult Pigeon Guillemot 145 13. Onset of incubation i n the Pigeon Guillemot . 150 14. Limits of the night s h i f t ' i n the Pigeon Guillemot 151 15. Incubation records from nest .43 154 16. Chick stage in Auks 168 17. Nestling period of the Pigeon Guillemot at \u00E2\u0080\u00A2Mandarte Island 170 TABLE \u00E2\u0080\u00A2 ' Page 18. Some food species of Pigeon Guillemot chicks at Mandarte Island 173 19a. Types of food brought to.5 nests, Pigeon Guillemot 176 -19b. Share of the sexes in \"feeding, Pigeon Guillemot . . \" 176 2 0 . Reject f i s h species found in Pigeon Guillemot nests 178 21 . Rate of f i s h t r i p s to young i n Pigeon Guillemot 182 2 2 . Feeding rate experiment 184 2 3 . Growth i n the Pigeon Guillemot 187 24. Weight of adult and chick at point of nest .departure, compared 189 25. Chick body temperature, Pigeon Guillemot . . . 196 ACKNOWLEDGMENT This.study would never have been carried out-but for the help of numerous persons and i n s t i t u t i o n s . On the f i n a n c i a l side, I g r a t e f u l l y acknowledge generous grants from the Woodrow Wilson National Fellowship Foundation (winter 1958/59), National Research Council of Canada (summer\u00E2\u0080\u00A21959, winter -1959/60) and Fisheries Research Board of Canada (summer i 9 6 0 , winter 1960/61). On the academic side, my supervisor, Dr. M.D.F. Udvardy, deserves my,warmest thanks. He f i r s t suggested the project, and was ready with further references, suggestions, and h e l p f u l c r i t i c i s m at every stage, including the rather-exhausting (for both of us) pro-cess of writin g . Dr. B e n d e l l has taken the trouble to read the bulk of the manuscript, and my presentation has been much improved as a r e s u l t . The v i s i t s of Dr. Cowan to the is l a n d \u00E2\u0080\u00A2 i n .1959 did much to sharpen my intere s t on certain questions. F i n a l l y , I owe much of my intere s t on the temperature problems to discussions with Dr. Koskimies In the 1959 season. On the technical part of the work, Dr. K. B e a m i s h k i n d l y . v e r i f i e d plant i d e n t i f i c a t i o n s , Dr. C. Lindsey took great pains to i d e n t i f y the f i s h remains, and Mr. G. van Eerten devoted much time to the preparation of extension leads for the telethermometer. For .help outside t h i s University, I.wish to mention p a r t i c u l a r l y the s t a f f of the National Photo Library, Ottawa, for providing an excellent enlargement of an a e r i a l photograph of Mandarte, making possible construction of Map 2. On the p r a c t i c a l side, I owe a great debt to G.P. van Tets, who carried out basic work on the guillemots the two summers preceding my project. G.F. van Tets i n 1959*. and F. Tompa .in I 9 6 0 , helped me in the longer 'Observations, tedious work f o r them I.am a f r a i d . F i n a l l y , two families l i v i n g nearby.went, to much trouble to make the summers pleasant times indeed for the 'birdmen'--the Koskimies's of Helsinki, l i v i n g i n Sidney i n 1959 whilst Dr. Koskimies carried out his physio-l o g i c a l experiments, and the Mathews's of Randle's Landing. TABLE OP CONTENTS Page INTRODUCTION A. Scope of study and previous work 1 B. - Study area and- methods 4 DAILY RHYTHM 12 Summary 23 VOICE AND DISPLAYS 24 Summary 43 THE BREEDING SEASON I. PRE-EGG STAGE A. Length and general description 44 B. Copulation .1. description 46 .2. constancy . 50 3. sex and mate recognition. 53 4. rate 55 C. Colony - structure 1. the pair-bond 62 2. nest-site f a i t h f u l n e s s 'Nesttreue 1 . . . 65 3. f a i t h f u l n e s s \u00E2\u0080\u00A2 t o perching \u00E2\u0080\u00A2 s i t e 69 4. t e r r i t o r i a l i t y \u00E2\u0080\u00A2 . 72 5. the non-breeders ?4 D. Comparison with other auks 80 Summary of pre-egg stage 83 I I . EGG STAGE A. The nest 87 B. Egg-laying 1. seasonal pattern 9 1 2. d a i l y pattern 97 3. i n d i v i d u a l pattern 98 C. The clutch 1. clutch size 101 2. i n t e r v a l between eggs\u00E2\u0080\u0094the laying i n t e r v a l 104 3. replacement of l o s t eggs 106 Page D. Incubation 1. general description of int e r v a l s from laying to hatching 110 2. the meaning of ''incubation period' . . 114 3. brood-patch and incubation temperature i n birds . . . . . . . . 118 -4. incubation temperatures in.the Pigeon Guillemot . .-. .':. . . . -133 a. nest temperature .. \u00E2\u0080\u00A2 136 b. minimal egg surface \u00E2\u0080\u00A2:' / .temperatur.es \u00C2\u00AB... . \ 139 c. brood-patch temperature . . . . l 4 l 5; Incubating.rhythm in.the Pigeon Guillemot 146 a. onset of incubation .. .\u00E2\u0080\u00A2 149 b. description of steady -incubation . .. \ 150 Summary of egg stage 160 I I I . CHICK STAGE A. The chick stage i n Auks;, statement of the ' , problem . . . 166 B. -.Length of the n e s t l i n g period in \u00E2\u0080\u00A2 the Tystie 169 .. C.. Feeding \u00C2\u00AB-1. food species -.- . . . 171 2. feeding rate . 179 D. Growth 186 E. Thermoregulation .1. Ontogeny of body temperature i n pre c o c i a l birds ' 190 ..2. Chick body temperatures i n the Pigeon Guillemot \u00E2\u0080\u00A2 195 F. Termination of the chick stage .. ?.. ... ...--\u00E2\u0080\u00A2*. 198 Summary of chick stage . . 201 \u00E2\u0080\u00A2, General summary 204 APPENDIX: PRODUCTION ,-STATISTICS . . . 207 LITERATURE CITED . . . . . . . 212 INTRODUCTION A. Scope of Study and Previous Work \" The North P a c i f i c - B e r i n g Sea area i s the present-day centre of d i s t r i b u t i o n of the sea- b i r d f a m i l y Alcidae,,the auks, and no doubt t h e i r a n c e s t r a l home ( F i s h e r & Lockley 1954; 267? Johansen 1958: 56-65, 108-110). In t h i s region one. i s presented w i t h 17 l i v i n g species of diverse h a b i t , p r o v i d i n g a f a s c i n a t i n g m a t e r i a l f o r study of a group w i t h so many p e c u l i a r i t i e s ' t h a t i t i s often considered a d i s c r e t e order (Alcae; Stresemann 1927/34, 1959; Kartaschew i960, et a l . ) Yet to my knowledge no study of any auk, based on marked b i r d s , has been reported from the P a c i f i c . I t was my i n t e n t i o n , t h e r e f o r e , t o work w i t h banded b i r d s i n an auk species -active by day, where the obser-vat i o n s of two' summers might supply a general p i c t u r e of s o c i a l s t r u c t u r e and p a r e n t a l behaviour, so i n t e r e s t i n g i n these c o l o n i a l l y - n e s t i n g b i r d s . When I learned that G.P. van Tets had done considerable banding of adult Pigeon Guillemots at a colony on the B r i t i s h Columbia coast, where a permanent f i e l d camp had been e s t a b l i s h e d f o r cormorant study, I found a l l my requirements s a t i s f i e d . ' Indeed the p r e l i m i n a r y data he and h i s a s s i s t a n t s had gathered i n two seasons made\" \" i t p o s s i b l e f o r me to expand the study i n t o a general survey of breeding b i o l o g y . My programme was t o d i r e c t a t t e n t i o n to nature of the pair-bond, mating a c t i v i t y , and s o c i a l - s t r u c t u r e i n the pre-egg stage, 1 2 incubation rhythm and temperatures i n the egg stage, and f i n a l l y i n the chick stage investigate feeding, growth, and advent of thermoregulation.in the young. Throughout, the colony was to be disturbed as l i t t l e as possible, to accumulate production s t a t i s t i c s , and figures on\u00E2\u0080\u00A2Incubation and ne s t l i n g periodsj the method was thus observational rather than experimental. Doubt-less the programme was overly ambitious, but I .do not for a moment regret t h i s , f or I have gained valuable experience on many topics. Before describing study area and methods, a word on the species-status of the Pigeon Guillemot, and previous f i e l d study on auks. The systematic p o s i t i o n of the Pigeon Guillemot has not been s e t t l e d . Salomonsen (1944) has suggested treating i t as a.further chain of P a c i f i c subspecies linked with the circumpolar Black Guillemot, Cepphus g r y l l e . This view.has been followed by Fisher & .Lockley (1954), Kaftanowski (1951) and Kai?taschew . ( i 9 6 0 ), among others. Storer \u00E2\u0080\u00A2 ( l 9 5 2 ) designates Cepphus columba.adianta as the subspecies. In my area, whilst\u00E2\u0080\u00A2the A.O.U. Check L i s t (1957: 250-251) maintains Cepphus columba columba. Depending on which of these be accepted, Salomonsen's inter p r e t a t i o n .would be Cepphus g r y l l e adianta or C_. g_. columba. I. .have adopted the l a t t e r terminology, but to avoid confusion follow the vernacular names as in the A.O.U. Check L i s t j thus Cepphus g r y l l e of the AOU i s the Black Guillemot, Cepphus columba AOU. i s the Pigeon Guillemot.. When speaking of the grylle-columba complex (Salomon sen \"^s species, the AOU's 3 superspecies) I employ the folk-name Tystie. The reader may thus s u i t the L a t i n nomenclature to his fancy. Because of i t s wide\u00E2\u0080\u00A2distribution many have observed the Tystie, and short accounts are scattered through the b i r d l i t e r a t u r e of many countries. I r e a l i z e well that I have consulted only a portion of these. In addition, there have been several special studies. Winn's (1951) study of the Black Guillemot i n the Bay.of Fundy 1946-47, Uspenski's (1956) report on studies over a number of years i n the Russian A r c t i c , including this.species, and f i n a l l y the work of Thoresen & Booth (1958).on the Pigeon Guillemot in Skagit County, Washington, near my own study area in 1957, were a l l available to me before I started my work. These provide i n t e r e s t i n g comparative material on breeding biology, but as none of them dealt with individually.marked, birds behavioural data are few. Storer's (1945, 1952) work, l a r g e l y anatomical and taxonomic, includes some behaviour observations on Black & .Pigeon Guillemots. Since completing my field-work Kartaschew's ( i960) excellent summary has appeared, giving access to much of the Russian work on the Black Guillemot and other North A t l a n t i c Alcae, and parts of Kaftanowski's (1951) valuable t r e a t i s e , covering the same species have also been available. There are excellent recent accounts of some auks (Paludan 1947 on Alca torda, L o c k l e y l 9 5 3 on Fratercula a r c t i c a , N/rrevang 1958 & Tschanz 1959 on Uria aalge, Pennycuick 1956, Uspenski 1956.&.Kartaschew i 9 6 0 on Uria lomvia) but as I have never 4 v i s i t e d c o l o n i e s of any of these I have drawn only l i m i t e d comparisons w i t h my Pigeon Guillemots. B. Study Area and Methods The study was c a r r i e d out on Mandarte I s l a n d (48\u00C2\u00B0 38' N,\u00E2\u0080\u00A2 1 2 3 \u00C2\u00B0 17* W) on the inner south coast of B r i t i s h Columbia. Mandarte l i e s among the Gulf Islands i n Haro S t r a i t , i n more p r e c i s e terms east of Miner's Bay, an indenta-t i o n on the c e n t r a l east shore of Sidney I s l a n d (see Map l ) . Mandarte, commonly c a l l e d Bare or Ridge I s l a n d , i s a barren limestone escarpment tending SE-NW, some 1 0 0 meters broad and 7 0 0-long, r i s i n g a b r u p t l y from the sea t o a maximum e l e v a t i o n of 29 meters (95 f e e t ) at the NW corner. In form the i s l a n d (see Map 2) suggests a g i a n t rocky t a b l e t i l t e d i n t o the sea. Prom a low broken c l i f f some 3-4 meters high s k i r t e d by a broad wave-cut platform, along the NE f a c i n g shore, the land r i s e s away to the p r e c i p i t o u s SW f a c i n g shore,.where c l i f f s ranging from 10 to 29 meters, w e i r d l y eroded, are undercut by Malaspina G a l l e r i e s (see F i g s . 1 and 2 ) . Midway a groove scores the long a x i s of the i s l a n d , and here the s o i l accumulation supports shrubbery and a few gnarled t r e e s . Near the north end s e v e r a l Douglas F i r (Pseudotsuga m e n z i e s i i ) and.2 Grand F i r (Abies grandis) s u r v i v e , and along w i t h s e v e r a l Arbutus (Arbutus m e n z i e s i i ) , a t r e e c h a r a c t e r i s t i c of the r e g i o n , and a l u x u r i a n t growth of Willow ( S a l i x sp.). form the 'big t r e e s ' , the only v e g e t a t i o n Map/. HARO STRAIT, EAST PORTION Brethour-7 Domville\u00E2\u0080\u00948 Halibut\u00E2\u0080\u009415 Rum 12 Coal 2 Forrest-13 Ker 3 VARIA Comet\u00E2\u0080\u0094 9 Gooch\u00E2\u0080\u0094/ / Reay 6 Sidney Spit-14 Dock 4 Greig 5 Rubty 10 Tsehum Hbr-I i F i g . 1 Mandarte I s l a n d , the low NE f a c i n g shore, as viewed from the north. Note barren 'meadows' d e l i m i t e d by narrow s t r i p s of brush. Campsite at l e f t . G u l l s , g u i l -lemots and oystercatchers are the n e s t i n g sea-birds here. F i g . 2 Mandarte I s l a n d , the c l i f f y SW f a c i n g shore, viewed from the south. Clump of tr e e s shows r e l a t i o n to F i g . 1. Cormorant, p u f f i n , and gui l l e m o t n e s t i n g t e r r a i n . 5 to break the i s l a n d skyline ( F i g . 3). Elsewhere a, mixed shrubbery composed of Waxberry (Symphoricarpos sp.), Wild Rose (Rosa sp.), Ocean Spray (.Holodiscus. discolor) and Wild Black Berry.(Rubus macropetalus) i n that order of abundance, along with several minor elements, covers'the area of deeper s o i l . A scattering of Saskatoon'Berry (Amelanchier f l o r i d a ) .Wild Cherry (Prunus emarginata) Crab Apple (Malus fusca), and at the extreme south end, Garry Oak (Quercus garryana) protrude above the shrub. In the open areas coarse grasses p r e v a i l , and Quamash (Camassia quamash) i s abundant;.in sheltered spots a variety of herbaceous plants,. mostly xerophilic,. may be found. There i s no evidence that the i s l a n d ever supported a vegetation more luxurious than at present, f o r the pockets of rocky thin s o i l andl. the meagre p r e c i p i t a t i o n (less than 30.inches annually,-Kendrew& Kerr -1955) set stringent l i m i t s . I t i s however the nesting sea-birds that make Mandarte Island unique. The present.(i960) breeding b i r d population runs as follows: Double-crested cormorant, Phalacrocorax auritus 135-150 pa i r Pelagic cormorant, Phalacrocorax pelagicus 375_400 pa i r Black Oystercatcher, Haematopus bachmani 1 (?2) p a i r Glaucous-rwinged Gull, Larus glaucescens 1800-2000 pa i r Pigeon Guillemot, Cepphus g r y l l e columba -100-110 pa i r Tufted P u f f i n , Lunda c i r r h a t a 2 pa i r Northwestern Crow, Corvus caurinus .25 p a i r Red-winged Blackbird, Agelaius phoeniceus 2-4 pa i r Song Sparrow, Melospiza melodia 50 p a i r The status and hi s t o r y of sea-birds on Mandarte has been detailed elsewhere (Drent & Guiguet i n press); s u f f i c e i t here to say-that\u00E2\u0080\u00A2the Double-crested and Pelagic Cormorant as well as the Glaucous-winged Gull are on the increase, the Tufted Puffin stable, and the others lack adequate previous counts. The estimates l i s t e d are based on.complete nest counts save for the g u l l ( p a r t i a l count and calculation) and the Song Sparrow, where P. Tompa.. (pers. comm.) has given a pro v i s i o n a l figure from his study of'the species on Mandarte, now. in progress. Only one mammal, the Deer Mouse (Peromysous maniculatus) presently inhabits the island, the introduced European Rabbit (Oryctolagus cunicuius) having died out c .1955-56 .(for history of t h i s species i n .\u00E2\u0080\u00A2 the Province, see Carl &-.Guiguet 1958: 11-13). There are winter records for Mink (Mustela vison) which i s abundant on surrounding islands. A more detailed description of the islan d and i t s vertebrate l i f e i s i n preparation (Drent &.van Tets MS). Certain plants and the sea-fowl have formed an important resource to the native peoples i n by-gone times, and Mandarte Island i s s t i l l an Indian Reserve. At present infrequent egg-collecting i s the only r i g h t exercised by the owners. Although wardens have l i v e d on the islan d off and on since at least 1915 (see Anderson 1916) and J.A. Munro of the Canadian W i l d l i f e Service documented status of the sea-birds on a number of v i s i t s 1921-37 (Munro 1925, 1928, 1929, 1937), intensive b i r d work commenced in 1957 when G.P. van Tets, w i t h h i s a s s i s t a n t J . Takacs, came to the i s l a n d , t o .study-the cormorants (van Tets 1959). Since that time students from the U n i v e r s i t y - of B r i t i s h Columhia have r e s i d e d on the i s l a n d as f o l l o w s : 1957 G.P. van Tets & J . Takacs 3 May - 4 September 1958 G.F. van Tets & D. Kennedy. 1 May - 24 August 1959 G.F. van Tets 24 A p r i l - 15 September R. Drent 6 May - 27 August 1960 R. Drent & F. Tompa 5 May - 1 September G.F. van Tets 2-7 May & -27 J u l y -8 August Over the years a permanent camp,has\u00E2\u0080\u00A2been e s t a b l i s h e d .on Mandarte, so that i t was p o s s i b l e to . l i v e continuously -on the i s l a n d i n .the periods s p e c i f i e d , w e e k l y . t r i p s being made to nearby Sidney f o r m a i l and s u p p l i e s . Under these i d e a l c o n d i t i o n s of l i v i n g at the colony, I was able to devote almost my f u l l time to.study-of the Pigeon\u00E2\u0080\u00A2Guillemot i n the summers of 1959 and .'60. In addi-t i o n G.F. van Tets and.his a s s i s t a n t s had p r e v i o u s l y l o c a t e d over 50 nests and banded both a d u l t s and chicks wherever p o s s i b l e , so.that when I began .my work I had a lar g e s e r i e s of nests w i t h past -history duly.recorded, and-a good number -of banded b i r d s . F i r s t , a word on banding procedures. The t o t a l s run as f o l l o w s : Pigeon Guillemots banded on Mandarte I s l a n d . 1957 20 a d u l t s 49 chicks 1958 11 a d u l t s 25 chicks 1959 14 a d u l t s 52 chicks 1960 \u00E2\u0080\u00A2 20 .adults 34 chicks T o t a l s 65 .adults 160.chicks 8 Adults were captured on the nest during incubation, .\u00E2\u0080\u00A2 a method \u00E2\u0080\u00A2depending much on chance, but with repeated v i s i t s we were eventually successful in the deeper nests. A l l adults caught were banded with the standard aluminium rings of the W i l d l i f e Service (size 5), and.starting in 1958 with stout p l a s t i c colour-bands that we made ourselves, as w e l l . The aluminium rings were proven.to l a s t 4 years, and.undoubtedly can endure much longer; \"the p l a s t i c \u00E2\u0080\u00A2 bands when c a r e f u l l y made w i l l l a s t .1 year or.-a l i t t l e longer. When adults were recaptured, aluminium bands were replaced if.2 years old or more, the p l a s t i c bands i f 1 year or more. The numbers of adults colour-banded were: 1958 6 1959 -23 (21 new) 1960 35 (23 new) The aluminium bands could be read by telescope in favourable conditions,.and.the colour-combinations could be deciphered at moderate distances, even when the birds were paddling about in the water. Work with these known birds was v i t a l to the study. No recoveries elsewhere have been reported (up to August'i960). The chicks were also provided .with aluminium rings when about to leave the nest, and as most of the nests were checked thereafter the number banded consists of birds successfully;fledged. Prom t h i s group .5 have so.far'been reported found elsewhere (4 of them dead), and 7 more have been sighted back on Mandarte Island.in subsequent seasons. 9 \u00E2\u0080\u00A2Nest records constitute the other -4-year'body\u00E2\u0080\u00A2of data. A l l nests were numbered as found with aluminium tags in 1957/58, replaced with consecutive painted numbers in 1959/60. Since the. same nests are used year a f t e r year a good sample has been accumulated, and the history of most runs over several seasons. The nests along the island crest and those on the c l i f f s on the SW facing shore could be checked .only during cormorant banding operations, but those along the NE facing shore together with those on a small rock just south.of Mandarte (termed 'south island') could be checked frequently and form the main material. The number of Pigeon Guillemot nests in, the main observation series, in cases where eggs at least appeared, and the frequency of checks, are detailed below. Mandarte^ i t s e l f South Island 1957 33 checked every 1-3 days 9 checked 14 times 1958 32 checked every 1-3 days 9 checked 6 times 1959 45 checked d a i l y 15 .checked 10.times 1960 .45 checked d a i l y 18 checked 10 times Altogether b y l 9 6 0 102 nests had been located: 3 on a small skerry to the north, 80 on the main island, and 19 on south i s l a n d . Of these at least 82 were i n use in the i960 season ( 3 , 6l,.and 18). Of the 20 nests that remained empty in i960 a few.had become unsuitable (6 on main island) but the balance appeared occupied. Since some nests have yet to be found, the closest estimate that can be made for present colony size i s 100 p a i r . A l l nest data are entered on standard cards and have been placed in the f i l e s of.the B.C. . Nest Records Scheme in the Department of Zoology, University F i g . 3 (above) Mandarte I s l a n d , showing 'big t r e e s * and l o c a t i o n of the two g u i l l e m o t b l i n d s ; 'north b l i n d ' to f a r r i g h t . F i g . 4 ( r i g h t ) View l o o k i n g n o r t h from 'south b l i n d 1 (see F i g . 3) to i l l u s t r a t e rugged beach t e r r a i n : wave-cut p l a t f o r m , the gu i l l e m o t assembly grounds, and low broken c l i f f , o f f e r -i n g many n e s t i n g s i t e s ( l l i n the p i c t u r e ) . Nesting g u l l s on c l i f f - c r e s t . F i g . 5 The ' n o r t h b l i n d * a r e a , s h o w i n g l o c a t i o n o f t h e g u i l l e m o t n e s t s m o s t i n t e n s i v e l y s t u d i e d ( a r r o w s ) . G u i l l e m o t a s s e m b l y g r o u n d on t h e b e a c h h e r e m o s t l y c o v e r e d b y h i g h w a t e r . G u l l s n e s t e d t h r o u g h o u t t h e o p e n a r e a , c r o w s , b l a c k - b i r d s , a n d s o n g s p a r r o w s i n t h e s h r u b . 10 of B r i t i s h Columbia. Map 2 shows the location of Pigeon Guillemot nests on Mandarte Island, also the two driftwood blinds erected in 1959 and.. '-60 to allow all-weather-observation (see Pigs. 3, 4,5). My general d a i l y schedule was to devote the morning'to continuous observation from the blinds (o645-1045 i n 1959? o700-1030.in 1960j a l l times in t h i s paper are P a c i f i c Stand-ard) then at mid-afternoon .to carry out the nest-check,, which would take from l-g-3 hours. The remainder of the day was taken up with work on other species, camp maintenance, and record-keeping. The number of days where the regular morning observation was carried out from the north b l i n d (main source of behavioural data) were di s t r i b u t e d as follows: 1959 I960 May 8* 19 June 23 ' 2 2 July 23 18 August 16 14 * b l i n d completed 21 May, 1959 A number of all-day and 24-hour watches were also carried out. F i n a l l y , \u00E2\u0080\u00A2 b r i e f v i s i t s were paid to 5 other Pigeon Guillemot nesting s i t e s in the B r i t i s h Columbia Gulf Islands ( B a l l i n g a l l , Java, Imrie, Dock, and Halibut i s l e t s ) . Pigeon Guillemots can be seen on the waters surrounding\u00E2\u0080\u00A2Mandarte Island at a l l 'times of the year, but they come ashore there only during the breeding season. The birds st a r t to v i s i t the nesting grounds at least a month before the eggs are l a i d , spend another month i n incubation, and f i n a l l y tend the chicks f o r 5 weeks or more. General 3D 00 V 8 I I I I I I I I I I chicks hatched ~i i i i i i i i i i i i i\u00E2\u0080\u0094 i n i r clutches commenced /2/5 /6-/9 2c*Z3 24-27 26-3/ /-4 STS 9-/2 /3/*? 20-23 24-27 2f-3/ /-4 se 9-/2 /3va \ N *1 N\ I I I I I I I I I I chicks departed Jo CO* I I I I I I I I I I L I I I I I I I J 1 L J I I L_J I I 1 I I I I I I 1\u00E2\u0080\u00941 I I\u00E2\u0080\u0094L phenology-at Mandarte i n 1959 and 1960.(very sim i l a r \u00E2\u0080\u00A2 seasons) is- set out- in F i g . 6. The three periods Pre-egg,\u00E2\u0080\u00A2Egg, and Chick Stage (to-follow.Richdale 1s 1951 terms)roughly\u00E2\u0080\u00A2equal for the Pigeon Guillemot at t h i s colony, w i l l serve as con-venient subdivisions i n t h i s paper. I was unable to arrive at the island before the start of the pre-egg stage, so my account of t h i s period i s incomplete. Also, my-work ended before the l a s t chicks had.left\u00E2\u0080\u00A2the island, but my data for t h i s l a s t phase are reasonably complete. Before treating the pre-egg stage, i t w i l l be useful to summarize the rhythm of adult attendance at the colony throughout the season, and give a catalogue of voice and dis-plays. DAILY RHYTHM F u l l attendance of the a d u l t Pigeon Guillemots at the colony--!.e., on the rocky beaches, at the n e s t - s i t e , or w i t h i n s i g h t on .surrounding w a t e r s \u00E2\u0080\u0094 i s only observed i n the morning hours. This i s . e s p e c i a l l y c l e a r when the b i r d s f i r s t r e t u r n . t o the c o l o n y ' a f t e r the winter,, when care of eggs or young does not complicate matters, but as a g e n e r a l i t y , the morning peak holds t r u e throughout the season. Perry ( 1 9 4 8 ) , Storer'(1952: 146, 1 4 9 ) , Uspenski ( 1 9 5 6 : 8 2 ) and no doubt others have commented on t h i s , and Suomalainen ( 1 9 3 9 ) provided some f i g u r e s , , but the only systematic q u a n t i t a t i v e work has been.that of Koskimies ( 1 9 4 9 ) . Koskimies c a r r i e d out h o u r l y censuses throughout the d a y l i g h t hours on 5 dates i spread from mid-May.to e a r l y \u00E2\u0080\u00A2 J u l y , counting the numbers of B l a c k Guillemots a f l o a t i n .a c e r t a i n s t r e t c h of water o f f a breeding area on the south F i n n i s h coast. On a l l occasions a sharp . r i s e i n numbers was,evident when i t became l i g h t i n - t h e morning, and.the number dwindled away..again i n the e a r l y .afternoon. Koskimies suggests (p. 1 0 ) that the m a j o r i t y . o f the b i r d s l e f t the nest.during the morning, g i v i n g a peak i n b i r d s observed, and t h a t t h e \u00E2\u0080\u00A2 f a l l i n numbers i n . t h e \u00E2\u0080\u00A2 a f t e r -noon was due to greater a t t e n t i v e n e s s by. the occupied p a r t n e r , w h i l s t the o f f - d u t y partner p o s s i b l y moved,further out. to the open . sea to feed. 1 2 13 I gathered data on.this t o p i c by counting the number of b i r d s ashore and a f l o a t i n the p o r t i o n of the colony c l e a r l y v i s i b l e from my b l i n d , at. q u a r t e r - h o u r l y i n t e r v a l s , . whenever -my other -observations p e r m i t t e d . The counts thus give the number of b i r d s at.the colony but not.in.the nest, at a n y t i m e , when under undisturbed c o n d i t i o n s . In p r a c t i c e I obtained numerous records from o645-1045 ( a l l times given are P a c i f i c Standard) through the season,-and a few. long-term records. Mo.st of - the f i g u r e s stem from 1959? as - frequent reading of the temperature recorder i n . i960 l e f t no-time f o r -counts whenever that instrument was in.use. \u00E2\u0080\u00A2Numerous watches.throughout the ni g h t showed that other -than b i r d s i n c u b a t i n g or brooding, the Pigeon Guillemot does not spend the night a t , t h i s colony. The a r r i v a l of the of f - d u t y partners along w i t h b i r d s that have n e i t h e r eggs nor small young, i s a dramatic event j u s t as it-becomes l i g h t enough t o make out-the b l a c k forms f l y i n g i n from the sea; t h u s - w e l l before s u n r i s e . Two,examples ( I had been i n the b l i n d .since 2300): 12 J u l y 1959 o230 f i r s t . l i g h t o300 touch of rose i n sky-to east,.telescope search y i e l d s no pigeon g u i l l e m o t s o323 f i r s t pigeon .guillemot.heard o330 2 ashore o345 16 ashore,. 1 a f l o a t ; (can make notes without f l a s h l i g h t ) ,o400.23 present ( r e p r e s e n t i n g the t o t a l to be expected here) o4l5 24 present, e t c . o434 sunrise 14 21 J u l y 1959 o300 f a i n t rose t o East; no pigeon g u i l l e m o t s present o315. s t i l l no pigeon g u i l l e m o t s o345 3 a f l o a t , now 2 more f l y i n , then 4 more,, a l l f l y i n g i n .from f a r - o u t to-.the south 0356 can do without f l a s h l i g h t o400.21 present; o4l5 20 p r e s e n t , . e t c . ( a l l have a r r i v e d ) o438 sunrise Where,, then, do those b i r d s not occupied.at the nest .spend the night? I b e l i e v e they sleep i n r a f t s on the sea f a r from land, b u t - I have only one observation. In an.attempt to i d e n t i f y . a r a f t of some 50 a l c i d s t h a t always formed at .dusk near-a kelp bed (Cod Reefs) some 2.5 kilometers ( l - | m iles) from the colony, I crossed .over \u00E2\u0080\u00A2 to Rubly-Island the evening of 29 July,1960, w i t h two other observers. We were no .closer there,. and had to.-abandon the attempt in. the f a i l i n g l i g h t , \u00E2\u0080\u00A2 b u t .on our r e t u r n to Mandarte we f r i g h t e n e d up a number of Pigeon Guillemots; one group of 10 had d e f i n i t e l y formed a , r a f t about midway. I never noted them there by. day, and as i t .was p r a c t i c a l l y dark the b i r d s had probably gathered there to s l e e p . Whether the- l a r g e r a f t was t h i s species or Br a c hy r a mp bus, marmoratum, which commonly fed.along'the Gooch Island.shore at dusk, was never deter-mined . A s - w i l l be shown l a t e r , . the Pigeon G u i l l e m o t , i s h i g h l y a t t e n t i v e , not l e a v i n g the eggs f o r more than about 15 minutes at a time,-at any p e r i o d of the day. Thus the sudden r i s e i n numbers o f ' ' v i s i b l e b i r d s ' at the colony before dawn i s due to 'the r e t u r n o f ' b i r d s not occupied i n i n c u b a t i o n , that have spent the night elsewhere; e a r l y and l a t e i n.the season t h i s w i l l comprise the whole p o p u l a t i o n . The d e c l i n e i n numbers l a t e r in, the day, on the other hand, i s , as Koskimies r i g h t l y -suggested, owing to.a movement to the 'feeding grounds the l o i t e r i n g . - b i r d s f l y i n g , o f f by, ones and twos u n t i l the colony appears deserted. This outward f l i g h t I could observe w i t h ease i n . t h e f i r s t h a l f of May, when . a l l the birds' l e f t the colony'before noon: by telescope I traced t h e i r f l i g h t t o t h e i r \u00E2\u0080\u00A2 d e s t i n a t i o n , , as t y p i c a l l y once on.the wing they continued r i g h t out of the area, not making the t r i p by stages. A few flew.-in close to the Gooch I s l a n d shore,, but the majority-headed northwards to land close onshore to Sidney S p i t , . 4 - 5 - kilometers (2^-3 miles) away. Indeed i n the whole area Pigeon Guillemots can most c o n s i s t e n t l y be found \u00E2\u0080\u00A2along the shoal NE shore of Sidney I s l a n d , and I once saw.one of my colour-banded b i r d s t h e r e . L a t e r I found that the same area was the major source f o r the f i s h brought to\u00E2\u0080\u00A2the- growing c h i c k s ; the waters about the i s l a n d (always beyond -the kelp-f r i n g e ) and.to a minor extent Gooch I s l a n d waters,-were a l s o used. This feature of a .distant feeding ground has been noted for\u00E2\u0080\u00A2another B.C. colony (Passage I s l a n d , Howe Sound, - Racey 1922) and- the Point Lobos colony studied by S t o r e r ' (1952: 137) Probably - the r e f o r e enhanced feeding opportunity i s . the c h i e f f a c t o r causing withdrawal from waters about the colony during the afternoon,.but the need f o r a s u i t a b l e r e s t i n g area i s a l s o important. In the case of Mandarte I s l a n d withdrawal t o the Sidney S p i t area removes the' b i r d s from disturbance by Glaucous-winged G u l l s , which s t e a l f i s h when they can,, as w e l l as from the strong surface t i d e s p r e v a i l i n g about the i s l a n d , which r e q u i r e the b i r d s to paddle co n t i n u o u s l y . t o main-t a i n p o s i t i o n . No doubt the f a c t o r s are complicated.and- to a c e r t a i n extent l o c a l , as the B l a c k Guillemots of Bonaventure I s l a n d commonly, feed close onshore there -(Storer 1952: 137)? and Bergman (1939: 61-62 - Map 16) i n d i c a t e s t h a t the a d u l t B l a c k Guillemots s t u d i e d by him on the south F i n n i s h coast d i d .'their feeding w i t h i n . a c i r c l e of 1.5 km. r a d i u s , centred on the breeding colony. Palmer '(1949) quotes observations i n d i c a t i n g extended f e e d i n g . f l i g h t s on,the Main Coast, however. Of course the t i d a l argument w i l l not h o l d . f o r the colony i n t h e ' B a l t i c . i n v e s t i g a t e d by Koskimies. My ( r a t h e r incomplete) data w i l l now.be examined f o r seasonal t r e n d s . The graphs h e r e . ( F i g . 7) have been .con-s t r u c t e d i n half-hour c l a s s intervals,.-the average of the even hour 'and 15 past g i v i n g 'the h o u r l y value, that of t h e - h a l f and. 45 past the h a l f - h o u r l y . The sources.of e r r o r are many--'foreign 1- b i r d s entering'the count area, -'home' b i r d s d r i f t i n g -away. or a v o i d i n g - d e t e c t i o n on the grassy c l i f f - t o p s , e t c . , so. that only the l a r g e r f l u c t u a t i o n s are* l i k e l y - t o be meaning-f u l . Of course the number of b i r d s out of s i g h t i n t h e i r nests must be taken i n t o account. I. d i d not a r r i v e on the i s l a n d e a r l y enough.to.wit-ness the f i r s t l a n d ings, but from the notes of G.F. van Tets and c o n s i d e r a t i o n of the rhythm when f i r s t observed (6 May Numbens of gui/lemofs visible from north blind ^ \ & \ \ * \ X s * \u00C2\u00A3 i960) conclude that these take place i n .the l a s t week of A p r i l , c o n s i d e r i n g t h i s an 'average 1 year. Apparently.-the morning a r r i v a l i s governed p r i m a r i l y by l i g h t i n t e n s i t y (data from 16 May to 9 August) throughout; the gradual s h i f t of the morning r i s e shows a c o r r e l a t i o n w i t h changing day-length (the data of Koskimies show t h i s a l s o ) . I t seems l i k e l y t hat time of departure depends mainly\u00E2\u0080\u00A2on inner f a c t o r s however, being e a r l y at f i r s t and s h i f t i n g t o a l a t e r and l a t e r time through May; the same process occurs i n reverse at the close of the season. Thus on 6 t h May the l a s t b i r d l e f t f o r the feeding grounds 0826; on.the 9 t h at o940; 13th o930; and c f . the average 10-13th May.59-for an adjacent p a r t of the colony. By the end of the month the b i r d s l i n g e r much longer (see 29 May, u n f o r t u n a t e l y incomplete). Up to t h i s p o i n t the b i r d s concerned were not i n c u b a t i n g , and.my next long counts f a l l at the end of t h i s phase, so .the e f f e c t of t h i s a c t i v i t y on the rhythm cannot be demonstrated; however, as stated.above the Pigeon Guillemot i s h i g h l y a t t e n t i v e , so.that other than a decrease i n number'the ' v i s i b l e b i r d counts 1 i n d i c a t i n g , as t h e y , w i l l the unemployed birds,, should.show no,basic change. The data of Koskimies bear t h i s out ( h i s colony has much the same chronology as mine, see Koskimies 1949\". 11 and Bergman 1939: 76 f o r an a d j o i n i n g a r e a ) . My three J u l y dates however provide an opportunity to assess the s h i f t from i n c u b a t i o n to feeding, v i z . 1st date: .3 s u c c e s s f u l nests, 1 feeding and 2 i n c u b a t i n g ; 4 f a i l e d nests T \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i n \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 r 1959 i i i i I I I I i i i i i i j i i i i i i i J i i i i i i i i i i i i i i i i 4 6 8 /0 12 14 16 18 20 Time in hours Fig 7b DA/LY RHYTHM\u00E2\u0080\u0094 LONG PERIOD COUNTS cont'd 18 remainder non-breeders; on the second date 2 feeding, 1 incub-a t i n g ; and on the t h i r d a l l 3 f e e d i n g . Bearing i n mind the weaknesses of the method the graphs are remarkably s i m i l a r , the only r e g u l a r . t r e n d being p o s s i b l y an increase i n l a t e afternoon a c t i v i t y . Feeding continues throughout the day, so that small numbers r e g i s t e r e d at the close of the day may be due p r i m a r i l y to the presence of feeding parents, p a r t i -c u l a r l y as i n the absence of t h e i r f e l l o w s Pigeon Guillemots are h e s i t a n t to come ashore and t a r r y long offshore before d e l i v e r i n g the f i s h and moving o f f . The average number-of b i r d s observed per p e r i o d i n the time o400-1030 was almost p r e c i s e l y the same on the three days ( 2 0 . 4 , 2 0 . 6 , 20.7) i n d i c a t i n g that there i s an equal chance to count the members of a p a i r when in c u b a t i n g , as when feeding young. This seems reasonable, f o r during the former one may count the o f f - d u t y partner a p a r t of the time, the i n c u b a t i n g mate but r a r e l y ; and during feeding\u00E2\u0080\u00A2though both are a c t i v e t h e i r i d l e time at the colony i s r e l a t i v e l y s hort. In any case, c o n s i d e r i n g the f i r s t date, where 2 b i r d s of the morning average of 20 were feeding, and another 2 i n c u b a t i n g , i t w i l l be c l e a r that the unoccupied b i r d s are s t i l l bound to a morning of s o c i a l rounds at the colony, g r a d u a l l y moving o f f s t a r t i n g around noon, and remaining away the r e s t of the day. The August count (9th) where the c h i c k i n the f i r s t nest had flown, and feeding continued i n the other two (thus 4 b i r d s i n v o l v e d i n p a r e n t a l d u t i e s ) shows a morning-on, Time a. m. 7 8 9 10 I i Time a. m. 7 8 9 10 II Fortnightly means in half-hour classes May June July August i i i i - - i i i i i _ 8. DAILY RHYTHM-MORNING AVERAGES 19 afternoon-off p a t t e r n as w e l l , w i t h the s t r i k i n g d i f f e r e n c e that the number of b i r d s i s very much l e s s than i n J u l y , a f t e r the f i r s t 1-g- hours f o l l o w i n g l a n d i n g . I t may be argued that the f i g u r e s from a s i n g l e day should not be taken as d e c i s i v e , so at t h i s p o i n t I s h a l l t u r n to the o645-1045 d a i l y counts (see F i g . 