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Ecological segregation among plankton-feeding alcidae (aethia-a and cyclorrhynchus) Bedard, Jean 1967

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ECOLOGICAL SEGREGATION JSMDNG PLAIQCTON-FEEDING ALCIDAE (AETHIA and CYCIORRHYNCHTIS)  by J e a n H . Bedard M, S c . , U n i v e r s i t e L a v a l  A thesis of  submitted  i n partial  fulfillment  t h e r e q u i r e m e n t s f o r t h e degree o f DOCTOR  OF PHILOSOPHY  i n the  Department  o f Zoology  We a c c e p t t h i s  thesis  a s conforming  t o t h e required__giandard  THE U W E R S I T I 1  OF BRITISH ^ COLUMBIA  J u n e , 1967  In p r e s e n t i n g f o r an that  thesis  Library  publication  w i t h o u t my  written  June 18,  permission be  representatives  this  thesis  of  British  ZOOLOGY  1967  Columbia  for  the  requirements  Columbia, I agree reference  and  for extensive copying of  g r a n t e d by  the  Head o f  s h a l l not  this  my  It is understood that  for f i n a n c i a l gain  permission  The U n i v e r s i t y o f B r i t i s h V a n c o u v e r 8, Canada Date  University  p u r p o s e s may  his  of  Department of  the  agree that  for scholarly by  in p a r t i a l f u l f i l m e n t o f  s h a l l make i t f r e e l y a v a i l a b l e  I further  Department or or  thesis  advanced degree at  tha  study  this  be  copying allowed  11  ABSTRACT Among the North A t l a n t i c marine b i r d s , o n l y one plankton-feedbuig and adjacent  species f i l l s  the  n i c h e (Plautus a l l e L., A l c i d a e ) while i n the North P a c i f i c  seas, no l e s s than f i v e a l c i d s occupy i t . A comparison o f the  f e e d i n g and n e s t i n g h a b i t s was  made i n o r d e r to understand how  the f o o d  resources and the n e s t i n g h a b i t a t were p a r t i t i o n e d between three o f these  spe-  c i e s , the C r e s t e d a u k l e t ( A e t h i a c r i s t a t e l l a ( P a l l a s ) ) , the Least a u k l e t (A. p u s i l i a ( P a l l a s ) ) and the Parakeet a u k l e t (Cyclorrhynchus ( P a l l a s ) ) , The  study was made on S t . Lawrence I s l a n d , Alaska, d u r i n g the  summers o f 1964The  1966.  to  two  c r i s t a t e l l a . 300 body s i z e . The  psittacula  congeneric  s p e c i e s d i f f e r markedly i n s i z e ( p u s i l l a 90  g;  g) t the Crested and the Parakeet a u k l e t s are o f e q u i v a l e n t  three s p e c i e s have d i u r n a l h a b i t s . The  two  Aethia are a c t i v e  on the n e s t i n g c o l o n i e s d u r i n g the morning and the evening and f e e d at sea i n e a r l y a f t e r n o o n and e a r l y momingo Cyclorrhynchus  i s p r e s e n t on  the  c o l o n i e s i n the morning and e a r l y afternoon o n l y and spends the r e s t o f the day at sea, f e e d i n g . A e t h i a c r i s t a t e l l a and.A. p u s i l l a e x h i b i t the same type o f response to the food source  $ both have a d i v e r s i f i e d d i e t i n May-July ( c a r i d e a n  l a r v a e , h y p e r i i d s , mysids, gammarids) and r e s t r i c t themselves to one  dominant  p r e y item d u r i n g the c h i c k - r e a r i n g p e r i o d (August-September). A. p u s i l l a then concentrates i t s f e e d i n g on Calanus finmarchicus Thysanoessa spp. The  two  and  A. c r i s t a t e l l a  a u k l e t s have l a r g e l y o v e r l a p p i n g h a b i t s and  on  share  the same f e e d i n g grounds. They d i f f e r markedly i n d i e t , but more so i n the s i z e of the p r e y organisms used and these d i f f e r e n c e s can be accounted f o r by d i f f e r e n c e s i n b i l l - s i z e  alone.  S l i g h t l y over h a l f o f the d i e t o f Cyclorrhynchus  was made o f c a r n i -  vorous macroplankton ( l a r g e h y p e r i i d s , f i s h , e t c . ) . The Parakeet auklet  I l l  d i f f e r s from i t s p o s s i b l e competitor,  the C r e s t e d a u k l e t , by occupying a  s l i g h t l y higher t r o p h i c l e v e l and by d e v o t i n g more o f i t s time to f e e d i n g . The  two  s p e c i e s , however, are found on the same f e e d i n g grounds and are p r e -  sumed to u t i l i z e the same f e e d i n g depth-range. D i f f e r e n c e s i n d i e t between the two  are p r o v i s i o n a l l y a t t r i b u t e d to d i f f e r e n c e s i n b i l l s t r u c t u r e and  bill  shape. I n A e t h i a . the r e v e r s a l to monophagy d u r i n g the c h i c k - r e a r i n g p e r i o d seems to r e f l e c t a sudden i n c r e a s e i n the a v a i l a b i l i t y o f palanus Thysanoegsa. T h i s , i n t u r n , i s b e l i e v e d t o have importance i n the t i m i n g o f the breeding t i m i n g i n Cyclorrhynchus.  and  determining  season. No obvious f a c t o r i s r e s p o n s i b l e f o r which breeds s l i g h t l y l a t e r than e i t h e r o f the  two  species o f A e t h i a . The Crested and the L e a s t a u k l e t s seem to depend upon p r e y organisms t h a t o s c i l l a t e widely i n abundance and a v a i l a b i l i t y .  The  Parakeet a u k l e t depends to a g r e a t e r extent upon organisms whose supply i s more o r l e s s constant throughout the Segregation  year.  i n n e s t i n g i s complete between the two  rhynchus i s a c l i f f - n e s t e r while A e t h i a occupies  genera. C y c l o r -  t a l u s s l o p e s . I n the l a t t e r  h a b i t a t , the marked d i f f e r e n c e i n body s i z e between the two  s p e c i e s i s again  r e s p o n s i b l e f o r segregation - through the a c t i o n o f one p r i n c i p a l f a c t o r , the average rock diameter on the s l o p e s . The d e n s i t y o f A. i n c r e a s e s l i n e a r l y with i n c r e a s i n g boulder  criptatella  s i z e : the d e n s i t y o f A.  pusilia  decreases both with d e c r e a s i n g boulder s i z e and with the d e c r e a s i n g abundance o f i t s l a r g e congener,, From a knowledge o f the average s i z e o f the p a r t i c l e s in  the n e s t i n g h a b i t a t , one  the two  can p r e d i c t a c c u r a t e l y the r e l a t i v e abundance o f  species o f A e t h i a . The p o s i t i o n o f the plankton-feeders  marine b i r d s i s examined,, Feeding adaptations  i n the community o f d i v i n g (degree o f tongue c o r n i f i c a t i o n ,  p a l a t a l breadth, number and arrangement o f p a l a t a l p a p i l l a e ) f o l l o w a gradient  XV  o r a r e g u l a r m o d i f i c a t i o n throughout t h e f a m i l y . On the b a s i s o f these v a r i a t i o n s , which can be expressed  as a r a t i o ( B i l l - w i d t h / Gape), a model i s  . constructed t h a t g i v e s a g r a p h i c a l r e p r e s e n t a t i o n o f the breadth o f the e c o l o g i c a l f i e l d o c c u p i e d by the f a m i l y . Two d i s t i n c t l e v e l s emerge : the f i s h - f e e d e r s (uria,. Alca) and the p l a n k t o n - f e e d e r s  (Aethia,. P l a u t p s ) : an  intermediate l e v e l can be d i s t i n g u i s h e d ( F r a t e r c u l a . Lundq)* The s p e c i e s o f the l a t t e r group p r e s e r v e adaptations t h a t a l l o w them t o u t i l i z e  plankton-  and f i s h - f o o d s . The model allows u s t o r e c o g n i z e and d e f i n e s p e c i a l adaptat i o n s with r e s p e c t t o o t h e r members o f the f a m i l y and t o recognize the main trends i n e v o l u t i o n o f body s i z e and f e e d i n g adaptations w i t h i n t h i s  taxo-  nomic group. I n comparison with younger f a m i l i e s o r o r d e r s , most members o f the A l c i d a e a r e d i s c r e t e and w e l l - d e f i n e d e c o l o g i c a l l y . Among the three planktonfeeders s t u d i e d , the o v e r l a p i n requirements  i s v e r y s m a l l and no s i g n o f  competition f o r f o o d o r f o r n e s t i n g was found.  TABLE OF CONTENTS ABSTRACT TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES ACKNOWLEDGMENTS INTRODUCTION PURPOSE OF THE STUDY CHAPTER I . BREEDING BIOLOGY INTRODUCTION Distribution Arrival Circadian Rhythm o f A c t i v i t i e s Behaviour Age Categories Reproduction Molt Seasonal Changes i n Body Weight Incubation and Chick Stages Predation Winter Distribution CHAPTER I I . SEGREGATION IN FEEDING INTRODUCTION METHODS The Study Area The Food Samples The Analysis of ibod Habits  vi  38  RESULTS Foraging The Food Complex  a) Calanus finmarchicus b) Calanus oristatus  48 51 53 54  a) Thvsanoess.a spp.  55  A) Parathemisto libellula  56  e) Gammaridea f) Others g) F i n a l Remarks The Feeding of Aethia and Cyclorrhynchus SOME ECOLOGICAL CONSIDERATIONS Timing o f the Breeding A c t i v i t i e s  57 58 58 59 63 63  Body Weight of Laying Females and Feeding Relations 67 SEGREGATION IN FEEDING Introduction Time Element Spatial Element Depth of l i v i n g CONCLUSIONS CHAPTER I I I . SEGREGATION IN THE NESTING HABITAT INTRODUCTION THE PROBLEM AND ITS SETTING Statement o f the Problem Control.of Density METHODS Description o f the Nesting Habitat  75 75 77 78 80 81 86 86 87 88 89 91 91  98 Quadrats  vii Censusing  101  Analysis  103  Interpretation of the Census Data  10A  Farther Corrections  10A 10$  RESULTS Analysis of Density a )  Pusilla cristatella  c )  D  total  105 105 108 111  d) R e l a t i o n of Density with Other Habitat Characteristics Analysis of Relative Abundance (P) a) P with Average Rock Diameter b) P with Other Factors DISCUSSION AND CONCLUSIONS The Control of Density and Relative Abundance  114 115 115 115 117 117 122  Segregation i n Nesting a) Segregation between Aethia p u s i l l a and A.  cristatella  b) The Nesting o f Cvclorrhynchus CHAPTER I V . THE PLAMTON-FEEDERS IN THE COMMUNITY INTRODUCTION The B i l l i n Alcidae a) Feeding Adaptations b) A meaningful Ratio The Model Ratio of Character Difference  122 125 128 128 129 129 134 135 146  viii CONCLUSIONS  251  SIMiARI AND CONCLUSIONS  155  LITERATURE CITED  162.  APPENDIX I  169  APPENDIX I I  171  APPENDIX I I I  175  ix LIST OF TABLES Table  1.  Arrival dates i n May of auklets on St. Lawrence Island, during the three years of study  2.  Overlap i n the diet used by the parent bird (food i n the gullet) and carried to the chick(food i n neck-pouch)  65  3.  Proportion, i n volume, of the diet made of gammarid araphipods ( a l l Size categories) during the pre-laying period i n Aethia p u s i l l a and ^» cristatella, i n various years  70  U% Organic composition of various crustaceans of the types used by the auklets, i n percentage of dry body weight  9  72  5.  Weight changes i n Aethia pus i l l , a,. A. c r i s t a t e l l a and Cyclorrhvnchus psittacula between arrival (birds collected prior to June 15) and the end of the breeding season (birds collected during the l a s t week o f August and the f i r s t week o f September 74-  6,  Corrected census figures and selected slope characteristics i n the quadrats of Sevuokok and Kongkok colonies 100  7.  Summary o f correlation and regression s t a t i s t i c s for the analysis o f Density (D) and Relative Abundance (P)  8,  B i l l characteristics, body weight and ratio Bill-width / Gape i n various Alcidae  107 136  X  LIST OF FIGURES Figure 1»  Patterns of daily attendance of Aethia spp* and Cyclorrhynchus psittacula on the slopes of the colony of Sevuokok Mountain at various times during the breeding season  11  Estimated dates of hatching and fledging in the colony of Sevuokok Mountain i n 1964, 1965 and 1966  17  3.  Body weight changes in Aethia pusilla during the summers 1964 to 1966  20  4.  Body weight changes i n Aethia cristatella during the summers 1964 to 1966  21  Body weight changes i n Cyclorrhynchus psittacula during the summers of 1964 to 1966  22  6.  Location map showing St. Lawrence Island, Alaska with the main places names mentioned in the text  30  7.  Approximate position of the depth contours around the western end of S. Lawrence Island  32  Average weight of food (in grams) carried to the chick in the neck-pouch of auklets  36  The amounts of various prey in the diet of Aethia pusilla throughout the summer of 1964 only  39  10.  The amounts of various prey in the diet of Aethia pusilla throughout the summer of 1966 only  40  11.  The amounts of various prey i n the diet of Aethia pusilla throughout the summer of 1965 only  40  12.  The amounts of various prey i n the diet of Aethia cristatella throughout the summer of 1964 only  Al  13.  The amounts of various prey i n the diet of Aethia cristatella throughout the summer of 1965 only  41  14.  The amounts of various prey in the diet of Aethia cristatella throughout the summer of 1966 only  42  15.  The amounts of various prey i n the diet of Cyclorrhynchus psittacula during the chick-rearing period (food i n neckpouch). 1965 only  42  The amounts of various prey in the diet of Cyclorrhynchus psittacula during the chick-rearing period (food i n neckpouch). 1966 only  43  2.  5.  8. 9.  16.  XX Figure 17.  The amounts of various prey i n the diet of Cyclorrhynchus psittacula. Combined data for a l l years  18. The amounts of various prey i n the diet of Aethia pusilla throughout the summer. Combined data for a l l years.  43 44  19.  The amounts of various prey i n the diet of Aethia cristatella, throughout the summer. Combined data for a l l years  44  20  Relative importance (in volume) of various prey types of various size categories i n the early summer diet of Aethia pusilla and A. cristatella^ food i n gullets)  46  Relative importance (in volume) of various prey types of various size categories i n the food brought to the chick during August and September (food i n neck-pouches)  47  22. Body weight (in grams) and fat condition of females upon arrival (A) and at laying (B) i n various years  69  21.  23.  Location of a l l known colonies of Aethia pusilla and A. cristatella and concentrations of Cyclorrhynchus psittacula, on St. Lawrence Island, Alaska.  24. View of one sector of the colony of Sevuokok Mountain; 25.  The glacial cirque of Kongkok along the south-western coast of St. Lawrence Island  26. Profiles of the major types of slopes encountered on St. Lawrence Island, .Alaska 27.  92 93 94 97  Relationship between the Density of Aethia pusilla and the Average Rock Diameter i n the colony of Sevuokok  106  28. Relationship between the Density of Aethia pusilla and the Average Rock Diameter i n the colony of Kongkok  106  29.  Relationship between the Density of Aethia pusilla, and the Standard Deviation of Average Rock Diameter (S) i n the Kongkok colony  109  30.  Relationship betxraen the Average Rock Diameter (X) and the Density of Aethia cristatella i n the colony of Sevuokok  110  31.  Relationship between the Average Rock Diameter (X) and the Density of Aethia cristatella i n the colony of Kongkok  110  32. Relationship between Average Rock Diameter and Density of the two species of Aethia  112  xii  Figure 33,  3A»  35. 36»  37,  Relationship between the Average Rock Diameter (x) and the Total Density (numbers of Aethia cristatella and A^ pusilla combined)  113  Relationship between the size homogeneity of rocks (Standard Deviation of Rock Diameter, S) and the Total Density (numbers of Aethia cristatella and A> pusilla combined)  113  Relationship between the Average Rock Diameter (X) and the Relative Abundance (P) of the two species of Aethia  116  Relationship between the Standard Deviation of Rock Diameter (S, or Homogeneity) and the Relative Abundance (P) of the two species of Aethia  116  Comparison of the relationship between Average Rock Diameter (X) and the Relative Abundance (P) of Aethia pusilla and A. cristatella i n the colonies of Sevuokok and Kongkok  119  38, Generalized model showing the segregation between Aethia cristatella and A^ pusilla on the nesting slopes according to the Average Rock Diameter 39,  AO,  Al,  123  Profile of the b i l l , palatal surface, tongue i n sjLtu and extruded tongue in profile i n A) Plautus alle. B) Ptyco— ramphus aleutica. C) Aethia pusilla  131  Profile of the b i l l , palatal surface, tongue in situ and extruded tongue i n profile i n A) Cyclorrhynchus psittacula. B) Fratercula corniculata  132  Profile of the b i l l , palatal surface, tongue in ^itu and extruded tongue in profile in A) Brachyramphus marmoratum. B) Cepphus columba. C) Uria aalge  133  A2, The relationship between Body-weight (cubic root) and the ratio Bill-vddth / Gape in Alcidae  141  A3. Breadth of the ecological field occupied by the Alcidae  1A3  44,  Generalized model based upon the data contained i n F i gures A2 and A3  1^7  I xiii  ACKJDWLEDaiSNTS  This reserach was supported by a grant from the National Research Council of Canada to Dr.M. D. F. Udvardy. I am indebted to many people who helped at one stage or another of the study i Doctors B. M. Bary, D. Chitty, I. MoT. Cowan, H. D. Fisher, D. M. Hopkins, D. J. Randall and M. D. F. Udvardy. Dr L. E. Bousfield provided identifications for the Gammaridea, while Dr T. E. Bowman identified the Hyperiidea. Dr Paul LeBlond gave assistance i n the preparation of parts of the data for analysis. Mr Magnar Norderhaug and Mr Lowell Spring kindly provided some of the specimens used in the study of feeding adaptations. While i n the field, the Eskimos of Gambell helped on numerous occasions t I am grateful i n particular to Gerard Kanooka for his most dependable assistance. Spencer G. Sealy and the late Henri Talbot helped during intervals of the field program. At a l l stages of this study, I tremendously benefited from discussions, scientific or otherwise, with Dr F. R. Fay of the Arctic Health Research Center. His understanding, keen interest and suggestions are gratefully acknowledged. While at the University of British Columbia, I benefited from financial assistance from i the H. R. MacMillan Family, La Societe Zoologique de Quebec, the Canadian Wildlife Service and the University of British Columbia. My wife, Lise, helped i n intangible but essential ways.  i  INTRODUCTION  Thinking about communities has not always mat with general approval and community ecologista have often found themselves on the defensive In attempting to justify the existence of their level of endeavour and their method of examining the: biosphere* Operational definitions of the concepts used by community ecologista are either lacking or, else, surrounded by hopeless confusion* Niche, niche brea dth, environmental diversity,, fixed levels of competition, species diversity models, time-lag factors are conceptual representations of natural events that have not been adequately defined nor lend themselves at the present time to scientific measurements that are acceptable to a l l ecolo gists* No doubt the difficulties stem largely from the enormous increase i n complexity between the level of single species populations and the level of multi-species systems * for the scientist working at the first one and already mentally harassed by the intricacies and the inextricable relations that characterize his own level, any attempt at surrendering into simple terms the multiplicity of interactions taking place i n communities Is ill-timed and Illusory* Indeed, however clever the models proposed by community ecologists, they carry so many assumptions and usually sacrifice so much generality and precision that they are considered by many as useless additions to the ecological literature* However, i n recent years, the approach to the theory of community structure far from being dampened by criticism has gone through  2  a revival and, we must agree progress. Levins (1966) recently  recog-  nized in unequivocal terms the complexity of the problem faced and suggested that the approach to the theory of community structure cannot be all-inclusive and must rather be many-sided and he suggested the use of clusters of models that would penult an approach to the same problem from different angles* Since models are usually restricted to depleting changes i n a few components at a time, the complexity of the system studied imposes upon ua that a l l the variables which vs can adequately recognize, define, and measure be grouped i n separate models s n  . . . v e attempt to treat the same problem with several alternative models  each with a different simplification but with a common biological assumption* *• hence, our truth i s the intersection of independent lies * (Levins, 1966). PURPOSE OF THE STUDT The aim of the: present work was to establish the values of the major constants of niche specificity i n three sympatric plankton-feeders of the family Alcidae. The species designated, Aethia cristatella (Pallas), Aethia  m^lfa  (Pallas), and Cyclorrhynchus psittacula (Pallas) are largely  sympatric both i n summer and winter, share common nesting grounds and share common food resources i a the pelagic neritie zone of the northern seas. In boreal, subtropical or tropical environments, one would not think of examining and comparing the ecological requirements of species so markedly different as the Crested, the Least and the Parakeet auklets. Bat i n subarctic waters, the number of ecological opportunities i s generally much smaller and one can expect an increase i n the intensity of interspecific relationships* The situation was particularly interesting i n view  3 of the fact that i n the North Atlantic, only one species of the family (Plautug alle (L.)) f u l f i l l s the plankton-feeding niche while i n some areas of the North Pacific, as many as five alcids subdivide this same niche i n some obscure way* Obviously, large differences were expected at the start; perhaps i t would have been possible to predict the basic food-types that the above species: would make use of, given the types of prey available, the body-size and bill-size of the birds themselves and a few hints about their relative and absolute abundance* Differences i n feeding and nesting are, I think, adequately described i n the following pages* But the aim of the study was rather to give a functional interpretation of the patterns of niche partitioning* How did radiation occur around this particular food resource, pelagic plankton ? What are the structural adaptations and what i s their role i n determining segregation i n feeding ? What i s the degree of overlap i n habits and can any of the differences i n feeding and nesting be accounted for by differences in behavioral responses to the environment ? At another level of integration, I hoped that an analysis of the feeding and nesting requirements could help us to account for observed differences i n distribution, relative proportion of one species to the other and, possibly, local abundance* Not so much to be able to formulate clear answers to such broad questions, but rather to enable us to formulate meaningful questions and set up meaningful hypotheses concerning their eventual solution* Prior to the start of this study, information on the habits and biology of the forms named above could have been summarized i n a few lines* This of course, hampered seriously the formulation of i n i t i a l  questions i n a very precise manner. For this reason, the approach throughout this study i s outright descriptive. Whenever an interpretation of an observed system or phenomenon i s proposed i t i s usually i n the form of an elementary hypothesis warranting either experimental testing or careful duplication of observations i n nature. Partitioning of the food resources or partitioning of the nesting territory implies fundamentally concepts of community structure and for this reason, an attempt i s made to integrate our knowledge of the relations between the various elements of this community i n which the plankton-feeding species form only one level or segment. Hairston (1959) assumed that food would be the only satisfactory way of expressing community organization. This was accepted by Engelmann (1961) who further added t "the niche or status of an animal i n the community might therefore be defined i n terms of the amount and kind of food i t eats, hence ultimately i n terms of energy consumed. This general reasoning was accepted and I attempted to define at least qualitatively the kinds of food eaten by the various species under study. However, although "space" (i.e. nest-sites ) does not qualify i n Hairston's mind as a major feature of community organization, the material here presented covers segregation both in feeding and i n nesting. The group of birds under study affords us very good material into which gradation from one niche to the other can be followed through gradients i n feeding adaptations and general biological characteristics such as body—size. I t seems that owing to their exclusive occupancy of a broad ecological zona, the aloids give us an opportunity to examine a "natural  11  community, remarkably free of inter-group interactions - as i s  5  oo common i n terrestrial situations - and in which the structure can be reckoned with without the use of elaborate assumptions* The gradation of feeding adaptations i s free of major breaks or discontinuities* This was certainly not the case i n Rosenzweig's recent study (1966) of community structure i n sympatric Caraivora s i n the latter group, differences i n feeding behaviour, i n hunting strategy between hunting sets and between elements of the hunting sets as well as differences i n social behaviour so profundly affected the ecology and the position of the animals i n the oommunity that i t became almost impossible to seek their mutual relationships* "Niche" was defined as "the constellation of environmental factors into which a species (or other taxon ) flts (Hayr, 1963)* In the n  following text, niche i s generally used to characterize series or groups of species similar i n adaptations ( such as saying that the plankton-feeding niche i s subdivided among at least five species in the North Pacific )• When niche i s used to describe the requirements of one single species, the text makes i t dear* C!omraunity has been defined as the assemblage B  M  i n time and space of mutually interdependent species (Slobodkin, 1963)* For reasons outlined i n Chapter III, community i s generally used here i n an extended meaning t I w i l l use i t to refer to the family Alcidae as a whole though i t i s obvious that not a l l the species of this family are spatially assembled*  CHAPTER I  BREEDING BIOLOGY  INTRODUCTION Because of the scarcity of published information ©a these species, a brief review of the main patterns of their breeding biology i s deemed necessary* The information summarized here has been gained concurrently to the main lines of research t i t i s however, far from complete and many of the specific patterns which are lumped here may indeed prove upon careful inspection to be meaningful, characteristic and adaptive differences*  Breeding distributions of the Crested, Least and Parakeet anklets have been mapped and analysed by Udvardy (1963). It will suffice here to say that the Parakeet auklet has the most ubiquitous distribution i n the Bering Sea* I t nests along the eastern coast of this basin ( Nunivak Island} Swarth, 1934 * Sledge Island; Cade, 1952 » Punuk Islands; Fay & Cade, 1959 ) while no Aethia has been reported there* The Crested and the Least auklets have a generally overlapping distribution in the summer, except i n the Kurile Islands and on the south side of the Alaska Peninsula where the Crested auklet alone breeds* Arrival Arrival dates for the St* Lawrence Island waters for the three years of the study are grouped i n Table 1* I t w i l l be noted that the order  of arrival and settling on the slopes i s * Parakeet - Least and Crested auklets. This confirms the findings of Fay & Cade (1959). We w i l l see later however, that the Parakeet auklet, altough the f i r s t to settle on the nest-sites appears to be the latest i n breeding. A l l three species appear i n the leads far offshore ( over 15 km ) % few days before they appear i n the proximity of the land. Settling on the breeding colonies happened four days after the birds were f i r s t sighted from land. Around the arrival time, the birds of the three species spend the day i n the opening leads among the pack-ice i n dense rafts. Observations indicate that courtship activities are already carried on extensively at that time. Towards evening ( 1500 - 2100 h ), but much more so in early morning ( 0130 - 0900 h ) the flocks manifest a tendency to f l y and circle over the ice t as the date of settling upon the slopes approaches, the flocks appear more and more commonly in the vicinity of the nesting colonies. It i s not known whether the spring flocking i s merely a continuation of the winter social behaviour or a new phenomenon accompanying the gonadal development and the onset of the breeding season. It is probably a mere intensification of a year round phenomenon. This spring flocking behaviour has no relation with movements to and from the feeding grounds and represents purely a form of sexual bahaviour. Specialized calls which are attached to ritualized displays observed on land are a major component of those flights and indicate that even some courtship occurs during them t psittacula i n particular while i n such flocks utters almost continually a characteristic twittering c a l l associated with a male advertisement display given on land. Sound production in flights of criptat e l l a 1B less marked  than i n psittacula and finally least of a l l in pusilla.  8 Flocking i s a complex but important phenomenon which persists to a varying degree throughout the season i n cristatella and pusilla although the emphasis seems to change from a predominantly sexual behaviour i n the spring to a predominantly social gathering i n late summer* But i n psittacula? flocking seems to be a temporary phenomenon* upon arrival i n the vicinity of the breeding grounds, this species forms either homogeneous flocks ( averaging about 25 birds ) or else, associates in heterogeneous flocks with Aethia ( preferably cristatella; ) or Uria, spp* But soon after the birds have settled on the colonies, there i s a remarkable breakdown i n the degree of social cohesion* flocks of Parakeet auklets; are seldom observed after June 15 and the few encountered turned out to be made of sexually immature birds* As i s common i n almost a l l the Alcidae, the settling on the slopes i s accompanied by large variations i n attendance during the f i r s t few days* The birds may disappear completely for a whole day or for one daily session. The pattern 1B unpredictable and i t s significance, i f any, unknown* The birds settle i n late May when more than three-fourths of the colony surface are thickly covered with snow. At least two or three weeks elapse before the nesting sites are substantially free of snow and ice. But the scattering of the birds over the snowy slopes i s certainly not random s on a large snowfield covering parcels of nesting habitat known from previous years observations, the birds seem to settle almost exclusively over the snow directly above the nesting sites destined to be occupied.This implies a remarkable sense of location. Pairing and the presence of mate retention was not studied for lack of banded birds. Pairing seems to be rapid, and by the f i r s t  9  Table 1 . Arrival dates i n May of auklets on St. Lawrence Island during the three years of study.  £• psittacula 1964  First seen i n offshore leads  -  1965  1  3  1966  9  &. c r i B t a t e l l a 1964  1965  -  -  1966  1  8  &» pnslila 1964  -  1965  1966  -  15  f^fsK  15 18 20 15  18 20 15 18 21  First seen on slopes  19  22  2 1 2 4  20  24  20  22  24  10 week in June, pairs were located from observation blinds and vere recognized throughout the season. Orcadian Rhythm of Activities There are considerable modifications i n the daily rhythm of activity i n the course of the summer. Minor differences have been observed between Aethia; pusilla and £. cristatella but these are ignored i n the summary that follows. The birds are diurnal and a l l activities on the colonies are inhibited during twilight and night periods* The pattern of activities on the nesting colonies i s markedly bimodal with a more prominent peak of activity i n the morning* The pattern of daily attendance at the colony i s schematized i n Figure 1. Both species of Aethia have largely concordant patterns and have been lumped i n Figure 1 : minor differences i n attendance have been noticed and may prove upon closer study to have significance. No estimates of numbers ( absolute ) are implied i n the semi-schematic graphs of Figure 1* For instance, the evening peak i s usually made up of lesser numbers of birds than the morning one* The basic difference between the two genera i s obvious; i n this Figure. Cvclorrhynchua: has only one peak of attendance around mid-day and i s never found on the slopes i n the evening except for the odd bird coming back for nest relief* In ether areas, A. cristatella has been characterized as noeturnally active ( Portenko, 193A, quoted by Gizenko, 1955 )• In Aethia. the mid-day period is; spent at sea feeding. Daring darkness, most of the birds assemble on the water in large rafts » this was checked throughout June, and courtship activities were observed during the twilight period that prevails at that time* However, some birds,  11 Figure 1 • Patterns of daily attendance of ^ethia, spp. and Cyclorrhynchus psittacula on the slopes of the colony of Sevuokok Mountain at various times, during the breeding season. The graphs are eemi-quantitative only and cannot be compared between periods. For instance, the absolute density of birds on the slope in mid-June and mid-July i s of course larger than that i n late August, when only breeders carrying food to the nest can be observed. In mid-July ( incubation period ), the breeders present on the slope represent the off-duty individuals. Unshaded zones under the curves represent, breeders * horizontally shaded zones, non-breeding birds. On the time axis, the duration of twilight i s indicated by oblique shading t the duration of darkness by blackened areas.  AETHIA  CYCLORRHYNCHUS MID-JUNE  TIME  TIME  12 singly or i n pairs spend twilight on the nest-site, particularly during the few days prior to laying. Feeding at night or at dawn has never been checked by actual collection of feeding birds. Individuals collected on the colony i n early morning have empty crops but this cannot be taken as a sign that they do not feed prior to landing because digestion i s known to be very rapid* But isolated Least auklets were repeatedly observed feeding from the shore during darkness and no doubt feeding on a large scale occurs before the birds come back on the slopes. The generalised scheme proposed i s applicable to the colony or population of Aethia and Cyclorrhynchus as a whole, but individual birds may indeed have different schedules* In fact, some AethjLa can almost always be found feeding over the vast area surrounding the western end of St* Lawrence Island* Behaviour Courtship and displays have been analysed i n some detail i n a l l three species but w i l l only be sketched here* Pair formation may occur during early flocking and arrival* Though the prevalence of paired birds i n the flocks may indicate that some of the pairs are formed even prior to arrival* After settling, the birds engage in courtship activities which take up an important share of the total daily period* The system i n the three species can be characterized as a male-centered system in which typical stereotyped male postures and vocalizations are produced to attract presumptive females t immature birds do engage to a large extent i n these activities as "intruders" and their interference is constant* Social and sexual behaviour remains the most prominent feature of the l i f e on the colonies throughout the summer, until the departure  13 of the non-breeders around mid-August, After that time, vocalisations are seldom heard and the remaining birds are engaged exclusively i n feeding the chicks* Copulation has never been observed either on sea or on the surface of the slopes* It would be surprising i f i t could at a l l occur i n such places owing to the peculiar intruding system mentioned above and to the fact that immature birds would quickly disrupt and prevent efficient copulation i n such situations* It i s known to occur only on the nest i t s e l f ( this i s true for the two genera ) • In Aethia and Cyclorrhynchus. every bird seems to be attached to a particular sector of slope and there i s no evidence of interchange taking place, even among non-breeders* There i s nothing in Aethia equivalent to the "loitering grounds" found in other alcids ( Johnson, 19A1 ), where special rocks or areas, sometimes a l i t t l e away from the nesting places are staked out and used indiscriminately by a l l the birds belonging to the adjacent colony* In Aethia. the rock surfaces can be called "loitering grounds" but they belong only to those birds that are associated with the immediately adjacent nesting territory* In Gycl.orrhynchua, where the nests are distributed i n much smaller concentrations, the birds generally assemble on a central, communal display area, usually a large boulder, from which they radiate to their respective nest-site* Nesting colonies and nest-sites w i l l be described in more detail in Chapter III* The birds are presumed to be territorial and to defend a single interstice or nest cavity ( Type "C" territory, Hinde, 1956)* Evidence for this i s however difficult to obtain* But other alcids nesting i n similar situations were found to have such a system ( Drent,1965  u i n gepphug columba: Lockley, 1953 i n Frqtercula arctica ) and to defend the approach of their respective nest-site ( Bedard, 1967 i n Alca torda) • Ovarian and oviducal development i n Aethia starts rather abruptly around June 15* Only one f o l l i c l e reaches development and can be ovulated. No sign of re-laying has ever been observed despite adequate sampling. It i s doubtful i f i t could occur i n view of the large ratio egg-weight / body-weight which reaches 18.6$ i n pusilla and 14*3% i n cristatella. Less information i s available for Cyclorrhynchus. but It appears to follow i n a l l respects a very similar