8 ) . These have been averaged f o r f o r t -n i g h t l y I n t e r v a l s , from the second h a l f of May, when I occu-p i e d my permanent b l i n d , onwards. The number of days observ-a t i o n a v a i l a b l e i s 8, 11, 11, 10, 9, 12, and 4, so that i n a l l but the l a s t f o r t n i g h t each f i g u r e i s based on about 20 counts (each half-hour count being based on two q u a r t e r - h o u r l y counts as explained e a r l i e r ) . The counts were taken w i t h the same system throughout, the f i r s t of the morning being omitted to allow ample time f o r the b i r d s to recover from the d i s -turbance I always caused when e n t e r i n g the b l i n d . I hope the number of days used w i l l remove f l u c t u a t i o n s due t o weather, et c . The f i r s t p o i n t to n o t i c e i s that the numbers are most n e a r l y constant i n the l a s t h a l f of June and the f i r s t h a l f of J u l y , i n d i c a t i n g that the b i r d s stay longest at the colony i n t h i s p e r i o d ; before t h i s the stay ashore lengthens, and t h e r e a f t e r i t d e c l i n e s . There i s evidence that the f i r s t group to lengthen t h e i r stay i n May, and the l a s t to c u r t a i l t h i s i n August, are the 'breeders', i . e . mated b i r d s , possessing nests where eggs at l e a s t have appeared. Thus ,in May-the banded b i r d s of t h i s category (4 i n i960) stayed each day w e l l beyond the p o i n t where numbers began s h a r p l y . t o f a l l o f f and f o r August t h i s was l i k e w i s e t r u e . I t Is c l e a r \u00E2\u0080\u00A2that some b i r d s are shortening t h e i r shore-period b y - e a r l y August at l e a s t ; thus the average number-of\u00E2\u0080\u00A2'visible b i r d s ' per p e r i o d from the l a s t h a l f of May onwards i s 19, 19, 21, 20, 18, 16, 13, and.the close of season drop i s d e f i n i t e l y s i g n i f i c a n t . I t w i l l be remembered that by 1 August feeding was c o n t i n u i n g in,two nests, i n one the c h i c k had.flown,, (the l a s t c h i c k l e f t the other two 14 and 19 August) whereas the remaining 4. nests were empty, having f a i l e d that season to produce c h i c k s . One might f i r s t suspect,. t h e r e f o r e , that the f a i l e d breeders were l e a v i n g e a r l i e r f o r - t h e feeding grounds, but observation of banded b i r d s i n t h i s category-(3 i n 1959, 6 i n i960) showed th a t they - continued\u00E2\u0080\u00A2to pass a f u l l morning l o i t e r i n g .at the colony at.-this stage. (Note presence of the 3 1959-birds on the 9 August graph;:the-whereabouts of a l l banded b i r d s being recorded at each count, or whenever-mover ments were apparent.) F i n a l l y , b i r d s whose chicks-have flown l i k e w i s e continue to r e t u r n to.the c o l o n y - t h e r e a f t e r , apparently f o r a f u l l morning (2 - banded b i r d s i960). I conclude that the non-breeders are the b i r d s .cur-t a i l i n g t h e i r - s h o r e - t i m e at t h i s stage ( e a r l y August). I have but meagre land records on t h i s group; one 2-year o l d -j o i n e d the morning assemblies r e g u l a r l y - 1 6 J u n e \u00E2\u0080\u0094 2 August 1959, and another 2-year o l d 11 June\u00E2\u0080\u009417 August i960. In the l a t t e r case observations from 30 J u l y on (6) were a l l made e a r l y , s h o r t l y a f t e r I had entered the b l i n d ; and he was not noted 19, 22, 24,. 28,, 30 August when the 'breeding'- b i r d s were, s t i l l seen. I do .not know when.the non-breeders come ashore f o r the l a s t - time;.they may s t i l l appear i n the pre-dawn gathering u n t i l l a t e i n the season. Numbers from the counts are suggestive. I f by. mid-August the breeders alone spend a f u l l morning at the colony, the number observed o700-1045 .should approximate t h i s group. In the 4 days 16-19 August a v a i l a b l e we should expect 13 b i r d s (6 p a i r and one of the feeding p a i r to be - counted,,cf. above), and i n f a c t t h i s was the average number observed. When the breeders shorten t h e i r colony-stay I do not know, probably t h i s . i s a gradual procedure i n - the second h a l f of August. By the end of the month ha r d l y any b i r d s are to be seen a f t e r . t h e . e a r l y morning; thus on.30 August i960.most of the b i r d s l a y , o f f s h o r e i n r a f t s but between o730-o830 .enough landed,to give me1 4 of the 8 banded breeders; the next day/though I was i n the b l i n d 0650-0830 no b i r d s landed at a l l , and I.could,see only 1-2 b i r d s at a time, f a r .offshore. Along the e n t i r e east shore I counted .7 b i r d s at o845, a l l f a r out; i n May 120-150 would be v i s i b l e here as a maximum. I t would be i n t e r e s t i n g to.determine the e f f e c t s of the weather on the rhythm described, but my-material, :is i n s u f f i c i e n t ; I thought the b i r d s stayed longer - about-the colony, on r a i n y overcast -days, but the f i g u r e s do not show. t h i s . 22 The d a i l y rhythm has been o u t l i n e d ; a word of \u00E2\u0080\u00A2 i n t e r -p r e t a t i o n . The observation of Uspenski (1956:. 82.) that i n ' t h e constant l i g h t of the A r c t i c summer \u00E2\u0080\u00A2 (Novaya Zemlya)' the unoccupied B l a c k Guillemots come ashore at the colony to spend the n i g h t s l e e p i n g on the rocky beaches,, but that the peak of a c t i v i t y s t i l l occurs i n the morning hours, suggests that the Pigeon Guillemots of Mandarte I s l a n d spend the nigh t at sea because the b i r d s shun the land by dark-(thus no .nest r e l i e f or feeding occurs by night),.and secondly, t h a t the morning peak i s the expression of a p h y s i o l o g i c a l rhythm and i s com-parable to the morning peak of ac t i v i t y . s h o w n by. b i r d s i n general (Palmgren -1.949). Other auks show marked rhythms at the breeding places a l s o , but there i s a b e w i l d e r i n g d i v e r s i t y : some are no c t u r n a l i n . t h e i r movements to and from the nest (e.g. Synthliboramphus antiquum, Ptychoramphus a l e u t i c u s , Gerorhinca monocerata, f o r r e f s . see Drent & -Guiguet i n p r e s s ) , and of the d i u r n a l species some show b r i e f attendance at the c o l o n y , e a r l y and l a t e i n the season, j u s t as i n the T y s t i e (e.g. U r i a . a a l g e , F r a t e r c u l a a r c t i c a ; F i s h e r & Lockley 1954, Perry 1946, Lockley 1953). For F r a t e r c u l a Myrberget (1959) has demonstrated that f u l l e s t attendance at the colony can be expected i n . the evening, as a l s o .stated by Lockley (1953: 78) (thus opposite to the T y s t i e ) . Me w i l l t u r n l a t e r to the problem of feeding rhythms. 23 SUMMARY Daily-attendance of adu l t Pigeon-Guillemots at the colony f o l l o w s a marked rhythm. Prom the f i r s t time that the Pigeon Guillemot comes ashore at Mandarte (end A p r i l ) t o the l a s t ( e a r l y . September) only b i r d s i n c u b a t i n g or.-brooding small young spend the nigh t at the i s l a n d ; a l l others sleep i n r a f t s at sea f a r from the colony. The b i r d s r e t u r n en masse as i t grows l i g h t ( w e l l before dawn) and-the - ensuing \u00E2\u0080\u00A21 shore-time 1 during which the b i r d s . v i s i t the.nest and c l i f f -top, c a r r y out water d i s p l a y s , mate, e t c . , e t c . , lengthens through May-to reach a maximum end June/early J u l y , a f t e r which i t dwindles s h a r p l y to the close of the season. This rhythm of -morning-on afte r n o o n - o f f i s obeyed by.-all but in c u b a t i n g and feeding i n d i v i d u a l s \u00E2\u0080\u00A2 ( i . e . , i n pre-egg stage by . . a l l , and l a t e r by-non-breeders, f a i l e d breeders, and .off-duty p a r t n e r s ) . S i g h t i n g s of banded b i r d s suggest that the l a s t group-to prolong the morning stay at the beginning of the season, and the f i r s t t o c u r t a i l t h i s at t h e . c l o s e , i s -that of the inexperienced.non-breeders. By comparison w i t h observation i n the Russian A r c t i c (Uspenski 1 9 5 6 ) i t i s suggested that the T y s t i e sleeps at sea at the Mandarte colony because i t shuns the land by-dark, and f u r t h e r - t h a t the morning peak i n colony a c t i v i t y has a deep-seated basis,, and i s comparable t o . a c t i v i t y rhythms i n other b i r d s . Afternoon absence i s to some extent due to feeding and r e s t i n g r e q u i r e -ments . VOICE AND DISPLAYS In the two seasons I have only succeeded i n assembling a general catalogue of'the most frequent d i s p l a y s and c a l l s of the Pigeon Guillemot; no.dummy-experiments were .made. My.method was t o record a l l behaviour-chains i n ,as: much d e t a i l as p o s s i b l e , r e g a r d l e s s of whether I could i n t e r p r e t events-at the time;.emphasis.was place d on t r a c i n g ;the a c t i o n s of banded b i r d s . L a t e r the . notebooks, .were worked over,-and the type of s i t u a t i o n i n which c e r t a i n c a l l s and d i s p l a y s appeared were assembled. The meaning of t h e . d i s p l a y s could.then be deduced. I h e s i t a t e to record.my incomplete observations,;but as I b e l i e v e my r e s u l t s w i t h m a r k e d - b i r d s . w i l l serve to c o r r e c t the i n t e r p r e t a t i o n s published by Storer -(1945, 1952) and Thoresen & Booth (1958) a catalogue here may be u s e f u l . D i s p l a y s s t i l l anomolous to me are omitted, and I have been unable to recognize the d i s p l a y described by. Williamson (1951) f o r the Bl a c k Guillemot. Only.'brief mention.of other species . i s made. Outline ( a l l l i s t e d c a r r i e d out by-both sexes) The lunge abbreviated a t t a c k , i n t i m i d a t i o n -d i s p l a y Hunch-whistle...... t h r e a t - d i s p l a y Chuckle-waggle.... appeasement B i l l - d i p p i n g ..... expression of-uneasiness when on the water 24 25 Scream alarm c a l l (arid a s s o c i a t e d posture),. w i t h m o d i f i c a t i o n s : P u f f i n c a l l . , given when Lunda c i r r h a t a f l i e s . past Hiss-scream.. given i n s i t u a t i o n s of extreme f e a r Chipping f l i g h t - c a l l T r i l l e d song, t w i t t e r i n g , and b i l l i n g f a m i l y communications Duet f l i g h t s f o r m a l i z e d chases, not employed \u00E2\u0080\u00A2within-the p a i r ; aggression Water games communal d i s p l a y s on the water and beneath the surface, dominated by aggressive and appeasement d i s p l a y s l i s t e d e a r l i e r ; not d i r -e c t l y connected w i t h c o p u l a t i o n The Lunge ( F i g . 28) S t o r e r (1952) describes t h i s c o r r e c t l y as a type of aggressive d i s p l a y , p. 148; F i g . 6 l , p. 136. This may be given ashore or. a f l o a t . The b i r d makes a sudden rush, w i t h head and neck outstretched, the b i l l d i r e c t e d at opponent and u s u a l l y . s l i g h t l y : agape;.-'the wings may be unlimbered, but there i s no.sound. An i n t i m i d a t i o n gesture which i s u s u a l l y s u f f i -c i e n t to ;make opponent f l e e and sometimes used w i t h success against crows (Corvus c a u r i n u s ) . I t may merge i n t o overt aggression, the a t t a c k e r grabbing the opponent by the wing, neck or t a i l whereupon both tumble to the water, or i f already a f l o a t d i v e . When a.resident objects to,over-close approach by an i n t r u d e r \u00E2\u0080\u00A2 h i s . r e a c t i o n i s normally;the hunch-whistle (see on), but when in.an aggressive mood ( e s p e c i a l l y during or j u s t a f t e r 26 copulation( the lunge appears. 1 * I 20 June 1959. o710. 45 sees, c o p u l a t i o n Blueband (male) and.unbanded mate; ended by female. Stranger \u00E2\u0080\u00A2then lands, dr i v e n o f f at once by lunge of female, who.leaves shortly, t o . f l y n o rth around i s l a n d to ' feeding grounds. 3 June 1959. o713. Blueband-0 are i n t e r r u p t e d . i n t h e i r waddling ( c o p u l a t i o n p r e l i m i n a r y ) . b y a r r i v a l of stranger, 'whom Blueband lunges. 11 June i960. 0815. K a r l comes ashore, greeted by. K i t t y (male), long c o p u l a t i o n at once, i n t e r r u p t e d by Stranger,, whom K a r l '(female) d r i v e s o f f w i t h a lungej a l s o another S.who had come ashore next K i t t y . R arely the lunge i s used w i t h i n the p a i r : 25 June-1960. 0952. Long- ( c . 30-40 sees.) but unsuc c e s s f u l c o p u l a t i o n , male s l i d e s o f f to r i g h t ; mutual lunge t h e r e a f t e r ! Hunch-Whistle ( F i g s . 9-13) Given both ashore and a f l o a t . \u00E2\u0080\u00A2 The t a i l i s cocked up,.head.thrown back .and drawn i n , and b i l l wide agape. This posture .is accompanied by loud skyward p i p i n g : , \"weep weep weep weeeee\", w i t h accent on.the l a s t , drawn-out note,, and the sequence repeated\u00E2\u0080\u00A2over and again. At high i n t e n s i t y (ashore) the b i r d r e a r s up-with wings akimbo (as i n chuckle-waggle) and neck outs t r e t c h e d , but the b i l l i s s t i l l p o inted v e r t i c a l l y . A th r e a t d i s p l a y evoked by over-close approach of a.strange b i r d ; o f t e n . t h i s s u f f i c e s to discourage the i n t r u d e r a f t e r a b i t , sometimes i t merges i n t o aggression (lunge) or \u00E2\u0080\u00A2appeasement (chuckle-waggle). I f nearby the mate may be c a l l e d over by t h i s d i s p l a y , . though often to l i t t l e purpose. I t was i n t h i s secondary r o l e t h a t Thoresen & Booth (1958: 10, P i g . 9 Hunch-whistling; note wing stance ( c e n t r e ) . B i r d at r i g h t the i n t r u d e r . F i g . 10 Mutual hunch-whistling Gape and head posture c h a r a c t e r i s t i c . F i g . 11 Mutual hunch-whistling on the water. Note cocked t a i l and wing stance. Again the c o r a l gape i s d i s -played. 27 F i g . 9, descr. p. 9) noted.the d i s p l a y . 14 May. I960,, 1026. A ashore, B J u s t o f f rock, formerly perched, there; C f l i e s over from next beach-area, obviously doesn rt belong here (shows anxiety),, lands, next A who hunch-whistles; C- backs off,- B comes ashore, waddles (as i f male i n co p u l a t i o n p r e l i m i n a r i e s ) , . then lunges at C, who . - f l i e s o f f ; A & ,B s e t t l e and b i l l . ( t h e r e f o r e a mated p a i r ) . 1032 i n t r u d e r again (?C) lands nearby; A again hunchr-whistles, B waddles; a f t e r about 2 minutes i n t r u d e r f l i e s o f f , hunch-whistling ceases at once; both A & ,B crane and peer; A even f l i e s over. to.rock where i n t r u d e r had perched, peers about and f i n a l l y s e t t l e s . Here the mate a i d e d . i n . d r i v i n g o f f the i n t r u d e r ; more often ..however the mate drawn . to the hu n c h r w h i s t l i n g p artner gawks . and waddles about w i t h mincing steps, sometimes attempting to b i l l with-the mate, without a t t a c k i n g the i n t r u d e r d i r e c t l y ( i n i960 5 such cases versus 2). 28 May i960. 0926. 0, lands, c. 2 f e e t from K-K; c. 1 minute l a t e r K i t t y (banded male) s t a r t s hunch-w h i s t l i n g ; K a r l ( h i s banded mate) stands up, \"weeps\" q u i e t l y , gawks about; minor g u l l panic c a r r i e s 0.away 0928, K-K sil e n c e d . -25 May i960. o844. - 0 . lands c. 5. f e e t away from e s t a b l i s h e d p a i r , one of which hunch-whistles, h u r r i e s over to i n t r u d e r ; \u00C2\u00A9flies off,, and by . then .the partner has a r r i v e d a l s o , and stands about l o o k i n g f o o l i s h . A new i n t r u d e r lands 5 f e e t away, hunch-whistling on part of f i r s t b i r d continues, \u00E2\u0080\u00A2 f i n a l l y t hat i n t r u d e r goes too; i n n e i t h e r case d i d the second partner \u00E2\u0080\u00A2 aid., the hunch-whistler. o845. Both s e t t l e . The i n t e r p l a y between hunch-whistling and o u t r i g h t aggression . i s - - i l l u s t r a t e d by the f o l l o w i n g : 6 June i960. o940. A moves up, on B, B hunch-whistles, A continues, B lunges, grasps bend.of wing; A f r e e s i t s e l f and f l e e s . 18 May i960. 0650. Mutual hunch-whistling on water leads t o mutual t h r u s t i n g (abbreviated'lunges); develops i n t o scrapping, b i r d s o f f i n underwater-f l i g h t . P i g . 12 An i n t r u d e r ( c e n t r a l b i r d ) has j u s t landed at the perch-s i t e of an e s t a b l i s h e d p a i r , one of whom hunch-whistles. F i g . 13 C o n t i n u a t i o n . Intruder leaves; both members of estab-l i s h e d p a i r now humch-whistling. They subsided a moment l a t e r . 28 Again, i n t e r p l a y w i t h appeasement (chuckle-waggle) w i t h spectators j o i n i n g i n : - ( u n i d e n t i f i e d stranger) 23 May I 9 6 0 . o840. 01 (mated male) and 0 land on GM f o l l o w i n g duet f l i g h t , K i t t y (mated male) hops down to 0, chuckle-waggles, then b r i e f hunch-whistling, then chuckle-waggles again; another unhanded b i r d \u00E2\u0080\u00A2 j o i n s i n , so three w i n d m i l l s ( a l l three chuckle-waggling); 01 then o f f i n duet f l i g h t w i t h 0.again; K i t t y s e t t l e s . Both elements e x h i b i t e d : 18 May i960. 0630. Two b i r d s mutually hunch-\u00E2\u0080\u00A2\u00E2\u0080\u00A2 w h i s t l i n g ; ' merges i n t o lunge ( w i n g s . l i f t e d ) , each time however merges into.chuckle-waggle at c r i t i c a l p o i n t : b i l l s a c t u a l l y met, end on, c l e a r l y aggres-s i o n held b o t t l e d up w i t h d i f f i c u l t y . 0650 On water now, hunch-whistling i n t o t h r u s t i n g , develops i n t o scrapping, o f f i n underwater f l i g h t . Chuckle:-Waggle ( F i g . 14) Storer \u00E2\u0080\u00A2 (1952) described t h i s d i s p l a y - ( p . 146-147, F i g . 6 c - d , p. 136) and termed.it aggressive (p. 148). I t may be a counterpart of the ''ecstatic p o s t u r e 1 described, i n A l c a t o r d a , U r i a aalge, and F r a t e r c u l a a r c t i c a by Conder (1950). The d i s p l a y may be given on land or a f l o a t . The t a i l i s cocked up, the wings akimbo/ and c h a r a c t e r i s t i c i s . t h e p e c u l i a r s i d e - t o - s i d e waggling of_the outstretched head and neck; the crown f e a t h e r s are e r e c t . This is'accompanied by an e n e r g e t i c t w i t t e r or chuckle, the b i l l but s l i g h t l y open, \" t i t i t t i t i t i t \" e t c . An appeasement d i s p l a y , obviously combining t h r e a t (body a t t i t u d e as i n hunch-whistle, neck out-s t r e t c h e d as i n lunge) w i t h endearment ( s i d e - t o - s i d e head P i g . 1 4 Chuckle-waggle (foreground) as part of water games. P i g . 15 B i l l - d i p p i n g ; head plunged i n to depth of eye. 29 movements; t w i t t e r i n g ) . Often appears i n f i g h t s when the attacked b i r d shows tendency to stand ground: 27 May 1959. 0637. Old round of landings and squabbles f o l l o w i n g my disturbance i n e n t e r i n g blind...one of these becomes v i o l e n t , the newcomer being held f a s t by the bend of the wing w h i l s t he thrashes about rock. The moment of release he chuckle-waggles, and f i n a l l y s e t t l e s . I n t e r p l a y w i t h aggression shown i n the f o l l o w i n g : 6 June i 9 6 0 . o952. 25 sec. c o p u l a t i o n i n t e r r u p t e d by stranger ( s ) , who hops over as soon as c o p u l a t i o n s t a r t s . Female r i s e s , male s l i d e s o f f , lunges at S\u00E2\u0080\u0094who stands ground and gapes b a c k \u00E2\u0080\u0094 t h e n lunges i n t u r n ; male shrinks back w i t h sudden hop, S presses forward, male chuckle-waggles, then lunges back; S chuckle-waggles i n t u r n ; one more bout, male then chuckle-waggles w i t h h i s mate, S o f f . 14 June i 9 6 0 . 08IO. K i t t y (male whose mate absent f o r the day) roaming about 1 f l a p p i n g 1 (see pre-egg stage). 0 lunges, K i t t y lunges back; 0 lunges again, K i t t y chuckle-waggles; then K i t t y lunges i n t u r n ; i n t e r e s t d i v e r t e d by another; 0 subsides. I t may a l s o be used by an i n t r u d e r before any aggression by r e s i d e n t : 17 August 1959. 0806. K i t t y ( f a i l e d breeder here) l e f t behind on c l i f f , v i s i t e d by stranger,, who chuckle-waggles immediately on l a n d i n g ; K i t t y goes i n t o s t i f f hunch-whistle, but f i n a l l y chuckle-waggles b r i e f l y ; an i d l e r h u r r i e s over to j o i n i n , stranger moves up, and a l l s e t t l e . 3 June 1959. o936. Long c o p u l a t i o n ( c . 75 sees.), b i r d s preen t h e r e a f t e r o939 stranger lands, chuckle-waggles w i t h female; male takes a c t i o n and chases stranger o f f i n duet f l i g h t a f t e r a b i t , l a n d i n g again beside h i s female i n a couple of minutes. Here chuckle-waggling served to f o r e s t a l l aggression to l ) gain p o s i t i o n , and 2) attempt to e s t a b l i s h rapport w i t h a b i r d not the mate. I d l e r s f r e q u e n t l y are t o l e r a t e d as close spectators to f i g h t s , feeding t r i p s to the chick, or c o p u l a t i o n s , 30 by chuckle-waggling at the c r i t i c a l moment. 23 May I960. o 7 4 l . Blueband (mated male) hunch-w h i s t l e s , 0 ( i n t r u d e r ) chuckle-waggles i n r e t u r n ; 2 bystanders toddle over, one chuckle-waggles; 0 f l i e s o f f , B f o l l o w s i n d u e t - f l i g h t , laboured because of strong wind; B lands again .o744. 11 August 1959. 1010. Female lands w i t h blenny, 3 b i r d s ( i n c l u d i n g the mate) mob.the f i s h e r ; they are i n t e n s e l y e x c i t e d and chuckle-waggle c o n t i n u a l l y ; but f i s h d e l i v e r e d at once, and female f l i e s north around i s l a n d to feeding grounds 1012. To what extent chuckle-waggling i s used between the members of a p a i r i s unclear; besides i t s occurrence during f i s h t r i p s as above (a f u r t h e r example below) I have one record f o l l o w i n g e v i c t i o n of an i n t r u d e r : 22 May i960. o843. Blueband (mated male) has dropped to water o f f next beach s t r e t c h , c l e n c h i n g t a i l or i n t r u d e r ; f i n a l l y both bob to surface, B hunch-w h i s t l e s , i n t r u d e r weaker but l i k e w i s e ; o f f i n duet f l i g h t , i n t r u d e r l e a d i n g ; 3 a r c s , i n t r u d e r lands ashore on the second, and B lands on f a v o u r i t e perch where he chuckle-waggles w i t h mate. 20 J u l y 1959. o746. Flounder to nest #48; f i s h e r passes i t to mate who c a r r i e s i t w i t h i n ; meanwhile f i s h e r chuckle-waggles and a f t e r a time--when I can see mate r e a p p e a r i n g - - f l i e s o f f to Gooch I s l a n d (a feeding area f o r t h i s p a i r ) . I have not been able to work out e q u a l l y c l e a r examples when t h i s d i s p l a y i s used on the water, but the character of appeasement i s c l e a r \u00E2\u0080\u0094 b i r d s bob.to the surface over-close, chuckle-waggling ensues, ending e i t h e r i n o u t r i g h t aggression or w i t h the b i r d s moving apart by paddling, d i v i n g , e t c . The composite nature of the d i s p l a y has been mentioned; Tinbergen (1959) t h e o r i z e s t h a t a l l d i s p l a y s are i n f a c t the overt expression of inner c o n f l i c t s . B i l l - D i p p i n g ( F i g . 15) This occurs only on the water. The b i r d t h r u s t s the. b i l l r a p i d l y under the surface; only the b i l l may be wetted but more commonly the head i s plunged i n to the l e v e l of the eyes. No sound accompanies the a c t i o n . This nervous r e a c t i o n may be e l i c i t e d at a l l times of the year by over-close approach by boat, e t c . , and at the breeding colony when the b i r d s are h e s i t a n t to land (e.g. f o l l o w i n g a disturbance, or when b r i n g i n g f i s h to the nest at midafternoon when the beach i s empty of g u i l l e m o t s ) . This a n x i e t y - i n d i c a t o r i n the T y s t i e has been o f t described before (e.g., Witherby et al,194l: 162, Storer 1952:135, Thoresen & Booth 1958: 26-28). I t i s doubt-l e s s homologous to the nervous b i l l - d i p p i n g described i n A l c a torda, U r i a aalge, and F r a t e r c u l a a r c t i c a by N/rrevang (1958: 64). I agree w i t h him that the movement i s best i n t e r p r e t e d as an i n t e n t i o n diving-movement. The Scream ( F i g s . 16, 17) Thoresen & Booth 1958(l4) c a l l t h i s *a type of t h r e a t p o s t u r e a n d supply an e x c e l l e n t f i g u r e ; S t o r e r 1952 (l49) says that g u i l l e m o t s appear to l a c k an alarm note. Ashore or a f l o a t w i t h neck st r e t c h e d to f u l l extent, the b i r d peers about nervously, gapes (N.B. head held h o r i z o n t a l l y , c o r a l mouth-lining presented d i f f e r e n t l y than i n hunch-w h i s t l e ) and screams. This scream i s a long-drawn out raspy w a i l , \"wheeeeeoo\", and extent of gape and l e n g t h and volume of scream depend on stage of a n x i e t y . At h i g h \u00E2\u0080\u00A2 i n t e n s i t y ashore, \u00E2\u0080\u00A2 t h e \u00E2\u0080\u00A2 b i r d r i s e s up on i t s toes, the neck very long, turns the head nervously and gapes widely, but always h o r i z o n t a l l y . T h i s . i s the alarm r e a c t i o n of the Pigeon Guillemot,, caused f o r example by d i s t a n t g u l l p a n i c s , approach by man .or boat, \u00E2\u0080\u00A2unexpected noises i n the nearby b l i n d , low sudden f l i g h t s by g u l l s , crows, cormorants,. or oystercatchers.to.name.only the b i r d s w i t h which my guillemots.were i n d a i l y contact. Some-times even l o w - f l y i n g a i r c r a f t cause the b i r d s to scream. In short, anything t h a t makes, the b i r d s uneasy but does not frighten/them completely w i l l evoke the scream. The various stages of alarm can be e a s i l y observed when man approaches along the beach, at the colony: the most wary i n d i v i d u a l s scream, and as t h i s , i s an i n f e c t i o u s thing, soon a l l nearby, b i r d s j o i n . i n ; on continued approach the b i r d s r i s e up, then f l y out t o sea where uneasy screaming r a f t s form. \u00E2\u0080\u00A2 The gu i l l e m o t s do not r e t u r n to shore f o r some time a f t e r the disturbance - has passed, r e c o n n o i t e r i n g the shore i n small p a r t i e s p a d d ling up and down, a l t e r n a t i n g screaming w i t h b i l l - d i p p i n g . Sudden .panies--e.g., a Peregrine swooping.overhead\u00E2\u0080\u0094cause\u00E2\u0080\u00A2the b i r d s t o - f l e e the shore at once, and plop i n t o the water, where screaming r a f t s form. My Pigeon Guillemots d e f i n i t e l y r e a c t t o the g u l l s 1 , alarm c a l l s , even without seeing the cause f o r disturbance, j u s t as Turnstones that nest i n sea- b i r d c o l o n i e s do (Bergman 33 19^6). This could he observed repeatedly, e.g., a Bald Eagle approaches the i s l a n d from the opposite s i d e , and the g u l l s there panic; at my b l i n d the g u i l l e m o t s scream or take d i r e c t l y to.the water,. depending on the nearness of\u00E2\u0080\u00A2the g u l l alarm. E v e n t u a l l y -the eagle i t s e l f comes i n t o .view. A f u r t h e r \u00E2\u0080\u00A2 s i t u a t i o n causing great d i f f i c u l t i e s at times was- the i n s t a n t r e a c t i o n to s l i g h t g u l l disturbances caused by-my companions moving to and from t h e i r b l i n d s , \u00E2\u0080\u00A2 e t c . I cannot say i f the, g u i l l e m o t s reacted a l s o . t o crow-alarms, since the gulls.were u s u a l l y so quick t o respond to.these that there was no way-to k e e p . t h e . s t i m u l i apart. With a - c l e a r view, the Pigeon Guillemot apparently r e a c t s to b i r d s of prey before the Glaucous-winged G u l l , as I could s e v e r a l times v e r i f y f o r the Peregrine. The b i r d s w i l l also.scream i n . f l i g h t , and t h e . a c t i o n 'gives the sound.a p e c u l i a r - v i b r a t o r y , q u a l i t y . This was some-times .heard when the g u i l l e m o t s flew back to land again a f t e r \u00E2\u0080\u00A2a disturbance,. and.was most commonly heard when they;were a r c i n g past the n e s t - s i t e w h i l s t I was examining, the contents on.my rounds. That the d i f f e r e n c e i n sound i s due to the a c t i o n of f l i g h t , and. not to the use of a new..note i n .these circum-stances,, was demonstrated by.such as: 1 9-August i960. 0924. Screaming b i r d lands c l i f f -top; and the sound changes a b r u p t l y from the v i b r a n t throbbing scream to o r d i n a r y . r 34 P u f f i n C a l l A d i s t i n c t v a r i a t i o n of the scream, given w i t h the same posture (? hut only on.land) but w i t h a s t a c a t t o i n t r o -d u c t i o n : \" t i k - t i k - t i k - t i k - t i - w h e e e e e \" . Only noted when Lunda . c i r r h a t a flew past or landed. I t was remarkable at what great distances the gu i l l e m o t s reacted thus to a . f l y i n g p u f f i n ; I often had considerable d i f f i c u l t y l o c a t i n g the p u f f i n w i t h 8X b i n o c u l a r s long a f t e r the gui l l e m o t s had given the alarm. For example. 4 July . 1 9 6 0 ; p u f f i n c a l l - n o t e d o735? o740, 0750, 0830, 085O; and a s i n g l e Lunda l o c a t e d every time. S i g n i f i c a n c e of the c a l l i s . n o t c l e a r . Two\" p a i r of Tufted P u f f i n . n e s t on.the c l i f f s of the i s l a n d , on the other side from where.these observations were made, and there u t i l i z e much the same ki n d of rocky c r e v i c e s as do,the Pigeon Guillemots. The c a l l might be thought t o . i n d i c a t e antagonism of the gui l l e m o t s to p o t e n t i a l nest competitors,\u00E2\u0080\u00A2but t h i s would be premature as we have no.evidence of p u f f i n o u s t i n g g u i l l e m o t or v i c e versa. Hiss-scream .A f u r t h e r m o d i f i c a t i o n of\u00E2\u0080\u00A2the scream, which seems to be r a t h e r r a r e , as I have heard i t only. once. Bent (1919) has described t h i s v o c a l i z a t i o n f o r both B l a c k and Pigeon Guillemots, but Thoresen & .Booth (1958: 7) never heard i t (which bears out i t s r a r i t y ) . I would c a l l . i t a h i s s i n g , reedy scream, g i v e n . i n moments of extreme f e a r ; I heard i t 35 as f o l l o w s : Returning to camp from my b l i n d 1100 22 May 1959? I suddenly, rounded a corner of the b e a c h - c l i f f , thereby s u r p r i s i n g the g u i l l e m o t p a i r w i t h i n t h e i r nest #27; they q u i c k l y emerged and flew..off, one g i v i n g 'an angry h i s s i n g r a t t l e 1 before f l y i n g , o u t t o the water. In numerous captures of b i r d s on the nest I never heard t h i s , the b i r d s g i v i n g the o r d i n a r y scream or remaining s i l e n t . I should add that there are a number of s o f t 'weeps 1, 'muffled screams' e t c . whose i n t e r p r e t a t i o n s t i l l p uzzles .me, as not enough s i t u a t i o n s are represented i n my notes. Chipping Thoresen & Booth .(1958: 7) give 'whist w h i s t 1 , but do not i n d i c a t e meaning. Before t a k i n g f l i g h t \u00E2\u0080\u0094 e i t h e r from the water.^or from land\u00E2\u0080\u0094-that i s 'premeditated 1, i . e . , not the outcome of sudden panics, aggression, e t c . , but r a t h e r f o r such purposes as v i s i t i n g the c l i f f - t o p (always something of a t r i a l ) , c a r r y i n g . f i s h to-the young a f t e r a delay, or when f l y i n g o f f to the f e e d i n g grounds, from the colony, the Pigeon Guillemot shows unmistakable f l i g h t - p r e p a r a t o r y , movements (unlimbers wings, h a l f - r i s e s i f ashore, etc.) and chips continuously \" t s i p t s i p t s i p - t s i p t s i p . \" . The number of chips, given depends on motivation,;and the c a l l s continue i n t o the f i r s t p a r t 'of f l i g h t . This c a l l i s used away, from the colony too, and ,probably throughout the year, i n a l l cases s i g n i f y i n g i n t e n t i o n . t o f l y . F i g . 18 B i l l i n g , a ceremony between members of a p a i r . The b i l l s a c t u a l l y r a r e l y touch, but pass and repass each other. F i g . 19 T r i l l e d song, an i n t e r l u d e i n b i l l i n g 36 T r i l l e d Song, Twittering, and B i l l i n g (Figs. 18-21) Mutual b i l l i n g - i s a sure sign that the birds involved are a., mated p a i r ; occasionally attempts are made to b i l l out-side the pa i r , but I have never noted response i n t h i s case. Whether af l o a t , standing or set t l e d ashore, the participants twist the head so as to di r e c t the b i l l at that of the mate; a s l i g h t but d e f i n i t e waggling motion ensues, but the b i l l s r a r e l y touch, t h e i r ' t i p s continually passing and repassing one-another. This movement i s accompanied by a gentle twitter or/chuckle \" s i t s i t s i t s i t \" punctuated' at int e r v a l s by. the ' t r i l l e d song' (Thoresen &..Booth's 1958 term; rendering a f t e r Storer 1952: 148) \" s i t . s i t s i t seeeoo, s i t s i t s i t seeeoo\", the 'seeeoo' note being long-drawn out and r i s i n g , then f a l l i n g . During the t r i l l the b i l l is.wide agape, - whilst during twitter-ing (following Thoresen & Booth 1958: 8) the b i l l . i s but s l i g h t l y parted. Thus t h e - b i l l i n g ceremony d i f f e r s from chuckle-waggling - i n being-less exaggerated, the wags -.being less marked and the wings and t a i l not brought into play; from the hunch-whistle by extent of gape, head position,\u00E2\u0080\u00A2and i n being always directed whereas hunch-whistling i s but r a r e l y \u00E2\u0080\u00A2so; and from the scream by. an .absence of craning and nervous peering.with elongated neck and wide-open gape that character-ize the guillemot in alarm. B i l l i n g varies greatly i n intensity-depending on mood of the participants;. when the members of\u00E2\u0080\u00A2the pair.have not seen each, other f o r a long time (e.g., incubating partner meets mate i n early morning r e l i e f ) F i g . 20 B i l l i n g on the water; the b i r d on the l e f t i s t w i t t e r i n g . This i s always a d i r e c t e d a c t i v i t y . F i g . 21 More b i l l i n g ; b i r d on the r i g h t u t t e r s t r i l l e d song. the g r e e t i n g may, be prolonged, both g i v i n g the song; at other-times a b r i e f gentle t w i t t e r may be the o n l y sign of recog-n i t i o n . Both may be given i n the- absence of the partner,, and whether they serve to c a l l over -the mate i f nearby, or simply r e f l e c t .the mood of the c a l l i n g b i r d , I am unable to say. The t w i t t e r and. song are a l s o .employed, as a g r e e t i n g to the young when b r i n g i n g f i s h to the nest,, the young r e p l y i n g w i t h a squeaky.chitter within,, as has a l s o been noted by-Thoresen & Booth (1958: 8). This i s by no means an i n v a r i a b l e procedure', fe e d i n g often being c a r r i e d out i n s i l e n c e . B i l l i n g w i t h the a s s o c i a t e d t w i t t e r i n g _ or t r i l l i s d e f i n i t e l y - o f great importance i n i n i t i a t i n g . a n d . m a i n t a i n i n g the p a i r bond.' Thus unmated b i r d s ( s t a t u s .clear, banded b i r d s ) w i l l attempt to b i l l w i t h a number of birds, i n .turn (the e s t a b l i s h e d b i r d s never r e p l y i n g ) , as though i n an attempt-to s t r i k e up.an understanding; and.established p a i r s continue to b i l l and'.twitter whenever they,meet throughout the season. There i s no.doubt,-however, that the ' t r i l l e d song 1 i s u t t e r e d most f r e q u e n t l y i n the pre-egg stage,. a n d , i t s .use during feeding-has been mentioned, s o . i t apparently has both p a i r - r bond and f a m i l y s i g n i f i c a n c e . B i l l i n g i s a common pair-bond ceremony.in auks .(uria.aalge Perry 1946, N/rrevang- 1958, Tschanz 1959; A l c a torda .Paludan. 1947; P r a t e r c u l a . a r c t i c a Lockley 1953? a l l three Conder-1950) and i t would be of great i n t e r e s t to make d e t a i l e d comparisons. In the p u f f i n Lockley (1953: 4-5-47? 54 esp.) s t r e s s e s that i n c i p i e n t h i l l i n g i s d i s t i n g u i s h e d from the s i m i l a r t h r e a t d i s p l a y by the .side-to-side v i b r a t i o n ; i n t h i s species b i l l i n g a l s o serves t o . e s t a b l i s h rapport w i t h b i r d s outside the p a i r . In the Pigeon Guillemot chuckle-waggling f i l l s the l a t t e r f u n c t i o n , and i t may.be s i g n i f i c a n t that the s i d e - t o - s i d e waggle i s b a s i c here a l s o . Duet F l i g h t s F r i c t i o n i s frequent at the Pigeon Guillemot colony; the great ' c u r i o s i t y ' of\u00E2\u0080\u00A2the b i r d s - - t h e i r d e s i r e t o j o i n i n the a c t i v i t i e s - of \u00E2\u0080\u00A2 t h e i r neighbours, \u00E2\u0080\u00A2 whether - that be f i g h t i n g , feeding c h i c k s , f l y i n g to.the c l i f f - t o p , or anything, at a l l , leads to constant squabbling. The us u a l p a t t e r n when a stranger\u00E2\u0080\u00A2edges over too close to an e s t a b l i s h e d b i r d i s , as we have seen, f o r the r e s i d e n t t o hunch-whistle. I f t h i s t h r e a t i s not s u f f i c i e n t (the stranger\"hunch-whistling i n turn or perhaps only chuckle^-waggling) the . lunge i s r e s o r t e d , t o , perhaps even a b r i e f s c u f f l e f o l l o w s * I f i t comes to t h i s the r e s i d e n t w i l l o ften chase a f t e r the stranger when the l a t t e r takes f l i g h t , and f o l l o w close on his, t a i l , d u p l i c a t i n g every evasive t w i s t and turn,. dropping, to the-water when the stranger does. Here the chase may continue beneath the sur-f a c e , then perhaps the b i r d s w i l l pop out and continue, the stranger crashing amongst a s e t t l e d group ashore In an e f f o r t toescape i n the mob (sometimes s u c c e s s f u l , t h e - f o l l o w e r attack-in g the wrong b i r d ) . Sooner-or-later the chase ends and\u00E2\u0080\u00A2the 39 r e s i d e n t r e t u r n s to h i s f a v o u r i t e perch (N.B. i t was the magic c i r c l e of ' i n d i v i d u a l d i s t a n c e ' (Conder 194-9) that the i n t r u d e r \u00E2\u0080\u00A2transgressed, not a patch of 'sacred'- r o c k ) . Thus o r i g i n a t e the f l i g h t s a n d . a e r i a l s c u f f l e s ( t a i l tweaking, pouncing) considered by-some 'courtship f l i g h t s ' . Since I have been unable\u00E2\u0080\u00A2to f o l l o w p a i r - f o r m a t i o n w i t h banded b i r d s i t - i s pos-s i b l e that these f l i g h t s occur i n the e a r l y . s t a g e s . o f court-s h i p , but c e r t a i n l y the grand, m a j o r i t y i n v o l v e a member of an e s t a b l i s h e d p a i r together w i t h an i n t r u d e r ; they are aggres-s i v e i n c h a r a c t e r . The n e u t r a l term 'duet f l i g h t 1 i s suggested; two examples of formation: \u00E2\u0080\u00A2O853 8 Aug. 59: K a r l (mated female, not the p a r t n e r , f a i l e d breeder here) i n a running f i g h t w i t h unhanded b i r d (0); water f i g h t s , then short f l i g h t , - K a r l catches adversary by t a i l or f o o t , both, tumble to water; long f l i g h t to north, and back again, K a r l lands near i t s nest s i t e , adversary f o l l o w s but d r i v e n off. w i t h a lunge. 0820 27 May 60. K i t t y r i s e s , chuckles w i t h K a r l , .probably p r e l i m i n a r y to c o p u l a t i o n , 0,.who s e t t l e s beside K a r l c. 5 minutes ago, moves,, then f l i e s to water, K i t t y f o l l o w s , o f f i n duet f l i g h t , - 0 lands ashore, K i t t y r e t urns t o K a r l area, (mated p a i r i n pre-egg stage). Thus both partners may be i n v o l v e d as the 'chasers 1. That the i n t r u d e r s are by no.means always unattached b i r d s i s shown by the f o l l o w i n g : 1415 3 J u l y 60. Blueband (mated male nest #12), and Double-green (mated male nest #13) i n 43 hollow (perched on. ' f o r e i g n ' c l i f f top' s e c t i o n ) , , down to NM \u00E2\u0080\u00A2 ( t h e i r perching-home), chuckle-waggle j take to water, chuckle-waggle,. aggression c l e a r l y suppressed; dive and make shallow underwater chase; pop,up f o r short s u r f a c e - f l a p . c h a s e , away in.duet f l i g h t . 