pattern. Testicular development also starts rather abruptly i n early June, Upon arrival, males of both Aethia species  have gonads slightly  above the resting size ( as observed i n early September ), A sharp increase occurs in early June and testicular development reaches a plateau i n the third week of June and starts decreasing again only around the middle part of July, This increase following arrival on the breeding grounds i s observed also i n Urj-a spp ( Swartz, 1966 ) and differs from what i s observed i n migratory Passerines ( King, 1966 ) and several Anatidae. Ace Categories A large proportion of the birds attending the colony or present i n the neighbouring waters are sexually immature. Age at sexual maturity has never been ascertained by banding, but from an examination of large series of such immatures i s believed to take place at three years ( i n the third summer after hatching )• In Aethia pusilla two marked categories of immatures can be recognized. The f i r s t i s made up of birds in f u l l winter plumage presumed to be i n their f i r s t summer after hatching. They appear on the colony i n  ton^n  numbers ( less than  5%  of the total numbers ) for  15 a short period i n July. Their rhythm of activity and the degree to which they associate with flocks of breeders i s unknown. On the slopes, they are wary, engage very l i t t l e i n the social activities and give signs of very inquisitive behaviour. A second category, made up of birds presumed to be i n their second summer has an incomplete and extremely variable plumage. The amount of black on the breast i s usually much greater than i n the average breeding bird t but most characteristic i s the absence or very incomplete development of the white jugulum characteristic of mature birds. These immatures also differ from the breeders i n the average dimensions of the b i l l , wing and tarsus? secondary characters such as the presence of a horny  '•11611110^  on the culmen, the presence of filoplumes on the  forehead and the b i l l coloration show a large degree of variability when compared with the latter. This second category sometimes constitutes up to Z5% of a l l the birds visible on the slopes i n July. They engage actively i n social activities and courtship, and a small percentage i s known to breed successfully ( i n a l l years birds of that group were collected carrying, food to nearly fledged chicks )• These immatures are not known to form homogeneous flocks as will be the case i n cristatella. They apparently associate with flocks of adult breeders throughout the season. They have been found i n the surrounding waters as early as late May but apparently do not accompany the adults on the slopes until late June. They are s t i l l abundant and active i n early August after hatching but have disappeared by the third week of that month. They tend to appear later and to leave a l i t t l e earlier than their counterpart i n cristatella. This seems to be because P U S i l i a completes i t s breeding cycle slightly faster than cristatella.  16 In A* cristatella. th© distinction between two sub-adult groups i s not so clear and seems to reside i n statistical differences i n b i l l size, b i l l shape and the degree of development of characters such as b i l l plates and! crest length* Immatures however make up roughly the same percentage of the total population as i n pusilla. that i s 25%* They however, have daily patterns of activity quite different from those i n the breeders and db form homogeneous flocks* In general, immatures appear later on the slope i n the morning and leave later i n mid-day* They associate with adult birds on the colony and engage i n a large measure of social activity* As i n pusilla* some individuals of this group have been collected early i n the season but they db not appear i n significant numbers on the slopes before the middle of June, have a maximum of attendance i n mid-July and have disappeared at the end of the third week i n August* In Aethia spp* , criteria of size, b i l l coloration, molt condition, brood-patch development, etc* were used to discriminate between adults and immatures* But this distinction i s not always easy and for this reason I w i l l sometimes refer to "Known Immatures" and"Suspected Immatures" Immatures i n G. psittacula  are not safely recognizable i n  the f i e l d by plumage characteristics and much less i s known about them* Fragments of evidence indicate that they follow a pattern very similar to the one described for this group i n the preceding species* They are known to occur i n small homogeneous flocks on the feeding grounds even i n mid summer* Reproduction The relative occurence of the major events of the breeding season i s given i n figure 2 for the three years of study* Since no nests  17 2 • Estimated dates of hatching and fledging in the colony of Sevuokok Mountain in 1964, 1965 and 1966. In the left hand hald of the graph, points represent the estimate of the proportion of breeders on the slope carrying food i n the neck-pouch. The left hand half of the graph i s based on a number of estimates of the proportion of breeding birds left on the slope at various dates* Note the Inverted scale on the right.  is were followed, these curves are based upon estimates made at various dates of the proportion of adult birds carrying food to the nest ( hatching curve ) and upon estimates of the proportion of breeders left on the slope ( fledging curve ) t since these estimates were carried on i n areas which were traversed almost daily during three successive seasons, they are believed to represent fairly accurately the changes in population involved* A clear delay i n laying, hatching and fledging occurred i n both species, 1966 being the latest season of the three* The ecological significance of this delay cannot be fully interpreted because of the lack of information on pertinent factors such as weather and date of snow departure end for the lack of information on the biological effects of such a delay upon chick growth and survival* Cyclorrhynchus psittacula was i a a l l years about one or two days; later than cristatella i n timing of i t s breeding activities* In 1966, only one chick had left i n 17 nests by September 13, at a time when an estimated 80% of the cristatella chicks  had gone to sea ( S. G. Sealy,  personal communication)* Molt Upon arrival i n late May, a small proportion of the breeders i n both speoies of Aethia have not completed their partial prenuptial molt* Postnuptial molt i n breeders starts i n mid-July by the shedding of the flight feathers ( starting from the inner primaries ) and i s followed around mid-August by the beginning of the aolt of the contour feathers. Adults which are known to be failed breeders are released into a molt cycle plm-n^T to the one observed i n immatures ( of two years ) that ia t molt of the primaries starting around July 15 and molt of the body feathers  19 In the neck, head region and ventral pterylia starting between July 15 and the end of the same month. This i s not a random effect but allows the immatures to be at the maximum of their molt during August, when the food supply i s at a maximum ( Chapter II ) • Unfortunately however, few immatures were collected during August i n any year, for breeders carrying food only were selected and molt cannot be followed i n the immature group after early August* Infi.psittacula. a l l the specimens collected in May have completed their nuptial plumage and very few had started molting the innermost primaries at the end of the breeding season i n early September* Immatures however started molting during August and some were found on the colony at that time with intense; feather growth on a l l pterylia. The fact that there i s partial overlap between molt and breeding i n Aethia, but almost none i n Cyclorrhynchus will be tentatively interpreted after we have examined and compared the feeding habits i n the two genera* Seasonal Changes i n Body Weight Seasonal changes i n body weight are presented i n Figures 3, A and 5 and i n Appendix I. Some aspeots of these changes w i l l be further discussed i n the following Chapters* Let us remark, however, that Aethia, pusilla and A. cristatella manifest seasonal changes i n body weight very similar i n aspect and timing. The birds arrive on the breeding grounds at a maximum weight and have lost approximately 10% to 15% of the latter by the end of the breeding season. The major pattern i s a rapid loss of weight until mid-June t this i s followed by an increase which cannot be satisfactorily interpreted at this; time but most likely reflects changes i n the quality of the available food* I t is; not exclusively limited to females  20  3  • Body weight changes i n Aethia; p u n i l i a during the summers 1964. to 1966. Months are divided i n 10-day intervals. The b a r r e p r e sents one Standard Error on either side of the mean. Weight changes are shown ( broken line ) for non-breeding individuals ( "Known Immatures" and "Suspected Immatures" ). For the intervals of June III and July I, female weight i s given minus weight of f u l l y shelled egg i n oviduct when present. Data for separate years are given i n Appendix I.  MAY  JUNE  JULY  AUGUST  SEPT  21 A • Body weight changes i n A e t h i a c r i s t a t e l l a d u r i n g the summers 1964. t o 1966. Months a r e d i v i d e d i n 1 0 - d a y i n t e r v a l s . The bar r e p r e s e n t s one Standard E r r o r on e i t h e r s i d e o f t h e mean. Weight changes are shown ( broken l i n e ) f o r n o n - b r e e d i n g i n d i v i d u a l s ( "Known Immatures!' and "Suspected Immatures" ) . F o r t h e i n t e r v a l s o f J u n e I H and J u l y I, female weight i s g i v e n minus weight o f f u l l y s h e l l e d egg i n o v i d u c t when p r e s e n t . Data f o r s e p a r a t e y e a r s a r e g i v e n i n Appendix: I .  22 Figure 5 • Body weight changes in Cyclorrhynchus p s i t t a c u l a during the summers of 1964 to 1966. Both sexes combined. Known Immatures excluded.  5 I  II JULY  I  7  III  13 i " ~ "~™T I  28  28 T~~  II AUGUST  30 — [  III  —  I SEPT.  1  23 but i s consistently revealed i n males as well ( egg weight, when the egg is fulled shelled i n the oviduct was substracted from the values of body weight i n Figures 3, A and 5 and i n Appendix I )• In most years, there i s an improvement i n body weight i n late July, just prior to the hatching of the egg* This i s interpreted as a response to improving feeding conditions with a minimum i n the level of pressures exerted by the breeding activities* The pattern i s largely similar i n psittacula ( Figure 5 ) although the lack of sufficient data force us to lump both sexes i n the comparison* The relative loss i n body weight throughout the breeding season amounts to less than 10$* In general, this species seems to be able to carry i t s breeding and nesting activities with a much lower threshold of energy expenditure* Extreme leanness i s seldom observed i n psittacula, but i s a common occurrence i n cristatella. where breeding birds can reach as low as 230 g , which represents almost 25% departure from the average weight upon arrival at the colonies* The high value of body weight upon arrival seems to be largely due to the accumulation of thick subcutaneous fat deposits* Does i t merely represent a continuation of the winter condition or do the birds go through a temporarily restricted phase of body weight increase just prior to arriving on the breeding grounds ? Data of Swartz ( 1966 ) for body weight changes i n Uria spp. above the Bering Strait are remarkably similar i n pattern* Incubation and Chick Stages In a l l three species, both sexes share the duties of incubation according to a pattern which has not been studied* However, both sexes seem to share equally the efforts needed to carry food to the nestling and  24 they  probably have equal shares of the Incubation as w e l l . The length of the incubation period and nestling stage are  presently under study by Mr S« G. Sealy s the length of the incubation period can be indirectly measured as about 30 days i n A. c r i s t a t e l l a and  0. psittacula. It i s slightly less than 30 days i n  A. p u s i l l a .  The nestling  stage i s approximately of the same respective length, or a l i t t l e longer. In the three species, the chick leave the nest when f u l l y grown. In b i l l , tarsus and wing dimensions, they then average slightly less than adult birds. The role of parents i n the departure of the chick, i f any, i s not known. But they are not accompanied by the parents at sea and they scatter according to an unknown pattern. They are incapable of sustained f l i g h t apparently, but are able to flutter from the slope to the sea. Chicks nearly grown are commonly seen exercising their wings on the rocky surfaces i n late August and early September. Some chicks have been seen to depart from the nest towards the sea around morning and mid-day, but no peak of departure could be observed at dusk as i s common i n other species (for instance Uria epp.f see Tuck, I960). Presumably, the most leave at night or very early i n the morning. In early morning, several chicks are usually visible i n the l i t t o r a l waters around the colonies. On particularly stormy days, a proportion of the fledglings seem unable to escape the strong tide rips and currents that prevail at the foot of Sevuokok Mountain and several can be found dying on the neighbouring beaches. The impact of such mortality i s impossible to measure because of the constantly patrolling larids which quickly remove the Carcasses before the observer has a chance to obtain a quantitative sample.  25  Predation was nowhere a marked influence in the colonies of St* Lawrence Island* I t i s well-known how small alcids are generally plagued to a large degree by various predators, though this was rarely quantified for any species ( Larson, i960; Salomonsen, 1951)* In the subarctic and boreal Pacific waters, the nocturnal habits of many forms (Ptycoramphus. Svnthlibor&nphus. Endomycbura) has no doubt rightly been attributed to predation by aerial predators* Dr I* MoT Cowan (personal communication) reports that no less than 30 nests of the Peregrine Falcon (Falco peregrines) were found on Langara Island ( Queen Charlotte Islands), probably the best alcid colony on the British Columbia coast. In the Aleutian Islands:, Murie reports that this Falcon feeds mostly on auklets (1959) and Gabrielson & Lincoln (1959) estimate that predation on by the Peale's Falcon i s "severe  11  pusilla  i n nearly every Aleutian colony.  In Sevuokok and Kongkok, predation by aerial predators was very limited. One Snowy Owl ( Kyctea soandiaca) was seen i n the Sevuokok colony during three years of observation. The Rough-Legged Hawk (Bqtao lagppus) i though nesting i n the vicinity was never observed hunting i n the colony except during the post-breeding f a l l dispersal period (early September)* The species i s known however, to feed on Aethia ( Fay & Cade, 1959). The Raven (Corvus corax) nested i n a l l years i n Sevuokok but i t s role i s more that of a scavenger than that of a predator* Interestingly, human predation appears to be the main cause for the absence of the Glaucous Gull ( Larus hyperborean) i n the Sevuokok colony. At least one pair attempted to nest i n every one of the three seasons of this study t a l l were unsuccessful i n hatching eggs owing  26 to repeated disturbances by the Gambell children... Patrolling adults of this species were a common sight but very seldom disturbed the auklets engaged i n social activities on the slopes. On the other hand, the Herring Gull (frarust araentatus) - known to breed only on the south side of the island, some 50 km away (Fay & Cade, 1959) - produced massive panic-flights by i t s mere appearance, especially among pusilla which responded more quickly than i t s congener*' No direct predation was ever observed by the Herring Gull, but the intensity of the response produced by i t s mere passage i s significant. Im Kongkok, Larus hvperboreus i s also a common sight and at least 6-10 birds were always visible within the cirque periphery. They were never observed to prey on, or attack any auklet and their role seemed to be that of scavengers. During ten days of observation, they appeared to rely exclusively on remains of fox k i l l s , over which they were often seen fighting. This i s the more surprising when one knows how this species can become a fierce and serious predator on small and medium-sized alcids such as Plautus; and Fratercula (Larson, I960). Foxes (Alonex) were present and active i n the two colonies studied. In Kongkok, the cirque periphery was divided among some five or six animals and territorial clashes were observed among them. Numerous V ^ T F were observed and found t by the remains of the wings scattered a l l over the colony, cristatella appeared to be the. main object of predation, although this needs to be more fully documented. An unknown amount of predation i s due to rodents. The ground squirrel (Citellus) and the red-backed vole (Clethriopomvs). although never observed to interact directly with the auklets, were held responsible for a large proportion of thee deaths among embryos and chicks. The latter  27  were often found mutilated i n a way that indicated rodent predation. To summarize, the apparent l a c k o f large scale predation i n the colonies studied i s an interesting phenomenon. What prevents i n particular a e r i a l predators (Falco, peregrlnus. £. rusticolus) from taking opportunity to use such immense and r e l i a b l e food store i s puzzling. Such a factor as high fog density could be a reason (through lowering the hunting efficiency). D i f f e r e n t i a l resistance to predators between species i a not known, but p s i t t a c u l a i s probably much l e s s subject to i t owing to i t s nesting habits that render i t l e s s accessible both to foxes and to rodents, which are here considered to be the most important predators. fflftfrff DiSvrtbutioq L i t t l e i s known about the d i s t r i b u t i o n o f the auklets during the winter. Preble & McAtee  (1923) note that A . c r i s t a t e l l a . along with  smaller numbers o f £• p u s i l l a and C. psittacula can be observed throughout t h e winter around the P r i b i l o f Islands. The three species also winter i n abundance i n the waters around the Aleutian Islands (Murie,1959). Along the American coast, only psittacula apparently goes as f a r south i n the winter as the states o f Oregon and C a l i f o r n i a . On the A s i a t i c side, a l l three species are present i n the Kurile chain (Gizenko, 1955) and A . c r i s t a t e l l a and C. p s i t t a c u l a are also common at that time around the shores o f Sakhalin and Hokkaido (Gizenko,  1955). The birds are reputedly  gregarious i n the winter, i n particular the genus Aethia ( Kozlova, Gizenko,  3955). L i t t l e groups o f psittacula are observed (Gizenko).  1957j  CHAPTER  II  SEGREGATION IN FEEDING  INTRODUCTION  The present chapter Is concerned with a description o f the d i e t of the three species o f auklets and with a functional interpretation o f the feeding patterns,. The multi-dimensional aspect o f the feeding t e r r i t o r y , the constantly changing d i s t r i b u t i o n o f the prey-items and the fact that WQ are dealing with highly evolved vertebrate predators renders the study of t h e i r feeding eminently d i f f i c u l t and complex. Many o f the conclusions are provisional and tests are proposed on some occasions, that would allow us to assess more objectively the importance of one o r the other factor i n the proposed scheme o f segregation. As I mentioned e a r l i e r , fundamental differences i n d i e t were expected at l e a s t between Aethia c r i s t a t e l l a and A. pusilJLa on the basis of differences i n b i l l size alone. Although predictable, the nature of these differences had to be determined and throughout the study,  extensive  c o l l e c t i o n of feeding birds were made to establish the d i f f e r e n t i a l use made of the food resources by the three species. At a l a t e r stage i n the study, the efforts were orientated toward finding the major ecological components attached to those differences such as differences i n feeding areas, feeding times,  etc  In spite o f the offered hypotheses and conclusions these r e s u l t s , as often i s the case with f i e l d work under a r c t i c conditions  29 have oot f u l f i l l e d the expectations at the planning stages o f t h i s project. The information i s often fragmentary o r purely descriptive i n nature} quantification based upon detailed r e p l i c a t i o n o f the work over a longer period o f time and on a broader geographic area would certainly increase the v a l i d i t y o f the conclusions reached. METHODS  Tfec Stttdy Area The f i e l d work was done around the western end o f St, Lawrence Island, Alaska (Figure 6), being centered mostly a t the colony located on Sevuokok Mountain i n the v i c i n i t y o f the settlement o f Gambell, The d i s t r i b u t i o n o f the auklets on the i s l a n d , as well as descriptions o f their colonies w i l l be found i n Chapter I I I , I s h a l l l i m i t myself i n the following l i n e s to notes on the marine environment used by the auklets. The general oceanographic conditions i n the neighbouring waters have been summarized by Barnes & Thompson and recently by Fleming & Hsggarty  (1938), Zenkevitch (1963)  (1966). That p a r t o f the Bering Sea  adjacent to the Bering S t r a i t , together with Anadyr Bay and the St, Lawrence Island waters are characterized as belonging to the low-arctic region (Zenkevitch, 1963, p 74-6) as indicated by the presence o f i c e i n winter and near-bottom temperatures either below the freezing point o r just above i t . St.Lawrence Island extends across two rather different water masses » on the eastern side, warmer and l e s s saline waters due to the proximity o f large Alaskan r i v e r s ; on the western side, cold and more saline waters originating probably from the Gulf o f Anadyr or some other "cooling center* o f f the Kamchatka coast (Barnes & Thompson, 1938; Fleming & Heg-  30 Figure 6. • Location map showing St. Lawrence Island^ Alaska with the Tn jn a  place names mentioned i n the text.  31 garty, 1966), In the waters off the western end of the island, the faunal groupings as indicated by zooplankton reveals a mixture of several elements and comprises representatives of such diverse groups as the South Oceanic, the Western Neritic and the Northern Oceanic faunal groups (Zenkevitch,1963). The general circulation i s northerly (Barnes & Thompson, 1938) and i n the channel or strait separating St. Lawrence Island from the Chukot. Peninsula, the funnel configuration of the passage further accentuates the rapidity of the current. Tidal reversal of this current i s common and strong eddies are created i n the waters where the birds were collected for the food habits analysis (Figure 7). Depths of slightly above 50 m are encountered about mid-way in the passage (Figure 7),  but rapidly diminish north and north-east of  the western part of the island. The waters west and north-west of Gambell are characterized by negative temperatures throughout the year below depths of 25 m (Barnes & Thompson, 1938) * this, water, apparently originating i n the Gulf of Anadyr reappears i n surface just north of St. Lawrence Island and i s a good indication of marked upwelling. This pronounced vertical mixing, coupled with clear horizontal components probably account for the abundance of marine birds and marine life; i n general i n the area. Bottoms; are sandy-gravelly and rather gently sloping. Extensive communities of benthic amphipods seem to develop i n these conditions and their importance will be discussed later. The zooplankton has been surveyed in the area by Johnson (1956) and several Russian investigators ( summary i n Zenkevitch, 1963). These investigations were however, usually conducted for limited periods of time, were often primarily taxonomies! in orientation and carry l i t t l e  32  Figure 7 • Approximate position of the depth contours around the western end of St, Lawrence Island. Vertically hatched area indicates where 95$ of the birds obtained for food habits in early summer have been collected. Drawn from Chart 93°2, united States Coast and Geodetic Survey.  33 information that can be useful i a the present type of analysis. The zooplanktonic forms that play a role i n the alimentation of the auklets w i l l be given some attention later. The food Samples Birds of a l l categories ( adults, immatures) were hunted from May until early -August on their feeding grounds. In early August, when hatching occurred, the birds were collected on the colony and then, only parents carrying food to the chick were selected. These are easily recognizable by the swollen condition of the neck » a special diverticulum of the buccal cavity, the neck-pouch, i s used as exclusive means of transport of food to the chick. During this phase, collection at sea was interrupted because of the prevalence of poor weather at that time and because preliminary examination ( see below ) revealed no difference between the diet of adult birds themselves and the diet they selected for their chick. In early summer, birds were; collected during the mid-day feeding period exclusively. This period lasts for approximately two hours between 1A00 and 1600 h .At the latter time, the birds gather i n flocks and experience indicated that due to rapid digestion, the food eaten had already reached the disintegration stage i n the gizzard and was beyond us©fullness for quantitative purposes. Efforts were made to obtain samples at regular intervals of eight to ten days during that early summer period, but weather conditions dictated i n a large measure the quality of the sampling. On suitable days, courses were set i n a north-easterly, westerly or south-westerly direction t efforts were made to stay on a rather regular course but this proved often impossible because of the constantly shifting  34 position of the birds from day to day and the unpredictable nature of their distribution* So that the pattern was more a random search than a strict and coordinated sampling* During the chick-rearing period, samples were collected on the slopes of Sevuokok Mountain every f i f t h day for a total of 40 days* Gener a l l y five birds of each species were obtained on each occasion* Collection was made during the peak period of feeding which occurs i n the morning. The large majority of birds were collected between 1000 and 1300 h i some were) collected as early as 0500 h and as late as 1500 h. In addition, small series were obtained during the morning and the evening (1900-2000 h) of the same day but no difference i n the qualitative composition of the food became discernible between the two periods* Birds at sea do store food i n a gullet which i s a simple d i l a tation of the oesophagus. Food i n the gullet i s generally i n excellent condition of freshness and quite suitable for quantitative and volumetric determinations. Gullets were not always f i l l e d sines digestion i s a continuous process and some contained less than one cc of food material. These were nevertheless used on the assumption that i n birds who have digested *M»7f of their meal there i s no reason why there should be any difference between what has been digested and what remains to be. Moreover, birds belonging to the same series (i.e. collected on the same day i n the same area) had remarkably consistent and similar food material i n the gullet. Since the birds collected together were averaged and since only the respective importance i n percentage i s used, the error i s believed to be small and no correction was designed for partly f i l l e d gullets. An error  however inevitably emerge i f one compares or adds  together food samples from the gullets, which represent always a variable  35 fraction of a meal with food samples from neck-pouches which represent one total food intake. This w i l l result i n an over-representation of the items taken i n the neck-pouches. For this reason, interpretations will rather be based upon comparisons; of blocks of samples rather than the whole* C. psittacula was difficult to collect on the feeding grounds for several reasons. The bird i s difficult to approach and tends to disgorge i t s gullet upon capture. It i 3 also spaced much more widely- and many times the amount of effort i s needed to obtain a comparable sample. The few samples obtained i n early summer were pooled ( Figure 17; Appendix II) and are used with caution. Birds carrying food to the nest were collected upon landing. This often resulted i n the spillage of the pouch contents which had to be retrieved from the ground. No correction was designed for these variable losses that affected about half of the samples. The f i l l e d gullet of Aethia pusilla can hold as much as 2.5 cc of food, but on the average contained between 1.2 and 1.A cc. The neck-pouch on the other hand can hold up to 11 cc of food (which i s approximately 12$ of the bird's weight) s the average contents i s given i n Figure 8. In Aethia cristatella. birds were collected whose gullet contained as much as 15 cc, but the average was usually around 6,0 cc. In Cyclorrhynchus psittacula no f i l l e d gullet was ever collected but i t probably can hold t  approximately the same quantity of food as i n A. cristatella. Food stored in the neck-pouch i n the two latter species can be very sustantial and can represent as much as 32 cc (Figure 8). The condition of the food i n the neck-pouch indicated a partial breakdown of the material and the existence of enzymatic (proteolytic)  36  Figure 8 • Average weight of food (in grams) carried to the chick in the neck-pouch of auklets. Filled neck-pouches only. The figure on the left of the bar is N. The bar itself represents one Standard Deviation on either side of the mean.  1  4l  i?9 AETHIA PUSILLA  11L  cf<j>  CYCLORRHYNCHUS PSITTACULA  do  6[ 13  I  24 [ AETHIA CRISTATELLA  i b  40  4.0  L  ^5  L—  12.0  W E I G H T O F F O O D , IN G R A M S  20.0  28.0  37 activity * this i s particularly true of C. psittacula. In the latter, fish- material was generally reduced to a whitish juice and the preys had to be counted by their bony remains. Large crustaceans, when broken during ingestion were also affected. Histological examination of the walls of the neck-pouch revealed no glandular structures but a very thickened and sloughing stratified, squamous epithelium. The enzymatic activity Is probably due to the secretions of the salivary glands * these secretions, besides playing a rSle i n binding the food material into a homogeneous mass and facilitating their transfer to the chick, may constitute an additional source of protein for the chick. The Analysis of Food Habits The food samples were stored i n formaldehyde and later examined under low-power microscope i n a grooved tray. The total number of organisms was tallied and catalogued for each sample. The number of items per sample varied of course with their size, averaging around 7 5 in cristatella and around 5 0 0 i n pusilla. The food items were sorted according to type and to size. The size was determined on overall length (tip of rostrum or cephalothorax to tip of telson), excluding long appendages such as the antennae of some gammarids for instance. The size categories were as follows t Size I (0.1 to 7 . 0 mm)}, Size II (7.1 to 15.0 mm)}  Size III (15*1 mm and over ).  Volume of the food i n preserved, samples was not an adequate measurement because the samples had to be washed before examination. Volume was however, determined indirectly i n the following manner. Unbroken organisms obtained i n standard plankton hauls or in particularly fresh digestive tracts were used to obtain several volumetric determinations ("wet volume").  38 Preys of similar size were used and several volumetric determinations were made on a large number of organisms* were averaged, and produced an index of volume which was used to convert the original numerical tallies i n volumetric ones* Volume for fish material was determined on museum collections of young Clupeidae of appropriate size* This index i s given i n Appendix II ("Volumetric Index"). Samples from both sexes were combined i n a l l analyses since preliminary examination revealed no significant differences between the two* No record was kept of the presence of mechanical admixtures since the gizzard was seldom inspected* However* i n the cases examined, such admixtures were only rarely found and do; not seem to play any role i n these plankton-feeders. In addition, during the 1965 season, regular plankton hauls were made i n the surrounding waters* using a 0.5 m conical closing not ( 0.0178'mesh opening). These hauls were made immediately i n areas where birds had been obtained and generally consisted Of three 10-minute horizontal hanlp at the surface, i n mid-water and close to the bottom (from 20 to 3 5 meters)* This technique was aimed at obtaining indirect information upon the feeding depth of the birds and their prey selection versus availability* I t proved ineffective and yielded results impossible to interpret* It was not repeated i n 1966* But some of the information i t provided was useful and w i l l be referred to at appropriate places later*  RESULTS Figures 9 through 19 illustrate the composition of the diet in the three species for the duration; of the study. Throughout these figures  39 KLgure 9 • The amounts o f v a r i o u s p r e y s i n the d i e t o f A e t h i a p u s i l l a throughout t h e summer o f 19 6A o n l y . Cumulative p e r c e n t a g e o f volume.  R E L A T I V E A B U N D A N C E ( % OF V O L U M E )  __^_L, , P , CALANUS FINMARCHICUS  CALANUS CRISTATUS EUCALANUS BUNGII EUPHAUSIACEA A L L CATEGORIES  MYSIDACEA A L L CATEGORIES GAMMARIDEA A L L CATEGORIES  HYPERIIDEA ALL  CATEGORIES  C A R I D E A III, CEPHALOPODA, F I S H I, II, III, PTEROPODA, ETC. C A R I D E A I, II  f  • f •  40  Figure 10 • The amounts o f various preys i n the d i e t o f A e t h i a pff,sfflg throughout the summer o f 1966 only. Cumulative percentage o f volume. Code as i n Figure 9,  Figure 31 • The amounts o f various preys i n the diet o f A e t h i a p u s i l l a throughout the summer o f 1965 only. Cumulative percentage o f the volume. Code as i n Figure 9.  41  F i g u r e 12. • The amounts o f v a r i o u s p r e y s i n t h e d i e t o f Aethia c r i s t a t e l l a throughout t h e summer o f 1964 o n l y . Cumulative percentage o f the volume* Code as i n F i g u r e 9*  F i g u r e 13 • The amounts o f v a r i o u s p r e y s i n the d i e t o f Aethia, c r i s t a t e l l a , throughout t h e summer o f 1965 o n l y * Cumulative percentage o f t h e volume* Code as i n F i g u r e 9 .  42  F i g u r e 24 • The amounts o f v a r i o u s p r e y s i n the d i e t o f ftethia c r i s t a t e l l a throughout t h e summer o f 1966 o n l y . Cumulative percentage o f the volume. Code as i n F i g u r e 9.  F i g u r e 15 • The amounts o f v a r i o u s p r e y s i n the d i e t o f Cycloixhynchra p s i t t a c u l a during the c h i c k - r e a r i n g period (food i n neck-pouch). Cumulative percentage o f t h e volume. 1965 o n l y . Code as i n F i g u r e 9.  RELATIVE B  A B U N D A N C E ( % OF V O L U M E ) •  »  e  .  g  .  A3  Figure 16 • The amounts of various preys i n the diet of Cyclorrhynchus psittacula during the chick-rearing period (food, i n neck-pouch). Cumulative percentage of the volume. 1966 only. Code as i n Figure 9.  Figure 17 • The amounts of various preys i n the diet of Cyclorrhynchus psittacula. Cumulative percentage of the volume. Combined data for a l l years. The point "A" represents a l l ( H » 12 ) early summer samples available. Code as i n Figure 9.  44  Figure 18 • The amounts of various preys i n the diet of Aethia, pusilla throughout the summer. Combined data for e l l years. Cumulative percentage of the volume* Code as i n Figure 9.  Figure 19 • The amounts of various, preys i n the^ diet of Aethi,a c r i s t a t e l l a throughout the summer. Combined data for a l l years* Cumulative percentage of the volume* Code as i n Figure 9.  45 the samples from early summer (gullets) are placed i n continuity with the samples from August and early September (neck-pouches). Some important remarks can be made on these graphs* - Crustaceans largely dominate a l l samples* Only i n psittacula db we find a significant representation of non-crustacean planktonic prey items such as cephalopods, pteropods, etc* - Particularly evident i n Figures 18 and 19 where a l l years are represented simultaneously, i s the remarkable change i n the diet as the season proceeds* In early summer, which includes the pre-laying and the incubation periods, many different types of prey alternate and occupy at various times a more or less important portion of the diet* During the chick-rearing period, starting i n early August, both Aethia spp* manifest a striking preference for one dominant food item* This abrupt change appears in a l l years between the latter part of July and the f i r s t sampling done on the colony i n a l l six sample-years* As i s apparent i n Figure 17, this reversal to monophagy does not occur i n psittacula ( see also Figures 15 and 16) and the species maintains at that period a rather eclectic diet* Finally, the diet i s presented i n histogram form i n Figures 20 and 21, which permits a direct comparison of the volumetric importance of the various prey -types and size categories i n a more detailed fashion* As noted above, i n order to bypass the difficulty of over-representation of the August sample, both the early summer and the August-September samples are kept separate* The original tallies i n numbers of prey items per period are given i n Appendix II*  46 Figure 20 . R e l a t i v e importance ( i n volume) of various prey types o f various s i z e categories i n the early summer d i e t of Aethia. p u s i l l a and Aethia c r i s t a t e l l a (food i n g u l l e t s ) . Samples from a l l years; and both sexes combined.  