40 In a case such as t h i s where 'equals'- are fighting? the roles of aggressor and fugitive' may he.reversed,during\u00E2\u0080\u00A2the duet f l i g h t s , e.g. 1012 29 July 60. o l (mated male of nest #14) lands on 11 slab, 0 lunges at once (probably 11-nest-owner), both p i t c h into air,, arc about together, both land 14 slab 0 hunch-whistles but leaves f o r gap; Clem (male of 01) lands, chuckles.with o l . Another insight i n t o . o r i g i n .is given by the following, a f a i l e d breeder but mated female joining an with the feeding birds i n t h e i r c l i f f - t o p . v i s i t 0717'14 Aug. 60. K i t t y brings another blenny (nest #4-3) >.< Clem (nest #14) accompanies him to the c l i f f -top, where she chuckle-waggles with unbanded\u00E2\u0080\u00A2bird (prob. feeding parent at #11),. 0 lunges, birds off i n duet f l i g h t , 0 .chasing Clem to and f r o ; when-ever 0 gets close attempts to nip.her t a i l . ( i t w i l l be remembered that Clem's mate was banded.) Water Games F i n a l l y a word must be said about the conspicuous group water displays described so v i v i d l y . b y Perry (1946, 1948) and mentioned b y - a l l who write of the Ty s t i e . \u00E2\u0080\u00A2 Tnroughout the season birds gather off the shores of the colony and carry \u00E2\u0080\u00A2 out i r r e g u l a r movements .to and f r o , the birds paddling e r r a t i -c a l l y u n t i l suddenly a tight crowd r e s u l t s . The birds .then .dive and continue group movements by f l y i n g close under the surface, the white wing-patches f l a s h i n g at each stroke;, they pop,up only, to dive again, or perhaps s k i t t e r \u00E2\u0080\u00A2 over the surface flapping-the wings as i n diving, at the same time paddling fu r i o u s l y , so an uneven progression f l o p - f l o p - f l o p r e s u l t s . 41 F i n a l l y , . a s spontaneously as i t began, the d i s p l a y i s over and the b i r d s disperse to paddle q u i e t l y about and f l y back to t h e i r perching s i t e s ashore. Who p a r t i c i p a t e s ? What f u n c t i o n have the d i s p l a y s ? Perry suggests an aggressive and\u00E2\u0080\u00A2sexual r o l e , and S t o r e r (1945) and Thoresen & Booth (1958) imply\u00E2\u0080\u00A2that the d i s p l a y s are a prelude t o c o p u l a t i o n . In p u f f i n , common, gui l l e m o t .(murre) and r a z o r b i l l , Conder \u00E2\u0080\u00A2 (1950) t h e o r i z e s t h a t s o c i a l d i s p l a y s have evolved.to make good the now r u d i -mentary d i s p l a y s w i t h i n the p a i r , i . e . , . s o c i a l d i s p l a y s are important f o r p a i r formation and maintenance,. and synchroniz-ing-the reproductive c y c l e of the p a r t n e r s . In my mind, the, water games should be thought of as a communal d i s p l a y that marks the b i r d as a c o l o n i a l s p e c i e s . The b i r d s do not p a r t i c i p a t e as p a i r s , indeed i n many.cases only one of the p a i r w i l l be present at the colony (e.g., i n c u b a t i n g b i r d down f o r - a b r i e f break of 5-10 minutes, or down a f t e r r e l i e f to bathe before f l y i n g o f f to the feeding .grounds; i n e i t h e r case may j o i n i n .the d i s p l a y s ) . A l l the aggressive and appeasement d i s p l a y s can be picked out i n the games (hunch-whistle, chuckle-waggle e s p e c i a l l y frequent, and chase but the b i r d s meet at random. I am convinced that the water d i s p l a y s and c o p u l a t i o n stand i n no causal r e l a t i o n s h i p \u00E2\u0080\u0094 I have records of banded b i r d s f i n a l l y c o p u l a t i n g a f t e r 1-|-1 3/4 hours of i n a c t i v i t y ashore at t h e i r perching s i t e . Water games are a group game, i n . which a l l b i r d s j o i n , r e g a r d l e s s of s t a t u s i n . t h e colony. Perhaps they p l a y a part i n cour t s h i p 42 ( i . e . , p a i r - f o r m a t i o n ) , but as I have no observations of t h i s a c t i o n i n banded b i r d s nothing d e f i n i t e can be s a i d . At .any r a t e t h i s cannot be the only f u n c t i o n , . f o r . e v e n i n the pre-egg stage the vast m a j o r i t y of the p a r t i c i p a n t s w i l l be mated birds, from previous seasons; and continuance of the d i s p l a y s , a l b e i t i n m i l d e r form, to the end.of the season has been mentioned. My .view, i s that a group of n e s t i n g Pigeon Guillemots . i s more than an aggregation brought i n t o being by the c l u s t e r i n g of s u i t a b l e n e s t - s i t e s ; r a t h e r the b i r d has the innate tendency to form c o l o n i e s , and s e c o n d a r i l y s i z e of each depends.on nest-s i t e a v a i l a b i l i t y . The only event i n which a l l g u i l l e m o t s of the colony p a r t i c i p a t e i s the water games; these are the means .of e s t a b l i s h i n g group l i f e , , the hall-mark of the c o l o n i a l s p e c i e s . The water d i s p l a y s thus correspond to the' vast c i r c l e - f l i g h t s of the p u f f i n (Lockley 1953: 7 8 ) , and the v a r i e d group\" d i s p l a y s of other c o l o n i a l b i r d s * Very l i k e l y they are the means whereby the press of numbers exerts i t s i n f l u e n c e , as suggested In the breeding of sea-birds by Fraser D a r l i n g (1938) i n h i s s t i m u l -a t i n g book. No doubt s o c i a l s t i m u l a t i o n as he envisaged i t was o v e r s i m p l i f i e d , p a r t s even .incorrect ( t h r e s h o l d of numbers, Richdale 1951, .1957, F i s h e r 1954) but the recent s t a t i s t i c a l .work of Coulson &-White ( i 9 6 0 ) on the K i t t i w a k e , R i s s a t r i d a c t y l a , shows that d e n s i t y of breeding b i r d s can have an influence--here a f f e c t i n g r e t u r n to the colony and commence-ment of l a y i n g (the denser c o l o n i e s thus have longer seasons). Water games i n the T y s t i e , then, can be thought of as supplying group reproductive s t i m u l a t i o n , (as discussed i n . a general way by Tinbergen 1951: 174), without s p e c i f y i n g what the measurable e f f e c t s may be. Summary and Conclusions .The more obvious d i s p l a y s and a s s o c i a t e d c a l l s of the Pigeon Guillemot are described and i l l u s t r a t e d . Two i n v o l v e aggression, 1 appeasement, 2 alarm, 1 s i g n a l s f l i g h t i n t e n t i o n , , and 1 serves f a m i l y communication. In a d d i t i o n the s i g n i f i c a n c e of d u e t - f l i g h t s and water-games are discussed (see o u t l i n e at s t a r t of s e c t i o n ) . According to d e s c r i p t i o n s i n the l i t e r a t u r e , the d i s p l a y s of murres (Uria.aalge S t o r e r 1952, Njzfrrevang-1958, Tschanz 1959j U r i a lomvia Pennycuick 1956) are similar\u00E2\u0080\u00A2among themselves, but very d i f f e r e n t from those i n the Pigeon Guillemot. The only.common t r a i t found was b i l l i n g , but the d e t a i l s d i f f e r (the Pigeon Guillemot never preens the mate as \u00E2\u0080\u00A2the nurres do) and b i l l i n g i s a l s o found i n as d i s t a n t a form as the p u f f i n ( F r a t e r c u l a a r c t i c a ) . On t h i s b a s i s the p r a c t i s e of a s s i g n i n g the T y s t i e to the genus U r i a as some workers do, seems very b o l d . Anatomical evidence i s a l s o against t h i s lumping (Kuroda 1954, Storer 194-5) to say nothing of n e s t i n g ecology ( c l u t c h - s i z e , n e s t - s i t e , p a t t e r n of c h i c k care; see Kartaschew, i960 f o r - a c l e a r c o n t r a s t ) . I . PRE-EGG .STAGE A. Length and General D e s c r i p t i o n The pre-egg stage extends from the time the b i r d s f i r s t come ashore at the colony f o l l o w i n g the w i n t e r , u n t i l the f i r s t egg Is l a i d by that p a r t i c u l a r p a i r . On m y , e a r l i e s t day of observation (6 May i960) the banded breeders from previous seasons were a l l present i n t h e . e a r l y morning i n the colony sector checked. I l a t e r determined the l a y i n g dates of the three p a i r i n . q u e s t i o n and reckoning from 6 May t h e i r minimal pre-egg stage was 40,(nest #43),.42 (nest #12), and 45 days {nest #14). The s i x t h was d e f i n i t e l y . n o t the f i r s t day the b i r d s had come ashore however; e s t i m a t i n g t h i s to.have taken place about 10 .days . e a r l i e r (see \" d a i l y rhythm 1 above) the true l e n g t h would be about,50-55 daysin these cases. These b i r d s l a i d w e l l past the mean date, however, so.since a l l breeders occupy/the colony about the same time some p a i r have a pre-egg stage as short as about 30,days. The pre-egg stage at Mandarte th e r e f o r e w i l l range from roughly. 30-60 .days. This i s much longer than the 2-3 weeks volunteered by Uspenski (1956: 80-81) and Kartaschew (i960: 67) f o r the Russian A r c t i c , as might be expected, f o r \u00E2\u0080\u00A2 i n adapting to a shorter favourable p e r i o d f o r n e s t i n g ( e s p e c i a l l y l a t e thaw of n e s t i n g holes) only the pre-egg stage allows of s i g n i f i c a n t r e d u c t i o n . In t h i s stage the mated p a i r s (and they are i n the maj o r i t y ) spend a great d e a l of time hauled.out o n . t h e i r .44 favourite perches along the beach, v i s i t the nest-site (used year a f t e r year, see on) and often adjacent parts of the c l i f f - t o p , being drawn along.with other f l y i n g birds, and f i n a l l y j oin in the communal water displays. Long .before egg-laying (my. records range from 11-39 days) the nests are -cleared out. Old eggs are ejected, plants plucked out, the f l o o r scraped clear, and any loose stone chips, s h e l l fragments etc., present i n the nest, pulled together into a l i t t l e heap with a -central depression, where.the eggs are eventually deposited. By - moving such fragments towards the entrance, I found that they were often returned to the heap, but once outside the nest-cavity generally ignored. Thus the guillemots toy only with materials already - present; indeed nests with a bare rock f l o o r receive no nest material. Similar conclusions have been reached by Bent (1919: 169) and Thoresen &-Booth (1958: 13) f o r the Pigeon Guillemot, and implied by Winn (1950) f o r the Black Guillemot; Fisher & Lockley. (1954: 277) however state that the l a t t e r species may carry.debris to the n e s t - s i t e . On Mandarte i t i s possible that these-.heaps are sometimes functional i n reducing egg-loss through r o l l i n g ; t h i s i s highest i n nests with a smooth rock f l o o r . The habit of ' v e s t i g i a l \"nest-rbuilding J (Perry 1946) in. many auks poses.:, an i n t e r e s t i n g evolutionary problem. The p u f f i n t r i b e (sensu Storer 1945) Fratercula, Lunda, and Cerorhinca gather grasses and other vegetation (Bent 1919? Lockley 1953)?. some nocturnal burrowers carry the nearest , 46 .vegetable r u b b i s h below;(e.g. Synthliboramphus, Ptychoramphus; f o r r e f s . see Drent & Guiguet i n p r e s s ) ; the hard-substrate nesters ( U r i a aalge e.g.,Perry 1946, \u00E2\u0080\u00A2 N/rrevang 1958, Tschanz 1959; A l c a torda Paludan 1947: 4 2 : 4 3 ) g e n e r a l l y heap.chips, bone fragments, g r a s s - s t a l k s , . o r other moveable rubbish, about .the' eggs as does the T y s t i e . In .general,. then, m a t e r i a l s a l r e a d y present about the n e s t - s i t e are used, and i n ' p a r t i -c u l a r the l a s t group shows an i n t e r e s t i n g s i m i l a r i t y t o some Li m i c o l a e (e.g., Haematopus, o f t described, Charadrius R i t t i n g h a u s 1953, Arenaria Bergman 1 9 4 6 : 40) where chips i f present about the nest s i t e are placed about the eggs. P u f f i n s , however, w i l l make a c t i v e g r a s s - c o l l e c t i n g . t r i p s (Lockley on F r a t e r c u l a ; own obs. on Lunda). B. Copulation 1. D e s c r i p t i o n Besides nest p r e p a r a t i o n and l o a f i n g about.the colony, c o p u l a t i o n i s a conspicuous fea t u r e of the pre-egg stage i n mated p a i r s . F i r s t , a d e s c r i p t i o n . Copulation always occurs ashore, almost always on the rocky beach (of '250 observed, 2 took place on the grassy c l i f f - t o p ) . I doubt i f any n e s t - s i t e on the i s l a n d . i s . s p a c i o u s enough t o . a l l o w .the action,-but Kartaschew ( i 9 6 0 : 68) s t a t e s that c o p u l a t i o n may occur i n the burrow. Moreover the copulations of a p a i r are g e n e r a l l y r e s t r i c t e d t o , t h e i r p a r t i c u l a r beach p e r c h - s i t e ; 47 thus? a l l 43 copulations observed in.1959? and a l l 24 i n i960 i n a p a i r where the male was banded? took place on the habitual low-water rock of the pair? or the high-water alternate, some 5 l d i s t a n t . The same holds true f o r other pairs with banded birds, though I have fewer observations there. The action i s i n i t i a t e d by energetic b i l l i n g . a n d twittering,' which may be' quite spontaneous (banded p a i r : ashore 92 minutes, of which l a s t 74 minutes immobile, before preliminaries undertaken), or often follows a r r i v a l of one member, the enthusiastic greeting ceremony ( b i l l i n g ) leading on to ;the next step; or f i n a l l y it.may-be i n i t i a t e d when both come ashore a f t e r a long absence. This i s e s p e c i a l l y marked i n the pre-dawn gathering when the birds come ashore aft e r the night's absence; a wave of copulation follows, each p a i r being interrupted by-intruders (those whose mates-have not yet returned ??). It w i l l be noted . that the three most common.situations leading to copulation have nothing-to do.with the communal water displays. Energetic b i l l i n g i n i t i a t i n g the action leads to c i r c l i n g , described by Perry (1948) and es p e c i a l l y by\u00E2\u0080\u00A2Storer (1945: 447-448). The birds (up on t h e i r toes) waddle about a small c i r c l e , the male on the outside (see Pigs. 2-2? #3). This may be b r i e f or repeated, the birds now c i r c l i n g clock-wise? now counterclockwise? u n t i l the female s e t t l e s and the .male mounts (Pig. 30). He maintains p o s i t i o n by fanning the wings when necessary ( d e f i n i t e l y only a balance movement; F i g . 2 4 Copulation. The male fans the wings v i g o r o u s l y to main-t a i n balance. This I l l u s t r a t e s a t y p i c a l p e r c h - s i t e . F i g . 2 5 The female r i s e s to terminate c o p u l a t i o n ; i n that i n s t a n t the male jabs at her nape (shown here). He managed to hang on a moment longer. 48 see F i g s . 2 4 , 3 0 , 3 1 , 3 2 , 3 3 ) , r e s t i n g back on the t a r s i which tend .to s l i p to the side and are ther e f o r e c o n s t a n t l y paddled i n an a l t e r n a t e rhythm, the claws r u f f l i n g the female's plumage. S t a r t i n g during c i r c l i n g , and contin u i n g u n t i l the moment he loses h i s p o s i t i o n atop the female, the male,, w i t h closed b i l l , gives a c h a r a c t e r i s t i c muffled note \"weep weep weep\" e t c . , i n rhythm w i t h h i s paddling motions; a l s o e r e c t i o n of the fea t h e r s about the eye accent the white e y e - r i n g . The female i s g e n e r a l l y p a s s i v e , but very r a r e l y throws her head back to gape at the male, when the b i l l s may a c t u a l l y touch; or she may scream, as i n alarm. Thoresen & -Booth ( 1 9 5 8 : 8) have a l s o noted the female to scream during c o p u l a t i o n . As an i n d i c a t i o n of the frequency of these v a r i a n t s , I noted 3 cases of gaping, 3 of screaming i n 101 copulations observed i n i 9 6 0 . These cases proved, i n c i d e n t a l l y , that the male was re s p o n s i b l e f o r the \"weep weep\" note. This might have been expected by,analogy to other a l c i d s (Alca t o r d a , U r i a ) or g u l l s . I am unable to . i n t e r p r e t these unusual cases of b i l l i n g ( s t i m u l a t i o n by -female) but i t i s i n t e r e s t i n g to note that t h i s , i s h a b i t u a l i n Al c a torda (Paludan 1947) and U r i a aalge (Njzfrrevang 1 9 5 8 ) . In almost a l l cases the female ends the c o p u l a t i o n by r i s i n g and throwing o f f the male ( F i g . 3 3 ) ; e a r l y i n the season the male often jabs at the female's nape ,at t h i s p o i n t (.Fig. 2 5 ) . He may maintain p o s i t i o n .a .few seconds longer t h i s way but u s u a l l y the female escapes at once, w h i l s t occasion-a l l y both f l o p down to the water before she fr e e s h e r s e l f . F i g . 26 S t a r t o f a s e q u e n c e show-i n g t y p i c a l i n t r u d e r i n c i d e n t f o l l o w e d b y c o p u l a t i o n . I n t r u d e r c e n t r e , o n e o f e s t a b -l i s h e d p a i r h u n c h -w h i s t l i n g i n f o r e -g r o u n d , m a t e g a w k s i n b a c k g r o u n d . F i g . 27 I A_ s u d d e n n o i s e i n t h e b l i n d a l a r m s a l l t h r e e ; t h e y s c r e a m . F i g . 28 moment l a t e r t h e i n -t r u d e r i s d r i v e n o f f b y a l u n g e . P i g . 2 9 With the i n t r u d e r success-f u l l y d r i v e n o f f , the p a i r b i l l . (This l e d t o c i r c l i n g , not i l l u s t r a t e d here.) P i g . 30 The male mounts a f t e r a b r i e f c i r c l i n g ; he has been 'weeping 1 through-out . F i g . 31 S t a r t of c o p u l a t i o n ; the female i s not f u l l y s e t t l e d and the male continues to fan h i s wings f o r balance. Note how h i s f o o t i s spread on the female's back. P i g . 32 C o p u l a t i o n . The male has been 'weeping' continu-ously? and t h i s f i g u r e c l e a r l y shows h i s closed b i l l . The female i s s i l e n t . P i g . 33 The female r i s e s and terminates the copula-t i o n ; the male, s t i l l 'weeping'? i s thrown o f f . F i g . 34 B i l l i n g f o l l o w s ; female on l e f t (note r u f f l e d plumage). The p a i r then s e t t l e d . This i s a normal feature of' e a r l y copulations however (banded p a i r s ) . S u c c e s s f u l copulations l a s t about, 30-75 . seconds, but the p e r i o d of a c t u a l contact i s s h o r t e r , the male depressing h i s t a i l from the s i d e , at i n t e r v a l s . In p r a c t i c e i t i s d i f f i c u l t to time the event because bystanders hurry over and often cause the female t o r i s e and.attack (the male hopped o f f to a t t a c k only once). A f t e r . a s u c c e s s f u l u n i n t e r r u p t e d copu-l a t i o n b i l l i n g f o l l o w s as a r u l e ( F i g . 3 4 ) , and very r a r e l y the male may remount ( 4 . c a s e s ) . T y p i c a l l y the b i r d s then s e t t l e q u i e t l y , and preening does not take p l a c e . u n t i l some time l a t e r . ( h e n c e the female can s t i l l be recognized by.her r u f f l e d plumage). Intruders during or j u s t a f t e r c o p u l a t i o n meet w i t h g r e a t e r aggression than at any other time. D e v i a t i o n s from the p a t t e r n of c o p u l a t i o n given above have been recorded. Storer (194-5 447-448) described c i r c l i n g a c c u r a t e l y , but thought t h i s c o n s t i t u t e d a second phase f o l l o w i n g communal water d i s p l a y ; my view i s that.t h e two are not d i r e c t l y r e l a t e d . Further, i n the one case where mounting was observed, a second c o p u l a t i o n f o l l o w e d s h o r t l y , w i t h the r o l e s of the two b i r d s reversed. I have never noted reversed c o p u l a t i o n i n marked mated p a i r s ( c . 80 o b s e r v a t i o n s ) . Thoresen & Booth's (1958: 9-12) d e s c r i p t i o n again i m p l i e s a connection w i t h water d i s p l a y s . I n t e r e s t i n g here i s that the female hunch-whistled ( c f . t h e i r F i g . 9, P. 10) which they conclude served t o a t t r a c t the male; as I have described, t h i s i s a t h r e a t - d i s p l a y , which serves i n c i d e n t a l l y to draw the 50 mate- over when nearby. Probably the female here was o b j e c t i n g to over-close approach by a stranger. I t .is not impossible that the p a i r was but r e c e n t l y formed, and that the female s t i l l showed tr a c e s of aggression towards her mate. In any event, hunch-whistling i s very d e f i n i t e l y - n o t a r e g u l a r f e a t u r e of the c o p u l a t i o n p r e l i m i n a r i e s . F i n a l l y Winn (1950) noted 3 cases where a female who had a 2-day o l d chick.apparently i n v i t e d c o p u l a t i o n , but upset the male when he attempted to mount; I have- no p a r a l l e l observations. 2. Constancy Copulation attempts by.members of a p a i r are thus always marked by \u00E2\u0080\u00A2 c i r c l i n g , .- e s p e c i a l l y n o t i c e a b l e through the constant 'weep-weep1\u00E2\u0080\u00A2of the male. Quite d i f f e r e n t are the attempts by the males f o r 'forced c o p u l a t i o n s ' outside the p a i r , observed f r e q u e n t l y i n unmated b i r d s (see a l s o \"non-breeder\", under\u00E2\u0080\u00A2\"colony . s t r u c t u r e \" ) , and i n mated,males apparently when the female has been long absent or i s unresponsive. The male, f u l l y e r ect on h i s toes, neck extended, \"weeping\" s o f t l y , . and fanning the wings vigorously\u00E2\u0080\u00A2to.keep balance, rushes a nearby -bird and attempts to mount without p r e l i m i n a r i e s . This i s u s u a l l y f o i l e d by escape, whereupon the male rushes a f t e r another b i r d ; often the attacked b i r d lunges, sometimes merely hunch-whistles, and In one case allowed the male to mount before r i s i n g to shake him o f f . In no case has one of these attempts been s u c c e s s f u l . At f i r s t I thought that these b i r d s , whom I w i l l c a l l ' f l a p p e r s ' because of t h e i r eye-catching 51 wing a c t i o n , were e f f e c t i n g t e r r i t o r i a l defence, since the r e s u l t i s often to c l e a r the surrounding rock of h i r d s j observation of'banded b i r d s showed that\u00E2\u0080\u00A2the above i n t e r -p r e t a t i o n \u00E2\u0080\u0094 a t t e m p t e d c o p u l a t i o n by.males, outside the p a i r - -i s i n f a c t the c o r r e c t one. I t appears that these ' f l a p p e r s 1 advance on a l l g u i l l e m o t s i n d i s c r i m i n a n t l y , and w i l l attempt to copulate w i t h any-bird that remains s e t t l e d long enough. Thus there are d e f i n i t e records of experienced ( i . e . , had bred s u c c e s s f u l l y i n previous seasons) as w e l l as unmated, males attempting copulations w i t h e s t a b l i s h e d mated males as w e l l as w i t h the 3 mated females c l o s e l y observed. The f o l l o w i n g are the cases where known males were attacked by ' f l a p p e r s ' : I 9 6 0 Blueband attempts to mount K i t t y 1 case (0918 23 May)' Unhanded male 3 cases (0521 8 June 1021 10 June, 1853 17 June) Male #57 o l 2 cases (1022 1 June, twice) Male #88 L e a s e (o935 24 June) Unhanded males 10 cases (o504 & O806 29 May, 0718 1 1 t h , o 8 4 8 - l 4 t h , o740 2 2 n d , 0 9 0 8 , 1 0 0 9 . 2 4 t h , 1050 2 6 t h , o920 2 7 t h June; . 0758 4 J u l y . Blueband had nested at #12 at l e a s t 1 9 5 8 , 5 9 , 6 0 , and was a w e l l known neighbour \u00E2\u0080\u00A2 of K i t t y ' s ( c . 75 normal cop. obs.); I suggest Blueband's mate was absent at,the time. K i t t y , male at #43 at l e a s t 1959, 60 has been mentioned f r e q u e n t l y - a l r e a d y ; he f o i l e d B's attempt by r i s i n g . o l , who ,had the d i s t i n c t i o n of being .the f i r s t g u i l l e m o t banded, nested at #15 i n 57 ( ? & 5 8 ) , a n d at #14 59&60, as r e l a t e d below. He was of a r a t h e r s t o l i d d i s p o s i t i o n and through h i s I n d i f f e r e n c e s i n g l e d out by ' f l a p p e r s 1 ; h i s , u s u a l r e a c t i o n .was to hunch-whistle, which g e n e r a l l y s u f f i c e d , but on 11 June, 0718 an unhanded f l a p p e r actually-mounted .for 15-20 .seconds: ' o l s l i d e s out, lunges at f l a p p e r , grasps wing.with v i c i o u s jab, both tumble to water and paddle off;.0723 o l r e t u r n s alon copulates as male w i t h mate (Presumed, not banded y e t ) . 1 #57 was a mated male from nest 24 (1957? 58, 59? & ; t o ) ; he was seen here (where he was d e f i n i t e l y a stranger) 5 times during the summer (73 obs. days), 4 of these times during h i s pre-egg stage. #88 on the other hand was banded as a n e s t l i n g i n #12 (Blueband's nest) 1958,\u00E2\u0080\u00A2and returned i n i960 to-come ashore r e g u l a r l y on t h i s s t r e t c h ; he formed no l a s t i n g bond, and was observed to behave as a ' f l a p p e r 1 5 times. There are s i m i l a r records f o r the 2-year o l d male #45 i n 1959. While d e a l i n g w i t h attempts at 'forced c o p u l a t i o n ' a f u r t h e r v a r i a n t , the f l a p p e r attempting ,to.mount a copulating, male i n t u r n , may.be mentioned: 2 cases i n 1959 (vs. 150 normal), 1 i n 60 (100 normal). In one case the f l a p p e r was i d e n t i f i e d : \u00E2\u0080\u00A2 8 June 60. o448. Unhanded-pair c o p u l a t i n g , o2 attempts to mount both; t r i p l e decker c o l l a p s e s as female p u l l s out; lose t r a c k of male but female lunges at o2; o2 then attempts to mount female, who gapes; o2 continues, female f l e e s t o water? 02 f o l l o w s ; female hauls out again? s e t t l e s ; o2 f o l l o w s but f i n a l l y takes to water and p a d d l e s - o f f . o2_ was a male from the next nest-group south (35 meters)? n e s t i n g ,at #17 1957? 58? & 60; he-was a stranger-here,- seen on 6 .dates i n i960 (Of 73 obs. days), 5 i n .his pre-egg stage, on 3 of these acted as f l a p p e r . In .summary? attempted c o p u l a t i o n outside the p a i r i s recognizable by 'flapping'? the vigorous wing-fanning of the -males i n v o l v e d . Unmated males' make frequent attempts, and f l a p p i n g has-been observed i n mated males (3 of the 4 c l o s e l y \u00E2\u0080\u00A2watched, and 2 others)?.apparently when.their mate i s absent from the colony? or-unresponsive (observations on.colour-banded pair. K a r l and'Kitty,.quoted below). Plappers advance on any s e t t l e d g u i l l e m o t , r e g a r d l e s s of i t s sex or st a t u s i n the colony. None of the attempts observed (more than 30 i n i960) were s u c c e s s f u l . 53 3. Sex and Mate Recognition Do the examples c i t e d above i n d i c a t e that the male's scheme of sex r e c o g n i t i o n . i s d e f e c t i v e , j u s t as Nethersole-Thompson.(1951) has- recorded.'mistakes' i n the monomorphic Tringa n e b u l a r i a ? Rather, I b e l i e v e that the high i n n e r urge of these 'flappers'^--unmated males and mated males whose mate has been.long absent--over-rides a recognition.scheme s u f f i -c i e n t i n ordinary circumstances. Tinbergen (1935) has d i s -cussed sex r e c o g n i t i o n i n b i r d s , and i n t e r p r e t s cases s i m i l a r to the above, i n that the male contents himself w i t h an inade-quate object when the inner urge i s h i g h . Makkink (1936) recorded male R e c u r v i r o s t r a avosetta c o p u l a t i n g .with the ground or water surface, which c e r t a i n l y s u i t s t h i s i n t e r -p r e t a t i o n as Makkink was convinced, that Avocet could recognize sex by subtle means. I t i s s i g n i f i c a n t - t h a t Richdale (1951) who a l s o discusses the problem, i s convinced that the mono-morphic Me_\u00C2\u00A3ad^ p_tes_ ajrtop_odes_ recognizes sex by s i g h t . F u r t h e r Lockley.(1953).with long experience has come to d i s t i n g u i s h sex i n F r a t e r c u l a a r c t i c a by head contours and b i l l shape. I must admit that so f a r I have been unable to f i n d s e x - d i s t i n g u i s h i n g characters i n the Pigeon Guillemot, the only clue being a c t i o n s immediately concerned w i t h c o p u l a t i o n ; but I b e l i e v e that the s i t u a t i o n i s too s u b t l e to be r e s o l v e d i n .two summers. Storer \u00E2\u0080\u00A2 (1952: 126, 127) found e x t e r n a l d i f f e r e n c e s s l i g h t i n museum skins of the T y s t i e \u00E2\u0080\u0094 the sexes did..not d i f f e r s i g n i f i c a n t l y in.wing, t a r s a l , or 54 culmen measurements\u00E2\u0080\u0094but he did. f i n d b i l l depth c o n s i s t e n t l y greater i n males, and that females in.some populations of the B l a c k Guillemot showed more white on the outermost primary (a , s t a t i s t i c a l concept). On .the matter of mate r e c o g n i t i o n my observations show., that . the members of a p a i r d e f i n i t e l y recognize each other, at l e a s t by s i g h t , as the f o l l o w i n g examples show (colour-banded p a i r ) : 17 June i 9 6 0 . o902. K a r l (female) a r r i v e s on p e r c h - s i t e ( f i r s t a r r i v a l f o r . t h e day, watched since o310). o913. K a r l , immo-b i l e up.to now, turns to water, h u r r i e s over to edge of boulder, peers out i n a n t i c i p a t i o n - - I now.see a g u i l l e m o t swimming r a p i d l y towards.her, c. 15 f e e t d i s t a n t , head outstretched--t h i s b i r d .lands;.intense b i l l i n g and t w i t t e r i n g , Karl-& K i t t y \u00E2\u0080\u00A2(male down from incubation) r e u n i t e d . Long c i r c l i n g f o l l o w s , no r e s u l t . 17 May i 9 6 0 . 0830. K i t t y (male) leaves p e r c h - s i t e , paddles f a r out, then i n duet f l i g h t over c l i f f w i t h unhanded -bird; lands offshore a g a i n ; . K a r l (female) f o l l o w s from p e r c h - s i t e i n c. 3 minutes, paddles out s l o w l y u n t i l about 10 ' from male (who approaches r a p i d l y ) , when .she . speeds pace;.they meet and .joinothers to form l i n e . Thus r e c o g n i t i o n of\u00E2\u0080\u00A2the 'male.does not depend on r e a c t i o n t o .the g r e e t i n g ceremony when .the b i r d s meet at the p e r c h - s i t e or other'common ground, - but the mate i s recognized as an \u00E2\u0080\u00A2 . i n d i v i d u a l r e g a r d l e s s of the s i t u a t i o n . This i s no doubt the .\u00E2\u0080\u00A2rule w i t h b i r d s that p a i r f o r ' l o n g periods (e.g. Larus argentatus Tinbergen 1953? \u00E2\u0080\u00A2 Megadyptes antipodes Richdale .1951? 1957? - F r a t e r c u l a a r c t i c a ..Lockley 1953). What\u00E2\u0080\u00A2the extreme distance of r e c o g n i t i o n in.the Pigeon Guillemot i s ? or whether voice i s a l s o used? I am unable to say. 1 clutches started average per 4-hr. watch Qo 1 C/> I Co \"> CO I 1 \"6 c^ i 1 s3 i CD I 1 \u00E2\u0080\u00A25. C\"i \u00E2\u0080\u00A28 8' o> i ' \u00E2\u0080\u00A2 \u00E2\u0080\u00A2 \u00E2\u0080\u00A2 i -a I c^ ! -T 1 1 1 ] l 1 r -4. Copulation Rate 55 Records were kept of the number of c o p u l a t i o n s , and i n i960 a l s o attempts ( d i s t i n g u i s h i n g c i r c l i n g from f l a p p i n g ) during :the morning - observation p e r i o d s . At t h i s stage of the n e s t i n g c y c l e 36 periods are a v a i l a b l e from 1959 (o645-1045), 44 i n i960 (o700-1030). Counts were taken from p r e c i s e l y the same s t r e t c h of beach in: b o t h seasons (North B l i n d ) , and egg-l a y i n g i n the nests i n v o l v e d .(7) was known,to the nearest day. Each day the c o p u l a t i o n r a t e i s f a i r l y steady u n t i l l a t e morning ( l a s t , hour \u00E2\u0080\u00A2 of the observation p e r i o d ; see P i g . 35) so that my counts should provide 'an adequate sample f o r t h i s small p o r t i o n of the colony. The m a t e r i a l ( P i g . 35) has been grouped to show weekly averages of the copulations observed per 4 hour p e r i o d , and shows that copulations occur e a r l y and f r e q u e n t l y , and.drop o f f once, egg-laying i s w e l l underway. This p a t t e r n i s sub-s t a n t i a t e d .very\u00E2\u0080\u00A2clearly'by the copulations of 'the banded male Blueband ..with h i s mate (the best- v i s i b l e of \u00E2\u0080\u00A2 the \u00E2\u0080\u00A2 banded b i r d s ) . These are p l o t t e d by the average number of \u00E2\u0080\u00A2 copulations per'10 hours i n 4-day I n t e r v a l s f o r each season. The f i r s t was noted 24 days before the f i r s t egg i n 1959,\u00E2\u0080\u00A228 i n i960; i n another pair'(K-K) the i n t e r v a l was 23. I t w i l l be remembered tha t the b i r d s had been coming ashore at l e a s t 14 and 17'days r e s p e c t i v e l y p r i o r to that i n I960,-and probably c. 10.days more than.those records i n d i c a t e \u00E2\u0080\u0094 t h u s 3-4 weeks before the f i r s t completed c o p u l a t i o n ; the males made attempts some days 56 . e a r l i e r . From that p o i n t on the r a t e increased slowly, and jumped to a maximum i n the 12 days preceding egg-layingj during l a y i n g .a sharp drop .occurred, and..none at a l l were noted t h e r e a f t e r . The two years agree w e l l . Data from other banded b i r d s i n . i 9 6 0 , i s l e s s complete owing to o b s e r v a t i o n a l d i f f i -c u l t y ; main p o i n t s as f o l l o w s : K-K likewise.showed maximum r a t e i n . t h e l a s t 12 days, and attempted c o p u l a t i o n on the day of the second egg; Greylag, female banded on .her f i r s t egg the day l a i d , copulated f i v e times e a r l y the f o l l o w i n g morning, a l l l e s s than 2 0 ,sees, and probably u n s u c c e s s f u l ; on the day of\u00E2\u0080\u00A2the second egg and one t h e r e a f t e r - o n l y attempts were noted. In the case of replacement clutches c o p u l a t i o n i s renewed; i n one pair'(banded male o l , i 9 6 0 ) c o p u l a t i o n was noted again 21 days a f t e r the \" l a s t egg of the f i r s t c l u t c h , and., the s i n g l e egg of the replacement was l a i d approximately 3 days l a t e r . Double-green, male banded on the f i r s t egg the day of l a y i n g , deserted as a r e s u l t , and was seen.to copulate 7 days a f t e r the second egg had been l a i d ; doubtless t h i s i n v o l v e d a replacement attempt though no f u r t h e r eggs were l a i d i n that nest. The Pigeon Guillemot i s thus c l e a r l y i n a c l a s s w i t h many waterfowl and sea-birds, where co p u l a t i o n occurs e a r l y and r e p e a t e d l y . i n the pre-egg stage, and ceases during or s h o r t l y before egg-laying. Richdale (1951: 175 f f . ) has c o l l e c t e d examples (penguins, grebes,- Royal A l b a t r o s s , 57 Canvas-back, Avocet,-Oystercatcher, Black-headed g u l l , Common Tern) to which one may add'Herring Gull (Paludan 1951), Turn-stone (Bergman 1946), Greenshank (Nethersole-Thompson 1951), Redshank (Grosskopf 1959), and Caspian Tern (Bergman 1953: 15) --no doubt the Laro-limicolae as a group - follow, the pattern. The only other auk where concise data are available, Alca torda (Paludan .1947: 39) f i t s the group: the f i r s t copulations in ,the colony\"being noted shortly a f t e r the birds come to land again,-and 2-3 weeks before the f i r s t eggs;.they apparently cease when the egg i s laid..(as i s the case i n Fratercula a r c t i c a Lockley 1953: 25). Causation and function of t h i s extended copulatory period can only be speculated upon at present. Quantitative data for birds i n , t h i s class are,those of Bergman (1946) for Arenaria interpres, and-Collias & Jahn (1959) fo r Branta canadensis. Bergman's excellent graphic .presentation (p. 85) shows attempts upon a r r i v a l , with successful copulations s t a r t i n g a few,days later,, and ,ceasing .during .egg-laying--so far the pattern i s similar to that in the Pigeon Guillemot -r-but the attempts continue well into \u00E2\u0080\u00A2incubation. Direct comparison with my data i s perhaps not wise, since copulation i n the Turnstone to a certain extent has the character 'of a displacement a c t i v i t y (Bergman 1946: 80-83). The material of C o l l i a s & Jahn shows copulation i n Branta already 20 days before the f i r s t egg, and ceasing .at the close of laying, but the data i s too small to find.a peak 58 p e r i o d . At what p o i n t c o p u l a t i o n i s f u n c t i o n a l i n f e r t i l i z a -t i o n , i n . the Pigeon G u i l l e m o t . i s d i f f i c u l t to say. According to Stresemann.(1927-34: 252) & Portmann ( i n Grasse 1950) f e r t i l i z a t i o n occurs i n .the upper reaches of 'the oviduct, as soon as the egg'has been .taken up. by the i n f u n d i b u l a r l i p s ; i t may a l s o occur j u s t before t h i s (Benoit i n Grasse 1950). Since the second egg i s ovulated only when , t h e \u00E2\u0080\u00A2 f i r s t has l e f t the uterus (Stresemann l o c . c i t . , Romanoff 194-9: 214, \u00E2\u0080\u00A2 by i n h i b i t i o n of r e l e a s e o f ' l u t e i n i z i n g \u00E2\u0080\u00A2hormone from p i t u i t a r y ; o v u l a t i o n i n chicken f o l l o w s a b o u t h o u r a f t e r o v i p o s i t i o n ) , the l a y i n g i n t e r v a l provides a measure of the maximum time r e q u i r e d .for passage through the oviduct: p r o v i s i o n of albumen, egg membranes, and s h e l l (Stresemann op. c i t . 379-380). The time of passage has been a c c u r a t e l y - determined f o r the chicken (23.5 hours, Romanoff 1949: 230) which c l o s e l y approaches the l a y i n g i n t e r v a l i n ' l o n g . c y c l e s ; f o r . t h e goose at 20-24 hours (.Chen, Stresemann 259), and f o r the pigeon \u00E2\u0080\u00A24l hours. The l a y i n g i n t e r v a l i n the Pigeon Guillemot i s 3 days, so on :this b a s i s we can expect f e r t i l i z a t i o n to occur c. 72 hours before l a y i n g i n each case, but as sperm r e t a i n . t h e i r v i a b i l i t y i n the oviduct f o r long periods (Pheasant 52 days Stresemann op. c i t . ) the time at which c o p u l a t i o n i s e f f e c t i v e cannot be s t a t e d . I t may-be asked, who.controls the r a t e \u00E2\u0080\u0094 d o e s the female have a l i m i t e d r e c e p t i v e period.(as i n mammals; 59 Howard's view) or are both so l i m i t e d ( A l l e n ' s view; f o r a f u l l d i s c u s s i o n see Richdale 1951: 175ff.). When.the r a t e of attempted.copulations w i t h i n mated p a i r s ( c i r c l i n g ) i s p l o t t e d , an .inverse- curve t o those completed r e s u l t s : when the l a t t e r are at \u00E2\u0080\u00A2 a peak the number of attempts i s at a minimum. T h i s . i s true f o r ; both group, and i n d i v i d u a l data \"(Blueband). ' Unfort-u n a t e l y i t was r a r e l y p o s s i b l e t o observe which sex f a i l e d to c a r r y on i n .these cases. Thus the 2 i n t e r p r e t a t i o n s are s t i l l p o s s i b l e : l ) the r e c e p t i v e periods of both are i n synchrony; before and.after the peak inner s t i m u l a t i o n .is below t h r e s h o l d ; 2) the male i s ready to copulate over a long p e r i o d , but the female responds only.over a f a i r l y short i n t e r v a l , p r i n c i -p a l l y the 12 days preceding egg-laying. In an.attempt to make a d e c i s i o n , the a c t i v i t i e s of K a r l (female) & . K i t t y (male) i n , t h e pre-egg stage w i l l be analyzed i n . d e t a i l . F i r s t , the male spent a greater- amount of time about.the colony than d i d the female (6l% versus 34 3/4 out of the t o t a l 81 observation .hours;.these are minimal f i g u r e s since t h e i r movements could not always be t r a c e d ) . P e r t i -nent observations f o l l o w : : o755 9 May female absent; K i t t y - a t t e m p t s cop. w i t h unhanded b i r d s o720 23 May K i t t y attempts cop. w i t h unhanded b i r d a f t e r K a r l f a i l s to respond o710; 1730 managed a 5-sec. cop. w i t h K a r l , who dumped .him at that p o i n t ; K i t t y \u00E2\u0080\u00A2 . gabbed at her neck; K a r l f lew . of f at o821, K i t t y 1007. 