AETHIA 50'  N =  CRISTATELLA 107  401  SIZE  CATEGORIES  47  Figure 21 • Relative: importance (in volume) of various prey types o f various size categories in the food brought to the chick during August and September (food in neck-pouches). Samples from a l l years and both sexes combined. Code for size categories as in Figure 20.  R E L A T I V E IMPORTANCE ( % OF T O T A L V O L U M E ) H  W  o  _2_  o  o  CALANUS FINMARCHICUS CALANUS CRISTATUS EUCALANUS BUNGII HYPERIIDEA  EUPHAUSIACEA  MYSIDACEA  CARIDEA  O  •4  2 GAMMARIDEA  FISH  II  oo  O  r o  x O  w a  I—I  >  43 Foraging As shown i n Figure 1, both species of the genus Aethia have a bimodal peak o f a c t i v i t y on the colonies* Feeding i s also following a non-overlapping bimodal sequence : i t - takes place i n the afternoon and also at daybreak o r early morning. Both species make extensive: and complicated f l i g h t s to and from the feeding grounds. Information on these movements i s d i f f i c u l t to obtain at best but they can be generalized as follows. Movements from the feeding grounds to the colonies are spectacular and quite' cohesive} they have the appearance o f an uninterrupted "stream" o f b i r d s . Movements from the colonies to the feeding grounds are more or l e s s e r r a t i c , each flock departing at i t s own time and taking i t s own d i r e c t i o n . For an observer placed i n Gambell, movements following the afternoon feeding period are generally orientated toward the south-west while the movements following the morning feeding period proceed i n an opposite d i r e c t i o n . The d i f f i c u l t y i n establishing the patterns with accuracy, which would lead to interesting observations on the ways the birds disperse on their feeding grounds, on the influence o f some factors such as wind, fog, etc. upon the direction they take, comes from the presence of three major nesting aggregations, roughly 5 0 km apart (Figure: 23) on the western h a l f o f St. Lawrence Island. There i s evidence that the birds o f a l l three areas meet over what could be c a l l e d , common feeding grounds- around the north-west end of the i s l a n d . The birds f l y to and from the feeding grounds i n flocks o f approximately 2 0 - 5 0 individuals, usually of homogeneous composition. The l i n e a r aggregation o f many hundreds o f flocks constitutes what has been termed a "stream" above. Such flocks p i t c b on the water at appropriate places i early i n the season, the birds may engage or rather pursue  A9  courtship a c t i v i t i e s before actually engaging i n feeding. The birds soon start d r i f t i n g apart and feeding i n d i v i d u a l l y . They have the tendency to dive against the: current and for t h i s reason, after a certain time, they are spaced i n a l i n e a r fashion, the main a x i r o f the r a f t p a r a l l e l i n g the current d i r e c t i o n . This gives r i s e to "strings" of feeding b i r d s . Spacing of the birds at the height of feeding i s d i f f i c u l t to measure and could not be quantified. Aethia pu,cdlla are often found within sight of each other, roughly  100-200  m apart. A flock o f A. c r i s -  tfttella i n the midst o f the feeding period w i l l have scattered considerably, the average distance between the birds being roughly estimated a t  £00-500 m.  Although both species s t a r t i n a punctiform formation of equivalent s i z e , they end up i n a different relationship to each other after feeding has reached a height,' This i t s e l f may be subject to variation with the a v a i l a b i l i t y o f food, the birds tending: to move l e s s when they have settled i n waters r i c h i n zooplankton, but more when the area i s l e s s favourable to feeding. Occasionally, A.  pusilla was found i n very dense feeding groups;  t h i s occurred for instance on a few occasions when pronounced and sustained north-easterlies would bring the appearance i n surface of deeper waters along the west coast o f the islando Several thousand birds could then be found feeding i n a narrow s t r i p o f the l i t t o r a l zone. This feeding by " l o c a l enhancement" (Hinde, 19ol) has been observed only once i n A^  crista-  tella * From ffli the evidence gathered i a some 30 collecting t r i p s , there i s complete overlap between the feeding grounds o f the two species of  Aethia. In other words, individual c r i s t a t e l l a were found interspersed  amidst a loosely arranged feeding raft- o f p u s i l l a and v i c e versa.  50  However, on three occasions, the following situation was encountered son long ranging transects, up to 75 km of water were surveyed with total absence of one or the other species. This indicates that they may select their feeding grounds according to slightly different criteria. As a rule, pusilla was more regularly distributed, being present in comparable numbers in the littoral zone as well as 30-50 km offshore, while  cristatella  on  the other hand, was seldom found less than one half to one km offshore. After feeding, the birds take to flight and settle close to the nearest neighbour, or close to an already gathered nucleus of satiated birds. This leads within an hour or so to the reconstitution of the original flocks, which soon take to flight. Less is known about the feeding and foraging of C.  psittacula.  Birds have the tendency to fly singly and, as mentioned earlier, the few small flocks encountered on the feeding grounds turned out to be immatures. No estimates of the distance between feeding individuals can be given, but this distance is by far greater than what was observed in A>  cristatella.  C. psittacula was, however, regularly found in company with either one of the two auklets as well as in company of  tJria  spp.and Cepphus  coluaba.  Like cristatella. i t was seldom observed less than one km offshore with the exception of Kavalghak Bay (Figure 6 ) which, apparently due to strong circulation in its vicinity attracted numerous individuals of many species of marine birds. Few observations were made at sea during the chick-rearing period but these indicate that the auklets have a tendency to operate on a much more individual basis than earlier on in the season s flocks are noticably smaller, and, in late August, the spectacular movements from the feeding grounds to the colonies are not observed.  51  The Food Complex I n c l o s e d * fresh—water systems where an adequate e v a l u a t i o n o f t h e f o o d complex i s p o s s i b l e , we can d e v i s e i n d e x e s o f " e l e c t i v i t y " 3 r a t i o s between t h e abundance o f a f o o d i t e m p r e s e n t and t h e amount o f t h i s i t e m consumed b y t h e p r e d a t o r ( i v l e v , X 9 6 l ) . Adequate ©valuation o f t h e f o o d complex i n m a r i n e environments s t i l l remains t o be o b t a i n e d ( s e e i r o n , 1 9 6 2 ) , and t h e b e s t t h a t c a n be done i s t o produce: e s t i m a t e s and q u a l i t a t i v e statements a s t o t h e presumed c o m p o s i t i o n and d i s p e r s i o n o f t h e f o o d e l e ments and t h e a e s s a r e d p r e f e r e n c e s e s & T e i i e d : by t h e p r e d a t o r s * I n t h e p a r t i c u l a r case which concerns u s , t h e problem would f u r t h e r be worsened by t h e n e c e s s i t y o f h a v i n g comparable and q u a n t i t a t i v e sampling t e c h n i q u e s t o e v a l u a t e t h e c o m p o s i t i o n o f b o t h t h e p e l a g i c and t h e n e a r - b e n t h i c faunas* Furthermore, a c t u a l t e c h n i q u e s are v e r y p a r t i a l t o some organisms and i t i s w e l l known f o r i n s t a n c e t h a t standard h a u l s do not capture fast-swimming forms l i k e e u p h a u s i i d s i n a r e p r e s e n t a t i v e manner* T h i s was c l e a r l y i l l u s t r a t e d i n August 1965 when s i x p l a n k t o n h a u l s i n areas used by f e e d i n g a u k l e t s ; f a i l e d t o produce more than t e n F u r c i l i a s t a g e s and a d o l e s c e n t Thysflnoessa spp* a t a t i m e when the c o l l e c t e d b i r d p o p u l a t i o n managed t o o b t a i n p r o b a b l y upwards o f 30 m e t r i c tons o f t h i s p r e y i n two hours o f f e e d i n g i n t h e same waters* N e v e r t h e l e s s , some g e n e r a l i z a t i o n s c o n c e r n i n g the f o o d - s p e c i e s can be made* These c o n s i d e r a t i o n s are based upon a v a i l a b l e l i t e r a t u r e as w e l l as on t h e rudimentary sampling done i n 1965* W i t h i n t h e study a r e a , i . & . from Gambell t o 25 km west, s o u t h west and n o r t h , t h e d i s t r i b u t i o n o f most consumed f o o d i t e m s i s z o n a l a t mid-day w i t h a steady i n c r e a s e i n d e n s i t y f o r every form down t o near t h e bottom. O n l y secondary i t e m s such a s p t e r o p o d s , Medusae, and a few o t h e r s  52 seem to have a zonal distribution that follows a reverse trend. Bigelow (1926) i n his classical study of the Gulf of Maine found that the 0-25 m layer was rather barren, containing eggs and nauplii of copepods, young stages of hyperiids, amphipods and euphausiids i the bulk of the zooplankton with Calanus. Euthemisto. Thvsanoessa. Sagitta. etc. could be found below 25 meters. The plankton hauls indicated clearly that only a narrow selection of the avilable zooplankton i s used for feeding by the auklets. Many super-abundant forms of apparently suitable size such as Medusae, Ctenophora, Chaetognatha, Oikopleura, etc. are largely ignored and have seldom been encountered i n the digestive tract of the birds ( the likelyhood of these softer forms being digested too quickly to be found i s rather slight). On the other hand, super-abundant forms which would require a special filtering apparatus to be collected economically such as Pseudocalanus; - an ever-present and ever-dominant form - Metridia. copepods and barnacles nauplii do not figure i n the diet. Oscillations i n the abundance and availability of food i n marine subarctic environments i s very restricted to a couple of seasonal blooms relatively short i n duration. Moreover, the restriction applies only to the bloom of two or three major types of organisms. The supply can also vary with years and Nemoto (1957) after extensive analysis of the feeding of whales i n the southern Bering Sea concludes that i n some years, some forms that usually dominate can be lacking almost totally ("krill years , Calanus years"). n  M  A brief interpretation of the cycles of abundance of the most important organisms i n the diet of Aethia spp. and Gyylorrhynchus psittacula must be given.  53 ft • Calanms  flnmarchicus , Raymont (1963) has summarized  t h e major  studies  on the distribution, breeding and vertical migration of this important copepod* In the English Channel, several broods are produced each  year,  the first brood of the summer reaching maturity in approximately one month* One or two more broods will follow and in early fall, the last one will reach the Copepodite stage V before moving to deeper waters for the winter* No detailed study of Calanus; i s available for the area under consideration. But #stvedt (1955) working in the Norwegian Sea, described the appearance of spawning C. flnmarchicus in the 0-200 m layer between April and June : this was followed by their disappearance in June and July and by an outburst of non-breeding individuals (Copepodite V) in the surface layers in  early  August and September (summarized in Laevastu, 1962), These findings are quite similar to the cycle of abundance of Calanug revealed by i t s occurrence in the diet of Aethia pusilla (Figures 9, 10, U and 18), In all three years, there seems to be an early peak of maturation of  C^gnts. in  early summer, although the incomplete: sampling does not indicate  i t s extent  very clearly * this would constitute the early summer spawning and,  indeed,  the plankton hauls of 1965 showed an increase of copepod nauplii in the surface layers to a maximum in mid-June and a complete disappearance in late July* According to this interpretation, the rapid increase in early August (Figure 18) would represent the appearance in the surface layers of non-breeding individuals. Preliminary examination of  the Oalanus  found  in the digestive tract of pusilla seem to support this interpretation. It is interesting to examine and. compare curves of total abundance of various Copepodite stages obtained by various investigators (for instance, Marshall & Orr, 1955; Digby, 1954; Kielhorn, 1952) j the rapid increase in late summer of advanced stages (V) or adult stages in  54 the surface l a y e r s i s r e g u l a r l y followed by a temporary diminution i n abundance expressed as a " d i p " following immediately the peak i n numbers** This pattern i s reproduced i n the three years during which  pusilla was  sampled (Figures 9, 10 and l l ) : i t i s d i f f i c u l t to avoid the conclusion that t h i s " d i p " i s o f the same nature as those observed by regular sampling techniques and r e f l e c t s a temporary decrease i n the a v a i l a b i l i t y of Calanus i t s e l f * No s a t i s f a c t o r y explanation has, to my knowledge, been proposed to account f o r t h i s phenomenon* The problem of diurnal migration o f t h i s copepod further comp l i c a t e s the p i c t u r e * I n the prscoat mm  howsvor, stoat b i r d s were c o l l e c t e d  i n waters o f l e s s than 35 n i n depth and there i s evidence that a l l three auklets can reach t h i s depth while feeding* But i n that connection, i t i s i n t e r e s t i n g to mention that Bogorov (1946) observed Calanus swarming at the surface during the summer months of continuous daylight* He found no d a i l y v e r t i c a l movement t o deeper waters but observed that the copepods would maintain themselves i n the uppermost l a y e r s . b . Calanus c r l s t a t u s • Another macro-copepod, Calanus. c r l s t a t u s makes a substantial contribution to the d i e t of at l e a s t one auklet, C. p s i t t a c u l a . and occasionally makes up to 20% of the d i e t o f Aethia spp. I t i s a wellknown warm water form t stocks o f overwintering animals (Stage v) keep i n deep waters, below 500 m s breeding occurs i n deep water i n mid winter and juveniles migrate to the surface layers where they apparently reach the l a t e Copepodite stage (V) before vanishing from the surface i n e a r l y f a l l to overwinter at depth (Beklemishev, 1954, quoted by Raymont, 1963, Nemoto, 1957). These l a t e stages are very abundant close to the surface during the summer and Nemoto (1957, 1959) speculates that the species must there form extensive swarms. I t i s caught i n abundance by the p l e n t i f u l f i n  whales % M c h a r e known t o o b t a i n t h e i r f o o d b y " s w a l l o w i n g " r a t h e r t h a n by "skimming" t h e s u r f a c e w a t e r s . P i n whales c o u l d a p p a r e n t l y n o t f e e d upon P l a n u s c r i s t a t u s i f i t d i d n o t appear i n the form o f dense swaras (Nemoto, 1957). L i k e C. ftemarchi<?us  f  C. c r i s t a t u s i s a p p a r e n t l y a f i l t e r -  f e e d e r ( M a r s h a l l & O r r , 1955J O s t e r b a r g e t . a l . , 1964) t h a t makes use o f p h y t o p l a n k t o n and suspended p a r t i c l e s . The i r r e g u l a r o c c u r r e n c e o f t h i s form i n th® d i g e s t i v e t r a c t o f a u k l e t s may be e x p l a i n e d b y t h e f a c t t h a t t h e study a r e a i s toward the l i m i t o f i t s n o r t h e r l y d i s t r i b u t i o n . I n 1965, i t appeared i n May and e a r l y J u n e ( c r i s t a t e l l a and p u s i l l q . F i g u r e s 11 and 13) a l t h o u g h i n 1966 i t was n o t found u n t i l J u l y and e a r l y August ( F i g u r e s 10 and 14). c . Thysanoessa epp.  Two e u p h a u s i i d s were i d e n t i f i e d i n the f o o d samples,  Thyganoesga: j n e r m j g and T . r a s c h i i . B o t h forms which were about e q u a l l y r e p r e s e n t e d i n numbers are. o f l o w - a r c t i c - b o r e a l t y p e ( E i n a r s s o n , 1945). Both spawn d u r i n g the: s p r i n g i n t h e N o r t h A t l a n t i c where they a p p a r e n t l y r e a c h m a t u r i t y i n two y e a r s . I n v e r y c o l d N o r t h A t l a n t i c w a t e r s , spawning seems t o o c c u r o n l y i n the: s p r i n g o f the. t h i r d y e a r and s i m i l a r l y , t h e B e r i n g Sea p o p u l a t i o n s o f T . i n e r m i s a r e t r i e n n i a l (Nemoto, 1957, 1959). I n t h e G u l f o f Anadyr, soon a f t e r t h e i c e c o v e r thaws, euphaus i i d s (Thysanoessa spp.) r i s e t o t h e s u r f a c e where spawning swarms are encountered i n t h e seconf h a l f o f J u n e (Ponomareva, 1963). l i s can be seen i n F i g u r e s 12, 13 and 19, an appearance o f Thysanoessa i n t h e d i e t o f the. C r e s t e d a u k l e t i n J u n e p r o b a b l y r e f l e c t s t h e sudden a v a i l a b i l i t y o f t h i s p r e y i n the s u r f a c e l a y e r s . U n f o r t u n a t e l y , s e x u a l m a t u r i t y c o u l d not bo determined o n t h e s e i n d i v i d u a l s owing t o t h e i r poor c o n d i t i o n o f p r e s e r v a t i o n . A d o l e s c e n t forms showing almost grown e x t e r n a l s e x u a l c h c r c c t e r a , a s w e l l a s younger age groups a r e found i n the s u r f a c e l a y e r s u n t i l  56  September (Nemoto, 1957). Ponomareva (1963) also reports having observed sexually immature Thysanoessa in the "surface film" during the month of June and i n broad daylight. Her analysis (1963) also clearly indicates that the largest proportion of juvenile T. jnermis are present in the 0-50 m layer » 95 to 100$ of the large juvenile stages of T. raschlj are encountered i n the same layer during the summer ( individuals above 17 mm in overall length) • The Thvsanoessa represented i n the diet of Aethia cristatella during August shoved no sign of sexual maturity and belonged to size classes of 17 to 25  mm.  The correspondence between the cycle of abundance of this prey and the feeding of Aethia cristatella i s interpreted as follows. In June, the birds benefit from the appearance in surface of spawning individuals and make temporary use of this food source. In August, the auklets utilize adolescent or juvenile stages of Thysanoessa that distribute i n the surface layers. The sudden appearance of this prey i n the layers accessible to the birds i s not. entirely explained, but presumably resembles the pattern of seasonal vertical migration described for Calanus finmarchicus (p 53) and i s controlled i n a rather c r i t i c a l manner by environmental factors. d . Parathemisto l i b e l l a l a . Hyperiid amphipods, almost wholly represented by Parathemisto libeHula. rank third i n importance i n the diet of auklets. Dunbar (1957), referring to the abundance and importance of this pelagic amphipod i n arctic and subarctic waters says * "It forms the most important jHm<- i n the food chain between the copepods and other small planktonic forms on the one hand and the vertebrates on the other..." The young have direct development and are released at 2-3 mm i n size (Dunbar, 1957). Very young individuals from 2 to 5 mm in length were found in May, June and July i n the gullet of Aethia pusilla i n particular, and most likely repre-  57 sent individuals released i n the preceding spring. Dunbar (1957) observed swarms of adolescent individuals but very l i t t l e seems to be known about the habits of large animals (that can reach 60 mm i n length according to Bowaan, I960). They are well known carnivores on the smaller copepods but l i t t l e i s known about their swarming habits and actual patterns of distribution i n the surface and subsurface layers.  