0715 25 May b r i e f circling.,K-K, K a r l not i n t e r e s t e d o752 28 May.. 30 .sees, cop., ended b y - K a r l , K i t t y jabs, c l i n g s to'back of-her-head, both tumble to water; land again o754. 0832 29 May c i r c l i n g , K i t t y (present since o500) ge one fo o t on, K a r l (present since 07OO) won't s e t t l e . 6o o844,4 June 50 sec. cop, K i t t y jabs as K a r l r i s e s to end 0736.6:June 40 sec. cop, 75 sec. cop at o904, :these a n d . a l l subsequent K i t t y . d o e s not jab at c l o s e . o524 8 June K i t t y attempts cop, K a r l f i n a l l y f l e e s to water; 0620 b r i e f cop, 0651 c.90 sec. cop ( c l o s e d obs. 07OO) 0815 11 June K a r l a r r i v e s ( K i t t y ashore since o700), long cop. at once; again o912. o8l0.l4 June K i t t y - ( p r e s e n t alone since entered b l i n d o700) f l a p p i n g ; K a r l not present; '. t h i s .was the d a y before the 1st egg. o644 17 June (day of second egg) K a r l not present, K i t t y down from egg since 0615; attempts to mount unbanded b i r d , who lunges; up to eggs again; 0913 down again, meets K a r l , who a r r . 0902; long waddle f o l l o w s but without r e s u l t ; K i t t y hops over and attempts cop. w i t h stranger, -who moves o f f ; o 9 3 0 another unsuccess-f u l attempt w i t h K a r l ; no f u r t h e r obs. 0853 21 June & o857'25 June: K a r l attacked Double-green (mated male nest 13) and unbanded male resp., who attempted cop. I conclude t h a t the male shows a long period..of readiness to copulate compared.to a l i m i t e d p e r i o d of r e c e p t i v i t y i n .the female. Richdale (1951) has reviewed.the problem and c o l l e c t e d examples where such seems to be the case (Rednecked Phalarope, Snow Bunting, ducks, penguins, and the Royal A l b a t r o s s ) . On .the b a s i s of f i e l d . d a t a , t h e r e f o r e , the Pigeon Guillemot shows a p a t t e r n common to.many;birds. Since e x p l o s i v e development of the ovocyte on to l a y i n g r e q u i r e s about.13 days'.or l e s s i n .this species ( see .'replacement l a y i n g 1 ) , the suggestion can be made that the hormonal changes in v o l v e d may regu l a t e the r e c e p t i v e phase i n the female Pigeon Guillemot. I can o f f e r -'only \u00E2\u0080\u00A2 grouped data, \u00E2\u0080\u00A2 however, so can say no more but that the r e c e p t i v e phase appears to be roughly the two weeks p r i o r t o . l a y i n g . 6 1 Though both sexes Incubate, i t was apparently,the l a c k of response of the female-during egg-laying that brought c o p u l a t i o n ito a n - e n d . i n ; t h i s s p e c i e s j . t h i s suggests Charadrius alexandrinus, Tringa totanus, and Tringa n e b u l a r i a , where such\u00E2\u0080\u00A2is u s u a l l y the case ( R i t t i n g h a u s 1 9 5 6 , Grosskopf 1 9 5 9 ? Nethersole-Thompson 1 9 5 1 resp.).' M a r s h a l l ( 1 9 5 4 ) s t a t e s that i n a l l b i r d s s t u d i e d so \u00E2\u0080\u00A2 f a r ' t h e male o u t s t r i p s . t h e female by f a r i n gametogenetic development, and i s p o t e n t i a l l y ready f o r c o p u l a t i o n long before the female; the p a t t e r n above i s thus c o n s i s t e n t w i t h anatomi-c a l f i n d i n g s . Lehrman ( 1 9 5 9 ) brings forward evidence that the cou r t s h i p of the male st i m u l a t e s ovarian development and r e c e p t i v i t y i n . t h e female and suggests the hormones ope r a t i v e ; e s p e c i a l l y s t r i k i n g are the experiments w i t h caged S t r e p t o p e l i a r i s o r i a ( r i n g dove). On .the other hand Richdale ( 1 9 5 1 ? 1 9 5 7 ) . h a s strong evidence that the male has l i t t l e impact on^the c y c l e of the female in.Megadyptes antipodes. I t i s c e r t a i n l y too e a r l y f o r sweeping g e n e r a l i -s a t i o n . C. Colony Structure Intensive study of c o l o n i a l . s e a - b i r d s has shown.that f a r from being the d i s o r d e r l y mobs they appear to the casual observer? o r g a n i s a t i o n i s i n t r i c a t e w i t h an.emphasis on main-t a i n i n g .family bonds\u00E2\u0080\u0094thus Tschanz ( 1 9 5 9 ) has d i s p e l l e d notions of communal feeding and,egg adoption .in U r i a aalge, .62 . a n d . c l a s s i c . i s the.work of Richdale, who discusses 6 Tubi-nares and.several penguins w i t h great f a m i l i a r i t y i n h i s books (1951 , -57) . 1 can o f f e r but a sketch of s o c i a l s t r u c t u r e i n , t h e Pigeon Guillemot, since very few banded non-breeders could be observed, and'I have been unable t o . f o l l o w . p a i r - f o r m a t i o n i n marked b i r d s . The dominant p a t t e r n i s f o r year-tor-year s t a b i -l i t y : the mated p a i r remains i n t a c t i n successive seasons, use the same beach p e r c h i n g - s i t e , , and the same nestr-site so long as t h i s remains. Young.birds r e t u r n to-their'home colony \u00E2\u0080\u00A2 a t ' l e a s t when two years o l d (3rd calendar year),\u00E2\u0080\u00A2and attempt to secure a mate; to what extent n e s t - p r o s p e c t i n g occurs at t h i s age, and when the b i r d s f i r s t breed, I cannot say. 1. The Pair'Bond Banding of ad u l t s on .the nest commenced by G.F. van Tets in.1957 i n d i c a t e s that maintenance of the\u00E2\u0080\u00A2bond over a long p e r i o d i s the.'rule: 4 successive seasons: 1 record (#4l) 3 : 2 record (#S-1, # S - l l ) 2 : 1 record (#43) In these cases eggs were l a i d i n . t h e same nest-burrow each season. Capture on,the nest was the.method of 'banding, \u00E2\u0080\u00A2and depends on t a k i n g the b i r d unawares; recapture i s g e n e r a l l y much more d i f f i c u l t . In most .nests we succeeded i n banding .only 1 of the p a i r ; where both were banded recapture often . f a i l e d . Telescope-check was p o s s i b l e only i n : l i m i t e d areas; 63 f o r ' a l l these reasons the records are scant. Opposed.to these i s one case of M i v o r c e 1 u n f o r t u n a t e l y l a c k i n g complete d e t a i l : Nest 1957 1958 1959 I960 #17 Male Banded o2 o2 recaptured (no b i r d caught) o2 recaptured Female not caught banded 79 ( empty....) not caught #24 Male Banded 18 18 recaptured 18 recaptured 18 recaptured Female Banded 20 not caught 79-mated w i t h 18 not caught We had poor l u c k i n catching the females so the s t o r y Is incomplete, but the female 79 mated w i t h the male 18 i n h i s nest #24 (adjacent nest group, 50 meters south of #17) as determined by repeated observation i n c l u d i n g c o p u l a t i o n (79 had.been colour-banded i n 58) in.the year 1959? though the male from nest #17, w i t h whom she was mated i n 1958, was s t i l l a l i v e ( i t cannot be proved, however, th a t he was present at the colony). In the f o l l o w i n g season both males acquired banded mates i n t h e i r r e s p e c t i v e nests, and eggs were incubated to hatching i n both; I was unable to determine the females i n v o l v e d . Eggs were l a i d i n nest #24 each of the f o u r seasons, but nest #17 missed out the year the female was absent. The pattern, .suggested .for the Pigeon Guillemot by these data, where the b i r d s p a i r f o r many seasons but divorce can occur, has been discussed i n d e t a i l by Richdale (1951s 132ff.), who e s t a b l i s h e d the p a t t e r n in.the penguin Megadyptes antipodes w i t h an impressive m a t e r i a l ( c f . Richdale 1957s 9-17), and concluded that i t probably holds f o r a l l penguins but King and Emperor. Richdale found.the same 64 p a t t e r n i n the 5' Tubinares i n v e s t i g a t e d (Pelecanoides u r i n a t r i x , P a c h y p t i l a turtur,, Pelagodroma marina, .Puffinus g r i s e u s , and Diomedea s a n f o r d i , see 1957' 17), and c o l l e c t e d f u r t h e r examples from the l i t e r a t u r e : i n Oceanitus oceanicus and P u f f i n u s t e n u i r o s t r i s extended matings were known, i n P u f f i n u s p u f f i n u s divorce as w e l l . In .the Laro-Limicolae r e t e n t i o n of mate was known .in Larus aygentatus (see a l s o Tinbergen. 1 9 5 3 : 9 7 - 9 8 ) and Sterna hirundo, and the p a t t e r n appeared to be followed i n some Passeres as w e l l . For the sea-birds one may add the f a s c i n a t i n g .observations of Drost (l951j> 1955) on Larus argentatus, r e v e a l i n g divorce though long p a i r i n g s are the r u l e ; i n Sterna tschegrava (caspia) Bergman (1953) observed r e t e n t i o n of mate from year'to year, as d i d C a r r i c k & Dunnet 1954 i n Fulmarus g l a c i a l i s , . In the L i m i c o l a e there i s much v a r i a t i o n : . t h e s h u f f l e of partners i s more frequent than r e t e n t i o n , in\u00E2\u0080\u00A2Charadrius alexandrinus ( R i t t i n g h a u s 1 9 5 6 ) , C_. melodus (Wilcox 1 9 5 8 ) , and i n 17 versus 27 cases i n Tringa totanus where Grosskopf'( 1 9 5 9 ) noted ..that when ,the. r e t u r n of one partner from the w i n t e r - q u a r t e r was delayed, the other'took a new mate, an i n t e r e s t i n g s a f e t y f a c t o r f a c i l i t a t i n g prompt remating i n case one of 'the p a i r \u00E2\u0080\u00A2has die d over the winter;.the complicated, marriage r e l a t i o n s of Tringa n e b u l a r i a i n c l u d i n g mate r e t e n t i o n and ..divorce, have been described by;Nethersole-Thompson\u00E2\u0080\u00A2(1951)\u00E2\u0080\u00A2 i n . A r e n a r i a .interpres Bergman ( 1 9 4 6 : 5 3 - 5 5 ) found the p a i r i n t a c t .in a l l cases c o n t r o l l e d (up,to 3 seasons),\u00E2\u0080\u00A2but the 65 sample i s s m a l l . F i n a l l y , i n the only auk where data are a v a i l a b l e besides ours f o r ' t h e Pigeon Guillemot, the same pa t t e r n . h o l d s . Uspenski ( 1 9 5 6 : 35) r e p o r t s r e t e n t i o n of mate i n U r i a lomvia, w i t h one record of divorce (two years' data, 7 p a i r over one year, 4 t o .the second; not c l e a r where divorce occurred). 2 . N e s t - s i t e F a i t h f u l n e s s Re-use-by, the same b i r d s of the nest-burrow.of the previous season as has been shown -for the Bla c k Guillemot i n Quebec and New Brunswick (23 cases, up .to 4 years,.-to same colony; 3 on,same nest i n . consecutive years; S t o r e r l 9 5 2 : 158) i s i n d i c a t e d by t h e - f o l l o w i n g : 4 consecutive seasons: 6 cases (24,4l,4l,S-l,S-2,S-ll) at l e a s t 3 seasons : 7 cases ( 1 2 , 1 7 , 2 8 , 3 1 , S r - 1 , S-11>S-12T at l e a s t 2 seasons : 6 cases ( l 4 , 3 4 , 4 3 , 4 3 , S - 4 , S - 1 3 , S - 1 5 ) These represent.the number of times i n d i v i d u a l b i r d s were recaptured i n the burrow,(on eggs), or w e r e - d e f i n i t e l y known to be u s i n g .that\u00E2\u0080\u00A2burrow,(band numbers or - colour combinations read by telescope) i n cases where eggs were produced. The f i v e exceptions\u00E2\u0080\u00A2tend.to prove the r u l e of extreme Nesttreue: i case of g u l l i n t e r f e r e n c e , and 4 where the nest became unusable or unfavourable; i t i s s i g n i f i c a n t .in.the l a t t e r - t h a t despite a dense p o p u l a t i o n no other g u i l l e m o t s nested there when the o r i g i n a l occupants had moved. 66 In 1959? nest #2 ( i n use in.58) remained empty, and the adjacent.nest #4 r e c e i v e d 3 eggs,.the f i r s t . 2 being l a i d on the same day (normal c l . 2). I n o t i c e d that.an e a r l y nest of Larus glaucescens s t r a d d l e d the entrance of nest #2, and concluded that the female, barred from.her own nest by the incubat-in g g u l l ( g u i l l e m o t s are e a s i l y cowed by the much l a r g e r g u l l s ) l a i d i n the nearest a v a i l a b l e hole, already i n use as nest #4. Events i n i960 bear t h i s out: on 3 June I banded a g u i l l e m o t on.2 eggs i n nest #2, w i t h an empty g u l l nest across the entrance; on .the 4th the f i r s t g u l l egg .was l a i d and the guillemot nest was not again v i s i t e d ( d a i l y checks) u n t i l on the 10th I decided to memove the now-complete g u l l c l u t c h . On.the 11th the g u i l l e m o t nest had.been v i s i t e d already, and on.my next check (13th) I banded the mate of the b i r d caught .the 3rd; an i n c u b a t i n g b i r d was seen on 4 occasions subsequently, but the eggs f a i l e d to hatch, no doubt the 7 days 1 c h i l l i n g had, k i l l e d the embryos. Nest #4, by the way, had but a s i n g l e egg i n i960 (hatched s u c c e s s f u l l y 20th June). The second case: nest #33? a deserted r a b b i t burrow i n use as a guillemot nest when .found 1958, and again ,59? was washed away over the winter 59/60; curious happenings ensued i n the adjacent nest #31? a, spacious c a v i t y under a l e a n i n g boulder, in,1960. On 11 June the f i r s t egg\" (a) appeared, followed.by another (b) i n a d i f f e r e n t spot on the 12th;'(a) disappeared by the 13th. w i t h no f u r t h e r change u n t i l the 20th when an egg (c) was added to the s u r v i v o r '(b). On 23 June another egg (d) was l a i d at the o r i g i n a l spot (where (a) had been) fo l l o w e d by another (e) on .the 26th. This l a s t set (d&e) l a i d at the normal i n t e r v a l on the same spot as i n previous seasons, was incubated by, the ' r e s i d e n t 1 p a i r of nest #31? the female (banded 1958) being captured on these eggs 14 J u l y , b&c l y i n g c o l d and deserted a foot c l o s e r to.the entrance; d&e hatched on 22&23 J u l y ; b&c f a i l e d . Obviously two females (one the nest-owner, the other presumably from #33) were u s i n g the same c a v i t y , but d i f f e r e n t nest-bowl t h e r e i n ; only the 'owners' s u c c e s s f u l l y hatched .t h e i r eggs. E x a c t l y how the 2 females c o n t r i b u t e d to l a y i n g the f i r s t 3 eggs i s not clear\u00E2\u0080\u00A2however. The t h i r d case concerns the s h i f t of a banded b i r d .from nest #34 (some distance from #33 considered above) to the adjacent #36. Nest #34 (found in.58, 67 b i r d captured on eggs 59) remained empty i n .i960, and the banded occupant was captured on p i p p i n g eggs i n nest #36 ( i n use 1957 & 58, empty 59). Nest #34 was a 'poor* nest, being r a t h e r open and prone to g u l l disturbance; perhaps the p a i r s h i f t e d . t o #36 when t h i s became a v a i l a b l e , but other i n t e r -p r e t a t i o n s are p o s s i b l e : divorce or death of mate, e t c . The f o u r t h case i s - s i m i l a r : a male banded on eggs i n nest #15, 1957 was found to nest i n #14 1959; i n 58 the nest #15 had r e c e i v e d a s i n g l e egg that never hatched, and remained empty 1959&60. Nest #14, 15 f e e t away, was used by the male 1959&60; eggs had been found i n a d i f f e r e n t p a r t of #14 i n .1958. Cause f o r the s h i f t may have been s h u f f l i n g of the ' r o o f 1 boulder when banding the young i n 57, as the n e s t - c a v i t y was made l e s s deep i . e . , undesir-able. Date and number of the 58 egg suggest a r e l a y , so i t may be that the male and h i s mate s h i f t e d to 14 i n 58, picked a poor spot (eggs here r o l l e d away, f a i l e d to hatch) returned #15 to r e l a y , and f i n a l l y e s t a b l i s h e d the s u c c e s s f u l nest #14 i n 59. Other explanations are e q u a l l y l i k e l y . The f i n a l case is.one of \u00E2\u0080\u00A2 1Umsiedlung 1 (Drost: 1953), that i s , change of home, due undoubtedly to human i n t e r -ference. When the campsite on Mandarte was e s t a b l i s h e d i n 1957, a guillemot nest was found there, and both parents banded on the eggs, not 10 f e e t from the cooking t a b l e . The b i r d s abandoned the eggs, and the burrow has remained deserted.ever s i n c e . On .19 June, i960, en a nest check at Imrl'e I s l a n d ( s t r a i g h t l i n e distance between nests 7.7. k i l o m e t e r s , or 4.8 miles) one of the p a i r (banded 16 .June 1957) was extracted-from a chamber beneath an immense g r a n i t e boulder. Young had been r a i s e d there the previous season (59), but we could f i n d no eggs on t h i s i 9 6 0 , v i s i t ; perhaps the b i r d we caught was the female there to l a y . Capture of the b i r d was awkward, t a k i n g about an hour's work s h i f t i n g boulders e t c . , and 68 as nothing f u r t h e r happened i n .that nest i n i960 i t . i s q u i te p o s s i b l e that the b i r d was forced to abandon a second.time. I t i s not.known whether.the mate from 1957 was present. This displacement by-human disturbance, of the breeding a d u l t from \u00E2\u0080\u00A2 the o r i g i n a l colony.-to another where i t probably bred .is e v i -dence f o r the view of Drost (1953) that the sea-birds t r e a t e d ..there (Larus argentatus and canus, Sterna s a n d v i c e n s i s , hirundo, m a c r u r a , . a l b i f r o n s , Haematopus o s t r a l e g u s , Charadrius alexandrinus) remain true to the colony where they f i r s t bred b a r r i n g ;unusual events ( h a b i t a t d e s t r u c t i o n , d i s -turbance by man or p r e d a t o r s ) . Such records of Umsiedlung .are of course exceedingly d i f f i c u l t t o obtain,.and i t .was pure l u c k to capture #05; nevertheless t h i s displacement must be \u00E2\u0080\u00A2unusual for-many-birds.have returned t o Mandarte despite d r a s t i c i n t e r f e r e n c e at t h e i r nest. That breeding b i r d s show..a strong attachment to the n e s t - s i t e of former seasons\u00E2\u0080\u00A2(Nesttreue) has been demonstrated in.many c o l o n i a l s e a b i r d s . In the penguin Megadyptes antipodes .Richdale (1951? 1957) has analyzed .the tendency i n d e t a i l , and found a strong Nesttreue i n other penguins and the Tubinares he studied (see l i s t above) to which one. may add Puff inus p u f f inus (Lockley 1947), P. gris e u s -(Lockley 1932), P_. t e n u i r o s t r i s (Serventy 1957a) and Fulmarus g l a c i a l i s ( C a r r i c k & Dunnett: 1954). In the Steganopodes the male Phalacrocorax a r i s t o t e l i s normally r e t u r n s to ^ the previous n e s t - s i t e (Snow - i 9 6 0 ), and i n the Laro-Limicolae a strong 1 1 s i t e - t e n a c i t y ' has been demonstrated i n . t h e 8 species l i s t e d above ( D r o s t l 9 5 3 f o r 'Larus argentatus see a l s o Tenbergen 1953: 82) and R i s s a t r i d a c t y l a (Coulson & White 1956, 1958) t o mention only.a few. F i n a l l y , i n .the Alcae a l l species studied show.a pronounced Nesttreue: A l c a torda (Landsborough-Thomson 1953, ' Kartaschew I 9 6 0 ; 21) , U r i a lomvia (Uspenski 1956: 35, Kartaschew- i 9 6 0 : 4 7 ) , .-Uria aalge (Canady F i e l d - N a t : 1924, 1925; C. & D.Nethersole-Thompson 1 9 4 3 ,\u00E2\u0080\u00A2Storer -1952: 156-157, Landsborough-Thomson .1953, Tschanz 1959, Kartaschew i 9 6 0 : 64), Cepphus g r y l l e ( S t o r e r -1952: 158,:and see aboye), F r a t e r c u l a ; a r c t i c a (Landsborough-Thomson 1953) . 'Geburtsortstreue 1 i . e . , f a i t h f u l n e s s to n a t a l colony, w i l l be mentioned-later. 3 . F a i t h f u l n e s s - t o the P e r c h i n g ; S i t e The strong attachment t o the nest ...is matched., by that f o r a p a r t i c u l a r perching s i t e on the boulders of the wave-cut p l a t f o r m that forms the beach on Mandarte I s l a n d . I soon found that the morning assemblies on the rocky beach were not haphazard aggregations of the b i r d s that bred i n ,the v i c i n i t y , for.'the marked mated b i r d s could..be expected at the same spots day a f t e r d a y \u00E2\u0080\u0094 t h e same barnacle-encrusted rock,\u00E2\u0080\u00A2the same corner of a l e v e l s l a b , e t c . Indeed w i t h close observation i t was e v i d e n t . t h a t each mated p a i r had a circumscribed home on the beach, which I w i l l c a l l t h e i r p e r c h - s i t e . Experienced breeders r e t u r n t o the same p e r c h - s i t e s year a f t e r year, f o r Fig. 36 Pigeon Guillemots NESTS a PERCH-SITES i i A--A beach perch sites Open gull meadow 1in .the o r i g i n a l p o s i t i o n . t o l e r a t e d . A d e f i n i t e 'de-fended a r e a 1 i s thus l a c k i n g . S t o r e r (.1952: 147) came to the same co n c l u s i o n . Nevertheless the perching s i t e has important f u n c t i o n s often a s s o c i a t e d w i t h t e r r i t o r y , i n other b i r d s (Hinde 1956). I t serves to put the.members of the p a i r -in 73 contact whenever present at. the colony-but unoccupied at. the nest, important i n l ) f a c i l i t a t i n g c o p u l a t i o n , 2) maintenance of the p a i r bond .throughout the season. A b e t t e r case can be made f o r ' t h e ' n e s t . t e r r i t o r y 1 , (which i s . i n almost a l l cases d i s t i n c t from the perching s i t e . due to beach and c l i f f s t r u c t u r e ) , as the f o l l o w i n g show: 1 June 60, 1016: a f t e r f l i g h t s from water t o c l i f f and down again, and long ;sojourn on t h e i r doorstep, (Ledge, c o n t i n u a t i o n of nest f l o o r ) p a i r 'Visit nest #27; chuckle-, remain w i t h i n c. 1 minute; show i n t o l e r a n c e to next p a i r over \u00E2\u0080\u00A2 ( s e t t l e d c. 20 f e e t away). One o f ' l a t t e r edges over towards nest #27; one of 27 p a i r f l i e s up at once, i n t r u d e r f l e e s ; 1044 repeat performance, 27 owner chases o f f i n duet f l i g h t (egg-laying i n #27 took place at the end.of the month). The f a c t that the same b i r d s use the nest year a f t e r year, i n .t h i s dense colony, i n d i c a t e s t hat.nest .defence.must be e f f e c t i v e . L a t e r , when feeding c h i c k s , t h i s i n t o l e r a n c e apparently d e c l i n e s , f o r a number of i d l e r s may l o a f about..the nest entrance without being .driven o f f by\u00E2\u0080\u00A2the busy parents. The same d e c l i n e in.nest-defence has.been observed i n F r a t e r c u l a a r c t i c a (Lockley 1953: 83). The concept of t e r r i t o r y -has long been a p p l i e d to the nest area of c o l o n i a l sea-birds (Howard . 1 9 2 0 ) . I was unable to.observe any,advertisement of the nest, but I could watch no new.nests being o c c u p i e d \u00E2\u0080\u0094 c e r t a i n l y - the b i r d s i n s p e c t a l l p a r t s of the i s l a n d , e.g. they have been noted ,to enter the wooden b l i n d s above the cormorant c o l o n i e s . 74 5. The Non-breeders Counts along the p a r t of the colony i l l u s t r a t e d ( F i g . 36) c o n s i s t e n t l y gave higher f i g u r e s than could be accounted f o r by the number of breeding b i r d s a s s o c i a t e d w i t h the known ne s t s . I t i s d o u b t f u l i f any nests were missed; certainly-none-.that produced chicks i n 1959 or \u00E2\u0080\u00A2\u00E2\u0080\u00A2i960.' The 7 nests ( i n which 7 b i r d s were e v e n t u a l l y .banded) account f o r \u00E2\u0080\u00A2 14 b i r d s , . b u t the morning average May-June-July was 20, which can be taken as a safe minimal f i g u r e (impact of breeding b i r d s v i s i t i n g from elsewhere would b e ' n e g l i g i b l e ) . In .this small s e c t i o n of the colony.c. 1/3 of the b i r d s were thus non-breeders. In f a c t . t h e r e were b i r d s i n . t h i s group banded on Mandarte as n e s t l i n g s . In 1959 2 two-year \u00E2\u0080\u00A2 olds were sighted here, 1 of which (#45) was a r e g u l a r member of the beach assemblies at l e a s t from mid-June ( l 6 t h ) to .early; August ' ( 3 r d ) ; in. i 9 6 0 3 two-year olds were.sighted, 2 of them only once, the other (#88) a r e g u l a r v i s i t o r -mid-June ( l l t h ) to mid-August \u00E2\u0080\u00A2(17th) being sighted 19 \u00E2\u0080\u00A2 times i n the i n t e r v a l (42 obs. days). In a d d i t i o n #45, now a three-year o l d , was seen on 6 ,dates i n e a r l y J u l y , and the other two-year o l d of the previous season was seen once (28 J u l y ) \u00E2\u0080\u00A2 i n a d i f f e r e n t p a r t of the colony by G.F. van Tets. F i n a l l y , a three-year o l d not seen i n 1959 was spotted 13 August i 9 6 0 . Of \u00E2\u0080\u00A2 importance here are #45 and #88, which came ashore r e g u l a r l y on.this s t r e t c h i n . t h e i r second-year-.(1959 and i 9 6 0 r e s p e c t i v e l y ) . Taking i n t o account the d i f f i c u l t y of reading hand .numbers i n . t h i s bird, hearing o r d i n a r y 8 - d i g i t hands,, and.spending most of \u00E2\u0080\u00A2 t h e i r 'time ashore s e t t l e d o n i t h e \u00E2\u0080\u00A2 t a r s i , I f e e l i t safe to consider #45 and 88 almost d a i l y members of the beach assembly at l e a s t between .\u00E2\u0080\u00A2 the extreme dates of s i g h t i n g . These b i r d s d i d not s e t t l e on the same spot each day .as d i d the breeding :b.irds, but s h i f t e d about a great, deal and I .am confident that n e i t h e r \u00E2\u0080\u00A2 succeeded.in a c q u i r i n g a mate I t i s i n t e r e s t i n g that both were males hatched along t h i s v e r y . s t r e t c h (45 i n nest #13? 88 i n #12). This may i n d i c a t e an a s t o n i s h i n g Geburtsortstreue ( ' p h i l o p a t r y ' ) , c o n s i d e r i n g \u00E2\u0080\u00A2the f a c t that they never have a proper look at t h e i r home before making t h e i r way.to the sea and away, but may only be coincidence. This suggests the burrow.nesting P u f f i n u s puf- f i n u s (Lockley 1947) and. P. t e n u i r o s t r i s (Sersenty 1956, 1957 a & .;b); i n the l a t t e r species strong G e b u r t s o r t s t r e u e \u00E2\u0080\u0094 r e t u r n t o a p a r t i c u l a r p o r t i o n of the n a t a l ' c o l o n y \u00E2\u0080\u0094 i s documented by a l a r g e m a t e r i a l . The two-year olds seen only once or twice ('passing through 1) came from a l l p a r t s of the i s l a n d . The f o l l o w i n g notes are s i g n i f i c a n t i n judging #88*s status In I960: 11 June noted o735 p l u s ; e x c e s s i v e l y shy (? one of f i r s t v i s i t s to.the colony) 15 June 0815-0830: attempting to mount unbanded b i r d repeatedly.' ( f l a p p e r ) , but d r i v e n o f f ; :ends i n .tussle, both dropping to water. 24 June 0935 b i l l s w i t h o l (mated male, whose part n e r was banded) not r e c i p r o c a t e d ; attempts to mount; dri v e n off,. 76 .26 June o703 f l a p p i n g f u r t h e r down the beach 27 June 0828 s e t t l e d r i g h t next to Bluebird? his. f a t h e r , but nothing s p e c i a l noted on p a r t of e i t h e r . 4 J u l y o8l2 unbanded b i r d attempts t o mount.88, who d r i v e s i t o f f .5 J u l y o755 s e t t l e s beside b i r d showing , ' y e a r l i n g 1 plumage, attempt to b i l l ; . t h e n oyer next K i t t y (mated male) who chuckle-waggles; 88 l i k e w i s e ; both s e t t l e . 13 J u l y o735 chipping long and l o u d l y , f i n a l l y arcs t o . c l i f f t o p (o745) but does not land u n t i l second t r y ; o b v i o u s l y very unsure of i t s e l f , . t h i s very l i k e l y the f i r s t c l i f f t o p v i s i t . 15' J u l y 0923 f l a p p i n g at unbanded b i r d . The behaviour of #45 in.1959 was s i m i l a r (thus I noted an attempt on h i s p a r t to mount the mated male K i t t y - 1 J u l y ; K i t t y drove him o f f ) . Both these b i r d s showed.a completely a d u l t appearance when f i r s t spotted, as d i d a l l - the banded b i r d s l i s t e d above. That both f a i l e d to breed i n t h e i r second year'(3rd calendar year) u n d e r l i n e s the heed for-long-term banding p r o j e c t s i n . a s s e s s i n g age at mat u r i t y ; perhaps i n less, crowded c o l o n i e s #45 and .88 would.have had t h e i r chance. The s t a t u s of #45. when seen i n h i s t h i r d year was u n f o r t u n a t e l y not revealed t o me. I t i s p o s s i b l e that he had acquired a mate elsewhere In the colony. What of the y e a r l i n g b i r d s ? .These can be recog-n i z e d by .-their plumage u n t i l the p o s t n u p t i a l moult (August) as they often r e t a i n a s c a t t e r i n g of white and dusky f e a t h e r s , and the wing-patch p a r t i c u l a r l y i s mottled, i n t h e i r f i r s t n u p t i a l plumage (Bent- 1919: 159-160-'Black, 170-171 Pigeon g u i l l e m o t ; Witherby et a l . 194l). In a d d i t i o n they - complete t h i s moult l a t e r ' t h a n o l d e r age groups 77 (Storer . 1 9 5 2 : 2 0 2 ) . Throughout May 1-2 of these b i r d s could be seen each morning, paddling about by themselves at extreme d i s -tances from shore, recognizable b y - t h e i r g e n e r a l l y brown colour; e s p e c i a l l y notable was the s u f f u s i o n of the wing-patch by.-brown. The f i r s t b i r d s of. t h i s group, were not noted a s h o r e . u n t i l mid-June, however;' 2 d e s c r i p t i o n s from my notes: Wings and back p r a c t i c a l l y a d u l t - l o o k i n g ,with c l e a r white wing-patch;.2 l a t e r a l streaks of white feathers \u00E2\u0080\u00A2 between.the wings, and.the head has many-white fea-thers g i v i n g i t a powdered appearance; f e e t are r a t h e r p a l e r than i n o t h e r ' b i r d s . (13 June 1959) P r i m a r i e s brown, wing-patch t i n g e d w i t h brown; other-wise the usual . charcoal w i t h a l i b e r a l s p r i n k l i n g of white f e a t h e r s , e s p e c i a l l y around - the face--conspicuous white a r c below.and behind.the eye. (1 J u l y 1959) I t can be concluded that .the predominantly brownish b i r d s spotted o f f the c o l o n y - i n May had about completed t h e i r f i r s t n u p t i a l moult and had s t a r t e d coming ashore. Whether a l l those that .showed but a f i n e s p r i n k l i n g of white were y e a r l i n g s i s not c e r t a i n , as I was not l u c k y enough to f i n d a banded b i r d among them; I t h i n k i t l i k e l y however, since I n e v e r observed such a c o n d i t i o n .in .banded two-year o l d s , or -in any breeding b i r d s ( u n t i l a d v e n t of p o s t n u p t i a l moult end August), and the y e a r l i n g Uria.lomvia l i k e w i s e shows a s c a t t e r i n g of white on the cheeks i n summer plumage (Uspenski 1956: 5 5 ) . - U s p e n s k i (1956: 83) observed Black Guillemots w i t h dark spots on the specula,, and sometimes 7 8 white, feathers, on the abdomen,, i n summer i n the Russian A r c t i c .coasts, and concluded .that these were immature non-breeders. S t o r e r \u00E2\u0080\u00A2 ( 1 9 5 2 : : 2 0 3 ).however, records 2 Alaska specimens taken.in .July, gonads enlarged, presumably breeding,. that showed white f e a t h e r s i n the underparts; but since gonadal enlargement i n adolescent (non-breeding) Larus hyperboreus at the breeding colony has been demonstrated (Marshall 1 9 5 4 f o r r e f . ) the above i s .not c o n c l u s i v e . Murie ( 1 9 5 9 : 1 8 6 ) observed Pigeon Guillemots with,'unseasonal'whitish s u f f u s i o n on the plumage, suggesting the w i n t e r d r e s s 1 from \" 2 4 June to 2 9 August i n Aleutian-waters, but makes no comment on p o s s i b l e status of the b i r d s . Whatever t h e i r age, b i r d s showing brownish s u f f u s i o n of the wing-patch and/or s c a t t e r i n g of white in.the otherwise black plumage observed by.rme were a l l non-breeders. . Records \u00E2\u0080\u00A2 of these b i r d s ashore at the o b s e r v a t i o n . s t r e t c h of beach at. North B l i n d . r u n as f o l l o w s : 1 9 5 9 I 9 6 0 F i r s t record ashore: F i r s t record ashore l 8 J u n e -.13 June ( ' June 1 8 , . 2 1 , 2 2 , - 2 4 , 2 6 , . 2 9 June 1 3 , 2 3 , 2 6 , 2 9 J u l y 2 , 4 , 5 , 1 1 , 17 J u l y 1 , 7, 1 1 , . 14,.. 2 6 Last record 17 J u l y Last record ..7 August \u00E2\u0080\u00A2These b i r d s were seen s i n g l y , and were e x c e p t i o n a l l y shy, and might paddle up and down a .-half hour or; more, showing d i s t i n c t l a n d i n g - i n t e n t i o n s , before coming ashore. I doubt whether they .ever made bold t o v i s i t the c l i f f - t o p . No sexual a c t i v i t y as in :two-year olds was noted; there could be no question but 79 t h a t these were unmated b i r d s . In summary, y e a r l i n g ( i n small numbers,. deduced from incompleteness of n u p t i a l plumage) and two-year o l d (commonly, shown by'banding) non-breeders j o i n the shore-assemblies at the colony, at l e a s t from mid-June on; t o what extent non-breeding occurs i n l a t e r age groups, and..when breeding f i r s t occurs, i s not known. Winn (1950) thought he detected a non-breeding group of c. 50' b i r d s o f f the 5 0-pair colony of Black Guillemots at Kent I s l a n d at two periods In J u l y , and-there'are more e x p l i c i t observations of immatures v i s i t i n g the colony i n other auks (see below). The v i s i t i n g of the colony by immatures during the breeding season i s a well-known phenomenon i n sea-birds, which g e n e r a l l y r e q u i r e s e v e r a l years t o mature. Richdale .(1951: 220 f f . ) has reviewed the numerous accounts f o r Tubinares, to which one may supplement the d e t a i l e d observations on P u f f i n u s t e n u i r o s t r i s reported by Serventy (1956, 1957b). In t h i s species the b i r d s f i r s t r e t u r n to the colony when 3-4 years o l d , a r r i v i n g l a t e , at hatching time; l a t e r , at 5, 6, 7 years, they a r r i v e during l a y i n g .and s t a r t t o b r e e d ( e a r l i e s t record. 5 years, some a r r i v e f o r ' t h e f i r s t time and do not yet breed at 7) . The. l a t e a r r i v a l of the immatures thus cor-responds w i t h my y e a r l i n g records i n the Pigeon Guillemot. In the Steganopodes, immatures at the gannet c o l o n i e s are w e l l -known, and from G.F. van Tets* work (1959) on Mandarte I s l a n d , 80 a l a r g e p r o p o r t i o n of.the - immature Phalacrocorax a u r i t u s and pel a g i c u s summer at the breeding c o l o n i e s where they were hatched. In the Laridae immatures have been found at.the c o l o n i e s of Larus c a l i f o r n i c u s (Behle 1958, Johnson 1956 a & ,b), Larus glaucescens (van Tets per s . comm.: band reading) and no doubt others. D. Comparisons w i t h Other Auks How does the co l o n y . s t r u c t u r e and mating behaviour of the Pigeon Guillemot, as sketched above, compare w i t h that of other auks? \u00E2\u0080\u00A2. I b e l i e v e that d u r a t i o n of the pair-bond over many seasons (without i m p l y i n g that the members of the p a i r stay together at sea in.winter,. which i s however not impossible) as proven in.my b i r d , and U r i a lomvia, together w i t h the strong attachment to the n e s t - s i t e of former seasons, proven i n my b i r d , A l c a , U r i a , and F r a t e r c u l a , w i l l prove u n i v e r s a l t r a i t s of the Alcae . With monogamy the r u l e sexual constancy w i l l be high, though in . t h e two b i r d s where observation on t h i s p o i n t has been p o s s i b l e males have been observed.to attempt c o p u l a t i o n outside the p a i r ; i n my.\"bird (the f l a p p e r s ) these attempts have never been s u c c e s s f u l , i n U r i a aalge (N/rrevang .1958) they.are apparently r a r e l y completed. Probably such \u00E2\u0080\u00A2escapades w i l l be found i n a l l . D e t a i l s of colony c o n f i g u r a t i o n can be tra c e d f u r t h e r only i n A l c a , U r i a and F r a t e r c u l a . Of these ( a l l d i u r n a l ) , wide d i f f e r e n c e s are attendant on l ) n e s t - s i t e u t i l i z e d , and 2) whether c o p u l a t i o n occurs at sea ( p u f f i n . t r i b e : F r a t e r c u l a Lockley 1953, et a l . , Lunda observed at-Mandarte) or on .land (the others l i s t e d ) . In the l a t t e r group p h y s i c a l . s t r u c t u r e of the nest area p l a y s a r o l e too, thus in.the U r i a aalge colony studied by Tschanz (1959) only, narrow niches were a v a i l a b l e , w h i l s t Johnson (19^1) observed.the same species n e s t i n g on broad f l a t c l i f f - t o p s ; o b viously the l o a f i n g , . t a k e - o f f , and nesting-mating areas w i l l d i f f e r . The most s i m i l a r arrange-ments to my Pigeon Guillemots were shown i n .the A l c a ..torda colony studied by Paludan .(19^7), where assemblies formed on s k e r r i e s , beaches, or f l a t c l i f f - t o p s , . a t v a r y i n g distances from the nests (here mostly placed under i r r e g u l a r \u00E2\u0080\u00A2 r o c k b l o c k s ) . At the assemblies c o p u l a t i o n occurred, and unoccupied b i r d s l o a f e d through the season. Whatever the d e t a i l s , I have no doubt that marking b i r d s w i l l show that the' e s t a b l i s h e d breeding b i r d s are h i g h l y . c o n s e r v a t i v e i n l o a f i n g and.mating spots as w e l l as n e s t - s i t e s , so f a r shown .in F r a t e r c u l a (Lockley 1953) and U r i a aalge (Tschanz 1959) besides my b i r d . Turning now.to.the problem of non-breeding and 'adolescence 1., species c r i t i c a l l y s t u d i e d s o . f a r agree w i t h my Pigeon Guillemots i n maturing only a f t e r a number of years, and.turning -up at the colony to 'prospect 1 near'the close of'the immature p e r i o d . No species has been studied adequately from t h i s p o i n t of view, but the. f o l l o w i n g , taken together, are i n d i c a t i v e : YEAR A l c a torda U r i a lomvia U r i a aalge Cepphus F r a t e r c u l a 3 \u00E2\u0080\u00A2matures 1 prob. not before t h i s P: 98 some can be seen o f f s h o r e ; plumage. U:55 f i r s t records banded b i r d s U: 55 some others breed f o r f i r s t time K: 47 seldom v i s i t colony K: 64 v i s i t r e g u l a r l y ; some breed: K: 64 others breed f o r f i r s t time K: 64 seldom v i s i t colony commonly \" v i s i t ; don 1 1 breed never seen at colony L: 129 v i s i t s colony L: 129 may breed L: 129 4 \u00E2\u0080\u00A2does breed L: 129 EXPLANATION: Sources: K..Kartaschew i 9 6 0 ; L..Lockley 1953; P..Paludan 1947; U..Uspenski 1956. 1st year i s the f i r s t year of l i f e , i . e . , summer f o l l o w i n g hatching : i n d i c a t e only two species where banding data was d e f i n i t e l y used. 00 ro So-far as I can see, c r i t i c a l records are Uspenski's f o r 'Uria lomvia, mine f o r Cepphus, and Lockley's f o r F r a t e r c u l a - - t h e f i r s t . t w o being based on banded b i r d s of known age, the l a s t age c l a s s e s recognizable by b i l l shape. For the others the o u t l i n e given seems based more or l e s s on .thoughtful c o n s i d e r a t i o n , as was Kaftanowski 1s (1951: 100) d i s c u s s i o n o f the p e r i o d of immaturity i n U r i a lomvia. Summary .-of Pre-Egg ; Stage 1. The pre-egg stage-of the Pigeon Guillemot at Mandarte I s l a n d (extending from the t.ime the b i r d s f i r s t come ashore at. the colony u n t i l . the f i r s t egg I s l a i d by that pair.) ranges from 30-60 days. Nest v i s i t i n g (up .to 39 days before l a y i n g ) , communal water d i s p l a y s , and c o p u l a t i o n are the c h i e f a c t i v i t i e s of e s t a b l i s h e d p a i r s . No observations of pair-formation.were secured. 2. Copulation, which almost always takes place on the rocky beach at the colony, i s described, and cases w i t h i n .the p a i r ( i n i t i a t e d by c i r c l i n g ) d i s t i n g u i s h e d from attempts at f o r c e d copulations without i t . The l a t t e r , . which\u00E2\u0080\u00A2have never been observed to be s u c c e s s f u l , are c a r r i e d out.by \u00E2\u0080\u00A2 males . (designated f l a p p e r s on account of t h e i r - e y e - c a t c h i n g wing a c t i o n ) \u00E2\u0080\u00A2 t h a t are l a r g e l y unmated birds,-and t o a .small extent males whose partners are unresponsive or have been long absent from the colony. This f l a p p i n g i s d i r e c t e d at 84 a l l s e t t l e d guillemots regardless of sex or.status within.the colony, but t h i s lack of discrimination i s looked upon as the outcome of a .high inner urge, not the lack of sex recognition .in -the male.. The Pigeon Guillemot definitely-recognizes the mate by sight as an i n d i v i d u a l , regardless of s i t u a t i o n . 3. Copulation rate i s described;.the f i r s t were noted 23, 24, and,'28 days before the f i r s t egg in.3 records from banded p a i r s . Copulation i s at a peak i n about the l a s t 12 days., f a l l s r a p i d l y during laying ( i . e . a f t e r the f i r s t egg), and none were noted i n marked pairs after'the second .(and l a s t ) egg had been .laid.. Consideration .of the rate of unsuccessful attempts within the p a i r , and\u00E2\u0080\u00A2analysis-of-the behaviour -of a colour-banded p a i r , led to .the conclusion that the male i s ready to copulate over a long period, but the female has a r e s t r i c t e d receptive phase. 4. As shown by\"banding, the Pigeon Guillemot pairs for a number -of years, but divorce can occur. 5. Re-use of the nest-burrow of previous seasons i s the rule i n established p a i r s . When the nest of former seasons becomes unusable,. the birds attempt to occupy the nearest available hole; t h i s has led to pairs sharing the same nest cavity, but where t h i s could be checked only the nest-owners- have been successful i n r a i s i n g young. One case of 1 Umsiedlung 1 due to human . interference is. known. 6. The strong attachment of mated birds to the nest i s matched by that f o r a p a r t i c u l a r perch-site on the 85 beach boulders, an attachment proven to l a s t from one season to another. These p e r c h - s i t e s are occupied by the b i r d s whenever at the colony but not busy at the n e s t - - c o p u l a t i o n occurs here, and the s i t e i s used f o r l o a f i n g throughout, the season. The morning assemblies on\u00E2\u0080\u00A2the beaches are thus u n d e r l a i n by a d e f i n i t e s p a t i a l o r g a n i s a t i o n at l e a s t . i n s o f a r as the mated b i r d s are concerned, and are not s t r i c t l y com-parable t o .the 'clubs' i n g u l l s . The p e r c h - s i t e s are s i t u a t e d near the water's edge, and are g e n e r a l l y the- c l o s e s t s u i t a b l e perch to the nest. Mated b i r d s are p r a c t i c a l l y confined to .their-home beach (the c. 10-15 m. s t r e t c h a b o u t , t h e i r perch-s i t e ) , . wandering elsewhere i n the colony being observed almost e n t i r e l y i n males during the pre-egg stage, i n sexual or aggressive circumstances. 7. The p e r c h - s i t e i s not s t r i c t l y a t e r r i t o r y , as i t i s a .'magic c i r c l e - ' about the b i r d that i s defended, not a p a r t i c u l a r s t r e t c h of rock. The nest area i s a ..true t e r r i t o r y , defence being most.marked i n the pre-egg stage. 8. Non-breeders formed 1/3 of a small s e c t i o n .of the colony (20 b i r d s ) most i n t e n s i v e l y watched. B i r d s banded as n e s t l i n g s on Mandarte were represented in . t h e non-breeders; the two that hauled out r e g u l a r l y i n t h e i r second year -on the s t r e t c h observed, were both banded there. Y e a r l i n g s i n f r e q u e n t l y ( i d e n t i f i e d by plumage) and two-year -olds com-monly (band. records) j o i n the assembly at the colony; none of these acquired mates. When breeding f i r s t occurs, and,to what extent non-breeding occurs i n l a t e r ages, i s not known. I I . THE EGG STAGE The Nest The Pigeon Guillemot i s extremely p l a s t i c i n nest-s e l e c t i o n , the main requirement being t o place the '.eggs under cover. Thus n a t u r a l holes and c a v i t i e s of a l l s o r t s are used, and where c o n d i t i o n s allow the b i r d may excavate a burrow f o r \u00E2\u0080\u00A2 i t s e l f j r a r e l y open s i t e s are u t i l i z e d . S t o r e r (1952: 143-146) has reviewed published d e s c r i p t i o n s of nest types i n Cepphus, and concludes that the greatest v e r s a t i l i t y i s shown i n the Puget. Sound r e g i o n , according to the w r i t i n g s of Dawson. Dawson & Bowles (1909:922-928) l i s t open ledges, abandoned puffin'burrows (Lunda c i r r h a t a ) , self-made burrows and even runways i n the grass (reported a l s o byEdson, 1929? who accompanied Dawson on a 1905 t r i p when the l a t t e r were discovered) besides the more usual s i t e s i n broken rock and n a t u r a l c r e v i c e s . Of these perhaps the most i n t e r e s t i n g from an e v o l u t i o n a r y viewpoint i s the a c t i v e excavation of burrows, where the s o i l allows t h i s - - t h i s h a b i t i s no doubt widespread i n the P a c i f i c Northwest, at l e a s t from Puget Sound to the Queen C h a r l o t t e I s l a n d s , but has -apparently not been recorded elsewhere, or f o r the B l a c k Guillemot. The f i r s t observation i s t hat of Menzies (Newcombe 1923 P- 34) who noted *;a high sandy c l i f f i n which a species of Diver burrowed very numer-ously l i k e Swallows' (21 May 1792, v i c i n i t y -of Carr I n l e t , 87 Puget Sound, cf. Hall 1933). Recently in nearby Skagit County, Washington, Thoresen & Booth (1958: 12-13) report nesting in burrows i n clay banks at Shannon Point, Fidalgo Island;. here Bank Swallow nests .(Riparia r i p a r i a ) apparently served as the s t a r t i n g point, but active burrowing has been observed. In B r i t i s h Columbia Guiguet (1953).has reported burrowing at the interface of rock c l i f f and t o p s o i l i n the Goose Islands, and has 'noted the habit at many other l o c a l i t i e s (see Drent & Guiguet, in press), his .impression being that where natural s i t e s are scarce burrowing i s resorted to where the s o i l allows i t . This i s an i n t e r e s t i n g forerunner of the habitual burrow-ing .of such auks as Ptychoramphus aleuticus, Synthliboramphus antiquum, and e s p e c i a l l y the Puffin.group (sensu Storer 19^-5: Fratercula, Lund a, Cerorhinca) . Other i n t e r e s t i n g s i t e s recorded by. Thoresen & ;Booth (in Skagit Cty.) are sheltered ledges on high rocky c l i f f s , and c a v i t i e s of rotten logs and other debris near the c l i f f -top. A further s i t e , u t i l i z e d i n B r i t i s h Columbia (and no doubt also i n contiguous areas) wherever available, i s the jumbled heaps of driftwood forming the beach debris, (Figs. 4 6 , 4 7 ) , recorded f o r the Goose Islands (Guiguet 1953) and many other points (Drent & ,Guiguet/ i n press). On Mandarte Island i t s e l f , the s o i l i s too thin and rocky to allow complete burrow excavation (even Lunda nesting here uses natural rock c a v i t i e s ) , and adequate beach debris i s number on NE facing shore Fig 38 MAIN NEST TYPES ON MANDARTE Pigeon Guillemot , l a c k i n g owing to c o n f i g u r a t i o n of the shore. The remaining p o s s i b i l i t i e s are f u l l y u t i l i z e d . Nest types here can be c l a s s i f i e d as f o l l o w s , i n d i c a t i n g the number of nests i n each category, of the 62 found along the NE f a c i n g shore, that i s , the nests w i t h which I was-most f a m i l i a r (see F i g . 38): 1. C a v i t i e s or chambers i n loose boulder jumbles \u00E2\u0080\u00A2 e s p e c i a l l y common i n l i t t l e geos along the beach; l i t t l e or no p r e p a r a t i o n save arrangement of loose chips e t c . of f l o o r i n t o nest bowl; 24 n e s t s . F i g s . 39-40. 2. N a t u r a l crannies i n rock masses; again l i t t l e pre-p a r a t i o n , bare f l o o r or t h i n s o i l accumulation; 18 nests. F i g s . 42-44. 3. Chamber excavated beneath a boulder cap; often an enlargement of a n a t u r a l hollow, but burrowing by the b i r d s t o some extent at l e a s t ; 14 n e s t s . F i g . 45. 4. Old r a b b i t burrows, excavated i n s o i l at c l i f f -c r e s t by Oryctolagus c u n i c u l u s , European r a b b i t , which was r e l e a s e d on the i s l a n d long ago ( C a r l & Guiguet 1958: 11; p r i o r to 1915? Anderson 1916) but has r e c e n t l y died out here ( l a s t report c. 1955-56; none seen 1957 on). These burrows are g r a d u a l l y disappearing through e r o s i o n , and i t i s obvious that the Pigeon Guillemots that use them cannot cope w i t h the rocky s o i l , t h e i r s c r a t c h i n g s being i n s u f f i c i e n t P i g . 39 T y p i c a l 'type l 1 g u i l -lemot nest at Mandarte (#7): a n a t u r a l c a v i t y In a boulder jumble, here j u s t above high water mark. The eggs can be dimly discerned at centre. F i g . 40 A close-up of the eggs i n F i g . 39. The f u l l c l u t c h of two r e s t on a chip b a s i n . Note thermocouple taped to l e f t egg, lead wire t o r i g h t . L a t e r the chicks h i d i n the cr e v i c e at r e a r . F i g . 4 1 I l l u s t r a t i n g the arrange-ment f o r t a k i n g incuba-t i o n temperatures: s e n s i t i v e j u n c t i o n i s the white knob at r i g h t . The wire i s taped to the egg, and extends away to the r e c o r d i n g i n s t r u -ment i n the b l i n d . P i g . 42 A 'type 2' g u i l l e m o t nest on the north s k e r r y , Man-da r t e : a n a t u r a l c l e f t i n the rock. Chicks v i s i b l e as a black blob at bottom, l e s s than 1 m. above high water mark. Black Turn-stones perched atop rock. P i g . 43 Close-up of the nest i n P i g . 42. The eggs were l a i d on the smooth f l o o r i n foreground. The chicks are cowering against the f u r t h e s t corner. Note c l e a n l i n e s s of nest I n t e r i o r : the chicks move t o the entrance t o defaecate. F i g . 44 Another 'type 2' g u i l l e m o t nest at Mandarte (#47; nest i n F i g . 42-43 l o c a t e d on skerry i n background). Another natu-r a l cranny i n a s o l i d rock mass, t h i s time w i t h i n a ' g u l l meadow'. F l a s h l i g h t marks the entrance. F i g . 46 A 'type 3 1 nest at Man-darte (#4), a chamber ex-cavated from the rocky s o i l , beneath a boulder cap. Entrance below the #4, at c l i f f c r e s t , some 4 m. above high water mark (base of p i c t u r e ) . P i g . 46 Beach debris at Imrie I s l e t , a small s e a - b i r d colony near Mandarte. Guillemot nest under block at r i g h t . G u l l s nested i n the grassy area behind; crows, b l a c k - b i r d s and song-sparrows i n the brush, and an oystercatcher j u s t to the l e f t of the p i c t u r e . F i g . 47 Close-up of g u i l l e m o t n e s t - s i t e In F i g . 46. The entrance i s above the p e n c i l ; the nest contained a s i n g l e w e l l -grown young ( 8 August i 9 6 0 ) . Such s i t e s are l a c k i n g at Mandarte, but commonly u t i l i z e d on the B.C. coast. 90 to balance the l o s s ; 3 of the 5 s t i l l i n use i n 1957 were abandoned by i 9 6 0 . 5 . Open ledge near c r e s t of 1 0 -foot brush-capped c l i f f . I n o t i c e d a b i r d , apparently i n c u b a t i n g , f l y down from t h i s spot the evening of 18 June (1959), and found a s i n g l e egg on a niche there, f u l l y exposed. I t was s t i l l present'\at 1500 on the 19th , but had been punctured and sucked by crows the next day. This open-nesting may be attempted more often than my records i n d i c a t e , f o r the evidence would s p e e d i l y be destroyed. As I rambled about the i s l a n d on my d a i l y nest-checks I came to know the NE h a l f i n t i m a t e l y , and became convinced that a l l p o s s i b l e crannies and c a v i t i e s are c u r r e n t l y i n use as g u i l l e -mot nests, or i f not there i s good cause ( e s p e c i a l l y i n t e r -ference by n e s t i n g g u l l s , see case of nest #2 given under 'nesttreue' above). The nest categories described above simply r e f l e c t the p o s s i b i l i t i e s , t h e r e f o r e . . Indeed on the o u t l y i n g rocks to no r t h and south only types 1 and 2 occur, but these are f u l l y u t i l i z e d . Other p a r t s of Mandarte were examined during cormorant banding, and i t i s my impression that the gui l l e m o t colony has roughly reached the l i m i t under present,'housing c o n d i t i o n s ' . The l i m i t a t i o n of n e s t - s i t e s on p o p u l a t i o n i s ex e r c i s e d i n two stages. F i r s t , . t h e colony s i t e must s a t i s f y c e r t a i n requirements (e.g., absence of mink). Secondly, each 5 -3 2 -' r o -s 4-3 2 / O Fig. 1957 48 1958 EGG-LAYING AT MANDARTE r_ n 1 i ._J J dates of commencement of first ciufches open- estimated solid-certain c J n n n \u00E2\u0080\u00A2 n s \u00E2\u0080\u00A24-3 Y 2. / -0 -1959 4- -3 ~ 2 -/ O I960 Y I I L \u00E2\u0080\u00A2 I I 1 - l k J . l ~J u N E 91 colony offers a certain number of c a v i t i e s as p o t e n t i a l s i t e s , and where the t e r r a i n allows additional burrows may be excavated. Before t h i s two-step l i m i t i s reached throughout i t s range, other factors may intervene (e.g., food supply, for sea-birds see Fisher & Lockley 1954 cap. 4 ) , and i t seems u n l i k e l y to me that the population of the Pigeon Guillemot i s controlled by nest-s i t e a v a i l a b i l i t y alone, except l o c a l l y . B. Egg-Laying 1. The Seasonal Pattern Records are available for the 4 seasons 1957-60, the date where each clutch was started being plotted i n F i g . 48. In the f i r s t two seasons the nests were not checked dai l y , the maximum error being + 2 days; i n 1959 and i 9 6 0 with d a i l y nest-checks the maximum error i s 24 hours. SLnce these checks were carried out at mid-afternoon, the egg was con-sidered as having been l a i d the morning of the day found, and so plotted (the s o l i d squares). Probably but few errors have crept i n with t h i s procedure, since i t i s u n l i k e l y that many eggs are l a i d a f t e r mid-day (see 'daily pattern'). The few cases in 1959/60 where the nest was found late have been plotted as open squares. In these cases laying date was deduced from laying i n t e r v a l where possible, hatching date, etc.; generally the error here w i l l be + 1 day. The same nests were checked each season, so as the known number i n the n e s t - l i n e on the NE f a c i n g shore increased, so d i d the sample of l a y i n g dates (19, 28, 36\", 4l cases r e s p e c t i v e l y ) . The data are analyzed In Table 1. Extreme dates from the 4 years are 18 May (1958 and i960) and 29 June -(1958; note that 28 June was the extreme i n both 1959 and i960), and these are probably near the l i m i t s f o r t h i s area. Bowles (1921) assembled the data of Washington o o l o g i s t s and found the e a r l i e s t date f o r a. f r e s h complete c l u t c h 20 May, the l a t e s t 2 J u l y . On the b a s i s of gu i l l e m o t abundance and c o l l e c t i n g d i f f i c u l t i e s on the outer ooast, i t can reasonably be assumed that these clutches stemmed from the Puget Sound area. Bent (1919) gives 9 May t o 23 J u l y as extremes f o r 32 sets from B r i t i s h Columbia and Washington, but as l o c a l i t i e s are u n s p e c i f i e d these do not help here. Thoresen & .Booth (1958: 9 &::l6) report l a y i n g to have com-menced about 20 May, w i t h a peak 5-20 June, f o r the F i d a l g o I s l a n d area, Washington, i n 1957. This i s i n agreement w i t h our data. Young have fledged from eggs l a i d at each extreme (18 May i960, 28 June 1959) so that we can say the egg-laying \u00E2\u0080\u00A2season (see N o l l 1955) f o r the Pigeon Guillemot on Mandarte I s l a n d extends about Tg- months from mid-May. to the close of June (1957 shows a smaller spread, but the sample here was s m a l l ) , w i t h heaviest l a y i n g o c c u r r i n g i n a three-week span. S i n g l e f r e s h eggs i n J u l y a r e , \u00E2\u0080\u00A2 i n my experience, replacements. TABLE 1. EGG-LAYING IN THE PIGEON GUILLEMOT Analysis of four seasons on Mandarte Island, B.C. Year 1957 1958 1959 i960 A l l years Sample size Mean date Standard deviation Range Mean date, 1957 nests only 19 June' 2.4 5.3 days 26 May -13 June 18 days June 2 .4 28 June 8.2 9.7 days 18 May -29 June 42 days June 8.5 36 .41 124 June 14.5 June 13.6 June 11.0 8.0 days 7.1 days 7 .8 days 24 May -28 June 35 days June 16.9 18 May -28 June 4 l days June 15.1 18 May -29 June 42 days Sample 19 14 15 vo Why has t h i s p a r t i c u l a r l-g- month span evolved as the l a y i n g season of the Pigeon Guillemot at t h i s colony, i.e., what are the 'ultimate f a c t o r s ' ? I have no data on t h i s question. Lack (1954) argues that supply of appropriate food f o r - t h e young i s the c r i t i c a l f a c t o r , and t h i s i s l e n t some support f o r sea-birds by Salomonsen (1955). Salomonsen compared phyto-plankton abundance w i t h breeding seasons i n 10 Faeroese sea-b i r d s , and found a suggestive c o r r e l a t i o n . Snow \"(i960), t h i n k s that the breeding season of Phalacrocorax a r i s t o t e l i s at Lundy ( B r i s t o l Channel) i s so timed that the young hatch at peak abundance of the sand-eel (Ammodytes spp.) i n surrounding waters t h i s i s the main food the n e s t l i n g s r e c e i v e . These data f o r sea-birds are, however, suggestive r a t h e r than c o n c l u s i v e . Comparison of the 4 seasons (Table l ) shows 1957 to have been the e a r l i e s t , 1958 somewhat l a t e r , and 1959 and i 9 6 0 l a t e r s t i l l and almost i d e n t i c a l . Are these d i f f e r e n c e s r e a l ? S t a t i s t i c a l a n a l y s i s shows the mean l a y i n g date to d i f f e r s i g n i -f i c a n t l y between a l l seasons but 1959-60 ;(p .05) . I t may be argued that the o r i g i n a l group of nests c o n s t i t u t e d the 'early l a y e r s ' , and that as the known number increased a more rep-r e s e n t a t i v e sample was achieved. However, i f the 1957 nests alone are considered, the same d i f f e r e n c e s are shown (see the t a b l e ) - - s o the b i r d s must r e a l l y have v a r i e d t h e i r l a y i n g date. The second o b j e c t i o n might be that .increased frequency of nest checks d i s t u r b e d the b i r d s , d e l a y i n g l a y i n g . To t e s t t h i s , I decided to make no nest-checks u n t i l the end of May i n i 9 6 0 ; \u00E2\u0080\u00A2 9 5 t h i s would give the b i r d s the chance to l a y ' e a r l y ' as they had done i n 1 9 5 7 and 1 9 5 8 , i f my disturbance were r e a l l y . i n v o l v e d . This seemed u n l i k e l y , since a l l checks were made i n the a f t e r -noon, when at t h i s stage the colony i s p r a c t i c a l l y deserted (see ' d a i l y rhythm 1). In f a c t l a y i n g was p r a c t i c a l l y i d e n t i c a l i n 1 9 5 9 and I960, though the d a i l y checks commenced 1 1 May i n 1 9 5 9 , 2 9 May i n i 9 6 0 . In short, the d i f f e r e n c e s between 1 9 5 7 , 1 9 5 8 , and I959-6O, seem r e a l . M a r s h a l l ( 1 9 5 ^ ) has argued c o n v i n c i n g l y that the environmental 'timers' ensuring that breeding occurs at the most favourable p o r t i o n of the year, vary g r e a t l y from one species to another, and even w i t h i n the species from one area t o another. There i s no o v e r - a l l master f a c t o r (e.g., day-length) but r a t h e r a number of f a c t o r s (weather, food, n e s t - s i t e s , mating d i s p l a y , etc.) p l a y t h e i r p a r t . In h i s view these f a c t o r s act t o allow culmination of the breeding c y c l e , not i n i t i a t i o n , which may be autonomous. At any r a t e , the s l i g h t d i f f e r e n c e s between seasons i n my Pigeon Guillemots may w e l l r e f l e c t d i f f e r e n c e s i n what M a r s h a l l terms the 'week-to-week succession of environmental experiences'. A i r temperature, water temperature, sunshine, a c c e s s i b i l i t y of the n e s t i n g c l i f f s ( i n h i b i t o r y here would be severe storms), a l l these f a c t o r s and doubtless many more, may i n f l u e n c e l a y i n g i n my b i r d s . C e r t a i n l y the a v a i l a b l e data a l l o w no c r i t i c a l t e s t of what f a c t o r s i n f l u e n c e l a y i n g i n the Pigeon Guillemot, but a i r temperature w i l l be considered. Many c l a i m that an increase i n a i r temperature s t i m u l a t e s l a y i n g , but t h i s i s r i g o u r o u s l y . proven f o r few b i r d s i n . n a t u r e . The Spotted F l y -catcher (Muscicapahypoleuca) may serve as a.model. Von Haartman.(1956).found a s i g n i f i c a n t r i s e i n .temperature on the 5 t h , 6 t h , and 7 t h days preceding the s t a r t of l a y i n g , a conclus-ion based on .records 1 of 14 seasons i n the same area.' This r i s e was believed, to co i n c i d e w i t h the s t a r t of.the 'explosive* phase of oocyte development. For waterfowl n e s t i n g i n marine condi-t i o n s Bergman.(1939: 68-77), \u00E2\u0080\u00A2 Nyroca f u l i g u l a ) Koskimies & Routamo (1953, M e l a n i t t a fusca) appear-to have shown a dependence on a i r temperature, although i n the same area Bergman ( l o c . c i t ) found ic e disappearance, not a i r temperature, c r i t i c a l i n Somateria m o l l i s s i m a and Mergus. merganser. This should be a warning against f o r m u l a t i n g 'general r u l e s ' . In the Laridae no s a t i s f a c t o r y \u00E2\u0080\u00A2evidence of a l a y i n g dependence on temperature i s a v a i l a b l e (Bergman l o c . c i t . , Paludan .1951). Turning now.to the Pigeon 'Guillemot m a t e r i a l , i t i s true that May a i r temperatures were h i g h e r . i n the e a r l y - n e s t i n g years of 1957-58 than i n the l a t e years 1959-60. The d i f f e r e n c e s occurred mainly in . t h e l a t t e r h a l f of the month, as shown by. t h e - V i c t o r i a weather-records ( 2 5\u00E2\u0080\u00A2kilometers south .of Mandarte). For 1959 and i960 a i r \u00E2\u0080\u00A2temperatures taken on Mandarte all o w a c l o s e r look i n t o .the problem. A p l o t of.mean .daily air-temperature and l a y i n g showed no c l e a r r e l a t i o n s h i p , ' so the precisely-known c l u t c h commence-ment dates from both seasons (49 i n a l l ) were t r e a t e d as f o l l o w s . For each nest the mean a i r temperature on each of the 20 days preceding l a y i n g of the f i r s t egg was recorded, and 97 then averages of a l l records f o r the day of l a y i n g , one day preceding, two days preceding, and so f o r t h , were taken. Tne o v e r - a l l average of the records was c a l c u l a t e d , and d e v i a t i o n s from t h i s mean recorded.for -each of the 2 0 ,days. The goal of the procedure was to f i n d i f a s i g n i f i c a n t r i s e occurred about the 13th-15th days before l a y i n g , as t h i s i s the p o i n t where rapid.development of\u00E2\u0080\u00A2the oocyte sets i n (see s e c t i o n , 'replacement of l o s t eggs'). These tedious computations gave n o . s t a t i s t i c a l l y r e l i a b l e r e s u l t , nor was anything achieved .from .a f u r t h e r manipulation .where d e v i a t i o n of mean .d a i l y temperature from.the long-term mean (taken from V i c t o r i a records) i n the 20.days preceding l a y i n g was considered. In summary, the i n f l u e n c e of air.-temperature on l a y i n g i n . t h e Pigeon Guillemot was considered, but a v a i l a b l e records are i n s u f f i c i e n t to .draw any con c l u s i o n s . 2. The D a i l y Pattern I,have no p r e c i s e data on.the time of day at which the eggs are l a i d , since nest-checks i n .the morning caused exces-. s i y e disturbance and had to be given up. Considering the marked d a i l y rhythm of attendance at the colony-one would suspect l a y i n g to be concentrated during the morning hours (as Winn 1950 suggests); the f o l l o w i n g at l e a s t exclude l a t e afternoon: Egg ( f i r s t i s A, second B ) Interval (time of check on successive days) B 1940-O900 B 2200-1130 A 2200-1130 B 2300-1500 B 2000-1530 B 1950-1530 B 1840-1320 A 1810-1300 B 1810-1340 B 1810-1345 -Two observations, with .the temperature-recorder in use in nests where the females were banded, are my-closest records: Karl (nest 43) l a i d between o705-o730 ( B egg) Greylag (nest 48) almost certainly\u00E2\u0080\u00A2between 08IO-09IO . ( B ) . 3. The Individual Pattern Does the female tend to .lay about, the same date each season, or at least do the birds lay within the same order in .the colony? In other words, are there consistently early and late layers? I have l i t t l e d i r e c t evidence with banded birds, but since the Pigeon Guillemot normally .-uses the same burrow year a f t e r year (see \"Nesttreue* above) an examination of the records f o r each nest may provide a hint. Deviation from the mean laying date each season, for a l l .cases where at-least 3 records are available, are set out in Table 2. Most nests,certainly\u00E2\u0080\u00A2more than half of the 24 l i s t e d , are consistent in laying date. Some are remarkably.uniform, for example nest #8 and #23 are early, #27 and #28 are l a t e . This suggests -that each female has a c h a r a c t e r i s t i c laying rank TABLE . 2. LAYING DATES IN INDIVIDUAL NESTS Dev i a t i o n i n days,, from the season .mean, i n a l l nests where 3 or-more records of l a y i n g date are a v a i l a b l e . Nest # 1957 1958 1959 I 9 6 0 4 -4 1 13* -27 7 1 - 1 3 -3 8 -13 -11 -9 9 0 - 2 - l 10 \u00E2\u0080\u00A23 -5 l n \u00E2\u0080\u00A2 1 0 -8 - 2 12 -12 8 3 13 7 -3 5 14 -21 0 6 17 3 ,0 1 20 -3 5 7 21 - 2 1 -3 - l 23 -7 - 2 -5 24 - 1 14 .8* 0 \u00E2\u0080\u00A2 '25 - 2 -5 3 27 3 -1 9 13 28 3 3 6 30 -6 - 1 0 .-3 x * 31 -8 13 .6* 32 -5 6 -3 3 35 11 0 - 2 36 .5 -6 4* 40 9 .-3 - 1 41 -6 - 4 -3 -6 NOTES: No entry a f t e r 1957 s i g n i f i e s no eggs were l a i d that season. * i n d i c a t e s that a .stranger was known.to be inv o l v e d 100 w i t h i n the colony,- hut i d e n t i t y of the female i s proven by banding i n only.one case. In nest #4l the same female l a i d . i n each of'the four \u00E2\u0080\u00A2 seasons, and i t w i l l be seen that she tended to be e a r l y . Further a n a l y s i s i s . n o t j u s t i f i a b l e , since l a y i n g dates i n 1957 and 1958 are onl y approximate, and there may be more cases than.are i n d i c a t e d where the female s h i f t e d , or was j o i n e d by another w i t h r e s u l t i n g confusion. I t may be pointed out, however, that the data do not support the idea of close synchrony w i t h i n small s e c t i o n s of the colony. The iden-t i t y of the b i r d s from season to season has no bearing i n . t h i s question, as the supposed synchrony r e s u l t s from mutual stimu-l a t i o n . The nests 7-9, 10-14, 20-25, and 30-36 occurred i n t i g h t bunches yet none of these groups shows a c o n s i s t e n t p a t t e r n ; there are l a t e and.early nesters i n each. My :data agree i n t h i s respect w i t h those of Tschanz (1959) Who f a i l e d t o demon-s t r a t e s t r i c t group-synchrony - i n U r i a aalge as Johnson (l94l) had suggested. This does not imply that l a r g e blocs of the colony may not d i f f e r in. l a y i n g dates because of s o c i a l i t y . The 1959 and i960 data .can be f u r t h e r considered. R e s t r i c t i n g ourselves to cases where layi n g - t i m e i s c o r r e c t to 24 hours, and i n a l l p r o b a b i l i t y the same female was i n v o l v e d in'both seasons, 13 cases remain. Since the mean l a y i n g date i n 1959-did not d i f f e r s i g n i f i c a n t l y . f r o m that i n 1960,.we may compare l a y i n g date i n the two seasons d i r e c t l y . When t h i s i s done ( F i g . 49) a strong c o r r e l a t i o n .is shown ( r \u00E2\u0080\u00A2= +.6l). This suggests again that each female has a . c h a r a c t e r i s t i c l a y i n g - r a n k 03 I\u00E2\u0080\u0094 1\u00E2\u0080\u0094 I\u00E2\u0080\u0094 1 \u00E2\u0080\u0094'\u00E2\u0080\u0094 '\u00E2\u0080\u0094 1 \u00E2\u0080\u0094I\u00E2\u0080\u0094>\u00E2\u0080\u0094 r --fe 20 V o I s I CO -i r \u00E2\u0080\u0094 i r \" 1 \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 i \u00E2\u0080\u0094 | \u00E2\u0080\u0094 r 3^ 10 Y v . 5Y o o CDZ O ' o o o -Q 13 nests o 1 I I I I I I I I I I 1 I I 1 1 1 1 1 ..1 1 1 1_ 5 10 15 20 25 June Date of clutch commencement in I960 Fig. 49 CORRELATION\" OF LAYING DATE IN THE SAME NESTS 1959 a 60 Line of regression plotted 101 w i t h i n the colony--probably not a c h a r a c t e r i s t i c calendar date, since we have seen that the \u00E2\u0080\u00A2 same \u00E2\u0080\u00A2 nests show..widely d i f f e r e n t mean .dates i n some seasons. I t j u s t happens that 1959/60 were p r a c t i c a l l y i d e n t i c a l . One may-theorize that each female has a c h a r a c t e r i s t i c response to.the environmental i n f l u e n c e s govern-i n g l a y i n g , as modified by age, e t c . Among the non-Passeres, Richdale (1957) has shown that the i n d i v i d u a l Megadyptes antipodes tends to l a y in.the same \u00E2\u0080\u00A2 r e l a t i o n t o the mean date each season, Koskimies (1957) has shown the same f o r M e l a n i t t a fusca, and Nethersole-Thompson (1951) has suggestive data f o r Tringa n e b u l a r i a . C. The C l u t c h 1. C l u t c h Size The t y s t i e normally l a y s 2 eggs to.a c l u t c h , sometimes only.onej.rarely\u00E2\u0080\u00A23 are reported (Bent 1919? Witherby et a l . 1941, S t o r e r 1952, Uspenski 1956, Kartaschew-. 1960:69, Gudmundsson 1953). Q u a n t i t a t i v e data are given by Winn (1950) and Thoresen & ;Booth -.(1958): Wirin 1950 Thoresen & Booth 1958 Bay-of Pundy, 19^7 Skagit Cty.,.Washington,1957 1 egg 9 nests 1 egg 9 nests 2 eggs ....39 nests 2 eggs ....33 nests-3 eggs .... 1 nest I have worked over the Mandarte I s l a n d data c a r e f u l l y , since apparent one-clutches.(by which i s meant a c l u t c h of only-1 egg) may be e i t h e r replacement\u00E2\u0080\u00A2layings, or the r e s u l t of 102 p r e d a t i o n . The data are detailed.enough to remove the f i r s t e r r o r source, and w i t h 4 seasons 1 records i t has-been p o s s i b l e - t o e s t a b l i s h which nests are prone to crow, p r e d a t i o n . B y . e l i m i n a t -in g these, I b e l i e v e only -'genuine 1 cases where but one egg was l a i d , remain. TABLE 3. MANDARTE ISLAND DATA ON CLUTCH\u00E2\u0080\u00A2 SIZE 1957 1958 1959 I960 T o t a l s Per Cent. ONE EGG 4 2 4 5 .15 9.3 TWO EGGS 33 \u00E2\u0080\u00A2 32 36 46 - 147 90.7 T o t a l cases 37 34 4l 51 162 100.0 MEAN CLUTCH 1.87 1.94 .1 .90 1.90 1.91 I t w i l l be seen :that.the one-clutches make up about 10$.of\u00E2\u0080\u00A2the 162 c l u t c h e s a v a i l a b l e . They were deposited during the normal egg-laying p e r i o d (the 15 records range from 18 May to 28 June). Of the 15 eggs 9-hatched, 8 of the chicks f l e d g i n g s u c c e s s f u l l y ; thus the one-clutches appear\u00E2\u0080\u00A2'normal'. No nests c o n s i s t e n t l y produced one-clutches,. but the 15 records stem from 11 nests where 35. records of c l u t c h , s i z e are at hand. In these nests, t h e r e f o r e , one-clutches appeared, 43$ of the time, compared t o 10$ f o r the whole sample. The assumption i s , t h a t some females (because of age or he r e d i t y ) have a tendency 103 t o , l a y single-egg c l u t c h e s . There are only two banding records however: one b i r d l a i d a one-clutch twice,.and a two.clutch twice, i n the 4 seasons ( a l t e r n a t i n g ) ; another bird* ..laid a one-c l u t c h once, and a two-clutch\u00E2\u0080\u00A2twice in . t h e 3 seasons a v a i l a b l e . \u00E2\u0080\u00A2 My-\u00E2\u0080\u00A2\u00E2\u0080\u00A21959/60 data have a bearing on supposed 3-egg c l u t c h e s . D a i l y checks i n .a- l a r g e s e r i e s of nests commenced before the eggs were l a i d , and allowed me t o . t r a c e events where more than 2 eggs appeared. In 1959 3 eggs were l a i d i n nest #4, but since the f i r s t - two were l a i d . t h e same day-(the t h i r d 3 days l a t e r ) , 2 females were d e f i n i t e l y i n v o l v e d . In i 9 6 0 5 eggs were l a i d a l t o g e t h e r in.nest #31. One egg .was l o s t , and the remainder formed two d i s c r e t e sets of two in:the nest c a v i t y ; again dates i m p l i c a t e two females. These cases have been discussed e a r l i e r (see 'Nesttreue') where i t was made almost c e r t a i n 'that i t was the female from' an a d j o i n i n g nest, made unusable t h a t season, that l a i d . i n a d d i t i o n : t o the nest-owner. The presence of addled.eggs (not always ejected .from the nest, though always f r o i m the nest-bowl) from previous seasons, and the complications of replacement l a y i n g , may f u r -ther account f o r r e p o r t s of 3 - c l u t c h e s . Bent (l9! f9\u00C2\u00AB 159) l i k e -wise casts s u s p i c i o n .on clutches of 3 eggs i n the Black Guillemot. In.short, there i s no evidence that .the c l u t c h of the T y s t i e i s ever, more than two. The f a t e of the three eggs l a i d i n nest #4 (by two b i r d s ) i s of i n t e r e s t . The nest chamber here i s sm a l l , so a l l the eggs l a y i n a common nest bowl. Now. the parents, 104 possessing but two brood-patches, could warm only two eggs at a time. By f e e l i n g the marked eggs at each nest check I found that now A&B, now A&C, and now B&C were warm\u00E2\u0080\u0094i.e., the b i r d s incubated any two eggs at random. As a r e s u l t of t h i s haphazard procedure only one egg hatched. Lockley (1947) has comparable observations' on P u f f i n u s p u f f i n u s , which has a s i n g l e broodpatch and a one-egg c l u t c h , t r y i n g to cope w i t h two eggs i n burrows used by two p a i r . To summarize t h i s s e c t i o n , 206 records of c l u t c h s i z e i n the Pigeon Guillemot on Mandarte I s l a n d have been c r i t i -c a l l y worked over, l e a v i n g 163 r e l i a b l e records f o r a n a l y s i s . These show.the usual c l u t c h t o be two, but clutches of one occur at l e a s t ' 9 $ of the time. There i s suggestive evidence that some females tend to l a y one-clutches, but none d i d so c o n s i s t e n t l y . The two records where more than two eggs appeared In.the nest were d e f i n i t e l y the work of two.females.. Observation of 3 eggs i n the same nest showed that the Pigeon Guillemot cannot e f f e c t i v e l y incubate more than two eggs, so that e v o l u t i o n t o greater c l u t c h s i z e would r e q u i r e m o d i f i c a t i o n of the brood-patches . 2. I n t e r v a l between E g g s \u00E2\u0080\u0094 t h e Laying I n t e r v a l We have seen.that about 90$ of the clutches of the Pigeon Guillemot on Mandarte c o n s i s t of two eggs; the i n t e r v a l between these averages 3 days. Tae same i n t e r v a l . i s shown by Winn's (l950).data f o r the Black Guillemot (see Table 4 ) . 105 TABLE 4. LAYING INTERVAL IN THE TYSTIE N u m b e r o f C a s e s I n t e r v a l Mandarte I s l a n d Bay of Fundy ('Winn 1950) 1959 I960 T o t a l 1947 0 days 0 0 .0 0 1 day 0 1 1 0 2 days 3 0 3 2 3 days 9 14 23 13 4 days 2 2 4 1 T o t a l cases 14 17 31 16 MEAN 2.9 3.0 3.0 2.9 days The records i n Table 4 are based on but one check d a i l y , so that the supposed 2 and 4-day records may w e l l have been three (Paludan 1951 discusses f u l l y the p o s s i b l e e r r o r s i n once-d a i l y checks). Beyond i n d i c a t i n g that the average i n t e r v a l between eggs i s approximately\u00E2\u0080\u00A272 hours, my data do not go on. Thoresen & Booth (1958: 17-18) imply 3 days to be the common i n t e r v a l i n the Pigeon Guillemot, though they men-t i o n cases of 1 and 2-day i n t e r v a l s without s t a t i n g frequency of nest-checks. Kartaschew (i960: 69) gives 2-3 days, Uspenski (1956: 8l) 4 observations of 3 days, f o r the Black Guillemot i n the Russian A r c t i c . 106 3. Replacement of Lost Eggs I made no d e l i b e r a t e experiments on t h i s t o p i c , but crow predation and other l o s s provided 8 observations, summarized i n Table 5. Loss of the c l u t c h never r e s u l t e d i n an a d d i t i o n a l egg at the normal l a y i n g I n t e r v a l of 3 days,, but ra t h e r i n a 'repeat c l u t c h 1 some 13 days a f t e r . t h e l o s s . T h i s was true i f the s i n g l e egg of the f i r s t c l u t c h was l o s t the day of l a y i n g , or even i f both eggs of the o r i g i n a l set were each l o s t on the 0-day.(c.f. nest #9). No replacements were ever noted i f only 1 of a 2-egg c l u t c h were l o s t . I t happens that i n a l l cases recorded the l o s s occurred e a r l y , w i t h i n 3 days of l a y i n g , and w i t h i n 5 of the s t a r t of the c l u t c h . I t i s probably not safe to conclude th a t repeat l a y i n g only occurs when l o s s i s e a r l y , however, since the data were obtained p r i m a r i l y from nests p i l f e r e d by crows, and crow p r e d a t i o n . i s heaviest on days 0-3. In other words, the method of t a k i n g the data made only cases where l o s s was e a r l y a v a i l a b l e . Apparently-the i n t e r v a l from l a s t l o s s to s t a r t of the repeat c l u t c h - - c . 13 days--is a measure of the time re q u i r e d f o r maturation of the oocyte up t o o v u l a t i o n ( c . 10 days) and pr e p a r a t i o n of the egg f o r - l a y i n g \u00E2\u0080\u00A2(c. 3 days). But few.of the b i r d s who l o s t t h e i r eggs attempted a repeat c l u t c h . Opposed to the 6 p o s i t i v e cases i n 1959/60 are 8 nega-t i v e , where l o s s occurred under l i k e c o n d i t i o n s : s i m i l a r l y soon a f t e r l a y i n g , and during the same p o r t i o n of the season. Of the 8 repeat clutches l i s t e d i n Table 5? 