A much rarer warm-water migrant,  Parathemisto p a c i f i c a  (small  size: species reaching at the most 5*3 mm (Bowman, I960)) was also encountered i n the gullet of A. p u s i l l a . A symbiote of jelly-fishes, H y p e r l a medusarum was also found i n 1966 and was used exclusively by C. p s i t t a c u l a . In marked contrast to the. copepods and euphausiids;, the hyperiid amphipods do not reproduce during the summer and do not show peaks of abundance of the type illustrated for Calanus flnmarchicus and .Thysanoessa spp. e . Gammaridea . A group of some importance must be mentioned, the gammarid amphipods. Some twenty species of this group were encountered i n the sampling of auklets. As expected, typical free-swimming epifaunal forms such as Atylus and Pontpgeneia make the bulk of the obtained genera (see Appendix III). However, such infaunal genera such as Anonvx. Monoculodes, Orchomenella and others appear i n varying numbers and this raises the question of how the birds obtained them. The relative importance of the various members of the group i s detailed i n Appendix III. Gammarid amphipods were dredged i n abundance throughout the surrounding waters and they appear to constitute a posst&neafc, r o l l able and important food source for a number of animals such as the Gray Whale (Eschrictius gibbosus) and a number of summering and wintering Anatidae. Virtually nothing i s known about the ecology of this group and  53 even t h e taxonomy i s . f a r from luminous* Gammarids are g e n e r a l l y absent from t h e d i e t o f the b i r d s a f t e r the end o f J u n e , T h e i r reappearance i n s m a l l numbers, i n company w i t h eumaceans ( D i a s t v l i s ) always c o i n c i d e with a d i m i n u t i o n i n t h e abundance, o f the. p r e f e r r e d f o o d i t e m s , i , e . i n the case o f A. p u s i l l a and e u p h a u s i i d s i n the case o f A .  copepods  cristatella,  I presume t h a t t h e a u k l e t s do n o t f i n d the gammarids v e r y p a l a t a b l e . f o Others, •  Decapoda l a r v a e ( T r i b e Caridea) occupy a temporary i m p o r t a n t  r o l e i n t h e d i e t o f A e t h i a p u s i l l a p a r t i c u l a r l y d u r i n g the month o f J u l y when t h i s , p r e y c o n s t i t u t e s about one h a l f o f t h e t o t a l f o o d i n t a k e , A n o t i c a b i e change t a k e s p l a c e i n the s i z e o f these l a r v a e , the s m a l l s i z e category ( i )  dominating i n June and the. l a r g e r s i z e c a t e g o r y ( l l )  dominating  i n J u l y , N e a r l y a l l t h e c a r i d e a n l a r v a e were r e p r e s e n t e d by a s i n g l e tified)  (uniden-  s p e c i e s ( f a m i l y Crangonidae ? ) , Cephalopoda, p t e r o p o d s , p o l y c h a e t e s and s m a l l f i s h e s were n o t  i d e n t i f i e d . The l a t t e r however, seemed t o be: p r e d o m i n a n t l y o f two f a m i l i e s t C o t t i d a e and Ammodytidae, g . F i n a l Remarks • F i n a l l y , a l l these z o o p l a n k t o n i c organisms show marked seasonal f l u c t u a t i o n s : i n biochemical composition. Fats i n p a r t i c u l a r are known t o v a r y w i t h i n wide l i m i t s and t h e p r e d a t o r s t h a t depend on t h e s e organisms p r o b a b l y f a c e a t one; time o r another i n t e r e s t i n g problems o f energy balance. There i s every r e a s o n t o b e l e i v e t h a t d u r i n g m i d - and l a t e summer, zooplankton i s p l e n t i f u l and a v a i l a b l e ( o r a c c e s s i b l e ) t o the b i r d s w i t h i n the 35 m depth zone, and t h i s , a s much a t mid-day as i n e a r l y morning. S h o a l i n g o f some o f t h e p r e y t y p e s may be a s i g n i f i c a n t f a c t o r i n t h e i r s u s c e p t i b i l i t y t o p r e d a t i o n by the a u k l e t s a t one time o r a n o t h e r . There are  59 reasons to believe that the s t r i k i n g increase i n abundance i n the e a r l y August food samples o f such prey types i s a r e f l e c t i o n o f t e h i r sudden a v a i l a b i l i t y to the b i r d s . This i s reasonably c e r t a i n i n the case of Calanus. but l e s s so i n the case o f Thysanoessa. I t can be emphasized at t h i s p o i n t that f a l l and winter feeding must be extremely d i f f e r e n t . I t i s known f o r instance that forms such as Calanus c r i s t a t u s r e t r e a t to deep waters i n e a r l y f a l l * As a whole, the surface l a y e r s must be r e l a t i v e l y barren and Zenkevitch. (1963) generalizes that the bulk o f the plankton biomass i n winter i s found below 200 m* Winter feeding ecology has never been studied t i t i s probably correct to say that the winter d i s t r i b u t i o n of the auklets closely corresponds to those areas o f strong upwellings such as are found i n the v i c i n i t y o f the Aleutian Islands and where deep water food material i s brought w i t h i n the feeding depth range o f the auklets* The Feeding of Aethia and Cyclorrhynchus Owing to i t s small body s i z e , and the correspondingly small size o f i t s beak, Aethia p u s i l l a has. access t h e o r e t i c a l l y to a smaller food spectrum than A* c r i s t a t e l l a . This concept, developped f o r Passerines where body-size differences are rather s l i g h t (Lack, 194-4) i s however, not quite v a l i d when applied to the present case where the s i z e - r a t i o i s o f the order of 3»1 . I n the want of calanoid copepods, Aethiq p u s i l l a has access to a much wider range; o f suitable preys that cannot be exploited economically by i t s l a r g e r congener. I n early summer f o r instance, p u s i l l a makes heavy use of small pelagic prey items as substitutes f o r the l a c k i n g copepods and uses small hyperiids (size I and I I ) , caridean larvae and, i n some years, the r a r e r Eucalamts bungil and Calanus c r i s t a t u s . j.ethla c r i s t a t e l l a during e a r l y summer, i n the want of what i s considered the p r e -  60 f e r r e d food i t e m , Thysanoessa, (see below) most f a l l back upon s m a l l s i z e organisms, presumably l e s s s u i t a b l e f o o d s o u r c e s . Indeed, i n e a r l y summer, a s much a s 7 3 , 7 $ o f the volume o f i t s f o o d i s made o f organisms o f v a r i o u s t y p e s b e l o n g i n g t o the lowermost two s i z e c a t e g o r i e s ( I and I I )  s during  the c h i c k - r e a r i n g p e r i o d , the r e l a t i v e importance o f s m a l l s i z e p r e y i t e m s has f a l l e n t o o n l y  3*0$ o f t h e t o t a l d i e t (these f i g u r e s c a n be d e r i v e d  from the d a t a t a b u l a t e d i n Appendix I I ) •  This gives r i s e to i n t e r e s t i n g  s p e c u l a t i o n s r e g a r d i n g the e n e r g e t i c b a l a n c e and t h e d i f f e r e n t problems f a c e d by the two A e t h i a , The. c l a s s i f i c a t i o n o f Calanus f i n m a r c h i c u s and Thysanoessa spp, as p r e f e r r e d f o o d i t e m s i s based upon t h e assumption t h a t any a n i m a l w i l l t e n d t o consume — w i t h i n the l i m i t s o f i t s a d a p t i v e c a p a b i l i t i e s -  prey  i t e m s which a f f o r d the h i g h e s t degree o f e n e r g e t i c i n p u t f o r t h e s m a l l e s t degree o f energy e x p e n d i t u r e s . T h i s assumption s h o u l d n o r m a l l y be r e i n f o r ced d u r i n g t h e c h i c k - r e a r i n g p e r i o d when t h e demands p l a c e d upon the b i r d s are a t a maximum. The approximate weight a t h a t c h i n g and a t departure f o r the n e s t l i n g s o f Aethj,^ spp, are known; the approximate d a i l y requirements t o o b t a i n such a g a i n i n weight can a l s o be o b t a i n e d ( c a l c u l a t e d by u s i n g the. e s t i m a t e o f 13,4. g o f f o o d f o r one gram o f weight g a i n i n c h i c k s o f U r i a l o r o v i a ; Tuck & S q u i r e s , 1955), I t becomes p o s s i b l e t o e s t i m a t e t h e d a i l y amount o f f o o d t h a t must be c a r r i e d t o the c h i c k . I n c r i s t a t e l l a . t h i s amounts t o about 80 g and i n p u s i l l a t o about. 30 g. Both p a r e n t s a r e r e s p o n s i b l e f o r the; c a r r y i n g o f t h i s f o o d , y e t , i f one a d u l t c r i s t a t e l l a , had, beside feeding  i t s e l f , to provide i t s chick d a i l y  w i t h 40 g o f  p l a n k t o n a^d depended o n l y upon ranall s i z e i t e m s o f c a t e g o r i e s I and I I , i t would be c h a l l e n g e d w i t h q u i t e a problem o f l o g i s t i c s . We can e s t i m a t e t h a t from e i g h t t o t e n times more e f f o r t would have to be i n v e s t e d i n  61 diving and i n feeding movements, Aethia PUS i l i a would most l i k e l y get by such d i f f i c u l t i e s at a much lower cost of energy. The general pattern can be sketched as follows i n Aethiq spp, 5 e a r l y summer dependence on benthic prey items, mid—summer dependence on semi-benthic and pelagic organisms such as- caridean l a r v a e , M a l i h y p e r i i d s , mysids and macro-copepods; during the chick-rearing p e r i o d , r e v e r s a l to monophagy (Calanus and Thvsanoessa). For the purpose of c l a r i t y , a l l s i z e categories o f various prey types were grouped i n the preparation o f Figures 9 to 19. For t h i s reason, p u s i l l a and c r i s t a t e l l a may appear to have s u b s t a n t i a l l y overlapping d i e t s . But they s e l e c t indeed very d i f f e r e n t sizes o f the same prey types. This: w i l l be; discussed at l e n g t h l a t e r , but w i l l be r e a d i l y apparent i n comparing the raw figures f o r various; s i z e categories between the two species given i n Appendix I I . Cyclorrhynchus psjffiqcula^ by comparison to Aethia and other members o f the family f o r that matter, has a s p e c i a l i z e d b i l l (see Figure 40, Chapter I V ) . l e t , the r e s u l t s presented above indicate that i t i s a d i v e r s i f i e d feeder. The upturned mandibles remind a scooping device that would be appropriate f o r c o l l e c t i n g food material on o r , near the bottom. There i s some contradictory evidence on that p o i n t . Mysidacea f o r instance, which appear e x c l u s i v e l y i n the deep hauls make a s i g n i f i c a n t proportion o f i t s d i e t . Some u n i d e n t i f i e d f l a t f i s h e s also appear i n the samples and have most l i k e l y been collected on or very close to the bottom. But, s u r face i n d i c a t o r s such as Clione. Ctenophora, Hyperia appear i n a few g u l l e t s i n d i c a t i n g the v e r s a t i l i t y o f the Parakeet a u k l e t ' s b i l l as a food-getting tool. Curvature o f the tcmia i s , i n i t s e l f , a common c h a r a c t e r i s t i c shared by many groups o f sea-birds (for instance the P r o c e l l a r i i f o r m e s ) .  62 The extent of the curvature f o r instance, i s quite pronounced i n the other plankton-feeding group o f the southern hemisphere, the Pelecanoididae. Of course, the curvature i n the present case i s i n the opposite d i r e c t i o n . B u t i t remains to be seen what exact type o f advantage i t procures o r , i n other words, what i s the adaptive value i n feeding o f such a modification of the b i l l structure* Parathemisto l i b e l l u l a i s a mainstay i n the d i e t o f G. p s i t t a c u l a . although i t u s u a l l y makes only between 30 and 50$ of the; t o t a l food intake* Thvsanoessa spp* becomes the second most important item i n the d i e t during August, and both C* p s i t t a c u l a and A* c r i s t a t e l l a make use of u n d i s tinguishable s i z e categories o f euphausiids. The two species o f Thvsepoeasq are also found i n roughly equal proportions i n p s i t t a c u l a . However, i t i s worth p o i n t i n g out that the increase i n r e l a t i v e abundance of Thyganoessa i n the Parakeet auklet corresponds with an increase o f t h i s prey i n the d i e t of c r i s t a t e l l a . This is: evident i n comparing Figures 17 and 19. The figures f o r i n d i v i d u a l years cannot be compared f o r s p e c i a l c o l l e c t i n g t r i p s had to be made to obtain p s i t t a c u l a and the day o f c o l l e c t i o n f o r that species i s at a variance of one, two or three days with the equivalent sample o f c r i s t a t e l l a . This tends t o indicate that p s i t t a c u l a i s merely reacting to the temporary super-abundance of a food item i n the environment* A l a s t remark about the feeding of p s i t t a c u l a has to do with the presence of food items that were not found i n the digestive t r a c t o f c r i s t a t e l l a . such as Cephalopoda and Polychaeta. I n p a r t i c u l a r , i n 1966, Hyperia medusarura appeared i n seven g u l l e t s or pouches of the Parakeet auklet. This h y p e r i i d , i n view o f i t s symbiotic habits on j e l l y - f i s h e s has probably a p e c u l i a r d i s t r i b u t i o n i n the environment. I t seems that the Parakeet auklet has somewhat d i f f e r e n t foraging habits and reacts i n a  63 d i f f e r e n t manner to p o t e n t i a l food organisms. But generalizations o f the magnitude o f those attempted with Aethia are d i f f i c u l t t o make a t the present time i n view o f the rather incomplete sample a v a i l a b l e ,  SOME ECOLOGICAL CONSIDERATIONS Timing o f the Breeding A c t i v i t i e s The remarkable: change i n d i e t that accompanies the s t a r t o f the n e s t l i n g period brings i n s t a n t l y to mind the i n t e r p r e t a t i o n that the c h i c k r e a r i n g period has been adjusted t o the period o f maximum available energy i n the form o f food. The thesis has been developped mostly by Lack (1954; modified i n 1966) and has received some support as w e l l as many i l l u s t r a tions o f varying q u a l i t y (Salomonsen, 1955; Holmes, 1966; Immelmann, 1963;etc. However, we must f i r s t examine another p o s s i b i l i t y , that o f a change i n d i e t as a behavioral change. In other words, the hatching o f the egg modifies the response o f the parents toward the food complex. This i s w e l l documented i n other families o f birds and Newton (1967) generalized that "most finches s e l e c t d i e t 3 f o r t h e i r young which d i f f e r from t h e i r own d i e t i n the breeding season". Within the family Alcidae I w i l l discuss i n Chapter 17 the case o f several species which are known to carry e x c l u s i v e l y f i s h e s (or l a r g e worms) to t h e i r n e s t l i n g although they, themselves, have a much more d i v e r s i f i e d d i e t . This p o s s i b i l i t y cannot be completely e l i m i nated but there is; a large body o f evidence that tends t o support the t h e s i s of a v a i l a b i l i t y and hence, timing, than the hypothesis o f behavioral change. I mentioned that c o l l e c t i n g at sea was discontinued during August but nevertheless, a few birds could be found at various times that carried food both i n the g u l l e t and i n the neck-pouch. F i f t e e n such cases  64 have been encountered and t h i s information i s presented i n Table 2 . The differences are so s l i g h t i n the case of c r i s t a t e l l a that they can be ignored. The case of p u s i l l a , i s not so convincing i n view o f the small sample s i z e . Secondly, the theory that animals w i l l tend to minimize the energy output f o r the maintenance of the steady state condition i s quite acceptable. I t would be i n t e r e s t i n g to f i n d birds so considerate of t h e i r environment that they would r e f r a i n from u t i l i z i n g the most economically worthy resources u n t i l they were compelled to do so t t h i s i s probably the more true of predators depending upon f u g i t i v e organisms widely o s c i l l a t i n g i n abundance i n the environment. Thirdly, the s t r i k i n g resemblance of some of the curves p i c t u r i n g the seasonal changes i n d i e t with conditions o f a v a i l a b i l i t y i n the marine environment observed by standard techniques (presence of a " d i p " or decrease i n abundance of Calanus; f o l l o w i n g immediately the peak o f density J see d e t a i l s on page 54) also supports the theory o f t i m i n g . The f a l l - o f f i n the abundance o f Calanus i n e a r l y September i s also interpreted as a r e f l e c t i o n of diminishing a v a i l a b i l i t y i n the environment ( Figures 9 , 10 and 11). F i n a l l y , I v l e v (1961) showed experimentally with f i s h e s that an increase i n feeding opportunities o f a given predator leads to an increase i n the e l e c t i v i t y o f preferred forms and to a decreased e l e c t i v i t y f o r those that are- normally avoided. To say that timing has been adjusted so that the auklets can benefit from t h i s increase i n the food supply implies that some o s c i l l a t i o n s are possible i n the timing o f the breeding season and t h i s seems to be the case. The birds spend as much as f i v e weeks on the breeding grounds before l a y i n g . I n p a r t i c u l a r l y good springs (1964), the n e s t - s i t e s are free from  65  Table 2 • Overlap i n the diet used by the parent bird (food i n the gullet) and carried to the chick (food in the neck-pouch). All a v a i l a b l e cases i n which food was present i n both parts of the digestive tract are pooled. Size categories given i n Roman numerals for some prey types are explained on page 37.  Aethia PUsil3,a(N= 6) Relative importance i n  Aethia,  cristatella(N»9)  Relative importance i n  numbers^of food items(%) Volume of food items($) POUCH  Volume(cc)  GULLET  POUCH  GULLET  17.5  4.3  90.46  74.05  6.18  2.15  Calanus cristatus;  1.45  11.19  10.13  11.34-  Eucalanus bun^U  -  Calanus finmarchicus  Parathemisto  libellula  "  (i)  .48  25.8  .22  -  .25  2.03  1.02  8.34  (III) .10  .25  4.40  .32  1.07  3.56 .71  1.16  77.30  76.17  "  (II)  » Thvsanoessa spp. (i) »  (II)  -  n  (III)  -  Caridea (i)  .65  »  5.61  (II)  33.8  -  8.65  "Volume of food in gullets of the six sampled pusilla volumetric comparisons.  