7 consisted of one egg only, 1 of two eggs ( g i v i n g a sea s o n - t o t a l of 4 eggs i n t h i s case). Since crow-prone nests were Involved by v i r t u e \u00E2\u0080\u00A2of'the method of securing the data,, success of the repeat clutches was low. In two, the c h i c k fledged; i n two the egg f a i l e d to hatch, and i n . f o u r crows o b l i g i n g l y removed the repeat eggs a l s o . In no case was a \u00E2\u0080\u00A2 t h i r d c l u t c h attempted however. Elsewhere i n the range of the T y s t i e , Winn (1950) recorded two .repeat clutches i n 15 days o r , l e s s , . Thoresen & Booth ( 1 9 5 8 : 16-17) give two cases i n approximately- 1 8 days ( o r i g i n a l set l o s t through weather, so d i f f i c u l t t o . f i x dates) One of these c o n s i s t e d of 1 egg, the other of 2 . F i n a l l y \u00E2\u0080\u00A2Uspenski (1956) records one observation of an 18 day i n t e r v a l . The response of other auks to.egg l o s s .is s i m i l a r . In Al c a torda Paludan ( 1 9 4 7 : 45-46) observed,two cases of a replacement c l u t c h , one at 17 days,- the other at 14-15 days, and Kartaschew ( i 9 6 0 : 21) s t a t e s that replacements are l a i d a f t e r 12-18 days. Because of t h e i r economic importance the murres have been thoroughly-studied i n . t h i s r e s p e c t . U r i a aalge r e l a y s i n 15-17 days (20 records; when these repla c e -ments were removed 5 l a i d a t h i r d egg a f t e r the same i n t e r v a l ) according t o Tschanz ( 1 9 5 9 ) ; NjzSrrevang (1958) l i k e -wise gives the i n t e r v a l as l 6,days, and records one case of a t h i r d egg. appearing 14 days a f t e r the f i r s t replacement had been l o s t . For U r i a lomvia Uspenski ( 1 9 5 6 : 131-132) TABLE 5. REPEAT LAYING IN THE PIGEON GUILLEMOT O r i g i n a l C l u t c h Replacement C l u t c h Nest Year # eggs Pate Age Lost # eggs Date Days a f t e r Days a f t e r Pate Minimal \u00E2\u0080\u00A2A B l a s t l o s s of Season Relay T o t a l 9 1958 2 Crow & c o l l e c t e d 0, 0 2 c24 June c l 6 13-14 1 fledged 4 eggs 27 1958 1 Crow 3 - 1 24 June c l 6 cl3 1 fledged 2 . . 21 1959 1 Crow 0 - 1 25 June 13-14 Crow 2 14 i 9 6 0 2 1 broken; set deserted 2, 0 1 c l 5 J u l y c24 Addled \u00E2\u0080\u00A2 .3 21 i960 2 Crows 1, 2 1 1 J u l y 18 \u00E2\u0080\u00A213 Crow 3 29 i960 1 Crows 3 1 c2 J u l y 9-12 Crow 2 45 i960 1 Addled, ? cause ? 1 c l J u l y c28 \u00E2\u0080\u0094 Addled 2 51 i960 2 Deserted ? 1 e l l J u l y c29 _M _ \u00E2\u0080\u0094 Crow 3 o CO 109 r e p o r t s that K r a s o y s k i gave an average of 16 days, Kaftanowski l 6 - 1 8 days, and Uspenski himself presents 16 records ranging from 15-22 days. In t h i s species 6.0$ of the females can l a y a second egg, hut only 1-2% a t h i r d ; a case of a f o u r t h , s u b s t a n t i a t e d by examination of the ovary, i s known. F i n a l l y , F r a t e r c u l a a r c t l c a i s reported to r e l a y a f t e r 14-17 days (Uspenski 1956: 91). In .short, a l l the auks studied replace l o s t eggs i n a-pattern comparable to repeat clutches i n other b i r d s . This i s e s p e c i a l l y \u00E2\u0080\u00A2 c l e a r i n the case of the T y s t i e , l a y i n g two eggs at an i n t e r v a l of three days; i f these are l o s t the best the b i r d can do i s l a y again a f t e r 13 .days. Quite d i f f e r e n t i s the s i t u a t i o n i n g u l l s , where Paludan (1951) has c a r r i e d out d e t a i l e d experiments on Larus argentatus and fuscus; here i f the eggs are removed as l a i d p r o t r a c t e d l a y i n g occurs. I f l o s s occurs l a t e r than 24 hours a f t e r B .has been l a i d , however, the supernumerary D can no longer be l a i d , so i n t h i s case a new c y c l e must be i n i t i a t e d , and the f i r s t egg of the repeat c l u t c h (which may a l s o be 3 eggs l i k e the f i r s t ) appears 12 days a f t e r l o s s , r e g a r d l e s s of when t h i s occurs. Ytreberg (1956) had l e s s success i n h i s work w i t h Larus r i d i b u n d u s , since d e s e r t i o n was so frequent, but e s t a b l i s h e d what were probably 2 repeat clutches at 11 and 12 days f o l l o w i n g l o s s . 110 D. Incubation 1. General Description of Incubation and Hatching Intervals i n the Pigeon Guillemot In t h i s section.figures from Mandarte Island, based on my d a i l y checks in 1959 and i960, w i l l be given. Defin-i t i o n of\u00E2\u0080\u00A2\"incubation period\" i s deferred to the next part. The eggs were marked with India ink the day l a i d , with the nest number (useful in tracing crow predation etc.) and A for the f i r s t , B f o r the second egg. In giving the i n t e r v a l from l a y i n g . u n t i l the chick i s free of the s h e l l , the p r i n c i p l e error l i e s in f i x i n g the laying date, since in most cases a l l I can say i s 'between 1400 on Monday and 1400 on Tuesday*. No guesses were made, the data being used only i f the egg appeared between v i s i t s on consecutive days. The egg was counted as l a i d on the day found, which i s most l i k e l y correct as the checks were made at midafternoon and i t i s l i k e l y that most eggs are l a i d in\u00E2\u0080\u00A2the morning. The date on which the chick was clear of the s h e l l was easier to determine, as f i r s t one has the warning of the pipping egg, then the degree of wetness of the- hatched chick, state of down, etc., as an aid; these records are correct to the nearest day. The maximum error i n the following i s thus c.34 hours, but i n most cases w i l l be less than 24. The two cases where but one egg was l a i d f i t \u00E2\u0080\u00A2the A egg pattern and have been so grouped. The data stem from 15 nests in 1959 and i960. I l l TABLE 6. PERIOD PROM LAYING OP EGG UNTIL CHICK IS FREE OP SHELL A Egg B Eg\u00C2\u00A3 r 31 days 5 28 days 2 32 days 2 29 days 3 33 days 3 30 days 3 34 days 1 31 days 1 32 days 2 Number of cases 11 11 Mean 32.0 days 29.8 days Since the laying i n t e r v a l i s three days (Table 4), these data require that, on the average, the chicks hatch one day apart, indicating that there i s some e f f e c t i v e incubation before the second egg i s l a i d : 1 2? My 'hatching data can be summarized as follows: the t y p i c a l pattern i s to f i n d the f i r s t cracks one day (when the peeping of the chick i s f i r s t heard), a d e f i n i t e hole the 112 next (the egg i s 'pipped 1) and a hatched c h i c k the t h i r d (17 of 21 cases) '. The voice of the unhatched chick, a hoarse dry cheeping, i s no doubt important i n preparing the parents f o r the feeding e t c . t o come. I t may a l s o f u n c t i o n d i r e c t l y i n ensuring continuous i n c u b a t i o n , since the pipped egg must not be allowed to dry out, and f u r t h e r p o s s i b l y p l a y s a r o l e along w i t h t a c t i l e s t i m u l i i n a l t e r i n g the stance of the a d u l t on the eggs, which presumably occurs i n . t h e guillemot as can be observed i n e.g., g u l l and cormorant on p i p p i n g eggs. Goethe (1953) performed experiments proving the r e a c t i o n of i n c u b a t i n g Larus argentatus t o the 'embryonic v o i c e ' even when t h i s was f i r s t heard f a r e a r l i e r than would be normal (egg s h u f f l e ) , and Nethersole-Thompson (1951) has c o l l e c t e d f i e l d observations on a number of species i m p l i c a t i n g the i n f l u e n c e o f the voi c e from the egg. Generally, the f i r s t - l a i d egg hatches f i r s t , the second one day l a t e r (5 of 7 cases), or 2 days l a t e r ( l case)] i t can happen th a t the eggs hatch i n reverse order ( l case; on successive days), no doubt due t o vagaries i n the temperature a p p l i e d to the eggs (hatching was not prolonged). I t . i s s i g n i f i c a n t that i n 2 of 3 cases the A eggs taped f o r \u00E2\u0080\u00A2temperature measurements hatched l a t e r than the B .eggs i n the same set, that were not tampered w i t h . I n t e r f e r e n c e by the tape of heat t r a n s f e r , r e d u c t i o n i n r e s p i r a t o r y surface, and f i n a l l y p revention of r o l l i n g , probably account f o r the 1 1 3 d i s c r e p a n c y , s i n c e ' t h e A eggs were d e f i n i t e l y i n c u b a t e d b e f o r e t h e B eggs a p p e a r e d , and h a t c h i n g was a p p a r e n t l y n o t p r o l o n g e d . I n s h o r t , n o r m a l l y t h e A e g g - h a t c h e s b e f o r e t h e B e g g , t h e a v e r a g e o f 7 c a s e s g i v i n g . 9 d a y . T h e r e a r e a p p a r e n t l y few r e c o r d s (as d i s t i n c t f r o m g u e s s e s ) i n t h e l i t e r a t u r e t o compare w i t h t h e s e . . Winn : ( l 9 5 0 ) g i v e s 1 2 r e c o r d s , b u t u n f o r t u n a t e l y does n o t make c l e a r t h e i n t e r v a l between l a y i n g and h a t c h i n g i n 7 o f t h e s e , and does n o t d i s t i n g u i s h A f r o m B eggs i n t h e o t h e r 5 ( 2 9 , 3 0 , 3 2 , 3 3 and 3 3 ) . T h o r e s e n & B o o t h ( 1 9 5 8 : . 1 7 - 1 8 ) g i v e t h e f o l l o w i n g ' ( p r o b a b l e e r r o r n o t d i s c u s s e d ) : A e g g : 3 1 , 3 1 , 3 1 , 3 4 , 3 5 , 3 1 , 3 1 days B e g g : 3 1 , . 3 1 , 3 1 , 3 1 days U s p e n s k i ( 1 9 5 6 ) : 8 l ) g i v e s 2 7 - 3 0 days f o r B e g g s , K a r t a s c h e w ( i 9 6 0 : 7 0 ) 2 7 - 3 0 days f o r A e g g s , - b o t h o f t h e s e i n t h e R u s s i a n A r c t i c . As f o r h a t c h i n g I n t e r v a l , Winn ( 1 9 5 0 ) s t a t e s t h a t A & B g e n e r a l l y h a t c h on t h e same d a y , and g i v e s 8 r e c o r d s where c h i c k s h a t c h e d l e s s t h a n 2 4 h o u r s a p a r t , b u t n o t e d e x t r e m e s o f 3 d a y s ; T h o r e s e n & B o o t h ( 1 9 5 8 : 1 8 ) g i v e 3 r e c o r d s o f 2 d a y s , 1 o f 8 h o u r s ; U s p e n s k i ( 1 9 5 6 : 8 l ) 1 - 2 d a y s , K a r t a s c h e w ( i 9 6 0 : 7 1 ) . 1 d a y . F i n a l l y , t h e h a t c h i n g p r o c e s s i s g i v e n as 3 - 4 days (Winn 1 9 5 0 , who a g r e e s w i t h H y d e ' s 1 9 3 7 d e s c r i p t i o n he q u o t e s ) , . 2 r a r e l y 3 { K a r t a s c h e w I 9 6 0 : 7 1 ) . H a t c h i n g d e s c r i p t i o n s c a n n o t r e a d i l y be c o m p a r e d , s i n c e , i n f o r m a t i o n f r o m o n c e - d a i l y i n s p e c t i o n s ( p r o b a b l y . a l l w o r k e r s b u t Winn) w i l l g i v e a d i f f e r e n t p i c t u r e f r o m more 114 f r e q u e n t checks. W i t h r e g a r d . t o t he i n t e r v a l f r om l a y i n g - t o h a t c h i n g , i t i s r e g r e t t a b l e t h a t so few have c l e a r l y s t a t e d -the o b v i o u s i n t e r v a l s , i n a d d i t i o n t o t h e i r i n t e r p r e t a t i o n s of how l o n g . s t e a d y i n c u b a t i o n p r o c e e d s . Where comparison w i t h my f i g u r e s i s p o s s i b l e , t h e r e i s agreement save w i t h Kartaschew*s statement f o r A eggs. The need f o r a s t a n d a r d f o rm i n r e c o r d i n g i n c u b a t i o n p e r i o d s w i l l be d i s c u s s e d i n the next s e c t i o n . 2. The meaning o f ' i n c u b a t i o n p e r i o d ' R e c e n t l y Moreau (1946), Swanberg -(1950) and N i c e .(1954) have sought t o e s t a b l i s h u n i f o r m i t y i n ' t h e r e c o r d i n g o f i n c u b a t i o n p e r i o d s . Swanberg and Nice advocate the use of H e i n r o t h ' s (1922) p r a c t i c a l r u l e , g i v i n g the i n c u b a t i o n p e r i o d as t h e i n t e r v a l f r om the l a y i n g of the l a s t egg t o the h a t c h -i n g of the l a s t young. The concept of the i n c u b a t i o n p e r i o d ( B r u t d a u e r ) , a g a i n t o f o l l o w H e i n r o t h , i s t h e i n t e r v a l from the s t a r t of s t e a d y i n c u b a t i o n by the p a r e n t , u n t i l t he young i s f r e e of the s h e l l . The b a s i s f o r the p r a c t i c a l r u l e i s the f r e q u e n t o b s e r v a t i o n t h a t s t e a d y i n c u b a t i o n s e t s i n when the c l u t c h i s complete, and as s u m i n g - t h a t the l a s t - l a i d egg a l s o h a t c h e s l a s t , a p p l i c a t i o n of t h e r u l e g i v e s a measure of the p e r i o d of s t e a d y i n c u b a t i o n n e c e s s a r y t o h a t c h the. egg of. t h a t s p e c i e s . Moreau has p o i n t e d out t h a t i f s t e a d y i n c u b a t i o n r e a l l y b e g i n s w i t h the l a s t egg, a l l t he eggs s h o u l d p r o v i d e -true p e r i o d s , so one should record the time from l a y i n g of the l a s t egg to hatching of 'each egg, and thus obtain a much l a r g e r sample. Since many b i r d s c a r r y out casual i n c u b a t i o n d u r i n g - l a y i n g , however, i t seems s a f e s t to r e s t r i c t the records to the l a s t egg where t h i s i s f e a s i b l e . C e r t a i n l y one p o i n t s t r e s s e d by Moreau should never be o m i t t e d : . l i m i t s of the data should be made c l e a r by g i v i n g the l i m i t s of e r r o r (+ 4 hours, + 1 day, e t c . ) . A l l three authors s t r e s s the need f o r s e t t l i n g on a sharply defined p e r i o d which w i l l be measur-able i n 1 p r a c t i c e f o r a l l b i r d s - - I t would be unwise t h e r e f o r e to r e f i n e the d e f i n i t i o n to the p e r i o d a f t e r the l a s t egg has been l a i d , but when steady i n c u b a t i o n has a c t u a l l y been observed to set i n , on to hatching as i n the examples given by Ryves (1946). But few observers w i l l be able t o determine the commencement of steady i n c u b a t i o n -as the conscientious C o l . Ryves has done, and to make comparisons p o s s i b l e a d e f i n i -t i o n based on more obvious e v e n t s - - l a y i n g and hatching--should be r e t a i n e d . As an example, Winn's (1950).data f o r the Black Guillemot are not comparable to mine since he c a l c u l a t e d i n c u b a t i o n p e r i o d from commencement of steady i n c u b a t i o n , not l a y i n g of the second egg. A necessary refinement of Heinroth's r u l e , however, as pointed out emphatically by Barth .(1955) and Von Haartman (1956) i s to record the i n t e r v a l from l a y i n g of the l a s t egg u n t i l the t h i c k from that egg (and not simply the l a s t of the c l u t c h t o h a t c h ) . i s f r e e of the s h e l l . Work w i t h marked eggs 116 TABLE 7. INCUBATION PERIODS IN AUKS Clutch I n c u b a t i o n P e r i o d size Mean Range No. of Authority observations Species Alca torda 1 egg 35-36 34.3 \u00E2\u0080\u0094 32-36 Uria lomvia 1 egg 32.8 30-35 30-36 Uria aalge 1 e^ 3 2 ( 3 ) , ' 3 4 ( 1 ) 30-36 Fratercula 1 e^ a r c t i c a Cepphus g r y l l e 2.eggs 29.8 28-32 27-30 .6 obs. 9 19 obs. ? 4 obs. ? 11 obs. s 40,42,43 3 obs. usu.35-37 may be 40-42 ? Paludan 1947: 51-52 Fisher & Lockley 1954.: 282 Kartaschew I 9 6 0 : 22 Uspenski 1956: 44 Kartaschew I 9 6 0 : 41 Uspenski 1956: 77 Kartaschew I 9 6 0 : 57 This paper, Table 6 Uspenski 1956:.81 Lockley 1953: 113 Kartaschew I960: 85 Laying of B .egg u n t i l chick from that egg free from s h e l l . i s d e s i r a b l e , f e a s i b l e i n . s e a - b i r d s w i t h small c l u t c h e s ( B a r t h ) , and where t h i s Is not done, s p e c i a l methods of c a l -c u l a t i o n must be employed (v. Haartman). Thus, f o r the pigeon g u i l l e m o t the 'handbook f i g u r e ' , an . a r b i t r a r y d e s i g n a t i o n f o r \u00E2\u0080\u00A2incubation p e r i o d , would be the i n t e r v a l from l a y i n g of B .egg u n t i l B c h i c k i s f r e e of the s h e l l , by my observations. 30 days (mean o f - 1 1 , range 2 8 - 3 2 , + 1 day). R e l i a b l e statements on i n c u b a t i o n periods i n the Auks have been c o l l e c t e d i n Table 1 . The problem of'how long steady, e f f e c t i v e incubation r e a l l y proceeds i s thus l e f t a separate question. Two f a c t o r s are i n v o l v e d here: when the d e f i n i t i v e i n c u b a t i o n rhythm becomes e s t a b l i s h e d ( i . e . , a t t e n t i v e n e s s and i n a t t e n -t i v e n e s s ) , and, secondly,.when the parent becomes capable of warming-the eggs s u f f i c i e n t l y to f u r t h e r t h e i r development, commenced i n the o v i d u c t . The summary of Kendeith ( 1 9 5 2 : 19-26) f o r the House Wren w i l l serve t o i l l u s t r a t e the gradual development of the i n c u b a t i o n rhythm. This species most commonly l a y s 5 - 6 eggs to the c l u t c h , one a.day, .and through the egg-laying p e r i o d the amount of time spent at the nest each day r i s e s p r o g r e s s i v e l y , c h i e f l y by the decrease of i n a t t e n t i v e periods (time away from nest, feeding etc.) that a l t e r n a t e w i t h the a t t e n t i v e periods of roughly 1 0 .minutes. The i n c u b a t i n g rhythm i s f u l l y developed on the day the l a s t egg i s l a i d ( 5 t h f o r the 5 - c l u t c h e s , 6 t h f o r the 6 - c l u t c h e s ) . The gradual development i s shown by c o n s i d e r i n g the percentage of time through the d a y l i g h t hours spent at the nest during 118 egg-laying i n . t h e 5-clutches:. from the O-day on:.5.0, . 1 2 . 3 , 1 9 . 9 , 3 2 . 2 , 5 3 . 3 $ . At night the same gradual development i s evident: although the female s t a r t s to spend every night i n the nesting' hole as soon as she accepts a male and. begins c a r r y i n g i n n e s t i n g m a t e r i a l , (p. 8 5 ) , the time she a c t u a l l y spends s i t t i n g on the eggs r i s e s g r a d u a l l y (Table 17 and pp. 84-85) through the egg-laying p e r i o d , so tha t at i t s close she incubates continuously through the n i g h t . A s i m i l a r gradual development of the i n c u b a t i n g rhythm during l a y i n g has been shown q u a n t i t a t i v e l y f o r Larus ridibundus (Ytreberg 1956) as an example f o r s e a - b i r d s . The second f a c t o r i n f l u e n c i n g the s t a r t of e f f e c t i v e i n c u b a t i o n , i s how soon the parent becomes capable of warming the eggs s u f f i c i e n t l y to f u r t h e r t h e i r development; t h i s i n v o l v e s the brood-patch and w i l l be discussed i n the next s e c t i o n . 3 . Brood-patch and Incubation Temperature i n B i r d s Most b i r d s incubate by p r e s s i n g a s p e c i a l l y modi-f i e d v e n t r a l area of bare s k i n , c a l l e d - t h e brood-patch, against the eggs, thus warming them w i t h t h e i r own body heat. Some exceptions to t h i s method are the Megapodes (using the heat of fermentation of vegetable mounds) and some Steganopodes, which use the webs of the fee t (e.g. Sula, Phalacrocorax, Stresemann 1927/34 393). Tucker (1943) has provided a general review. 119 TABLE 8 . TEMPERATURE OP THE FULLY-DEVELOPED BROOD-PATCH COMPARED TO BODY TEMPERATURE Species Brood-patch Temp Body Temp R \u00E2\u0080\u00A2 e. f e . r \u00E2\u0080\u00A2 e n c e Megadyptes eudyptula c 3 8 D . C Phasianus c o l c h i c u s Cepphus g r y l l e Charadrius alexandri-nus Charadrius duhius Charadrius nivosus Charadrius h i a t i c u l a 3 9 . 5 \u00C2\u00B0 C 3 9 . 6 \u00C2\u00B0 C 3 9 . 4 \u00C2\u00B0 C 4 0 . 8 \u00C2\u00B0 C 4 0 . 8 \u00C2\u00B0 C Troglodytes 4 0 . 6 \u00C2\u00B0 C aedon 3 7 . 7 \u00C2\u00B0 C Farner 1 9 5 8 : . d i f f e r e n c e not s i g n i f i c a n t 4 1 . 8 \u00C2\u00B0 C Westerskov 1 9 5 6 . 4 0 . 6 \u00C2\u00B0 C This paper, Tables 11 & 12 --- Walters 1 9 5 9 Walters 1 9 5 9 4 1 . 2 \u00C2\u00B0 C Wetmore, c i t e d by Walters 1 9 5 9 ; i n t e r -t h o r a x i c a l temp. 3 9 . 9 \u00C2\u00B0 C 4 1 . 3 \u00C2\u00B0 C Udvardy 1 9 5 3 : 31> standard p r o v e n t r i c u l a r temp. Baldwin & Kendeigh 1 9 3 2 ; body temp. 1 4 9 , B-p temp. 146. Body temperatures are c l o a c a l unless otherwise s p e c i f i e d . A l l brood-patch temperatures are means of considerable s e r i e s . 1 2 0 When the brood-patch i s f u l l y developed i t s tempera-ture i s regu l a t e d by the flow of blood i n the s u p e r f i c i a l v a s c u l a r networks, and c l o s e l y approaches i n t e r n a l body temperature. Species where considerable m a t e r i a l i s a v a i l a b l e are grouped i n Table 8. In a d d i t i o n , the maximum egg-surface temperatures reported by Ba r t h ( 1 9 4 9 ) represent the o c c a s i o n a l contacts of the thermocouples w i t h the brood-patch, and must approach body temperature c l o s e l y : Lagopus lagopus 4-1.7\u00C2\u00B0 C, Mergus s e r r a t o r 4 3 . 3 \u00C2\u00B0 C, Larus fuscus 40.7\u00C2\u00B0 C, Larus canus 4 l . 0 \u00C2\u00B0 C, Sterna hirundo 4 l . 0 \u00C2\u00B0 C. For Larus canus B a r t h ( 1 9 5 1 , 1 9 5 5 ) gives f u r t h e r data. Three ad u l t r e c t a l temper-atures were 4 2 . 0 \u00C2\u00B0 C, 4 2 . 0 \u00C2\u00B0 C, and 4 2 . 8 \u00C2\u00B0 C, and Ba r t h remarks that when the brood-patches came i n contact w i t h the thermo-couples temperatures close to t h i s were measured ( 4 l . 5 \u00C2\u00B0 , 4 2 . 0 \u00C2\u00B0 , 4 3 . 0 \u00C2\u00B0 C). F i n a l l y , the method of Bergman ( 1 9 4 6 ) should give temperatures somewhat lower than the brood-patch, but Arenaria i n t e r p r e s reached 3 8 - 4 0 . 6 \u00C2\u00B0 C, and values f o r Tringa totanus and Sterna hirundo f e l l w i t h i n .this range. That the eggs are not warmed ap p r e c i a b l y when the b i r d s i t s during - l a y i n g , may be due to i n s u f f i c i e n t develop-, ment of the brood-patch, and/or t o a f a i l u r e to b r i n g the patch In close contact w i t h the eggs. By way of i n t r o d u c t i o n , a number of b i r d s have been found to s i t on the eggs during the l a y i n g p e r i o d , without warming them to the touch. Ryves ( 1 9 4 3 b ) and Swanberg ( 1 9 5 0 ) have c o l l e c t e d such examples. 121 Ryves l i s t s C a r d u e l i s c a r d u e l i s , Emberiza calandra, E r i t h a c u s rubecula, Buteo buteo, Circus pygargus (the l a t t e r two by inference from l a y i n g and hatching i n t e r v a l s ) , Swanberg gives Nucifraga n u c i f r a g a , Corvus corone, Phalaropus lobatus, L u s c i n i a s v e c i c a , C a l c a r i u s lapponicus, quotes v a r i o u s authors on pigeons, and Arnold on Cyanocitta c r i s t a t a . In . a l l these cases the sex (or sexes) that normally incubates.was i n v o l v e d - -q u i t e d i f f e r e n t are the records of male on the eggs i n species \u00E2\u0080\u00A2where the female normally does the i n c u b a t i n g , see Ryves (1943a). For the Passeres, recent p h y s i o l o g i c a l study of the brood-patch ( B a i l e y 1952) when compared w i t h brood-patch temperatures as s t u d i e d i n the house wren (Baldwin & .Kendeigh 1932, Kendeigh 1952) goes f a r t o c l e a r :'up t h i s problem of i n e f f e c t i v e i n c u b a t i o n during.-laying. B a i l e y described four stages of brood-patch development from m a t e r i a l of a number of species, and c o r r e l a t e d these w i t h the n e s t i n g c y c l e i n Z o n o t r i c h i a leucophrys: 1. D e f e a t h e r i z a t i o n - - a s p e c i a l moult removing down f e a t h e r s j completed i n about one .day, and o c c u r r i n g \u00E2\u0080\u00A24-5 days before l a y i n g commences. 2. Vascularization--development of a r i c h s u p e r f i c i a l blood supply, r e q u i r i n g about 9 days, and completed by the time the c l u t c h i s complete. 3. Edema--the patch becomes f l a b b y and d i s t e n s i b l e t o more e f f e c t i v e l y cover the eggs, a process o c c u r r i n g 122 'during' i n c u b a t i o n 1 , i . e . , from completion of the c l u t c h onwards. 4 . Recovery--a gradual r e t u r n to the normal c o n d i t i o n , that s t a r t s when the young are 4 - 5 days o l d . Edema disappears f i r s t , then v a s c u l a r i t y ; i n . t h i s species \u00E2\u0080\u00A2the f e a t h e r s are not replaced u n t i l the f a l l moult. Thus stage 2 and 3 must be repeated f o r the next .brood. Further B a i l e y demonstrated hormonal c o n t r o l of these events. In Z o n o t r i c h i a leucophrys Estrogen ( e s t r a d i o l ) r e g u l a t e s v a s c u l a r i z a t i o n and, by s t i m u l a t i n g the p i t u i t a r y to r e l e a s e P r o l a c t i n , a l s o edema. Androgens played no r o l e . Normally the female alone possesses the brood patch and incubates i n t h i s s pecies, but by a d m i n i s t r a t i o n of s u i t a b l e hormones the brood-patch could be developed i n males. Selander ( i 9 6 0 ) s u b s t a n t i a t e d these r e s u l t s w i t h canaries, but f a i l e d to induce brood-patch formation i n Molotrrus a t e r . This species i s a p a r a s i t i c l a y e r , and has l o s t the i n c u b a t i o n patch through e v o l u t i o n , and as Selander showed, also,the c a p a b i l i t y of forming one. The gradual development of the brood-patch t r a c e d by B a i l e y i s f u l l y s u b s t a n t i a t e d by the f i n d i n g s of Baldwin & Kendeigh ( 1 9 3 2 : 148-149) on Troglodytes aedon. The female, which alone incubates i n t h i s species,, loses the f e a t h e r s of a v e n t r a l patch during 'the f i r s t egg-laying p e r i o d of the 1 2 3 season. A marked increase of the temperature a p p l i e d to the top of the, eggs d u r i n g - l a y i n g was shown, and i n the remainder of the p e r i o d temperatures were constant. Kendeigh ( 1 9 5 2 Table 1 7 and pp. 8 O-85) s u p p l i e s f u r t h e r data on t h i s species. During l a y i n g the heat a p p l i e d t o the eggs by n i g h t (a long p e r i o d , s u i t a b l e f o r comparison) increases in.an i r r e g u l a r way, spurts of ' f u l l heat\" being followed by ' p a r t i a l heat'. There i s a good deal of i n d i v i d u a l v a r i a t i o n i n the time when the c h a r a c t e r i s t i c temperature a p p l i e d throughout the Incubation p e r i o d i s a t t a i n e d , but a l l reach t h i s by the f i f t h n ight (when most clutches are complete). Loss of down fea t h e r s on the s i t e of the brood patch could be t r a c e d during l a y i n g , but as t h i s l o s s need be undergone only once each season, development of d e f i n i t i v e i n c u b a t i n g temperature occurs more r a p i d l y an succeeding n e s t i n g s . I t i s s t i l l gradual, however, as B a i l e y ' s stages 2 and 3 must be gone through each time. In how f a r the 'applied heat' depends on posture of the b i r d , or -on whether the f e a t h e r s surrounding the brood-patch are f l u f f e d up or not, remains obscure. Both Swanberg ( 1 9 5 0 ) and B a r t h ( 1 9 5 5 ) s t r e s s the l a t t e r p o i n t , and c i t e the observation of Arnold on Cyanocitta c r i s t a t a i n d i c a t i n g t h a t during -laying the b i r d sat on the eggs without f l u f f i n g the v e n t r a l feathers--thus the brood-patch was not placed i n contact w i t h the eggs. Do other b i r d s show a s i m i l a r gradual increase, dur-ing the e a r l y p a r t of i n c u b a t i o n , of the heat a p p l i e d t o the 124 eggs? I f so, many apparent anomalies i n inc u b a t i o n periods may be expl a i n e d . Previous stud i e s w i l l f i r s t be reviewed, then r e s u l t s i n the Pigeon Guillemot g i v e n . Usage of the term 'incubation temperature' depends on the apparatus and methods of the v a r i o u s i n v e s t i g a t o r s , and one must d i s t i n g u i s h whether temperature of the embryo w i t h i n the l i v i n g egg, of\u00E2\u0080\u00A2the egg-surface, or f i n a l l y of the brood-patch of the parent was i n f a c t measured. These w i l l be c a l l e d embryo,. egg-surface, and brood-patch temperatures f o r c l a r i t y . I t i s our problem here to f i n d what informa t i o n i s a v a i l a b l e f o r non-Passeres on development of brood-patch temperature through i n c u b a t i o n . In-the f o l l o w i n g \u00E2\u0080\u00A2 t h e r e s u l t s from d i f f e r e n t methods w i l l be a p p l i e d to the question of brood-patch temperature changes during i n c u b a t i o n . Many workers have used thermo-couples attached t o , or i n contact w i t h , l i v i n g eggs. Here measurements of brood-patch temperature w i l l be i n f l u e n c e d by thermogenesis of the embryo. To r e t u r n .to.the House Wren, Baldwin & Kendeigh (1932: 136-139) found that heat production of the embryo exceeded'heat l o s s toward the end of the in c u b a t i o n p e r i o d , so that on the 12th day ( i n c u b a t i o n p e r i o d 12-15, average 14 Kendeigh 1952) the embryo temperature was 0.6\u00C2\u00B0 C above the' incubator air\u00E2\u0080\u00A2temperature of 3 6 . 7 \u00C2\u00B0 C. In other words, i n f l u e n c e of c h i c k thermogenesis here w i l l be n e g l i g i b l e . Quite d i f f e r e n t are r e s u l t s w i t h the Chicken, i n v e s t i g a t e d w i t h a h i g h l y r e f i n e d technique by Romijn & Lokhorst ( 1 9 5 5 ? 1 9 5 6 ) . Before 1 8 days the embryos are p o i k i l o t h e r m i c , but a f t e r 1 0 days heat production r i s e s s harply, so that embryo temperatures begin to exceed incubator temperature ( 3 8 . 0 \u00C2\u00B0 C). By the end of in c u b a t i o n the d i f f e r e n c e i s 2 . 0 - 2 . 1 \u00C2\u00B0 C, the embryos having reached 4 0 . 1 \u00C2\u00B0 C. Quite apart from changes i n brood-patch temperature, t h e r e f o r e , we can expect a r i s e of the order of 2 \u00C2\u00B0 C at the egg surface i n the course of in c u b a t i o n , i n species where the embryo i s i n .size and manner of development comparable to the f o w l . Data taken w i t h the pheasant (Phasianus c o l c h i c u s ) i n nature bear t h i s out. Westerskov ( 1 9 5 6 ) measured top egg surface temperatures by p l a c i n g a thermocouple j u n c t i o n i n the centre of the nest at the top of the eggs, and r i g h t under the s i t t i n g hen, but . not i n contact w i t h the brood-patch. Continuous r e c o r d i n g at one nest from the day inc u b a t i o n commenced onwards showed a steady increase f o r t h i s temperature, from 3 3 . 3 \u00C2\u00B0 C on day 1 t o 3 6 . 3 \u00C2\u00B0 C on day 2 4 . I t seems.clear that heat production by the embryos was r e s p o n s i b l e , since no c o r r e l a t i o n w i t h a i r temperatures could be found, and other data showed that brood-patch temperature underwent no s i g n i f i c a n t r i s e i n the p e r i o d . We are now i n a p o s i t i o n to examine the evidence, species by species, f o r changes i n brood-patch temperature through i n c u b a t i o n . Maximum l e v e l reached w i l l be termed ' d e f i n i t i v e temperature 1. 1 126 Megadyptes antipodes Farner (1958) i n v e s t i g a t e d t h i s penguin w i t h thermo-couple placed at the i n t e r f a c e of egg surface and brood-patch. Temperature r e g i s t e r e d was 20-25\u00C2\u00B0 C during \u00E2\u0080\u00A2\u00E2\u0080\u00A2the f i r s t two .days of i n c u b a t i o n , i n c r e a s i n g g r a d u a l l y to c. 38\u00C2\u00B0 C at 15 days, and remaining steady at t h i s l e v e l t h e r e a f t e r ( i n c u b a t i o n p e r i o d i . e . , 2nd egg from l a y i n g to hatching, i s , 43.5 days, range 40-51 , Richdale. 1957: 3 0 ) . There was a v i s i b l e increase of v a s c u l a r i z a t i o n of the brood-patch i n the p e r i o d of i n c r e a s i n g temperature. Magnitude of the temper-ature increase and the f a c t that the same p a t t e r n was shown i n nests where the eggs f a i l e d to hatch make i t c e r t a i n that changes i n brood-patch temperature are indeed being measured, so we can conclude that i n t h i s species there i s a r i s e to d e f i n i t i v e brood-patch temperature over the f i r s t t h i r d of the in c u b a t i o n p e r i o d . Branta canadensis Kossack (1947) c a r r i e d out measurements i n a number' of ways, but the only method'giving f i g u r e s throughout incubation was that where thermocouples were taped t o the upper surface of the egg. Taking the va r i o u s nests together, an increase from 3 6 . 5 \u00C2\u00B0 C (day 2) t o roughly 40\u00C2\u00B0 C on the night before the eggs hatched ( i n c u b a t i o n p e r i o d given as. 127 26 days p l u s or minus 2 days) i s i n d i c a t e d . This d i f f e r e n c e can be explained by thermogenesis of the embryo, and allows us to conclude that the brood-patch temperature does not change s i g n i f i c a n t l y a f t e r i n c u b a t i o n commences. A c c i p l t e r g e n t i l i s , A c c i p i t e r n i s u s , F e r n i s apivorus Farner (1958: 256) has summarized the r e s u l t s of H o l s t e i n ' s (1942, 1944, 1950) researches on b i r d s of prey (the o r i g i n a l s were not a v a i l a b l e t o me). In A. g e n t i l i s the i n c u b a t i o n temperature (top of the egg) reached i t s maxi-mum (c. 4 l \u00C2\u00B0 C) at about the 22nd day, the inc u b a t i o n p e r i o d being 41-43. i n A. nisus the maximum ( 3 7 . 5 \u00C2\u00B0 C) was reached the 22nd day, in c u b a t i o n p e r i o d being 39-42 days, and f i n a l l y i n P_. ap ivorus the maximum of 39\u00C2\u00B0 C was reached about the 11th day, incubation p e r i o d being 37-38 days. Apparently a slow development of the brood-patch temperature, comparable to that i n Megadyptes, i s i n v o l v e d i n these three s p e c i e s . Phasianus c o l c h i c u s Westerskov (1956) placed a broad thermocouple atop the eggs i n s e v e r a l nests, such that i t would be i n contact w i t h the brood-patch of the i n c u b a t i n g b i r d . Records from the 8 t h day of in c u b a t i o n onwards showed no s i g n i f i c a n t change, averages of two s e r i e s ( 8 t h - 2 3 r d day, 1 0 t h - 2 4 t h day) g i v i n g 3 9 . 5 \u00C2\u00B0 and 39 .6\u00C2\u00B0 C. Judging from egg surface 128 temperature (thermocouples not i n contact w i t h brood-patch) records from s t a r t of i n c u b a t i o n on, d e f i n i t i v e brood-patch temperatures are already reached when the c l u t c h i s complete. Westerskov i s supported i n h i s conclusions by K e s s l e r (i960) who f o l l o w e d a d i f f e r e n t method. K e s s l e r glued thermocouples to the small end of the egg, the egg being s h u f f l e d and r o l l e d f r e e l y i n the nest, but without the thermocouple coming i n t o contact w i t h the brood-patch. He found no c o n s i s t e n t trends i n continuous recordings from 10 nests throughout the incubation p e r i o d . In c o n c l u s i o n , d e f i n i t i v e brood-patch temperature i s reached i n the pheasant by the time the c l u t c h i s complete and i n c u b a t i o n commences. Charadrius alexandrinus and dubius Walters (1958) i n v e s t i g a t e d brood-patch temperatures i n these species by r e s t i n g a mercury maximum-thermometer on the eggs, i n such a way that the b i r d a p p l i e d the brood-patch to the bulb when I t s e t t l e d to incubate. A great deal of checking and-direct observation was needed to v e r i f y the r e s u l t s , but r e l i a b l e data were obtained to show that i n both species d e f i n i t i v e temperatures had already been reached when f i r s t measured (C_. alexandrinus day 2-3, C_. dubius day 2, of steady i n c u b a t i o n ) . A s l i g h t r i s e was i n d i c a t e d , from 40\u00C2\u00B0 C at the s t a r t t o 42\u00C2\u00B0 C at the close of i n c u b a t i o n ( i n c u b a t i o n p e r i o d 26.3.days i n alexandrinus, mean of 43 observations, R i t t i n g h a u s 1956: l4o). This r i s e i s doubtless 129 the r e s u l t of embryo thermogenesis, but Walters draws other conclusions. The mean brood-patch temperature throughout in c u b a t i o n was 40 . 8 \u00C2\u00B0 C f o r -both p l o v e r s (C_. alexandrinus 65 readings, C_. dubius 18) . Walters a l s o captured b i r d s on the eggs, and found that the brood-patch was completely bare at the s t a r t of steady i n c u b a t i o n . R e s u l t s from h i s readings of brood-patch temperature i n captured b i r d s w i l l be touched on below. In summary,\u00E2\u0080\u00A2 the two p l o v e r s i n v e s t i g a t e d showed d e f i n i t i v e i n c u b a t i o n temperatures at the s t a r t of steady Incubation, when the c l u t c h had been completed. Arenari a i n t e r p r e s Bergman (1946: .40-47) made the best of war-time c o n d i t i o n s . i n h i s study, by d e v i s i n g a 1Thermometerei 1. An a l c o h o l thermometer, which could be read by telescope from a b l i n d , was i n s e r t e d i n a w a t e r - f i l l e d rubber b a l l , , r e p l a c i n g one of the eggs of the c l u t c h . Incubation sets i n w i t h the 3rd o f - 4 eggs (p. 3 8 ) . Bergman found a temperature of c, 30-31\u00C2\u00B0 C i n the f i r s t 7 days of i n c u b a t i o n , and a slow r i s e t h e r e a f t e r t o c. 34\u00C2\u00B0 C on the l 4 t h day, f o l l o w e d by a sharp r i s e to a maximum of 38-40.6\u00C2\u00B0 C .on the 18th day. This l e v e l was maintained to hatching, which u s u a l l y occurs 23-24 days a f t e r the t h i r d egg, i . e . , a f t e r steady i n c u b a t i o n has set i n ; r a r e l y as long as 26.27 days. Sterna hirundo and Tringa totanus stu d i e d i n the same way gave s i m i l a r r e s u l t s . Bergman discusses the weak p o i n t s of the method, which does not give r e s u l t s comparable t o other i n v e s t i g a t i o n s , and I f e e l i t best at present t o consider these f a c t s as suggestive of a gradual development of brood-patch temperature through \u00E2\u0080\u009E in c u b a t i o n , but i n need of c o n f i r m a t i o n . Larus canus Ba r t h ( 1 9 4 9 , 1 9 5 5 ) . h a s accumulated an immense m a t e r i a l on ithe i n c u b a t i o n temperatures of w i l d b i r d s , but has d i s -cussed the development of temperature only i n t h i s species. The readings were obtained w i t h a wooden.dummy egg w i t h thermo-couple i n s e r t e d to be f l u s h w i t h the surface at the top of the egg ( l n e s t ) , and w i t h the thermocouple extending up between untampered eggs so that, the j u n c t i o n was f l u s h w i t h the top of the eggs (2 n e s t s ) . Table 1 0 and P i g . 