too  small  to  warrant  66 snow and i c e two t o t h r e e weeks e a r l i e r t h a n t h e a c t u a l l a y i n g d a t e . The b i r d s i n f a c t seem t o breed a t the l a t e s t p o s s i b l e time i n t h e study a r e a . I n e a r l y September, weather d e t e r i o r a t e s r a p i d l y , snow f l u r r i e s are  frequent  as w e l l as heavy s e a s . These f a c t o r s have p r o b a b l y enough o f an e f f e c t t h a t t h e r i s k s i n v o l v e d i n l a t e b r e e d i n g must be compensated f o r by some g r e a t e r advantage. E a r l y snows a r e r e p o r t e d by t h e n a t i v e s t o provoke mass d e s e r t i o n by the p a r e n t s , presumably due t o the c l o g g i n g o f n e s t s e n t r a n c e s : t h i s has n o t been observed by o r n i t h o l o g i s t s however. A l s o , c h i c k s a r e known t o be washed ashore i n numbers when rough seas p r e v a i l at the time o f  depar-  t u r e (example, 6 September, 1965). These c h i c k s are i n extreme f a t c o n d i t i o n and t h e o n l y l i k e l y reasons f o r t h e i r d e a t h seem t o be t h e i r i n a b i l i t y t o cope w i t h h i g h winds o r t o a v o i d g e t t i n g trapped i n t h e zone o f heavy s u r f and t i d a l e d d i e s a t the base o f Sevuokok Mountain. F i n a l l y , the days become r a p i d l y s h o r t e r a t t h a t p e r i o d and t h i s i s f o l l o w e d by a c o r r e s p o n d i n g decrease i n the amount o f time aval Table t o the a d u l t s f o r c o l l e c t i n g food f o r the n e s t l i n g . When t e c h n i q u e s o f s a t i s f a c t o r y r e l i a b i l i t y w i l l enable us t o sample adequately the most important p r e y i t e m s i n the h a b i t a t , we w i l l be a b l e t o v e r i f y c o n c l u s i v e l y the h y p o t h e s i s supported above. But an i n d i r e c t way o f approaching a s o l u t i o n would be t o s t u d y the s e a s o n a l changes i n t h e d i e t o f A e t h i a i n o t h e r l o c a l i t i e s where the c y c l e s o f these important i  z o o p l a n k t o n i c organisms are b e t t e r known, and f i n d o u t how t h i s  adjustment  i s r e a l i z e d i n such c o n d i t i o n s . C. p s i t t a c u l a has a b r e e d i n g season c l o s e l y o v e r l a p p i n g t h a t o f A. c r i s t a t e l l a . There i s no obvious r e a s o n f o r t h i s s i n c e the former does not b e n e f i t d i r e o t l y from the i n c r e a s e , d u r i n g August, o f Calanus o r o f Thysanoessa. I t may however, b e n e f i t from i t i n an i n d i r e c t way s i n c e the  67 increase i n plankton biomass at that time probably means also an increase i n the same waters of the predatory organisms upon which  psittacula  feeds  predominantly. I t i s however d i f f i c u l t to suggest much more than that at the present time. Body Weight of Laving Females and Feeding Relations Belopol'skii (1957) i n an extensive study of the food-habits of the marine birds of the Barents Sea suggested i n some cases that a decrease i n body weight of tho breeding birds could be related to temporary failures i n the food supply. Unfortunately, none of the examples he used were very convincing or were adequately quantified. Seasonal changes i n body weight were illustrated i n Figures 3 and 4 for Aethia pusilla and i>  cristatella*  A weak attempt was then made  to interpret the relationship between periods of presumed increased or decreased energy demands and the observed gains or losses i n average body weight. U n t i l we have established experimentally tha major parameters involved i n the preservation of energy balance, any such attempt w i l l remain speculative. But one relation involving drastic changes i n body weight and apparently the nature of the food available i s worth examining i n some detail. In early July 1966, numerous females of Aethia  cristatella  were  found dead at the base of the colony or on the neighbouring beaches i n a condition of extreme emaciation. Reliable weights could not be obtained on most of these for the simple reason that scavengers had often damaged the carcasses. Values were obtained for two of these however and were 24-7.6 and 195.1 g. A total of eight cristatella were examined during this period i seven of them could be recognized as females and a l l had l a i d , as indicated  63  by the presence of a f r e s h l y collapsed f o l l i c l e i n the ovary. Other species were noted as w e l l i bodies o f Tufted P u f f i n s (Lunda c i r r h a t a ) . Homed P u f f i n s (Fratercula corniculata) and even Fulmars (Fulmarus f a c i a l i s ) were found during t h i s same period and females with collapsed f o l l i c l e s were also found among them. Furthernore, numerous females of c r i s t a t e l l a . w i t h collapsed f o l l i c l e and c r i t i c a l l y low body weight were collected on the feeding grounds at that time (lowest extremes encountered i n 1966, 236.7 and 237.8 g ) . Computing the body weight o f females at l a y i n g ( t o t a l weight minus the weight o f f u l l y s h e l l e d egg i n the oviduct) f o r 1966, the average was found to be markedly i n f e r i o r to the averages observed i n the two previous years (Figure 22). The same p a t t e r n was followed by Aethia p u s i l l a although none of the l a t t e r were found dead i n condition of emaciation. This decrease i n average body weight was also accompanied by a decrease i n average l e v e l s o f subcutaneous f a t i t h i s i s also shown i n Figure 22. As I have indicated e a r l i e r , we are not yet able to assess accurately the food complex and to devise an index of comparison betweea years. At the present, our s t a t i n g that a year i s a poor food-year i s generally  an g p o s t e r i o r i conclusion based upon very i n d i r e c t evidence such  as an increase i n the death o f nestlings of some species, o r an observed diminution i n the average body weight of f l e d g l i n g s . I r e a l i z e that t h i s form of reasoning i s a weakness o f the present discussion. But i n 1966, there was a c l e a r increase i n the r e l a t i v e abundance o f benthic gammarids during the p r e - l a y i n g period (Table 3> the data f o r 1964 are unfortunately too small to warrant d e t a i l e d comparisons). An increase i n the proportion of gammarids i n the d i e t was interpreted e a r l i e r as a sign of f a i l u r e i n the a v a i l a b i l i t y o f pelagic forms. The argument can be developped as f o l l o w s .  69  Figure 22 • Body weight ( i n grams) and f a t condition of females a r r i v a l ( l ) and at laying (B) i n various years. The bar represents one; standard error on either side of The figure immediately above or below the bar i s N. gories from A (extremely fat) to 0 (extremely lean).  /  upon vertical the mean. Fat cate-  70  Table 3 • Proportion, i n volume, of the d i e t made o f gammarid amphipods ( a l l size categories) daring the pre-laying period i n A e t h i a p u s - n i a and A. c r i s t a t e l l a i n various years* P r e - l a y i n g period includes all~samples taken between a r r i v a l and June 30 i n c l u s i v e l y . Both sexes combined.  N  T o t a l Volume of Food  in  H (cc)  % i n Volume of gammarids  Aethia p u s i l l a 1964-  7  7*5  70.6  1965  43  28.0  30.7  1966  38  49.0  54.4  3964  8  32.1  1.0  1965  20  55.3  21*7  1966  36  222.3  93.2  Aethia  cristatella  71 During the p r e - l a y i n g p e r i o d , s o c i a l a c t i v i t i e s e x e r t a h i g h i n f l u e n c e upon t h e c y c l e o f d a i l y a c t i v i t y and t h e b i r d s do spend a t the most, 10% o f t h e i r time i n a c t u a l f e e d i n g , an a c t i v i t y a t which they a r e most e f f i c i e n t t d u r i n g p r e l i m i n a r y t e s t s i n t a n k s , i n e x p e r i e n c e d c r i s t a t e l l a f l e d g l i n g s c o u l d consume as much as 12.5  c c o f s m a l l gammarids i n a 30-minute  t e s t ' i n v o l v i n g o n l y e l e v e n minutes spent i n a c t u a l d i v i n g . D u r i n g t h a t s h o r t d a i l y p e r i o d c o n s a c r a t e d t o f e e d i n g , i f the b i r d s do not f i n d an a d e quate s u p p l y o f p e l a g i c f o o d , t h e y w i l l t u r n t o t h e e v e r p r e s e n t and abundant b e n t h i c gammarids. B u t the l a t t e r do not p r o v i d e an adequate source o f energy ( o r cannot be a s s i m i l a t e d ) . Tuck Sc S q u i r e s (1955) observed t h a t young Uria, l o m v i a f e d on Gammarus. a l i t t o r a l amphipod, would d i e w i t h i n a few days w h i l e c h i c k s f e d b i t s o f f i s h , would develop a t a r a t e comparable to p a r e n t - f e d n e s t l i n g s . D u r i n g the t e s t s r e f e r r e d t o above, i t was observed t h a t a u k l e t s ( p u s i l l a and c r i s t a t e l l a ) l e f t t o f e e d on super-abundant l i v e gammarids would c o n s i s t e n t l y l o o s e weight and d i e w i t h i n t h r e e t o f o u r days. None o f these o b s e r v a t i o n s were c a r e f u l l y c o n t r o l l e d however, and t h e evidence c o l l e c t e d so f a r i s r a t h e r meagre. But f u r t h e r support t o the argument comes from an examination o f the o r g a n i c composition o f these gammarids. A v a i l a b l e a n a l y s e s on v a r i o u s c r u s t a c e a n s are grouped i n Table 4 , Gammarids d i f f e r from the o t h e r s c h i e f l y i n h a v i n g a h i g h e r ash content p e r u n i t o f d r y body weight t a l t h o u g h t h i s i s l e s s c l e a r i n Table A, gammarids a l s o t e n d t o accumulate s m a l l e r f a t r e s e r v e s than e s s e n t i a l l y p l a n k t o n i c organisms such as copepods and e u p h a u s i i d s . So t h a t , f o r an e q u a l volume o f f o o d , an a u k l e t f e d upon gammarids p r o b a b l y g e t a l e s s n u t r i e n t s t h a n when f e d upon c a l a n o i d copepods o r e u p h a u s i i d s . Indeed, s e v e r a l f a c t o r s can a c t i n combination : h i g h e r a s h c o n t e n t , l o w e r f a t r e s e r v e s , l o w e r a s s i m i l a t i o n e f f i c i e n c i e s by the  72 Table 4 • Organic composition of various crustaceans o f the types used by the auklets, i n percentage of dry body weight. From various sources. When season o f analysis i s given, the summer values have been used ( o r approximated from curves) from the o r i g i n a l publications.  "Copepods"  Fat  Carbohydrates  4 . 6 -19.2  0. - 4 . 4  C. f^nmarchjyus;  c  Euphausiids-*  c. 4.5  -  Neomysis integer ••Mysids"  35.0  c. 1 3 .  70.9-77.0  4.2-6.4  c.50.0  3.-4.  c.  2.2  69.  2  Eulimnogammarus^ Gmelinoides3  von Krey (1950)  0rr(1934)  15.  Raymont e t a l .  63.37  19.18  Zenkevitch,  -  13.55  Vinogradov,  (1963)  (1953) 7.21  *  15.82 6.84  48.83  29.68  Zenkevitch, (1963)  50.87  18.79  Kurennykh,  43.92  22.89  Kurennykh,  Gammarus locusta  1  Source  (1963)  Mvsis flexuosa "Amphipods"  Ash  F i s h e r (1962)  6.87  2  Proteins  (1967)  (1967)  26.70 -  21.69  23.68  Vinogradov,  (1953)  Wnnvctiohanes norvegica. TTiygamessa. r a s c h i i .  Average  f o r several species o f the Caspian Sea. Measurements by Bokova, quoted by Zenkevitch, 1963.  3  Fresh-water gammarids from B a i k a l Lake.  73 auklets, e t c . Only comparative t e s t s w i l l enable us to discriminate between these f a c t o r s . However, as a preliminary hypothesis, i t i s a t t r a c t i v e to propose that due to t h e i r higher content of amorphous material ( c h i t i n and c h i t i n impregnated with mineral s a l t s )per u n i t volume, and due possibly to t h e i r lower f a t reserves, gammarids do not provide an adequate source o f energy  f o r females during the p r e - l a y i n g p e r i o d . C r u c i a l to t h i s p r o p o s i -  t i o n i s the: f a c t that because of greatly increased s o c i a l pressures,  the  birds: spend only a l i m i t e d amount o f time i n searching f o r food. I t i s quite possible that gammarids could, at other periods, constitute a f i t t i n g source of energy. The weight of females at l a y i n g i s an i n t e r e s t i n g element i n the biology of a b i r d species because o f i t s dynamic i m p l i c a t i o n s . Current hypotheses (Siivonen, 1957; Wagner et a l . , 1965) imply that the p r e - l a y i n g feeding condition i n the females could u l t i m a t e l y have an e f f e c t upon popul a t i o n regulation through i n f l u e n c i n g the yolk q u a l i t y and u l t i m a t e l y the agg v i a b i l i t y and chick s u r v i v a l , o r , by d i s r u p t i n g the timing o f the breeding a c t i v i t i e s . M o d a l i t i e s o f such an influence are f a r from elucidated. The observations mentioned above are also surprising i n another respect t i t i s s u r p r i s i n g to f i n d that females i n presence o f a food shortage seem to have no a b i l i t y to h a l t f o l l i c u l a r development. I s indicated i n Figure 22, females can reach the incubation stage at a much-reduced body weight. I t w i l l be i n t e r e s t i n g to know whether or not t h i s diminishes s i g n i f i c a n t l y t h e i r chances of carrying on incubation. Unfortunately, the basic elements completing t h i s dynamic r e l a t i o n s h i p , egg v i a b i l i t y , chick growth and s u r v i v a l have not been compared between the sampled years. G. p s i t t a c u l a does not seem to be so markedly affected by such food shortages. This i s indicated i n Table 5 where the average weight  74  T a b l e 5 • Weight changes i n A e t h i a p u s i l l a , . A. c r i s t a t e l l a , and O y c l o r r h v n cans, p s i t t a c u l a between a r r i v a l ( b i r d s c o l l e c t e d p r i o r t o June~15) and the. end o f t h e b r e e d i n g season ( b i r d s c o l l e c t e d d u r i n g t h e l a s t week o f August and the f i r s t week o f September). Weight o f a d u l t b i r d s o n l y , both sexes. Weight c o r r e c t e d f o r presence o f f o o d i n neck-pouch o r g u l l e t . Data combined f o r 1964, 1965 and 1966.  Average Weight at Arrival (A)  N  Cg)  Average Weight a t end N. o f season (B) (g)  %  weight  decrease (A u 100%)  93.4  85  83.4  52  10.7  A. o r i g t a t e l l a  300.3  84  265.1  77  12.8  C. o s i t t a c u l a  297.4  11  281.1  29  A. p u s i l l a  5.5  75 decrease i n t h i s species between a r r i v a l and the end of the breeding season i s compared to the observed values f o r A e t h i a spp. The sample o f p r e - l a y i n g females i n p s i t t a c u l a i s too small to compare with A e t h i a and furthermore, food data are l a c k i n g f o r that p e r i o d . This decrease amounts to only 5*>5% o f the weight upon a r r i v a l while i t averages between 10 and 12% f o r A e t h i a . Levels of subcutaneous f a t are consistently maintained higher i n C. p s i t tacula  and extreme leanness was seldom observed. As a whole, the Parakeet  auklet seems to be able to carry on i t s breeding a c t i v i t i e s at a much lower cost and without having to go through periods of precarious energetic  balance  as the Least and the Crested a u k l e t s .  SEGREGATION IN FEEDING  Introduction "Competition f o r food i s often held p a r t l y responsible f o r the evolution and also f o r the maintenance of e c o l o g i c a l differences between related species but i t need not, of course, be s o l e l y responsible f o r t h e i r production since i t can o n l y operate once the species come together by which time they might already d i f f e r i n ecology"(Newton, 1967). I n the present ecological system, i t would be s t e r i l e to attempt to reconstruct the evolutive h i s t o r y that has l e d to the conditions that can now be observed and described. Some Passerines, o r i n general, forms o f recent i n c i p i a t i o n are much more appropriate, i n order to determine the relations o f competition and segregation* We assume here, however, that competition f o r food has held an important r o l e i n the actual segregation of the studied species (and of the members of the family as a whole). The present analysis i s concerned with summer feeding o n l y , and  76  moreover, i n one p a i r o f comparisons ( p s i t t a c u l a x c r i s t a t e l l a ) , only very p a r t i a l data ara a v a i l a b l e . One would expect that food preferences and ecol o g i c a l segregation could be best studied when the populations examined go through a period o f harsh and c r i t i c a l environmental conditions t i n the northern oceans, the f a l l and winter seasons would come to mind as c o n s t i t u t i n g such a period. Then, the adaptive nature of the b i r d s feeding habits, 1  foraging and food s e l e c t i o n would l i k e l y be more conspicuous. But we probably could not at the present time define what constitutes f o r the b i r d s a "harsh and c r i t i c a l period", Ashmole (i960) postulated that the abundance of t r o p i c a l oceanic b i r d s is: not regulated by the number of n e s t - s i t e s , nor by the feeding conditions: outside the breeding season; t h e i r abundance i s rather c o n t r o l l e d during the summer, since, as the number of b i r d s r i s e s i n a colont, the surrounding waters become depleted of food so that the animals must go f u r t h e r and f u r t h e r to obtain t h a i r subsistence* The idea i s borrowed here not f o r i t s regulatory postulate which remains unproven, but f o r the emphasis i t places upon the summer feeding conditions as being p o s s i b l y j u s t as c r i t i c a l i n some ways as the supposedly poor winter conditions. We cannot t a l k about food depletion otherwise than i n speculative terms t but we know that the auklets space themselves on the feeding grounds according to patterns sketched e a r l i e r t we can also l o g i c a l l y i n f e r that there i s a l i m i t to the distance which a b i r d can economically cover d a i l y to obtain i t s food t and we can also i n f e r that the task of having to feed a chick presents an undetermined but c e r t a i n l y p o s i t i v e addition to the energy requirements. In a way, i t i s possible to think o f the summer conditions i n marine birds as j u s t as d i f f i c u l t , i f not more, than the f a l l and winter conditions. During the l a t t e r period, d i s p e r s a l and a c t i v e movement, much lengthened amount o f time spent on the water and reduced l e v e l s of sexual and s o c i a l a c t i v i t i e s  77  must largely compensate for the reduction in abundance and availability of food organisms. Obviously, year-round observations and comparisons of feeding remains an ideal, but hardly within reach at the moment. Theoretically, segregation could be based upon structural or behavioral factors, although i t i s seldom possible to draw a clear line between the two sets of influence. In the category of structural differences, we could classify such things as bill-shape, tongue c o r n i f i c a t i c n , v i s i o n at depth, etc. In the behavioral category, the time of the day at which feeding i a done, the social or individual nature of the