3 of h i s 1 9 5 5 paper show that d e f i n i t i v e temperatures were reached by the end of egg-laying ( 3 - c l u t c h e s ) or s h o r t l y t h e r e a f t e r - ( 2 - c l u t c h e s ) . I t seems c l e a r that the maxima recorded i n h i s Table 1 0 represent brood-patch temperatures, the o c c a s i o n a l contacts of s k i n w i t h s e n s i t i v e j u n c t i o n . These would i n d i c a t e ' an increase from c. 3 0 - 3 1 \u00C2\u00B0 C.to c. 3 9 - 4 - 1 \u00C2\u00B0 C .during l a y i n g . B a rth presents an impressive s t a t i s t i c a l m a t e r i a l on l a y i n g and hatching i n t e r v a l s showing t h a t i n c u b a t i o n d u r i n g - l a y i n g cannot be f u l l y e f f e c t i v e , and c o r r e l a t e s t h i s w i t h the incomplete development of brood-patch temperature at t h i s \u00E2\u0080\u00A2 time. ' 131 E x c e l l e n t data are a v a i l a b l e f o r other g u l l s showing that i n c u b a t i o n i s i n e f f e c t i v e during l a y i n g , but must be n e a r l y or f u l l y e f f e c t i v e when the c l u t c h i s complete; these sub-s t a n t i a t e the p a t t e r n of r a p i d attainment of d e f i n i t i v e brood-patch temperature i n d i c a t e d by Barth. Paludan (1951) c a r r i e d out c l e v e r l y - p l a n n e d experiments- on Larus argentatus and fuscus. When eggs were s h i f t e d so as always t o l i e i n nests where l a y i n g was i n progress, embryonic development was c l e a r l y retarded; but when eggs were s i m i l a r l y s h u f f l e d so as t o remain i n the three-day p e r i o d f o l l o w i n g completion of the three-egg c l u t c h , development was p r a c t i c a l l y normal. Thus Paludan concludes (p. 89) that the e f f e c t i v e n e s s of incuba-t i o n immediately f o l l o w i n g completion of the c l u t c h cannot d i f f e r markedly from that of the remainder of the inc u b a t i o n p e r i o d . Ytreberg (1956) a r r i v e d at i n t e r e s t i n g conclusions from h i s work w i t h Larus r i d i b u n d u s . He observed that incuba-t i o n set .in on the day the f i r s t egg was l a i d (there was even broody behaviour i n empty nests) but the b i r d s were f i d g e t y and even when s i t t i n g c l o s e l y the eggs were not f u l l y warm t o the touch (pp. 6 7 - 6 8 ) . Even though incubation pro-ceeded some 8 8 $ .of the d a y l i g h t time during the f i r s t day of the l a y i n g p e r i o d , and some 93$ on the second (p. 6 8 ) , very l i t t l e embryonic development took p l a c e , as shown by comparison of l a y i n g and hatching i n t e r v a l s and embryo weights (pp. 8 I - 8 5 ) . Exchanging f r e s h l y - l a i d A eggs w i t h 132 C eggs f o r a few days, and then r e t u r n i n g the eggs to t h e i r o r i g i n a l nests, shortened development time of'the A eggs w h i l s t i t . l e n g t h e n e d that of the C;eggs. These phenomena are r e a d i l y \u00E2\u0080\u00A2explained i f we assume w i t h Ytreberg that brood-patch temperatures are not high enough during the l a y i n g p e r i o d to promote r a p i d embryonic development. In summary, i n g u l l s brood-patch temperatures develop g r a d u a l l y through the l a y i n g p e r i o d , reaching the d e f i n i t i v e l e v e l by the time the c l u t c h of three i s complete. The changes i n brood-patch temperature that we have j u s t reviewed are dependent on two f a c t o r s . On the one hand there i s a gradual p h y s i c a l development of the patch, and, secondly, the b i r d can c o n t r o l the amount of heat a p p l i e d to the eggs by v a r y i n g . i t s posture, or c o n t r o l l i n g \u00E2\u0080\u00A2 t h e super-f i c i a l blood c i r c u l a t i o n .in the patch. The extent of the l a t t e r source of v a r i a t i o n i s not i n d i c a t e d i n .the data at hand. I t i s i n t e r e s t i n g , however, that the house wren in, t h e l a t t e r p a r t of the l a y i n g p e r i o d , shows spurts of ' f u l l heat 1 f o l l o w e d b y . ' p a r t i a l heat' (see summary above). This suggests that p h y s i c a l l y the patch i s capable of a t t a i n i n g f u l l tempera-t u r e , but that i n c u b a t i n g behaviour of the bird--posture and p o s s i b l y c o n t r o l of c i r c u l a t i o n - - i s not f u l l y developed y e t . A s i m i l a r f l u c t u a t i o n of temperatures d u r i n g \u00E2\u0080\u00A2 l a y i n g i s shown by Barth-'s (1955) data on the common g u l l . The experiments of Baerends et a l . ( i960) w i t h Larus argentatus, concerning \u00E2\u0080\u00A2the r e a c t i o n of the in c u b a t i n g b i r d s t o a dummy egg whose 133 \u00E2\u0080\u00A2 temperature could he manipulated,further emphasize the regu-l a t i n g r o l e of the b i r d ' s behaviour. Feather movements, panting and standing up from the eggs, r o c k i n g motions and s h i v e r i n g could a l l be e l i c i t e d by temperature changes of the, dummy egg. The observations of Walters (1958) p u r p o r t i n g to show psychic c o n t r o l of brood-patch temperature by c i r c u l a t i o n c o n t r o l i n Charadrius alexandrinus and dubius,. are i n my opinion i n c o n c l u s i v e . Regardless of what f a c t o r s are i n f l u e n c i n g the recorded change i n brood-patch temperature, two broad groups are r e c o g n i z a b l e : b i r d s that reach d e f i n i t i v e temperature by the close of l a y i n g or s h o r t l y t h e r e a f t e r , . a n d those where t h i s occurs much l a t e r . To the f i r s t group we may place Troglodytes aedon, Branta canadensis, Phasianus c o l c h i c u s , Charadrius alexandrinus and C_. dubius, Larus canus and doubtless a l l g u l l s . To the second group belong Megadyptes antipodes, A c c i p i t e r g e n t i l i s , A. n i s u s , P e r n i s apivorus. The status of A r e n a r i a i n t e r p r e s i s u n c l e a r . We may turn now to consider how the Pigeon Guillemot f i t s i n t o t h i s scheme. .4. Incubation Temperatures i n the Pigeon Guillemot For a few days i n 1959, through the kindness,of Dr. Koskimies, and throughout the i 9 6 0 season, a very convenient type of temperature recorder, the 1telethermometer 1 manufactured by the Yellow Springs Instrument Co., was a v a i l a b l e . This device i s based on thermocouples and a potentiometer, but i s so constructed that temperatures can be read d i r e c t l y on a scale calibrated from -20\u00C2\u00B0 to + 40\u00C2\u00B0 C, without the observer having to es t a b l i s h a reference temperature (ice-bath, e t c . ) . The disadvantage of the appar-atus was that continuous mechanical recording was not possible, so that my records are fragmentary. In i960 the instrument was placed in my observation blind, and of the 12 channels 2 were reserved f o r air\u00E2\u0080\u00A2temperatures taken,in the b l i n d ( l . 5 meters and ground l e v e l ) , the other 10 used f o r nest temperatures, leads of from 20 to 200 feet extending to the 9 nearest nests. With the aid of my companions on the island, 3 24-hour watches were carried out, 2 further watches - through the daylight hours (o300-2000), and i n addition records were made at a l l times when I was i n the b l i n d . i n the normal morn-ing observation periods. In .this way 170 hours' records were accumulated. Of the 9 nests investigated, in 5 incubation pro-ceeded normally, and eggs hatched,\u00E2\u0080\u00A2in 2 the eggs f a i l e d to hatch but intermittent incubation was recorded, and f i n a l l y i n the 2 remaining desertion occurred shortly a f t e r the eggs were l a i d . Records.were commenced in each nest when the eggs were l a i d , and continued to hatching. Thus the c 150 hours available f o r each nest represent about 20^ -of the t o t a l egg period, spread from laying to hatching. My primary goal was to es t a b l i s h the incubating rhythm i n the Pigeon Guillemot, as the paucity of colour-banded birds, concealment of nest-entrance i n the broken t e r r a i n , 135 and frequent f l i g h t s of unoccupied b i r d s to and from the c l i f f - s i d e , made d i r e c t observation alone unrewarding. I t was f u r t h e r of the utmost importance that the eggs i n .the nests i n v e s t i g a t e d should hatch, f o r i f these f a i l e d I would be without s u i t a b l e nests to study p a r e n t a l behaviour i n the ch i c k stage,-and even my ch i c k m a t e r i a l would be g r e a t l y reduced. \u00E2\u0080\u00A2 I was th e r e f o r e exceedingly cautious when usi n g the telethermometer, and the temperature problem had to take second p l a c e ; I was e s p e c i a l l y r e l u c t a n t to experiment since d e s e r t i o n had occurred, i n 3 of the 4 nests where the instrument had been employed i n 1959. As a r e s u l t of these r e s t r i c t i o n s my temperature m a t e r i a l - i s of a p r o v i s i o n a l nature. F o r t u n a t e l y the b i r d s .accepted having the thermo-couple j u n c t i o n s ( h e r e a f t e r c a l l e d probes) taped to the s h e l l , so that I was able to f o l l o w the method of Kossack (194-7) . I chose to place the probe over the blunt pole of the egg, and the aim was .to record the brood-patch temperature. The standard probe ( F i g . 4 l ) was apparently uncomfortable to the b i r d s , and although restricting.movement the l e a d - i n wire was not s t i f f enough t o prevent r o l l i n g a l t o g e t h e r , so the probe came to l i e somewhat t o the side of the egg, i n most nests. Some movement was p o s s i b l e , and as the egg i s large and the temperature gradient from top to bottom great, the r e s u l t i n g f l u c t u a t i o n s s p o i l e d the record f o r incubation temperature. Data from these nests gave information on in c u b a t i o n rhythm. In two nests, however, a t h i n f l e x i b l e probe was used, and here the p o s i t i o n atop the egg was t o l e r a t e d , and brood-patch temperatures obtained. In a d d i t i o n I attempted to measure embryo temperatures i n one nest by I n s e r t i n g a probe i n t o the egg, but the parents abandoned. Temperature on the nest f l o o r next to the eggs was obtained i n one nest, and f i n a l l y numerous records of a i r temperature in.the nest were secured when the b i r d s were absent during -laying, and throughout i n the abandoned n e s t s . Temperatures at a l l s t a t i o n s were recorded every 5 minutes; l a t e r the m a t e r i a l was p l o t t e d on graphs f o r the 7 nests where incubation was r e g i s t e r e d . I t might have been p r o f i t a b l e to decrease the i n t e r v a l t o about 2\"; or 3 minutes, but i t was impossible to take readings at l e s s than 5 minute i n t e r v a l s and s t i l l keep an .eye on the banded b i r d s . a. Nest Temperature In summarizing r e s u l t s , i t i s l o g i c a l to begin by asking the question, to what extremes of temperature w i l l the egg 'be subjected when the parents are absent? Extremes from the longer spans of r e c o r d i n g have been c o l l e c t e d i n Table 9> where a i r temperature i n the nests i s compared to the general shade temperature as measured i n the observation b l i n d . The b l i n d was a s t r u c t u r e of dri f t w o o d , some 1 . 5 x 2 meters and 2 meters high, w i t h s o l i d roof and sides of r a t h e r open construct-i o n , so that the temperature measured at the height of 1.5 m. here w i l l correspond to that secured i n an ordin a r y louvered TABLE . 9 . NEST TEMPERATURES IN THE PIGEON GUILLEMOT Ranges i n Degrees C. Date Time Span Shade a i r temperatures 1.5 Meters Ground # Nest Temperatures 1. 24-hour records 17/18 June i960 3/4 J u l y 1959 11/12 J u l y 1959 20/21 J u l y 1959 M e a n .2. Overnight records 7/8 June i960 11/12 June I960 11/12 June i960 17/18 June i960 M e a n 3. D a y l i g h t records 2115-O230 2000-O340 2015-o4l0 1200-O320 1130- 1000 .9.0 - 19.9 .10.8 - 18.7 (12) 12.2 - 2 0 . 4 0915- 0800 10.1 - 17.0 (12) 11 . 6 - 16.0 13.3 - 16.0 o648- 0630 11.0 -. 21.7 (12) 14.8 - 18.2 ( 4 3 16 . 4 - 18.0 (13) 16.0 - 22.8 0 6 3 5 - 0 6 3 5 13 . 5 - 26.8 . (12) 15.9 - 20.3 (13) 1 6 . 6 - 25.2 10.9 - 2 1 . 4 1 4 . 6 - 18 . 4 8.9 - 16.2 8.8 - 13.0 8) 13.3 - 14.3 8.8 - 16.8 9.7 - 14.9 (48 11.7 - 18.7 8.8 - 13.2 9.7 - 13.7 M 13.0 - 15.2 9^ .7 - 19.5 11.1 - 18.1 (43) 13.2 - 16.2 9.1 - 16.4 9.8 - 14.9 12.8 - 16.1 26-June i960 O350-2000 10 .7 - 19.2 11. 3 - 18. 2 (14) 15.1 - 18.1 (13 15.0 - 18.0 3 J u l y i960 O315-2000 10 .7 - 23.3 11. 5 - 2 2 . 5 (14 15.2 - 22.1 (13 14.4 - 21.7 .19 J u l y i960 o400-2000 11 .9 - 20.8 13. 5 - 19. 8 .(14 17.6 - 26.8) (13 (48) 17.0 -15.8 -22.3 20.8 M e a n 11 .1 - 21.1 12. 1 - 2 0 . 2 -15'.7 - 21.4 Extremes from a l l I960 8. 8 - 24. 26.8 records (not a l l given here) 8 .8 - 25.0 0 11.7 - LO ^ 1 weather stand (Stevenson screen). In a d d i t i o n ground temperature was taken i n the b l i n d . Care was taken.that the probes were never i n the sun, or a f f e c t e d by the heat of lamps at n i g h t . Nest temperatures are r e g i s t e r e d by a probe on.the nest f l o o r , or-taped to an egg l e s s than 3 days o l d \u00E2\u0080\u0094 i . e . , without thermogenetic i n f l u e n c e \u00E2\u0080\u0094 a n d i n a l l cases when.the burrow was unoccupied. I t w i l l be remembered that p r a c t i c a l l y a l l nest c a v i t i e s on Mandarte I s l a n d are shallow, and surrounded by rock or at l e a s t capped w i t h i t , and these f a c t s e x p l a i n the main features of nest temperature: 1) change i s slow and steady 2) t o t a l range i s s i m i l a r to that of general shade air.temperature. The nest never reaches the general minimum, dropping w i t h i n 2-3\u00C2\u00B0 C of t h i s , a f a c t explained by the slow.cooling of the surrounding rock. At the other extreme the nest temperature commonly reached.the general maximum, and.even exceeded t h i s on sunny days i n nests where t h i n sheets of rock composed the roof or sides (e.g., #48, #13 i n the t a b l e ) . What, then, i s the extreme p o s s i b l e range i n the nest during the i n c u b a t i o n period? .The a v a i l a b l e records from i960 cover the span 8.8\u00C2\u00B0 - 25.0\u00C2\u00B0 C i n . shade a i r temperature .(at 1.5 m), the extremes i n the nests being 11.7\u00C2\u00B0 - 26.8\u00C2\u00B0 C. Extremes at V i c t o r i a i n the p e r i o d 15 May - 31 J u l y i960, a p e r i o d cover-i n g i n c u b a t i o n , i n a l l nests, were 6.0\u00C2\u00B0 and 27.0\u00C2\u00B0 C. We can s a f e l y conclude, t h e r e f o r e , that during .the season that the incubation temperatures were measured, the extreme a i r temperatures i n the nests i n v e s t i g a t e d would be c. 8\u00C2\u00B0 and 30\u00C2\u00B0 C. b. Minimal Egg Surface Temperatures As was mentioned above, d i f f i c u l t i e s of anchoring the eggs prevented me from o b t a i n i n g r e l i a b l e data showing change of upper surface egg temperatures through i n c u b a t i o n . I t i s of i n t e r e s t , though, to examine minimum temperatures during absence of the parent, now that the range of nest a i r temper-atures has been i n d i c a t e d . Data from 5 nests where the probe was taped to an egg i n which the embryo survived to the c l o s e of incubation give some idea of the c o o l i n g the egg may w i t h -stand without harm. The minima have been grouped i n Table 10. Chicks i n three of the nests (#7, #11, #43) hatched success-f u l l y , i n one (#9) the chick died i n pipping'because of the tape, and the l a s t .(#8) was l o s t i n a f r e a k accident. The parent snagged the l e a d - i n wire on day 24, and dislodged the egg ( c o n t a i n i n g a l i v i n g embryo) w i t h attached probe to the entrance, where i t was punctured and sucked by a crow. Obviously the c h i l l i n g r e s i s t a n c e of the embryo must match the c o n d i t i o n s normally met w i t h i n the nest. The only time when the .eggs of the Pigeon Guillemot are normally abandoned f o r long periods at low temperatures, i s overnight before steady i n c u b a t i o n has set i n . The temperatures given above, measured on the upper surface of the egg, must c l o s e l y 140 TABLE 10. COOLING OP THE.EGG DURING OVERNIGHT ABSENCE OP THE PARENT Day 1 Nest No. P a l l i n 2 Temperature (Degrees C.) Hours Exposure .1 # 7 15 - 13.0 at l e a s t 8 2 #43 15 - 13.8 at l e a s t 6 3 #43 \u00E2\u0080\u00A2 18 - 12.2 1 6 k 4 # 9 18 - 12.8** 5 ? 3f-5 # 9 27 - 13.2 5 #11 22 - 13.0 5 f 6 | 6 # 7 15 - 12.7 6 #11 22 - 14.0 5, 7 # 7 19 - 13.1** 1 12 # 8 20 - 12.4 NOTES: 1. Days are counted w i t h 0 the day the f i r s t egg i s l a i d ) since the embryos concerned were a l l A-eggs save #8, day w i l l give embryo age as w e l l . For #8 on day 12 the embryo was 9 days o l d . 2. Temperature gives f a l l the egg experienced i n the time span i n d i c a t e d . A l l absences are b e l i e v e d normal except the two marked **. approximate\"..// those the embryos experienced at such times. Young embryos commonly have a high c h i l l i n g r e s i s t a n c e (e.g., Moreng & Bryant 1956 on the fowl) but the record at 12 days is' of i n t e r e s t . Whether c h i l l i n g r e s i s t a n c e i s as w e l l developed as i n P r o c e l l a r i a p u f f i n u s i n v e s t i g a t e d by Matthews (1954), or i n f a c t the Tubinares as a whole (see Matthews) was not i n v e s t i g a t e d . L a t e r , during steady i n c u b a t i o n , i t was unusual f o r the upper egg-surface t o f a l l below 20\u00C2\u00B0 C In the b r i e f periods when the eggs were l e f t uncovered. 141 c. Brood-patch Temperature In nest #43 a f i n e f l e x i b l e probe was employed, which the b i r d s t o l e r a t e d atop the egg. F o r t u n a t e l y the s o i l f l o o r i n t h i s nest allowed me to anchor the egg f a i r l y w e l l by burying the l e a d - i n w i r e . I had some t r o u b l e w i t h egg movement, but secured two s e r i e s during the l a y i n g p e r i o d , and 10 from the 11th day on to the 28th day, when the probe was removed. Both eggs hatched on the 31st day (incubation-days are reckoned by counting the day the f i r s t egg was l a i d as 0 ). These data give temperature at the i n t e r f a c e of brood-patch and egg-surface, and thus correspond w i t h Farner's \"(1958) 'incubation temperature' and Westerskov's (1956),'brood-patch temperature 1, a term I w i l l employ a l s o . I could v e r i f y r e s u l t s from nest #43 i n the more a c c e s s i b l e nest #12, where an i d e n t i c a l probe was used. Here the f l o o r of loose chips on s o l i d rock prevented me from s i m i l a r l y anchoring the egg, but the i n c u b a t i n g male was captured s e v e r a l times d i r e c t l y a f t e r I had recorded the temperature. Thus a check of reading versus probe p o s i t i o n could be made, and s e v e r a l c r i t i c a l readings as w e l l as a long s e r i e s on day 9 were obtained. The r e s u l t s have been set out i n Table 11 and F i g . 50. In nest #12 the readings are s e l e c t i v e as explained above. The readings i n nest #43 represent a l l that were secured i n a t t e n t i v e periods on the day concerned, except f o r day 2 and 3 , where only the s t a b l e p o r t i o n s were considered. Almost a l l readings here were obtained w i t h the male i n c u b a t i n g , 142 TABLE,11. BROOD PATCH TEMPERATURES IN.THE PIGEON GUILLEMOT Nest * Day Date ( i960) # of Readgs. T t l . Mins. D e Mean g r e e s Min. C.. Max. 43 2 17 June 26 110 \u00E2\u0080\u00A2 34 .6 , 3 1 . 8 39.1 43 3 18 June 26 110 34.3 31.0 36.2 43 11 26 June I65 825 39^1 36.2 42.4 43 12 27 June 39 195 39.5 37.2 . 41 .0 43 14 29 June 37 . 185 39.5 37 .8 40.5 . 43 18 3 July 187 935 39.5 36.8 42.0 43 19 4 July 40 200 39.4 36.4 42.0 43 20 5 July 43 215 39.4 3 6 . 8 42 .0 43 25 10 July 21 105 39.8 36.7 .41 .5 43 26 11 July 22 110 38.7 37.1 39.3 43 27 12 July 37 185 40.2 36 .8 41.5 43 28 13 July 27 135 40.2 39.1 41.5 43 Day 11 to 28 i n c l . 618 3090 39.4 36.2 42 .4 41.3 39.1 37 .7 . 4 2 . 4 42.5 Days are reckoned as follows: 0 , day of f i r s t egg; the second and l a s t egg was l a i d day 3 in each nest; at the time the read-ings in 43 were taken on day 3 the second egg had not yet appeared. Bird captured on eggs and probe po s i t i o n v e r i f i e d . 12 6 23 June (l) 12 9 26 June 23 115 12 37 24 July (1)** 42 \u00E2\u0080\u00A28 1 40 ^ 38 II llll III I 29 / A 29 min B , 1 1 1 Average intervals, i i i i i i j i i i i laying to hatching i i i i i i i i i i i i i 36 34 32 O O O O IJ' \u00C2\u00B0 nest 43 \u00E2\u0080\u00A2 nest 12 i i i i i i i i i i i J I I J I L. 1 1 I I I o 5 10 15 20 25 30 Day of incubation Fig. 50 BROOD-PATCH TEMPERATURE Pigeon Guillemot cf cr cr cr \u00E2\u0080\u00A2^40\u00C2\u00B0 s 20 1 flexible probe atop first egg 9 _9 second egg is laid cr 10' 0 { air temperature in blind at 2 m. 7 nest 43 day 3 8 9 Time a.m. Fig 51 INCUBATION TEMPERATURE DURING LAYING I 8 - \u00C2\u00BB 4<9 \u00C2\u00A7 K . or 9 cr cr 9 9 cr cr nest * 7 8 + 48 -> 43 I nest 7 -> .9 \u00E2\u0080\u00A2> 48 down briefly \u00E2\u0080\u00A2i \u00E2\u0080\u00A2 t * ti comes: 1 flies ashore at off to perdt-site (- feeding grounds 7 9 V // L _ f _ +_ t _ j\u00E2\u0080\u009E (\u00E2\u0080\u0094}\u00E2\u0080\u0094f \u00E2\u0080\u0094t\u00E2\u0080\u0094t- -j -1 - h-\\u00E2\u0080\u0094i\u00E2\u0080\u0094\u00E2\u0080\u0094\\u00E2\u0080\u0094t\u00E2\u0080\u0094i\u00E2\u0080\u0094t~H 1 Day 20 ry flies in from north* 1 ) \Jl down down, returns, joins briefly, gull Q bathes and in water games etc disturbance + 9f fJ\u00C2\u00B0l' S/ and 33 days. When there were two.chicks In the nest, they d i d not n e c e s s a r i l y leave on the same day. Of the f i v e cases a v a i l a b l e , the chicks l e f t on the same day i n 2 (#9, #43), one day a p a r t . i n 2(#8, #11), and 3 days apart i n 1 (#36). In summary, the l a r g e s t group of records of n e s t l i n g p e r i o d i n the T y s t i e anywhere i n i t s range appears to be that from Mandarte I s l a n d . Here 15 observations gave a mean of 35 days,, and ranged from 29-39 days. C. Feeding 1. Food Species In the manner c h a r a c t e r i s t i c of the f i s h - f e e d i n g (as d i s t i n c t from plankton-feeding) auks,. the T y s t i e parents b r i n g whole f i s h to t h e i r young. The a d u l t s f l y i n from the feeding area c a r r y i n g one f i s h at a time, grasped by the head and dangling from the b i l l . Food h a b i t s of the T y s t i e have been e x t e n s i v e l y s t u d i e d (Madsen 1957, B e l o p o l s k i 1957 i n Kartaschew i960) and S t o r e r (1952: 138-139) has c o l l e c t e d 172 i n c i d e n t a l observations i n the l i t e r a t u r e . Winn (1950) and Thoresen & Booth (1958). have commented on the types of food brought, to the chicks i n t h e i r study areas.- S u f f i c e It. here to say that' the T y s t i e i s predominantly a f i s h - e a t e r , i n v e r t e b r a t e s a l s o being taken ( c h i e f l y Molluscs,- Crustaceans, and Polychaete worms), and f u r t h e r that the young are a l s o predominantly:raised on f i s h . At Mandarte I s l a n d the chicks are fed almost e n t i r e l y \u00E2\u0080\u00A2on f i s h . Observations from the n o r t h b l i n d (3 nests i n 1959, 2 nests i n i 9 6 0 ) provide some f i g u r e s . Of 662 items seen d e l i v e r e d over the whole c h i c k stage, 508 were d e f i n i t e l y f i s h , 6 were shrimp (Crustacea:.Malacostraca) and the remaining ikS were seen too b r i e f l y to be recognized. (At a distance some s c u l p i n s look l i k e shrimp.) -At no time were Polychaetes brought, i n f a c t the only i n v e r t e b r a t e recorded besides the shrimp was a . s i n g l e small squid, a p e r f e c t specimen of which was found d e l i v e r e d to one nest., but not eaten by the c h i c k s . This Cephalopod has been sent away f o r -determination, but r e s u l t s not yet r e c e i v e d . From the above data, t h e r e f o r e , f i s h formed a t . l e a s t 77$ o f the food brought t o the c h i c k s . Doubtless the percentage was i n r e a l i t y higher than t h i s , as i n the c l o s e s t nest to the b l i n d 128 of the 131 Items seen d e l i v e r e d could be i d e n t i f i e d , and a l l were f i s h . 173 TABLE 18.. SOME FOOD SPECIES OF PIGEON GUILLEMOT CHICKS AT MANDARTE ISLAND Petromyzonidae--Lampreys **Lampetra ayresi Gasterosteidae--Sticklebacks Gasterosteus aculeatus Embioticidae--Sea Perches Cyma'togaster aggregatus Ammodytidae--Sand Lances **Ammodytes tobianus X i p h i s t e r i d a e \u00E2\u0080\u0094 B e l t e d Blennies (sight records) Pholidae--Gunnels River Lamprey 3-spined Stickleback (sight record) Yellow Shiner (sight record) Sand Lance **Pholis laetus Bracketed Blenny Stechaeidae--Northern Blennies **Delolepls giganteus Lumpenidae\u00E2\u0080\u0094Eel-blennies **Lumpenus a n g u i l l a r i s Scorpaenidae--Rock-fishes (sight records) Cottidae--Sculpins *'*Leptocottus armatus Wry-mouth Eel-blenny **Myoxocephalus poly-acanthocephalus t**Triglops beani Cabezon Great Sculpin Ribbed Sculpin Ramphocottidae--BIg-headed Sculpins Grunt-fish Ramphocottus richardsoni (sight record) denotes specimen(s) i d e n t i f i e d by Dr. C C . Lindsey. The f i s h b r o u g h t . t o t h e y o u n g were c l a s s e d whenever p o s s i b l e a s : l ) l a m p r e y s ( P e t r o m y z o n t i d a e ) . 2S s t i c k l e b a c k s ( G a s t e r o s t e i d a e ) 3) s h i n e r s ( E m b i s t i c i d a e ) ,4) sand l a n c e (Ammodytidae) 5) B l e n n i e s ( X i p h i s t e r i d a e , P h o l i d a e , S t e c h a e i d a e , L u m p e n i d a e ) 6) r o c k f i s h ( S c o r p a e n i d a e ) 7) s c u l p i n s ( C o t t i d a e ) 8) G r u n t - f i s h . ( R a m p h o c o t t i d a e ) , 9 ) s e a - p o a c h e r s ( A g o n i d a e ) - \u00E2\u0080\u00A2 10) f l a t f i s h ( B o t h i d a e , P l e u r o n e c t i d a e ) ( P i s h n o m e n c l a t u r e t h r o u g h o u t f o l l o w s Clemens & W i l b y 19^9, C a r l , C l e m e n s , & L i n d s e y 1 9 5 9 ) . T h i s r o u g h d i v i s i o n was made whenever t h e f i s h c o u l d be s p o t t e d w i t h 7x b i n o c u l a r s , o f t e n v e r i f i e d by 25x t e l e s c o p e as w e l l . S p e c i e s i d e n t i f i c a t i o n was p o s s i b l e i n o n l y a few c a s e s , b u t on my d a i l y h a n d l i n g o f t h e c h i c k s i n b o t h s e a s o n s a number o f s p e c i m e n s were c o l l e c t e d . I n a few c a s e s , where t h e c h i c k s had been b u t r e c e n t l y f e d , i t was p o s s i b l e t o e x t r a c t n e a r - p e r f e c t s p e c i m e n s f r o m t h e g u l l e t , and a number o f f i s h e s were f o u n d on t h e n e s t f l o o r . These were c l a s s e d as f o o d s p e c i e s o r r e j e c t s p e c i e s on t h e b a s i s o f s i z e , s h a p e , and numbers f o u n d . I n f o r m a t i o n on t h e f i s h s p e c i e s u s e d as f o o d by t h e P i g e o n G u i l l e m o t c h i c k s on M a n d a r t e i s c o l l e c t e d i n T a b l e 1 8 . The s p e c i m e n s s u b s t a n t i a t e t h e o b s e r v a t i o n a l c a t e g o r i e s , and j u s t i f y m e n t i o n o f q u a n t i - , t a t i v e r e s u l t s . C o u n t s o f f o o d t y p e s d e l i v e r e d t o t h e n e s t s o b s e r v e d f r o m t h e n o r t h b l i n d a r e c o l l e c t e d i n T a b l e 19a and 1 9 b . They i n d i c a t e b l e n n i e s and s c u l p i n s as t h e m a i n i t e m s , t h e s e 175 making up at l e a s t 55$ of the t o t a l between them. Since the sample i s small (both in.time and number of n e s t s ) , and over 20$ -of the items u n i d e n t i f i e d , i t i s not j u s t i f i a b l e to regard the f i g u r e s as v a l i d i n d e t a i l f o r the food d e l i v e r e d at Mandarte I s l a n d . The main value of the counts i s that the great, v a r i a b i l i t y between nests i s made c l e a r , a v a r i a b i l i t y to be explained by i n d i v i d u a l feeding preferences of the a d u l t s . The main r e s e r v a t i o n i n making comparisons, i s to bear i n mind that many of the ' u n i d e n t i f i e d 1 items are l i k e l y to be s c u l p i n s . However i t i s q u i t e c l e a r t h a t the b i r d s i n nest #11 brought many more s c u l p i n s than, those i n nest #14; that f l a t f i s h were brought p r i m a r i l y t o nests #48 and #14, and so f o r t h . The share of the sexes i n nest #14, where p r a c t i c a l l y a l l items could be i d e n t i f i e d , . i s i l l u m i n a t i n g . The male was d e f i n i t e l y a blenny-s p e c i a l i s t , whereas the female brought a wide assortment,, i n c l u d i n g l a r g e numbers of f i s h r a r e l y aqcepted by the c h i c k (sea poachers and f l a t - f i s h ) . There i s some evidence that i n d i v i d u a l s p r e f e r c e r t a i n feeding areas--,thus b i r d s from nest #48 were the only ones to use Gooch Island.waters--but.systematic observation on t h i s p o i n t was impossible due to l i m i t e d v i s i b i l i t y of the Sidney I s l a n d s h o r e l i n e , the main feeding area, from the b l i n d . The second c o n c l u s i o n to be drawn from the counts i s t h a t the sexes take an equal share i n feeding the c h i c k s . The parents at nest #43 show.almost e x a c t . e q u a l i t y (52-48$) and i n nest #14 the pr o p o r t i o n s are l i k e w i s e close (45-55$). This i s a l l the more s t r i k i n g since the parents at nest #14 were of very d i f f e r e n t temperament. The male ( o l ) was n o t i c e a b l y phlegmatic, and spent a good deal of the time dozing on the l e v e l rock TABLE 19a. TYPES OP FOOD.BROUGHT TO 5 NESTS, PIGEON GUILLEMOT 1 9 5 9 1 9 6 0 Food type #48 #11 #14 #11 #43 Totals Petromyzontidae 3 1 2 5 11 Gasterosteidae 1 1 5 7 E m b i s t l c i d a e 1 1 2 3 7 Ammodytidae 6 1 24 31 X i p h i s t e r i d a e et a l . 20 108 75 23 20 246 Scorpaenidae 1 4 5 10 -Cottldae 1 74 12 29 116 Ramphocottidae 1 1 2 Agonidae - 38 11 11 Bothidae, Pleuronectidae 4 21 2 65 F i s h spp. (? L i p a r i d a e ) 2 2 T o t a l f i s h 6o 198 - 128 63 59 508 Shrimps 6 48 6 U n i d e n t i f i e d 31 39 3 27 148 T o t a l s - 91 243 131 90 107 662 TABLE '19b. SHARE OF .'THE SEXES IN FEEDING/ PIGEON- GUILLEMOT Nest 14 1959 Nest 43 I960 Food type ; M F ? M F ' ? Petromyzontidae 1 1 4 \ Gasterosteidae 1 5 Emb i s t l c i d a e 3 Ammodytidae 4 20 X i p h i s t e r i d a e e t c . .50 15 10 15 2 3 Scorpaenidae 4 Cottidae 8 4 Ramphocottidae 1 Agonidae 11 Bothidae, Pleuronectidae 1 20 2 F i s h spp. (?Liparidae) 2 U n i d e n t i f i e d 1 2 ' 2 5 15 '8 T o t a l s ~52 54\" 15 50 45 ~TT K5% 55$ 52$ 48$ EXPLANATION:. The above t a b l e s are compiled from a l l observations covering the c h i c k stage c a r r i e d out from the north b l i n d . Three nests where feeding occurred were observed i n 1959, 2 i n I960. In nest #14 (1959) and #43 (l96o).the parents were banded. Food types were i d e n t i f i e d by -sight; consult the t e x t . 177 near the nest entrance. The female, on the other \u00E2\u0080\u00A2hand, was shy, and often h e s i t a t e d t o c a r r y the f i s h below, an operation i n v o l v i n g a drop down a narrow v e r t i c a l c r e v i c e before the nest chamber could be reached. When the female paused at the entrance w i t h f i s h i t was common p r a c t i c e f o r the male to snatch the f i s h from her and b r i n g i t below hims e l f . Nevertheless the number of f i s h caught by each was very n e a r l y equal. There remains to be discussed the c u r i o s i t y of ' r e j e c t f i s h ' , that i s , f i s h brought by the parents but not accepted by the young. I t w i l l be remembered th a t nest ' #14 and #48 r e c e i v e d many f l a t f i s h , #14 i n a d d i t i o n sea-poachers. These seemed awkward f i s h f o r the c h i c k s to handle, and i t was no great . s u r p r i s e to f i n d hoards of the r e j e c t e d carcasses of these f i s h i n the nests concerned. Nest #48 held more than 2 dozen f l a t f i s h , nest #14 an even l a r g e r number of sea-poachers i n a v a r y i n g s t a t e of pre-s e r v a t i o n . I do n o t . t h i n k that the c h i c k s ever eat the sea-poachers, formidable armoured forms, but 'they may eat the f l a t f i s h r a r e l y , as I could not account f o r a l l that were seen .d e l i v e r e d . Rejects of both types were a l s o found i n other n e s t s . Specimens that c o u l d . s t i l l be i d e n t i f i e d are given i n Table 2 0 . The s u p p o s i t i o n i s that,the c h i c k s cannot swallow .these formsj c e r t a i n l y i f they d i d make the attempt, the r e s u l t s might be f a t a l . In C a l i f o r n i a Legg (1954) made almost d a i l y v i s i t s t o a Pigeon Guillemot nest, and found r e j e c t e d f i s h four 1 7 8 TABLE 2 0 . .REJECT FISH SPECIES FOUND .IN PIGEON GUILLEMOT NESTS Agonidae--Sea Poachers A v e r r u n c u s emmelane Anoplagonus i n e r m i s Bothidae--Sand-dabs C I t h a r i c h t h y s s p s . P l e u r o n e c t i d a e - - F l o u n d e r s L e p i d o p s e t t a b i l i n e a t a P a r o p h r y s v e t u l u s ? Limanda a s p e r a W i n d o w - t a i l e d Sea-poacher Smooth Sea-poacher Rock S o l e ' Lemon S o l e ? Y e l l o w f i n S o l e ( i d e n t i f i c a t i o n n ot c e r t a i n ) t i m e s . These were 1 C I t h a r i c h t h y s s o r d i d u s ( 1 0 6 mm)and 3 Sebastodes j o r d e n i i ( 1 2 1 , 1 3 5 , 1 3 5 mm), a l l of w h i c h , Legg c o n c l u d e s , were t o o awkward f o r the c h i c k s t o s w a l l o w . I t w i l l be n o t e d t h a t sand-dabs a l s o were found r e f u s e d on Mandarte. The o n l y d e a t h t h r o u g h c h o k i n g on a f o o d i t e m n o t e d on Mandarte, o c c u r r e d w i t h an o v e r s i z e b l e n n y . The c h i c k , a l m o s t r e a d y t o l e a v e the n e s t , was found dead, w i t h t h e t a i l of' the b l e n n y p r o t r u d i n g f r o m t h e mouth. E x a m i n a t i o n showed th e f i s h so t i g h t l y l o d g e d t h a t i t . c o u l d n o t be removed w i t h o u t s l i t t i n g t h e b i r d ' s t h r o a t . 1 7 9 U n f o r t u n a t e l y the head of the blenny was already digested so t h a t . i d e n t i f i c a t i o n and measurement was no longer p o s s i b l e . Judging from the circumstances death by choking seems obvious. I have not.run across r e p o r t s of choking i n other auk c h i c k s , but c e r t a i n l y a d u l t f i s h - e a t i n g b i r d s o c c a s i o n a l l y choke on t h e i r prey. I have n o t i c e d the f o l l o w i n g accounts: Podiceps grisegena Pelecanus o c c i d e n t a l i s Ardea herodias Mergus merganser Larus argentatus Larus glaucescens Dead; choked on s c u l p i n , prob. Priochthys notatus Holdom 1 9 4 7 Observed to choke t o death on huge Archosargus probatocephalus. S t u l l k e n 19W. 1 5 \" c a t f i s h lodged i n g u l l e t ; f i s h e x t r a c t e d and b i r d r e l e a s e d a l i v e . Cooch 1 9 4 6 . D i e d from choking, on carp. Ryder 1950. Dead; choked o n . s c u l p i n . (64gm). Wick & ;Rogers 1 9 5 7 . Pead; choked on m u l l e t . Paynter 1 9 4 7 . Dead; choked on f i s h . Holdom 1947. 2 . Feeding Rate Data on feeding r a t e are again taken from the north b l i n d note-books, where feeding was watched i n 3 nests i n 1 9 5 9 , and i n 2 i n . 1 9 6 0 . When i s the c h i c k f i r s t fed? .Some workers I n d i c a t e that f i r s t f eeding does not take place f o r s e v e r a l days,\u00E2\u0080\u00A2the chicks s u b s i s t i n g on the remnants of the 1 8 0 y o l k sac (Thoresen & Booth 1 9 5 8 , Kartaschew i 9 6 0 ) but my records i n d i c a t e that f i s h are d e l i v e r e d t o the nest s t a r t i n g n o . l a t e r than the age of one day. The chicks i n nest #11 i n 1 9 5 9 both hatched on the same day. I t happened that no observations were made then, but on day 1 , three f i s h were seen d e l i v e r e d between 0 6 2 5 and 1045. The young i n nest # 4 3 i n i 9 6 0 a l s o hatched simultaneously. Again the e a r l i e s t observations were made the f o l l o w i n g day, where 4 f i s h were d e l i v e r e d between o 3 4 5 - 1 0 3 0 . There i s an a l l - d a y observ-a t i o n ( o 4 0 0 - 2 0 0 0 ) when the c h i c k s i n t h i s nest were 3 days o l d . Twelve f i s h were d e l i v e r e d i n the p e r i o d , though the parents were s t i l l brooding most of the day. Feeding a l s o proceeded i n nest #11 when.the chicks were 2 days and 3 days o l d , and a l l days t h e r e a f t e r . Thus there are d i r e c t observations of f i s h being d e l i v e r e d to two nests where the young had.hatched simultaneously, and were only 1 day o l d ; they were a l s o fed at 2 and 3 days and a l l subsequent days. As i n d i r e c t .evidence of feeding at an e a r l y age, growth records show an average increase i n weight from day 0 to 1 , 1 to 2 , e t c . I t i s a l s o c l e a r that feeding continues so- long as the c h i c k i s i n the nest. In the three nests watched from the b l i n d where the chicks l e f t the nest normally, and the date of departure was determined, feeding continued on the l a s t day the chicks were present i n a l l three. In two nests the banded parents even returned w i t h f i s h the f o l l o w i n g morning, when the chicks had already l e f t . .The i n t e r e s t i n g question of how the r a t e of feeding may vary through the c h i c k stage, cannot be f u l l y answered by my data. I found 181 that the counts from the 4-hour morning observation periods represented too small a segment of the day f o r s a t i s f a c t o r y comparison, so can o f f e r only a few comments on the longer spans of observation, c o l l e c t e d i n Table 21. Comparison of feeding t r i p s t o nest #11 and #43 on 19 J u l y , I960, w i t h those to nest #11 on 9 August 1959, w i l l show an increase i n r a t e w i t h age. On the i 9 6 0 date the c h i c k s , 3-5 days o l d , r e c e i v e d 6 . f i s h each, on the aver-age, w h i l s t on'the 1959 date the 31 day o l d chicks averaged 12 each (each date o400-2000). Again, each c h i c k i n nest #43 14 August i 9 6 0 , when 29 days o l d , had already r e c e i v e d 6 f i s h i n the p e r i o d o455-1045, compared w i t h the 6 f i s h f o r the e n t i r e o400-2000 when 3 days o l d . The increased feeding w i t h age suggests that the demands of the young i n f l u e n c e the parents t o b r i n g more food. I f , then, hunger of the c h i c k s i s an important f a c t o r i n feeding r a t e , nests w i t h s i n g l e chicks should not r e c e i v e much more,;on the average, than h a l f of that d e l i v e r e d to nests w i t h two c h i c k s of comparable age. R e s u l t s of the o400-2000 9 August 1959 observations comparing nest #11 (two chicks) w i t h #14 (one chick) seem at f i r s t . t o r e f u t e t h i s . #11 r e c e i v e d 23 f i s h , #14 18. However, the records showed that of the f i s h brought.to nest #14, one was never d e l i v e r e d (parent chased o f f by g u l l ) , and 4 others were of the ' r e j e c t c l a s s ' , i . e . , would not be eaten by the chick. A l l brought to #11, on the other hand, were s u i t a b l e as food, and s a f e l y d e l i v e r e d . In TABLE 21. RATE OP FISHTRIPS TO ; YOUNG IN PIGEON GUILLEMOT 9 August,- 1959 o400-2000 19 J u l y , I 9 6 0 o400 - 2 0 0 0 17 July,\u00E2\u0080\u00A2i960 O345-1030 ..24 J u l y , i960 o420-1030 14 August, i 9 6 0 o 4 5 5 - 1 0 4 5 #11 # 1 4 o 4 4 5 o 5 2 0 m o446 0 6 5 7 m 0 5 0 0 * o 7 2 9 f o54o o 8 0 1 m 0 6 2 1 0 8 5 0 m o84o * o 8 5 1 f 0 8 5 8 o 9 0 1 m o 9 4 5 * o 9 l 4 f o 9 4 9 o 9 5 1 f o 9 5 3 1 0 2 3 f 1044 1114 f 1 1 2 7 . 1 4 0 9 m 1 1 3 8 1 5 5 0 m 1 1 5 6 * '1553 f 1 2 0 7 1 7 2 0 m 1 2 2 8 * 1 7 3 5 f 1 2 4 5 1 8 3 7 m 1 3 3 8 1 9 2 5 m \u00E2\u0080\u00A21412 1 4 3 0 1 5 0 9 1 5 2 3 1 7 2 2 2 3 f i s h \u00E2\u0080\u00A218 f i s h 2 chicks 1 chick days gm days gm 3 1 4 1 0 c 2 3 ? 3 1 440 #11 0 7 3 2 0 8 3 3 1016 1106 ii4o 1507 1515 1611 1747 1757 1816 1830 1932 13 f i s h 2 chicks days gm a 3 6 3 b5 90 #43 0 5 0 0 m 0 5 3 0 ? o 7 3 4 ? 0 8 1 9 m 1 1 1 3 m 1 5 1 8 f 1 5 3 9 m 1 6 5 3 f 1 7 0 5 m 1 8 3 4 m 1 9 1 2 ? . 1 9 5 5 ? 12 f i s h 2 chicks days gm a3 62 b-3 68 #11 o 4 3 0 0 5 0 1 0 6 3 0 0 7 0 6 0 7 1 1 0 8 0 2 6 \" f i s h 2 chicks days gm a l 40 b3 80 #43 0 7 1 8 f o843 m , 0 8 5 7 m 0 9 0 3 m 4 f i s h 2 chicks days gm a l 45 b l 50 #11 o 4 2 2 0556 0810 085O o 9 2 7 o 9 3 3 2 chicks days gm a 8 116 blO 170 #43 o448 f 0 5 3 8 m o 6 0 4 f 0 6 2 0 f 0 6 3 8 f 0 7 3 8 f 0 8 1 7 m o 9 4 0 f 1 0 1 1 f 2 chicks days gm a 8 1 2 8 b 8 1 3 8 # 4 3 0 5 0 0 f 0 5 5 0 m 0 6 1 5 f 0 6 2 8 m 0 6 2 9 f o 7 1 7 m 0 8 2 8 m 0 8 3 6 f o 9 4 4 f 0 9 5 8 m 1 0 2 5 f 2 c h i c k s days gm a 2 9 3 8 2 b 2 9 3 8 6 EXPLANATION. The t a b l e l i s t s the times of d e l i v e r y of f i s h t o the nest on the 5 longest observation periods, a l l under n a t u r a l c o n d i t i o n s . Where the parents were marked, the t r i p s are given as m (male) f (female) or ? (unknown). * at nest #14 i n d i c a t e r e j e c t c l a s s f i s h (see t e x t ) The number, ages, and weights of the chicks i n each nest i s given below, the column f o r that nest. \"a\" i n d i c a t e s young from ,the f i r s t egg, \"b ' that from the second. , f a c t , then, the s i n g l e c h i c k i n nest #14 r e c e i v e d 13 e d i b l e f i s h , compared, w i t h an average of 112 f o r each of the two chicks i n #11. Important evidence f o r the view that the demands of\u00E2\u0080\u00A2the chick, and not r i g i d h a b i t s of the a d u l t s , c o n t r o l feeding r a t e i s the f a c t that s i n g l e chicks do not grow f a s t e r , or leave the nest e a r l i e r , than chicks brought , up together w i t h another. An experiment t o show i n f l u e n c e of chicks on .feeding r a t e was c a r r i e d out 7 August i960 (Table 22). Nest #11 and #43' each\u00E2\u0080\u00A2held two c h i c k s , of l i k e age (21, 23 ahd 21, 21 days o l d ) . One of the #11 chicks was s h i f t e d to nest #43 at o430, and the feeding t r i p s from o435-1930 .recorded. The t h r e e - c h i c k nest was expected,to r e c e i v e more f i s h than the one-chick nest, p r o v i d i n g \u00E2\u0080\u00A2 t h a t the parents reacted to the change w i t h i n the day. In .fact #43 r e c e i v e d 35 f i s h , compared t o 20,in- #11. Weights of the chicks (taken at o430, before the change, at 1100, and f i n a l l y at. 1930 \u00E2\u0080\u00A2before the #11 c h i c k was replaced i n . h i s nest) are r e v e a l i n g . The chicks i n #43 made l i t t l e or no gain before 1100, though f i s h had been r e c e i v e d w i t h i n the l a s t hour, whereas the s i n g l e c h i c k i n #11 had put on 60 grams, though h i s l a s t f eeding had been almost 2 hours preceding weighing. I t can be imagined that the three chicks i n #43 were by then very hungry, and i n f a c t the male parent put on an a s t o n i s h i n g performance i n the e a r l y afternoon, b r i n g i n g 10 f i s h i n l e s s TABLE . 2 2 . FEEDING RATE EXPERIMENT 7 August, I960 F i s h T r i p s A g e & W .e i g h t D a t a (chicks) O 4 3 5 - 1 9 3 0 #11 ' # 4 3 11 P l a i n (a); alone in nest #11 Weight Age o 5 0 4 o 4 4 4 o 4 3 0 . 2 9 6 .0 2 2 days old o 5 1 2 o 5 0 3 m 1 1 0 0 3 5 5 5 9 at 2 1 days old, 3 2 6 gxn. o 5 4 5 o 5 4 0 f 1 9 3 0 3 6 0 64 2 3 days old, 3 5 2 o64l 0 5 5 8 m o648 o644 f o648 o 7 4 2 m 0 6 5 9 0 8 0 9 ? 11 Blue (b); sh i f t e d to nest # 4 3 0 8 1 9 . o 9 4 l f o 9 1 9 1 0 0 0 f Weight Age 1 2 5 9 1 0 5 4 f o 4 3 0 3 3 2 0 \u00E2\u0080\u00A2 2 4 days old 1 3 1 6 1145 f 1 1 0 0 3 2 6 - 5 at 2 3 days old, 3 4 4 gm. 1420 1 2 5 4 m 1 9 3 0 3 3 0 - 2 2 5 days old, 3 6 9 1 4 2 6 . 1 3 4 0 m 1 5 0 1 1 3 4 5 m 1 5 1 8 1 3 5 1 m 1 5 4 2 1 3 5 5 m 4 3 Green (a); l e f t i n nest # 4 3 1 6 1 8 1 3 5 9 m 1 7 0 2 1 4 0 8 m Weight Age 1 8 1 0 1 4 1 3 m o 4 3 0 2 9 8 0 2 2 days old 1 8 5 5 1 4 1 8 m 1 1 0 0 3 1 2 14 at 2 1 days old, 346 gm. 1 4 2 3 m 1 9 3 0 3 3 6 . 3 8 2 3 days old, 3 5 5 1 4 2 9 m 1 4 4 3 f 1 4 4 7 m 1 5 4 5 m 4 3 Plain (b); l e f t i n nest # 4 3 1 5 5 0 m I613 ? Weight Age 1 6 3 0 ? o 4 3 0 3 1 2 0 .22 days old 1 6 4 1 ? , 1 1 0 0 3 1 2 \u00E2\u0080\u00A2 0 at 2 1 days old, 3 2 6 gm. 1 7 0 0 ? 1 9 3 0 3 3 8 2 6 at 23 days old, 3 2 8 gm. 1 7 1 5 ? 1 7 3 0 f 1 7 3 2 m 1 8 2 0 ? 1 9 1 0 m 2 0 f i s h 3 5 f i s h 1 chick 3 chicks (experimental) EXPLANATION. At o 4 3 0 one of the two chicks of nest #11 was shifted to nest # 4 3 ; t h i s l e f t nest #11 with one chick, and nest # 4 3 with three, a l l of them being about the same age. The number of f i s h brought to each nest through the course of the day i s shown at l e f t . The chicks were weighed-at transfer ( o 4 3 0 ) again at 1 1 0 0 , and again at 1 9 3 0 , when the experiment was terminated and the chick returned to i t s r i g h t f u l nest. On the right.the weights ( i n grams) and weight change, age of the chicks, and weights on preceding and following days are given for the four chicks involved. time in hours 1 ' I 1 I ' I 1 1 ISO 4 8 . 12 16 20 h 9 August 1959 a a a cxr cr cr cr cr cr ^ 14 1 1 1 1 H-H 1\u00E2\u0080\u0094I 1 - 1 H H \\u00E2\u0080\u0094 1 C.23 ^ 99 9 9 9 9 9 | / / I H 1 1 : H \u00E2\u0080\u0094 I H 1 1 I I I I I 1 M H 1 31,31 ^ 19 July I960 % c7 c f c r c r c r c r 43 i ' 1 \u00E2\u0080\u0094 i 1 +H \u00C2\u00A3 1 \u00E2\u0080\u0094 i \u00E2\u0080\u0094 II 1 ~\ H 1 1 h H 1 H \u00E2\u0080\u0094 H 1 3fi 7 August I960 c r c r c r cy\u00E2\u0080\u0094 - c r cxr cr cr 43 - \u00C2\u00BB \u00E2\u0080\u0094 1 \u00E2\u0080\u0094 H 1 h H \u00E2\u0080\u0094 i 1 1 H 1 mn imi II II i 11 i i I I \u00E2\u0080\u0094 i H - P22222 9 9 9 9 9 9 9 9 9 9 / / H 1 \u00E2\u0080\u0094 H H 1 1 1\u00E2\u0080\u0094I H H - H 1 1 1 1 24 EXPLANATION vertical bars mark times of fish delivery at nest, horizontal line the period of observation. 4 6 8 /0 /2 /4 16 18 20 1 i i . J i i . i i i . i i \u00E2\u0080\u00A2 i time in hours Fig. 55 FEEDING RATE than an-hour. By the close of the day the two ' r i g h t f u l \" #43 chicks showed a good gain? and .the #11 1 v i s i t o r * was s t i l l about the same--so one can assume that he had received some. food, through the day. The l a t t e r chick made good his loss the following day, when :he undoubtedly was quicker to snatch the f i s h from the incoming parents than.his satiated nest-mate. The reverse shift--one of the #43 chicks to nest #11\u00E2\u0080\u0094was planned for 10 August, but most unfortunately both chicks i n nest #11 were k i l l e d (probably by well-grown g u l l chicks) on the 9 t h . The r e s u l t s from t h i s one day, then, must remain\u00E2\u0080\u00A2suggestive rather\u00E2\u0080\u00A2than conclusive. On the d a i l y pattern of feeding, the data given i n the tables, and plotted i n Pig. 55 w i l l show.that feeding continues throughout the daylight\u00E2\u0080\u00A2hours. I have been able to f i n d no simple t i d a l c o r relation, nor. any favoured period of the day f o r feeding t r i p s . Thoresen's data (Thoresen & .Booth 1958: Table VI):. likewise shows feeding well d i s t r i b u t e d through the day. Turning now to compare rate of feeding in the Pigeon Guillemot to that In other auks, quantitative data are available for Fratercula a r c t i c a , Uria aalge, and Alca torda. Lockley (1953: 93-105).found that Fratercula chicks receive, on the average, less than two feeding t r i p s per day, but as over 20 f i s h may be delivered at a time (p. 96) i t i s impossible to make comparisons. The murres, however, 186 b r i n g but one f i s h at a time, so Tschanz's -{1959' Table 17) data on number of f i s h brought by U r i a aalge i n the course of a watch o700-1900 at l e a s t make a rough comparison p o s s i b l e , n e g l e c t i n g t h e i n f l u e n c e of d i f f e r i n g f i s h s i z e . The murres brought but 4-5 f i s h - i n the day, and f i g u r e s f o r A l c a torda (Paludan 1947) i n d i c a t e a s i m i l a r low number. D. Growth The purpose of t h i s s e c t i o n i s simply to record my f i g u r e s on growth i n weight of the Pigeon Guillemot, from hatching to nest departure. E v e n t u a l l y an e c o l o g i c a l compari-son of growth r a t e i n , sea-birds ( o u t l i n e d f o r the auks by Kaftanowski 1951) as has been done f o r Passeres (von Haartman ,1954) w i l l be p o s s i b l e , but we must await f u r t h e r m a t e r i a l before t h i s can be p r o f i t a b l e . Table 23 and Pig.5 6 summarize weight records f o r \u00E2\u0080\u00A211 chicks i n 1959? 19 i n i 9 6 0 . This was the number of chicks of known hatching date s i t u a t e d i n a c c e s s i b l e nests, and i t i s unfortunate that p a r t i c u l a r l y i n i 9 6 0 many died before nest departure. The b i r d s were weighed d a i l y , . a t midafternoon, employing s p r i n g -balances. In .1959 two commercial balances were used, the f i r s t covering the range 0-150 grams, and accurate to the nearest 5 gm. (as determined by comparison w i t h a triple - b e a m balance), the second being used f o r a l l .subsequent.readings, and accurate to the nearest 10 grams. 187 TABLE,23. GROWTH IN THE PIGEON GUILLEMOT .1 9. 5 9 1 9 6.0 Both Years Age Sample Mean Range Age Sample Mean Range Age Sample Mean 0 10 .42 40-45 0 13 45 40-50 .0 \u00E2\u0080\u00A2 23 44 1 10 47 40- 50 1 19 50 38-65 1 29 49 2 10 54 45-65 2 19 58 44-70 2 29 59 3 11 59 45-65 3 18 70 51-84 3 29 66 \u00E2\u0080\u00A24 11 74 65-80 4 19 81 66-105 4 30 .78 5 11 83 70- 90 5 19 93 75-112 5 30 -90 6 11 . 96 80-125 6 16 . 105 85-125 6 27 102 7 11 113 90-135 7 19 123 86-150 7 30 \u00E2\u0080\u00A2 119 8 11 127 105-150 8 19 136 91-166 8 30 133 9 11 147 120-180 ' 9 19 155 113-214 9 30 152 10 11 159 130-180 10 16 -168 130-214 10 -27 164 l l 11 176 130-200 11 16 187 156-238 11 27 183 12 11 196 160-225 12 14 200 176-238 12 25 199 13 11 210 160-235 13 14 219 170-262 13 25 215 14 11 228 180-270 14 15 237 196-278 14 26 . 233 15 ' 11 241 190-270 15 15 249 210-290 \u00E2\u0080\u00A2 15 26 245 16 11 254 210-275 16 13 261 232-298 16 24 258 17 11 264 240-310 17 14 274 232-324 17 .25 269 18 ^11 281 260-320 18 13 296 266-340 .18 24 289 19 10 299 270-340 .19 12 310 280-355 19 22 305 20 11 303 275-340 .20 12 315 282-386 .20 23 309 21 11 314 260-370 21 10 .324 298-358 21 21 318 22 11 319 275-340 22 8 345 296-416 22 19 330 23 10 334 280-375 23 11 345 304-4l4 23 21 34o 24 10 336 .310-375 24 8 339 312-388 24 18 337 25 10 348 310-375 25 9 368 332-425 25 19 357 26 10 359 325-390 26 8 375 318-480 ,26 \u00E2\u0080\u00A2 18 366 27 10 366 320-4oo 27 8 369 344-420 27 18 367 i28 10 382 350-425 28 8 372 336-400 .28 18 377 29 10 374 340-400 29 8 - 384 330-406 \u00E2\u0080\u00A229 18 378 30 10 390 , 330-425 30 6 394 324-450 30 16 . .391 31 9 393 340-440 31 4 407 370-440 31 13 397 32 9 398 350-425 32 4 405 390-420 \u00E2\u0080\u00A232 .13 4oo 33 9 409 350-450 33 3 403 372-435 \u00E2\u0080\u00A233 . 12 4o8 34 7 408 375-440 34 1 424 34 8 4io 35 6 409 375-450 35 2 424 4l4-434 35 8 413 36 4 411 375-440 , 36 . 2 450 424-475 36 6 :424 37 2 415 390-440 37 2 426 410-442 37 4 421 38 2 420 400-440 38 2 427 390-464 38 4 424 39 0 39 0 39 0 Age i n days, counting day of hatching out as day/0 Weight, i n grams Consult t e x t f o r methods to 500\ -| 1 1 1 1 \u00E2\u0080\u0094 | \u00E2\u0080\u0094 r \u00E2\u0080\u0094 r \u00E2\u0080\u0094 r ^ ~ T | ' i ' i 400\ 300\ 200\ 100V 0 I \u00E2\u0080\u00A2 I \u00E2\u0080\u00A2 I I 1 I 1 1 1 1 1 1 \u00E2\u0080\u00A2 1 L. 0 5 10 15 Fig. 56 GROWTH OF Means of 1959860 data -j i i i i i i i i i i i i i i i 25 30 35 Age in days GUILLEMOT 188 The l a t t e r balance was a l s o used f o r ad u l t weights. P l a s t i c bags, and f o r the l a r g e r b i r d s a c l o t h bag of-known weight, were suspended from the balances f o r the weighings. In 1960,two B r i t i s h Trust f o r Ornithology p a t t e r n s p r i n g balances were a v a i l a b l e , the f i r s t . c o v e r i n g the range o-150 grams, and accurate t o the nearest,gram, the second covering the range O-4-50 grams ( c a l i b r a t e d i n tenths of ounces, a l l readings l a t e r converted) accurate t o w i t h i n 2 grams. Weighted p l a s t i c bags were employed w i t h these balances. This range of accuracy i s more than s u f f i c i e n t - i n weighing b i r d s where a, s i n g l e meal may be 40 grams (Lampetra a y r e s i fed a 230 gm. . c h i c k ) . For the B l a c k Guillemot, Winn (1950) weighed and measured two chicks at i n t e r v a l s ; h i s data f a l l w i t h i n the range of mine. Kaftanowski (1951) presents a growth curve f o r the same species i n the Murmansk r e g i o n , that agrees w i t h mine u n t i l about the 29th day; the divergence h e r e a f t e r can e a s i l y be explained by h i s smaller sample s i z e ( ? 5 b i r d s ) . Thoresen & Booth (1958) give weight data f o r Pigeon Guillemot chicks i n Skagit County, Washington, not f a r from my own study area. Their f i g u r e s show the same p a t t e r n , though t h e i r d a i l y means are somewhat higher. Since t h e i r sample i s never greater than 6 b i r d s a f t e r the 8 th day, and t h e i r extremes f a l l w i t h i n . t h e range of v a r i a t i o n of my sample, I a t t a c h no s i g n i f i c a n c e to the d i f f e r e n c e . 189 Table 24 compares weights of young at the p o i n t of nest departure, w i t h that of a d u l t s . In every case the weight of the young represents my l a s t record f o r that b i r d \u00E2\u0080\u0094 i t . h a d departed by the time of my nest-check the f o l l o w i n g day. The 20 young average 4 l l grams, and range from 372-500. The 53 a d u l t weights were secured during i n c u b a t i o n , and average 450 grams, w i t h a range of 400-500. TABLE .24. WEIGHT OF ADULT AND.CHICK AT POINT OF NEST DEPARTURE .COMPARED I n t e r v a l Number of Number of chicks a d u l t s 360-379 gms. 2 380-399 7 400-419 3 6 420-439 4 12 440-459 2 15 460-479 1 14 480-499 4 500-519 1 2 Sample 20 53 Mean 411 gm. 450 gm. Range 372-500 . 400-500 When i t leaves the nest to take up an independent e x i s t e n c e , the young Pigeon Guillemot thus 1 has a t t a i n e d , on the average, 92$ of the ad u l t weight. This i s l i k e l y c lose to the weight I t w i l l maintain as a y e a r l i n g , as St o r e r (1952: 132),determined that P i g . 57 Pigeon Guillemot chicks removed from the nest, w i t h eggs f o r comparison. 1 day o l d ( r i g h t ) and 2 day o l d ( l e f t ) s i b l i n g s from nest # 3 1 . The chicks are covered w i t h a u n i -form coa l b l a c k down at hatching, and have the eyes open. P i g . 58 Another 1-day o l d chick (#9), weighing 50 gm., taken from the nest. The wing stubs and prominent white egg-tooth show c l e a r l y . F i g . 59 A 12 day o l d ch i c k from nest #8, weighing 200 gm. Feather growth i s w e l l advanced v e n t r a l l y , but the dense white feathers s t i l l bear a downy t i p . F i g . 60 The chick from nest #4 ( F i g . 45) at 28 days, weighing 400 gm. and w e l l advanced on juvenal plumage. Note the egg-tooth s t i l l prominent. The b i r d has been banded. F i g . 61 The c h i c k from nest #4 at 34 days, t r a c e s of down s t i l l adhering, and egg-tooth n o t i c e a b l e , but ready to take to sea ( i t l e f t 4 days l a t e r ) . Note mottled white wing-patch. The b i r d was extremely l i v e l y and d i f f i c u l t t o photograph. I t here screams e x a c t l y l i k e the a d u l t . 190 there was a s i g n i f i c a n t d i f f e r e n c e i n wing-length between y e a r l i n g and older T y s t i e s and murres. That wing-length may be a good.indicator of weights i s i n d i c a t e d by comparing Johnson's (1944) mean f o r 6 9-adult Black Guillemots on the nort h shore of the Gulf of St. Lawrence, my weights, and the corresponding wing-lengths ( S t o r e r 1952: 162-163). The weights d i f f e r i n e x a c t l y the same r a t i o as the wing-length (my b i r d s are l a r g e r ) . The few f i g u r e s a v a i l a b l e f o r T y s t i e weights at nest departure are i n agreement w i t h mine. (Winn 1950, Thoresen & Booth 1958, Uspenski 1956: 52, Kaftanowski 1951) but samples too small f o r meaningful comparison. Kaftanowski r e p o r t s that' 1 1 b i r d s taken on the sea a f t e r nest departure averaged 440 grams, some 20.grams more than.the average a d u l t i n that area (Murmansk). P i g s . 57-61 I l l u s t r a t e the changes i n appearance from hatching to nest departure i n the Pigeon Guillemot. E. Thermoregulation 1. Ontogeny of Body Temperature i n P r e c o c i a l B i r d s It. has long been known that p r e c o c i a l b i r d s have some a b i l i t y to re g u l a t e body temperature as soon as they are hatched, or even before (review see Hensel 1955: 432-433) . C r i t i c a l observations on w i l d p r e c o c i a l b i r d s , t o show when thermoregulation i s complete\u00E2\u0080\u0094when homoiothermy a c t u a l l y sets i n - - a r e few however. Boni (1942) d e a l t w i t h three a l t r i c l a l b i r d s i n d e t a i l , and made some experiments on the p r e c o c i a l Coturnix c o t u r n i x by which he showed that thermoregulation was f a r from complete at one day-of age. Boni warns that newly hatched p r e c o c i a l b i r d s cannot simply be designated 'homoiothermic 1 i n contrast to the p o i k i l o t h e r m i c a l t r i c i a l species so f a r s t u d i e d ; r a t h e r temperature r e g u l a t i o n develops g r a d u a l l y i n both, but r e l a t i v e l y sooner a f t e r hatching i n the former. L a t e r work on what,may be termed p r e c o c i a l species (auks, g u l l s , game-birds, and a p e t r e l ) w i l l be reviewed, then r e s u l t s on the Pigeon Guillemot presented. The work of Kaftanowski and R o l n i k (reported by R o l n i k 19^-8, and posthumously by Kaftanowski 1951), based on exposure e x p e r i m e n t s \u00E2\u0080\u0094 t h e b i r d s were placed i n coolers of c. 10\u00C2\u00B0 C a i r temperature and t h e i r body temperatures recorded f o r s e v e r a l hours by t h e r m o c o u p l e s \u00E2\u0080\u0094 i n d i c a t e d a good degree of thermoregulation w i t h i n a few days of hatching, as f o l l o w s : Larus canus 2 - 3 days Larus argentatus T|-2 days R i s s a t r i d a c t y l a 6-7 days Alc a torda 5 - 6 .days U r i a aalge a f t e r 6 days Cepphus g r y l l e c4 days F r a t e r c u l a a r c t i c a 6-7 days The records on auks are of e s p e c i a l i n t e r e s t here. I t i s of paramount, importance to r e a l i z e that although the b i r d s at the ages i n d i c a t e d could maintain f a i r l y s t a b l e body temperatures, these were w e l l below, the adult, l e v e l . The a v a i l a b l e evidence would i n d i c a t e that a f t e r the f i r s t s p e ctacular improvement i n thermoregulation, development to reach the a d u l t c o n d i t i o n , true homoiothermy, proceeds by a gradual increase of the l e v e l at.which body temperature can be maintained under f i x e d outside c o n d i t i o n s . Thus F r a t e r c u l a 192 maintained a s t a b l e body temperature at c. 29\u00C2\u00B0 C,at the age of 6-7 days, but a s t a b l e temperature of c. 36\u00C2\u00B0 C at 13-14 days. Again, the l a t e s t record f o r ' U r i a lomvia (13-15 days) shows that though body\u00E2\u0080\u00A2temperature i s about s t a b l e , the a d u l t l e v e l has not yet been reached ( s t i l l at c. 37\u00C2\u00B0 C). The work of Barth'(1951) on g u l l s , based on exposure t e s t s under n a t u r a l c o n d i t i o n s , bears out t h i s i n t e r p r e t a t i o n . The young of Larus canus were found to maintain a st a b l e body temperature without e x t e r n a l heat a f t e r 20 hours, under normal c o n d i t i o n s ( a i r 15-20 C, no r a i n ) . The adu l t l e v e l was not a t t a i n e d before f l e d g i n g (29-33 days) however. The body temperature of the chicks rose from 38.0\u00C2\u00B0 C at 2.\ days t o c. 4 l \u00C2\u00B0. C at 22 days, compared to adul t temperatures of-40 .0\u00C2\u00B0^40.8\u00C2\u00B0 ( a l l measured i n air'temp. 1 3 - 1 8 . 5\u00C2\u00B0C). A s i m i l a r ' p a t t e r n was i n d i c a t e d f o r Larus argentatus and fuscus, w i t h a smaller m a t e r i a l . B a rth con-cludes that one cannot s p e c i f y a p a r t i c u l a r age at which thermoregulation,is e s t a b l i s h e d \u00E2\u0080\u00A2 in,the g u l l s , as attainment of homoiothermy comparable to that of adu l t b i r d s does not take place u n t i l a f t e r the b i r d s have f l e d g e d . In-North America.two.gulls have been b r i e f l y s t u d i e d , where age has been estimated by;body l e n g t h . R e s u l t s are i n accord w i t h Barth's work. Bartholomew.& Dawson - (1952) i n v e s t i g a t e d Larus o c c i d e n t a l i s i n n a t u r a l c o n d i t i o n s . They found some degree of thermoregulation before hatching., and no s i g n i f i -cant c o r r e l a t i o n between s i z e and body temperature i n the daytime range of 19-28\u00C2\u00B0 C a i r temperature, but at ni g h t 193 ( l 4 . 5 - 1 7\u00C2\u00B0C). there was evidence that the smaller b i r d s had a more- l a b i l e temperature. In a . l a t e r paper -(Bartholomew & Dawson .1954) these authors emphasize the greater\u00E2\u0080\u00A2thermo-r e g u l a r a t o r y a b i l i t y of even .the smallest g u l l s of t h i s s pecies, compared t o the a l t r i c i a l Pelecanus o c c l d e n t a l i s and 1Ardea\u00E2\u0080\u00A2herodias. Behle & Goates (1957) provide data f o r Larus c a l i f o r n i c u s . The b i r d s were again aged by body length, and though some a b i l i t y / t o r e g u l a t e body temperature was apparent even .in.the smallest c l a s s , the mean .temperature .increased p r o g r e s s i v e l y r i g h t t o the l a r g e s t c l a s s i n v e s t i -gated (11-12 inches body length, c 21 days o l d ) . At a i r temperatures of 1 0 - 1 1 \u00C2\u00B0 C,.the smallest c l a s s averaged c. 3 1 \u00C2\u00B0 C, the l a r g e s t c. 4 0 . 1 \u00C2\u00B0 ; one adul t r e g i s t e r e d 40.0\u00C2\u00B0 C. In summary, 1 the Larus g u l l s have some thermoregulatory . a b i l i t y at hatching, and a f t e r 1-2 days can.maintain .stable body temperatures i n : t h e range of normal.environmental con-d i t i o n s . The adu l t body\u00E2\u0080\u00A2temperature, and presumably a corresponding degree of homoiothermy, i s not achieved however, u n t i l about the time the young f l e d g e , or even l a t e r . There i s evidence that auks may f o l l o w the same pat-t e r n . The most extensive i n v e s t i g a t i o n on any p r e c o c i a l b i r d . i s that of Hoglund (1955) on Tetrao u r o g a l l u s . This work allows a t e s t of the above Ideas. F o r t y - f i v e chicks were r a i s e d indoors, at a room temperature of 20-25\u00C2\u00B0 C, and an a r t i f i c i a l heat source of 30-40\u00C2\u00B0 C provided, to s u b s t i t u t e 194 f o r the brooding hen. A f t e r 15 days the b i r d s were g r a d u a l l y \u00E2\u0080\u00A2moved outdoors. The chicks were thus r a i s e d ,in c o n d i t i o n s approximating those i n nature. D a i l y records of body \u00E2\u0080\u00A2 temperature i n these circumstances were kept, and experimental exposure to low temperatures without,the ' s u b s t i t u t e hen 1 a l s o c a r r i e d out. The d a i l y records provide a s t a t i s t i c a l l y - m e a n i n g f u l . c u r v e . Over'the f i r s t three days an abrupt r i s e , from 3 7 . 9 \u00C2\u00B0 C to 39 .6\u00C2\u00B0 C, was shown,,thereafter a l e s s e r but steady climb, to about 18 days. Prom that day on (records to 49 days) the d a i l y \u00E2\u0080\u00A2readings f l u c t u a t e d around 4 l . 6 \u00C2\u00B0 C , apparently, the normal temperature of.the a d u l t . On the ba s i s of t h i s curve, one would expect an abrupt improvement i n .thermoregulatory a b i l i t y over the f i r s t three days, and. t h e r e a f t e r a con-t i n u i n g improvement up t o 18 days. This i s i n f a c t - borne out to a n i c e t y by/the data from the exposure, t e s t s \u00E2\u0080\u0094 f u l l homoio-thermy -is not achieved u n t i l the l 8 - 1 9 t h day. The p a t t e r n i s -thus' i n f u l l accord w i t h the g u l l s \u00E2\u0080\u0094 r a p i d improvement over the f i r s t few days, and a gradual p e r f e c t i n g of thermoregulation . t h e r e a f t e r . The f i n a l species, P u f f i n u s t e n u i r o s t r i s , shows a very \u00E2\u0080\u00A2 d i f f e r e n t pattern.. Parner & .Serventy (1959) found the chicks could maintain a body temperature of 3 7 . 9 \u00C2\u00B0 Q ,on.the f i r s t day of l i f e , i n - a burrow.environment of c. 22\u00C2\u00B0 C. This i s i d e n t i c a l to-the temperature of quie t a d u l t s i n . t h e burrows, and i n d i c a t e s a much e a r l i e r ( i . e . , embryonic) p e r f e c t i o n of thermoregulation, than in\u00E2\u0080\u00A2the g u l l s and game-1 9 5 b i r d s reviewed. 2 . Chick Body Temperatures In the Pigeon Guillemot I planned work w i t h my Pigeon Guillemots t o i n c l u d e d a i l y readings of body temperatures i n a l a r g e s e r i e s of chicks of known age, and long-term r e c o r d i n g of body temperature by thermocouples at low air\u00E2\u0080\u00A2temperatures.\u00E2\u0080\u00A2 Chicks disappeared from.my study.nests at such an alarming r a t e , however ( c h i e f l y p r e d a t i o n by j u v e n i l e g u l l s ) , that only the f i r s t p a r t of the work could be c a r r i e d out. C l o a c a l temperatures were taken w i t h quick-r e g i s t e r i n g c l i n i c a l thermometers, read to the nearest 0 . 1 \u00C2\u00B0 F and .the readings l a t e r converted t o \u00C2\u00B0 C. The thermometer was i n s e r t e d as n e a r l y uniform as p o s s i b l e to the depth of 1 . 5 cm (the g reatest depth p o s s i b l e w i t h the smallest c h i c k s ) , and read a f t e r 120,.seconds. By t e s t i t was found that by that time 'normal 1 temperatures would be r e g i s t e r e d In.chicks of any age. A l l the chicks could be e a s i l y : e x t r a c t e d from the burrow., f o r \u00E2\u0080\u00A2 the readings, the procedure being to place the c h i c k on i t s back on a piece of heavy c l o t h , throw.a.loose f o l d of the m a t e r i a l over'the head, and i n s e r t .the thermometer. A l l readings were c a r r i e d out i n the shade, and were begun w i t h -i n two minutes of capture. Shade a i r temperature in.the b l i n d , close to most of the study nests, was taken at.the s t a r t of each d a l l y check. We have seen that t h i s temperature w i l l c l o s e l y approximate burrow .temperature. R e s u l t s have been 196 TABLE 25. CHICK BODY TEMPERATURE, PIGEON GUILLEMOT Degrees Centigrade c h i c k B o d y T e m p. A i r T e r n J?. Day # Chicks Mean T. Extremes Range Mean Extremes Ran\u00C2\u00A3 0 10 37.8 36 .4-38.7 2.3 21 15-24 9 2 13 38.2 37 4-39.0 1.6 .21 19-24 5 3 14 38.4 37. 6-39.2 1.6 21 18-24 6 4 12 38.4 37. 4-39.5 2.1 20 15-24 9 5 12 38.7 37 .4-40.0 2.6 21 18-24 6 6 \u00E2\u0080\u00A2' 15 38.9 38. 0-39.8 1.8 20 .18-23 5 7 14 39.2 37. 9-40.2 2.3 20 .18-23 5 8 15 39.1 ' 38 1-40.0 1.9 20 15-23 8 9 .16 39.2 38. 4-39.8 1.4 20 17-23 6 10 14 39.2 38. 4-40.1 1.7 21 17-22 5 l l 13 39.2 38 ,6-4o.l 1.5 21 15-24 9 12 12 39.4 39 .l-4o.l 1.0 22 15-24 9 13 11 39.6 39. 2-39.8 0.6 20 . 15-22 7 14 12 39.2 38. .2-40.1 1.9 20 17-23 6 15 10 39.7 38 .8-40.3 1.5 19 17-23 6 16 9 39.7 38. 4-40.4 2.0 19 17-25 8 17 10 \u00E2\u0080\u00A239.9 39 .4-40.3 0.9 17 .15-19 4 18 7 39.8 39 .4-40.7 1.3 17 15-20 \u00E2\u0080\u00A2 5 19 7 39.9 39 .3-40.5 1.2 19 15-23 8 20 8 \u00E2\u0080\u00A2 39.9 39 .3-40.7 1.4 19 15-22 7 21 8 .40.2 39 .3-41.2 0.9 20 ,15-25 10 22 6 40.4 39 .6-41.3 ' 0.7 23 19-28 9 23 8 4o.l 39 .6-40.9 1.3 24 18-28- 10 24 6 40.3 39 .3-40.7 1.4 22. 17-27 10 25 6 40.3 39 .6-40.8 1.2 19 17-28 11 26 5 40.4 39 .7-40.9 1.2 18 17-21 4 27 5 40.8 40 .1-41.2 1.1 19 .17-24 7 28 5 .40.4 39 .6-40.8 1.2 18 15-24 9 29 5 4o.7 39 .9-41.2 1.3 17 15-21 6 30 3 .40.7 40 .2-41.1 0.9 17 14-19 5 31 2 40.9 40 .7-41.1 0.4 19 17-20 3 32 3 40.6 40 .1-41.4 1.3 21 17-25 8 33 3 40.8 39 .7-41.9 1.2 23 18-28 10 34 :2 4o.9 40 .8-40.9 0.1 19 - 18-20 2 35 2 40.8 40 .6-40.9 0.3 18 \u00E2\u0080\u00A212-23 11 36 2 4l.o 40 .9-41.1 0.2 19 15-22 7 37 2 40.3 40 .1-40.4 0.3 18 13-22 9 38 2 40.9 40 .9-40.9 0 19 14-23 9 20 o v e r - a l l mean Fig. 62 BODY TEMPERATURE, NESTLING PERIOD Pigeon Guillemot gathered in- Table 25 and F i g . 62 . I t i s unfortunate t h a t , as some of the newly-hatched chicks d i d ..not show. a. temperature high.enough to be measured ( i . e . , l e s s than.35\u00C2\u00B0 C), no average f o r the 0-day chicks can be presented. I t w i l l be n o t i c e d that .air\u00E2\u0080\u00A2temperatures throughout are remarkably uniform, so one may accept the curve as showing body\u00E2\u0080\u00A2temperature of the Pigeon Guillemot chick, i n i t h e shade, at the air.\u00E2\u0080\u00A2 temperature of c. 20\u00C2\u00B0 C, at various ages. My f i g u r e s supplement, the work of R o l n i k and Kaftanowski on. the Bl a c k Guillemot .\".Kaftanowski (1951: 67-68) i n d i c a t e s that a s t a b l e body.temperature can be maintained by the ch i c k at 10\u00C2\u00B0 C air'temperature, as soon.as 4 days of age. However, Kaftanowski s t a t e s that the body temperature at 4-6 .days, some 37-48\u00C2\u00B0 C, i s w e l l below the adult temperature of 41-42\u00C2\u00B0 C, not a t t a i n e d u n t i l about the 24-27th day. Comparing my ch i c k f i g u r e s w i t h a d u l t temper-atures obtained w i t h the same methods, my b i r d s appear to.have reached ad u l t body\u00E2\u0080\u00A2temperature about the same time ( c . 25 days). As i n the g u l l s and game-birds, t h e r e f o r e , we can po s t u l a t e that though the Pigeon Guillemot possesses a..fair thermoregulatory a b i l i t y as e a r l y as the f i r s t day of age (extremes of 10 chicks 36.4r-38.7\u00C2\u00B0 -C, as against a i r temper-atures of 15-24\u00C2\u00B0 C), a degree of homoiothermy comparable to that i n a d u l t s i s not reached u n t i l toward the close of the n e s t l i n g p e r i o d . 198 I t i s d i f f i c u l t to say how long the Pigeon Guillemot chicks are normally'brooded. On day3* both parents i n nest #43 brooded,,so that most of the d a y l i g h t hours the chicks had a d d i t i o n a l heat, at air-temperatures ranging through 11 .9\u00C2\u00B0 -20.8\u00C2\u00B0 C. At nest #60 1 s u r p r i s e d the brooding parent on the nest at 1600; the s i n g l e c h i c k weighed.92 grams and could not have been l e s s than 4 days o l d ; brooding continued the next day (l900), but I d i d not see the parent two days l a t e r , when another weighing showed the c h i c k to be 140 grams,.i.e., not l e s s than 7 days o l d , checking w i t h the f i r s t o bservation. In . s h o r t b r o o d i n g was observed by day i n a nest w i t h two chicks 3 .days o l d , and-by l a t e afternoon/evening i n a nest w i t h a..single c h i c k , \u00E2\u0080\u00A2 4 days and then 5 days o l d . For the Bla c k Guillemot i n the Russian A r c t i c , Uspenski (1956: 82) s t a t e s brooding t o continue almost u n i n t e r r u p t e d l y f o r \u00E2\u0080\u00A2 t h e f i r s t 5-6.days. The p e r i o d of brooding, then, would correspond w i t h the e a r l y phase when the c h i c k can not yet maintain s t a b l e \u00E2\u0080\u00A2body temperature. F. Termination of the Chick Stage We have seen that the Pigeon Guillemot chicks d i s -appear, on the average, at 35 days of age, f u l l y feathered i n the juvenal plumage, having a t t a i n e d 9 0 $ .of \u00E2\u0080\u00A2the a d u l t weight, and w i t h homoiothermy comparable to th a t of the a d u l t - - i n short, a ' b i r d well-equipped t o earn . i t s own l i v i n g . I b e l i e v e the 199 chicks scramble down from t h e i r nests c h i e f l y at dusk or by ni g h t , as i s the p r a c t i c e of chicks brought up i n burrows ( s h e a r w a t e r s , . r a z o r b i l l , p u f f i n , - etc.) and thus w i l l avoid g u l l p r e d a t i o n . C e r t a i n . i t i s that i f they dawdle w i t h i n reach by day, they w i l l be k i l l e d and eaten by Larus glaueescens, a .nesting b i r d throughout the i s l a n d . F u l l y developed Pigeon Guillemot chicks r e l e a s e d by day, paddle s t r a i g h t out to sea and are seen about the i s l a n d no more, according to numerous experiments by G.F. van Tets (MS). This i s p r e c i s e l y l i k e the behaviour -of e x p e r i m e n t a l l y r e l e a s e d p u f f i n j u v e n i l e s ( L o c k l e y 1953). The suggestion that the Pigeon Guillemot chicks head away from the i s l a n d , and are c a r r i e d c l e a r by the t i d e s , i s borne out by the' f a c t that despite s p e c i a l search I never saw a j u v e n i l e about the i s l a n d , though I have observed .them o f f F o r r e s t I s l a n d , and near Sidney. Thoresen & Booth (1958) describe j u v e n i l e s f e eding o f f one of t h e i r . s t u d y i s l a n d s , however, so.the f a c t o r s may be l o c a l . Winn (1950) and Thoresen. (Thoresen & .Booth .1958) have a c t u a l l y witnessed departure from the nest, and i n d i c a t e that the j u v e n i l e s were coaxed from the nest by the parent dangling a f i s h before them. Un f o r t u n a t e l y I never observed t h i s c r i t i c a l happening, but my records on banded parents give i n s i g h t on par e n t - c h i c k r e l a t i o n s a f t e r nest departure. As has been noted above, feeding continues to the end of the n e s t l i n g p e r i o d . Further, at two nests banded parents brought f i s h a f t e r the young had l e f t . For example, i n nest #14 i n ,1959, the s i n g l e c h i c k was s t i l l present .1310.18 August. The next mornin I entered the b l i n d at o648, and at 0736 the female appeared w i t h a , s c u l p i n , , c a r r i e d . i t below.at 0738, but reappeared s t i l l c l enching the f i s h o739; same performance o752-o753. F i n a l l y she flew down .to. the water, and swallowed the f i s h at o8o8,.-then coming ashore at the p e r c h - s i t e of that p a i r . The male appeared at 0831 w i t h a blenny, c a r r i e d i t below. 0832, reappeared s t i l l h o l d i n g the f i s h ; same o833i; same o84l, a f t e r which he flew, down and swallowed h i s f i s h j u s t as the female had done, . to haul out on the beach t h e r e a f t e r . No f u r t h e r v i s i t s were noted, and at the close of observation (104.5) I checked the nest c a r e f u l l y and made sure that the,, c h i c k had indeed l e f t . This o b s e r v a t i o n . i s d i f f i c u l t to r e c o n c i l e w i t h the view..that the parents e n t i c e the young from the nest; i t would appear \u00E2\u0080\u00A2that i n t h i s case the parents were unaware of the chi c k ' s departure. However that may be, i t i s c l e a r ' t h a t the parents had not accompanied.their c h i c k away from the i s l a n d . Observation of the colour-banded p a i r at nest #43 .in.i960.showed t h a t they r e g u l a r l y j o i n e d the morning assemblies at the colony,long\u00E2\u0080\u00A2(at l e a s t 13 .days) a f t e r t h e i r chicks had l e f t the nest. The chicks l e f t after-1300 on 14 August, and the male parent brought a f i s h t o the empty nest the next morning, in.the manner of o l a t # l 4 . He spent the remainder of the morning-loafing about 'the colony as d i d the female. They were both observed r e g u l a r l y - i n the mornings, along w i t h the banded f a i l e d - b r e e d e r s , up .to 28 August. This was one of the l a s t days of.the g u i l l e m o t assemblies at the colony; none came ashore on .the 31st. My observations i n d i c a t e , t h e r e f o r e , t h a t the parents have nothing to do w i t h the c h i c k a f t e r i t has l e f t the nest, 201 has been assumed from stage of development of the young at nest departure (Uspenski 1956, Kartaschew. i 9 6 0 , et a l . ) , and suggested by the observation of j u v e n i l e s without a d u l t s (Thoresen & .Booth 1958, and my own f i e l d - n o t e s ) . Summary of Chick Stage 1. Three main methods of r a i s i n g the young are employed by auks: the young are escorted to s e a b y t h e par-ents .1) w i t h i n a few days of-hatching, or - 2 ) at about 2 0 .days, when 1/3 grown and clothed i n a mesoptile plumage, or f i n a l l y 3) the young leave the nest as f u l l y developed j u v e n i l e s ( c l o s e to adu l t weight, and w i t h complete Juvenal plumage), and have nothing f u r t h e r to do w i t h t h e i r parents. The T y s t i e belongs t o the l a t t e r c l a s s . 2 . F i f t e e n observations on nest departure at Mandarte averaged 35 days (range 29-39 days). 3 . Food brought to the ch i c k s at Mandarte was almost e x c l u s i v e l y f i s h ( at l e a s t 80$). By s i g h t i d e n t i f i -c a t i o n .the dominant foods were C o t t i d a e , and X i p h i s t e r i d a e and a l l i e s ; a.table of species i d e n t i f i e d i s give n . Proportions of the main f i s h types v a r i e d r a d i c a l l y from nest to nest, the d i f f e r e n c e s being explained by preferences of I n d i v i d u a l b i r d s . Some parents brought l a r g e numbers of f i s h u n s u i t a b l e as c h i c k food, and r e j e c t e d by .the l a t t e r 202 (Agonidae, Bothidae, P l e u r o n e c t i d a e ) . Pood items were brought one at a time, and the share of the sexes was equal. 4 . The chicks are fed as soon as the day f o l l o w i n g hatching, and feeding continues t o the end of the n e s t l i n g p e r i o d . Feeding i s spread through the d a y l i g h t hours (c .o400-2000) w i t h no obvious t i d a l c o r r e l a t i o n s . Rate increases w i t h age, and there i s good evidence that i t can be d i r e c t l y i n f l u e n c e d by-hunger of the c h i c k s . 5. Growth i n weight from hatching t o nest departure was f o l l o w e d i n a sample of i n i t i a l l y 11 and 19 b i r d s i n 1959 and i 9 6 0 r e s p e c t i v e l y . At nest departure the j u v e n i l e s average 4 l l grams (20 obs.), compared to an a d u l t mean of 450 (53 o b s e r v a t i o n s ) . 6. Ontogeny, of thermoregulation i n .the few p r e c o c i a l b i r d s so f a r studied i s discussed. In g u l l s , game-birds, and probably auks, chicks at hatching possess some thermo-r e g u l a t o r y a b i l i t y , ,and can maintain, a s t a b l e body, 1 9 5 9 ' , \ Zur B i o l o g i e des Rotschenkels (Tringa t_. totanus) I I . J . Orn. 1 0 0 : ; 2 1 0 - 2 3 6 . Gudmundsson, Finnur. 1953. I s l e n z k i r f u g l a r V I . T e i s t a (Cepphus g r y l l e ( L . ) ) . With E n g l i s h summary. Na t t u r u f r a e d i n g i n g u r i n n 23: 129-132. Guiguet, C.J. 1953. 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B i r d s observed on F o r r e s t e r I s l a n d , Alaska, during the summer of 1913. Condor 17: 20-41. Heinroth, 0. 1922. Die Beziehungen zwischen Vogelgewicht, Eigewicht, Gelegegewicht, und Brutdauer. J . Orn. 7 0 : . 1 7 2 - 2 8 5 . Hennessy, T.S. 1942. \" Banding provides age record f o r A t l a n t i c murre. Canada. F i e l d - N a t . 56: 122. Hinde, R.A. 1956. The b i o l o g i c a l s i g n i f i c a n c e of the t e r r i t o r i e s of b i r d s . I b i s 98: 340-369. Hoglund, N.H. 1955. Kroppstemperatur, a k t i v i t e t och f o r y n g r i n g hos t j a d e r n Tetrao u r o g a l l u s L i n . V i l t r e v y 1: I - 8 7 . ( w i t h E n g l i s h summary). Holdom, M.W. 1947. H o l b o e l l ' s grebe's strange death. Canad;.., F i e l d - N a t . 61: 21 . H o l s t e i n , V. 1942. Duehogen. Hirschsprungs F o r l a g , Copenhagen. 1944. Hvepsevaagen. Hirschsprungs F o r l a g , Copenhagen. _ _ , 1950. Spurveh8gen. Hirschsprungs F o r l a g , Copenhagen. 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