foraging, distinct preferences for l i t t o r a l or neritic waters, etc. These distinctions are most difficult to use and inextricably interrelated among themselves. When I break the discussion below in a number o f sub-sections, i t is acrc-^y a matter of convenience. Time element The unimodal peak of activity at the colonies exhibited by C. p s i t t a c u l a has- been contrasted to the observed situation i n A. c r i s t a t e l l a (Figure l ) . The possible result of such a difference could be that the two species are exposed to different food spectra, because of the c o n s t a n t l y changing vertical distribution of the plankton, or because they feed at different tide intervals. Let us consider the importance of t h i s element in early summer. As outlined previously, c r i s t a t e l l a has scattered on the feeding grounds by 1400 h and p s i t t a c u l a will do so about one hour later. But the important difference i s t h a t , whilst c r i s t a t e l l a comes back on the slopes in late afternoon, p s i t t a c u l a does not and presumably c a r r i e s on feeding until dark ( this was checked indirectly be observation, but not by collection). In the morning, p s i t t a c u l a reintegrates the nesting slopes  73 slightly later than c r i s t a t e l l a * On the whole, p s i t t a c u l a spends a p p r o x i mately 60$ more time at sea than c r i s t a t e l l a * We must await more r e p r e s e n tative and extensive collections before we can assess the importance of this difference i n time consacrated to feeding between the two genera. However, during the chick-rearing period, both species were collected at the same time of the day and had, quite certainly, been feeding simultaneously just prior to landing on the slopes. Differences imputable to this time factor can hence, be ignored, at least for this part of the analysis. Both species of Aethia show on the contrary, complete overlap of feeding period and certainly none of the differences observed i n diet could be due to such a factor. Spatial element In terrestrial environments, segregation i n different fragments of a territory i s common place and i s relatively easy to observe. In marine environments, the problem i s slightly different. Bailey (1966) established a correlation between sea birds density and the standing crop of zooplankton in the 0-200 meters layer. "This may suggest that some sea-birds at least have a behavioral mechanism enabling them to locate areas of high productivity, but whether this i s by random searching or by making use of environmental parameters such as the sea temperature i s at the present largely speculative "(p 258). In the case of breeding auklets, the problem i s posed at a quite different scale since the feeding grounds are limited to those areas that can be reached within a reasonable time. This i s not to say that the birds f i l l a l l the possible sea surface surrounding the western end of St. Lawrence Island. They certainly discriminate, and have seldom been  79 found feeding on the north-eastern side of Sevuokok Ifountain for instance. But within the economical navigational range that can be used, the type of environmental differences that could bring about significant changes i n the food spectrum are probably very slight. Tracts of water differ from one another according to temperature, temperature distribution, salinity, etc. t but these are not arranged spatially i n a constant fashion and they do not sort out according to a predictable pattern* Would birds segregate according to subtle differences of that type i s not a very attractive idea since, at the scale of the territory investigated, i t could not lead to differences of the. nature and degree observed. In their discrimination between various areas surrounding the island, the birds probably discriminate as to the likelyhood of finding fopd and this i s a mare step i n feeding rather than segregation. Finally, there is; only one reason why we cannot discard this possibility completely t the finding on three occasions ( out of some 30 sorties averaging between £0 to 50 km of linear search) of non-overlapping - at least partially - feeding distributions between Aethia pusills, and A. cristatella. Besides supporting the idea of discriminatory abilities, this would indicate that the two species do not necessarily select thair feeding grounds according to the same characteristics. But i n brief, the spatial element, although i t can operate outside the breeding season, plays probably a very minor role, i f any, i n accounting for the observed differences i n diet. As a rule, the three species of auklets share the same feeding grounds. The fact mentioned earlier that the Least auklet, as compared to the other two species, has a more ubiquitous d i s t r i bution while feeding at sea (being found i n the l i t t o r a l zone, i n shallow bays, as well as far offshore) can have only a minor influence.  80  Depth of diving The Crested auklet was collected over measured depths of 3 5 m with the gullet f i l l e d of benthic gammarids and cumaceans. The Least auklet was collected with similar food items over known depths of 2 5 m. No direct observation of this type i s available for the Parakeet, auklet. The figures given above represent neither extremes nor avegares, Hanna ( quoted i n Preble & McAtee, 1 9 2 3 ) reported diving abilities of 60 fathoms (120 m ) for Aetata  cristatella. It i s likely that within the study area, a l l three  species of auklets have access to the entire depth range (c. 35-40 m). We should eventually find differential diving abilities among the three species. But there i s no evidence that such a mode of segregation had a predominant, influence i n the course of the observation period, P u s t l l a i s probably the weakest diver of the three i n view of i t s small size, high buoyancy and the higher cost of attaining great depths'. The abundance i n i t s diet of larval forms of several planktonic groups which are more or less typical of the uppermost layers indicate that most of i t s feeding i s carried on at lower depth than either of the other two species. It may be mentioned also that C, psittacula and A, c r i s t a t e l l a . though of equivalent body size, differ considerably i n wing shape and wing area t this may affect their locomotion under water i n some unknown way. But other factors discussed later have evidently much more influence i n bringing about actual segregation than the present one. An argument against segregation by the. use of different depth ranges i s that, due to turbulence, currents, strong thermal layering, etc., none of the auklet species could depend upon the availability of preferred food items at a given depth range with a high degree of reliability, and this would be a very inefficient way of splitting the food resources. I t  81 seems more logical to propose for the time being that a l l t h r e e s p e c i e s make use to the utmost of their diving abilities, yet preserve a large degree of opportunism. There i s no reason to believe that a C r e s t e d auklet diving for food would not stop to feed upon Thysanoessa encountered j u s t below the surface. Feeding segregation by depth of diving would a l s o render difficult to explain why, during May and June 1966 for instance, the two species of Aethia were feeding on benthic prey items, but on pelagic ones during August,  CONCLUSIONS  I will try to summarize the relative importance of the likely modes of segregation examined so far s A e t h i a p u s i l l a and A, c r i s t a t e l l a have overlapping feeding periods, and generally overlapping f e e d i n g areas. Only the depth range utilized could account for some of the observed differences: i n diet. Yet, the importance of this factor seems secondary, at least in the study area. In comparing the pair p s i t t a c u l a x c r i s t a t e l l a , . we cannot make so definite generalizations', P s i t t a c u l a spends much longer on the f e e d i n g grounds than cristatella but the reasons for t h i s are not obvious. As f a r as i s known, both members of the pair use the same f e e d i n g areas and circumstantial evidence indicate that they have access to the same f e e d i n g depth range. In Chapter IV, I w i l l discuss the presence of a gradient i n feeding adaptation within the family. As will be noted then, both p u s i l l a and c r i s t a t e l l a can be considered as belonging to the same t r o p h i c l e v e l . They exhibit the same degree of adaptation for f e e d i n g on plankton : charac-  S2  ters of their trophic apparatus, width of the b i l l , tongue shape, tongue cornification, etc. are similar. Both species differ i n one major respect, the size of their b i l l . This difference is; so large (see Table 8) t h a t i t undoubtedly plays the determinant role i n forcing the two species to f e e d upon different prey items- or, more precisely, make use of different s i z e s of the same prey. Pusilla, does occasionally feed upon large Thysarioessa or large Parathemisto but, interestingly, only a fragment ( usually the last segments of Parathemisto) of such large organisms i s present i n the digestive tract . ingestion of large prey seems to present, insuperable problems and this; was verified qualitatively in captive p u s i l l a . But cristatella, can very well use Calanus finmarchicua and, i n numbers of prey ingested, c lanoid copepods, caridean larvae and small a  hyperiids make nearly 42% of the food organisms preyed upon, but barely &% of the volume of the food ingested (chi<&-rearing period s see Appendix II and Figure 2 l ) . In the case of cristatella x p s i t t a c u l a . nothing i s indeed so clear. Differences- i n the structure of the trophic apparatus do not give us a ready understanding of the observed differences in diet. It i s difficult to understand why the slightly longer and upturned mandibles of p s i t t a c u l a would be- more efficient for preying upon large pelagic amphipods. By using the same feeding are s and, most likely, the same depth range, p s i t t a c u l a a  comes certainly in contact with euphausiids and yet, does not mako v e r y intensive use of them while the overwhelmingly dominant cristatella, finds sufficient quantities to make of them i t s mainstay. We w i l l get answers to these questions only through carefully designed experiments on the feeding efficiency of both species exposed to various types and sizes of prey. I t may then also be possible to follow the  83 ontogeny of the food preferences. Hinde (1959) proposed the f o l l o w i n g e x p l a nation on the ontogeny of feeding behaviour i n b i r d s s young birds make broad attempts at many food sorts or potential foods and later, by experience, restrict themselves to those items t h a t they can take most efficiently. Newton (1967) after testing young finches i n captivity concluded :"hence, differences in diet between species are controlled by differences i n b i l l structure, rather than the b i l l structure being adapted to the d i e c.".  Pro-  bably, these differences i n b i l l structure between c r i s t a t e l l a and p s i t t a cula.  although not clearly understood at the present, will be coupled to  differences i n foraging habits. The latter has already been indicated i n discussing the presence of some "rare" foods i n the diet of the Parakeet auklet. But since we cannot at the present time look at how and why these, differences came about, we can nevertheless look at their net result. The Parakeet auklet concentrates itself upon macrc—zooplankton that i s classified at a higher position i n the food web. Hyperiids (Parathemisto libellula)  are well-known carnivores depending upon abundant c a l a n o i d cope-  pods for their feeding (Dunbar, 1957; Raymont, 1963). The C r e s t e d a u k l e t also uses Parathemisto but at a much lower degree and has a clear preference for animals of moderate size ( size II makes 7.6$ of its diet, s i z e III makes 2*3% i n volume) while the Parakeet auklet uses mostly l a r g e animals ( size II makes %0% and size III makes 33.9$ of its diet i n volume). Psittacula also exhibits a rather constant use of non-crustacean predators such as cephalopods, polychaetes and small f i s h e s . The l a t t e r prey-items total close to 12% of its diet and, as far as t h e sampling i n d i cates, this group of pray i s not of sporadic appearance i n the d i e t but i s used throughout the season. A. c r i s t a t e l l a . on the contrary, has l e s s than  84 1% of i t s diet made of such items. The overall result of these p r e f e r e n c e s  is that psittacula occupies a slightly higher position than c r i s t a t e l l a i n the marine food chains  by tending to concentrate upon maero-planktonic  predators. The difference i s significative and while the Crested auklet consumes a total of 5.1% i n volume of i t s total diet (chick-rearing period) for such predatory zooplankton, the Parakeet auklet derives as much as 50$ of i t s food budget from this group. This information i s given i n Appendix II and i n Figures 17 and  19.  This tendency i s related, i n p s i t t a c u l a . to the longer time consacrated to feeding, i t s much reduced density when compared to cristatella ( see next Chapter) and also i t s much more regular distribution throughout the geographic range. While A e t h i a c r i s t a t e l l a and A e t h i a pusilla are absent from the low productivity waters: of the eastern Bering Sea and St. Matthew Island (Johnson, 1956), Cyclorrhynchus;. i s present there ( p.6, Aethia spp.  Chapter  I).  seem to be restricted to those areas of high productivity where  they can depend upon marked seasonal increases in the biomass of a few p r e ferred organisms, t Cyclorrhynchus. depending largely upon carnivorous zooplankton which has typically a more or less stable abundance throughout the year (Grainger, 1959)  i s able to occupy successfully areas of lower productivity.  Finally, a word must be said of the different patterns of molt observed i n the. two genera, as possibly related to differences in feeding habits. It seems advantageous for ftethia spp.  to undertake molt during the  chick-rearing period for, both species can obtain during the l a t t e r p a r t of the breeding season preferred foods i n apparently super-abundance. Bat these foods disappear quickly from the accessible layers (at least Calanus) i n early September. On the contrary, Cyclorrhynchus. whose mainstay i s not known to oscillate so much i n availability, has the opportunity of spreading  85 more evenly its necessary energy expenditures and, as noted in Chapter I, does not start molting until the very end of the chick-rearing period. It will be interesting to repeat similar studies on the diet of these three auklets in different geographic areas J I venture to say that the basic food types will remain the same throughout the range but the birds will locally make use of the available taxonomic forms.  86  CHAPTER III  SEGREGATION IN THE NESTING HABITAT  INTRODUCTION The patterns of segregation in the nesting habitat were investigated i n order to see how they paralleled the patterns of segregation observed i n feeding. No doubt, radiation i n feeding habits and more generally i n feeding adaptations have been the major and most stringent element i n the evolution of the family Alcidae ( see Chapter I V ) . Bit to some extontj, radiation has also occurred permitting f u l l use of a limited choice of nesting situations. It i s appropriate to recall that no less than eight s p e c i e s of alcids, can be found i n some colonies of the Bering Sea, i n a simplified environment whose main and only feature i s rock i n various stages of disintegration. The object of this Chapter i s to examine the differences i n the nesting habitat of the two congeneric species that occupy the talus s l o p e s , Aethia  cristatella and A> p u s i l l a . A qualitative comparison of the n e s t i n g  habits between that genus and Cyclorrhynchus will then be given. I t i s impossible at the present time to examine the biological or adaptive components of this segregation to their f u l l extent. Segregation i s here examined in a purely descriptive; manner. Before going further, the reader must have i n mind an i d e a of the absolute and relative abundance of the species studied. In the colonies  87 v i s i t e d , the p r o p o r t i o n o f p u s i l l a . c r i s t a t e l l a - and p s i t t a c u l a was r o u g h l y 60, 4.0 and l e s s than 1% r e s p e c t i v e l y . Estimates o f t o t a l numbers ( breeders and immatures ) have been obtained i n the two c o l o n i e s o f Sevuokok and Kongkok, i n which a l l the i n f o r m a t i o n d i s c u s s e d i n the p r e s e n t chapter has been o b t a i n e d . The t o t a l estimates f o r the three a u k l e t s i n Sevuokok were 325,000 and i n Kongkok ( w i t h i n the p e r i p h e r y o f the cirque o n l y ) , 175,000. The p o p u l a t i o n s have most l i k e l y been under-estimated  i n both  cases.  THE PROBLEM AND I T S SETTING  Although Aethia, p u s i l l a , and A. c r i s t a t e l l a d i f f e r markedly i n body s i z e , they do n o t seem t o d i f f e r i n t h e i r a b i l i t y t o move about on l a n d * Both a r e extremely a b l e a t walking, running and even c l i m b i n g a l o n g nearv e r t i c a l boulder edges. I t can s a f e l y be assumed t h a t i f d i f f e r e n c e s are ever observed i n the m i c r o - d i s t r i b u t i o n o f t h e two s p e c i e s , these w i l l n o t be a t t r i b u t a b l e : t o d i f f e r e n t locomotory a b i l i t i e s . The two s p e c i e s make use f o r n e s t i n g purposes o f the mantle o f rock d e b r i s t h a t c o v e r s e n t i r e s l o p e s o r p a r t s o f s l o p e s . A t a l u s slope i s a d e f i n i t e geomorphic s t r u c t u r e , i . e . i t h a s c h a r a c t e r i s t i c s , l i m i t s , and i s t h e r e s u l t o f a c e r t a i n sequence o f p r o c e s s e s . But i t does n o t c o n s t i t u t e a uniform h a b i t a t . One can see wide, d i f f e r e n c e s i n the diameter o f the p a r t i c l e s t h a t c o n s t i t u t e the mantle from p o i n t t o p o i n t s i n p l a c e s , e r o s i o n has c r e a t e d severe g u l l e y i n g . I n o t h e r s , evidence t h a t new m a t e r i a l ^ Entitle 1 t h i s word i s used throughout the t e x t t o r e f e r to the c o v e r i n g o f cobbles and boulders on the t a l u s s l o p e s . I t i s a v o l u m e t r i c e n t i t y , the mantle i s l i m i t e d i n t h i c k n e s s b y the i n t e r - f a c e a i r - s l o p e on the one hand, and by the " f l o o r " on the o t h e r . The mantle does n o t exceed g e n e r a l l y f i v e (5) meters i n t h i c k n e s s . The f l o o r o r lower l i m i t o f the mantle i s made o f the u n f r a c t u r e d parent rock o r , more o f t e n , i s the r e s u l t o f the accumulation and s e t t l i n g o f f i n e to v e r y f i n e p a r t i c l e s with the p r o d u c t i o n o f a r e l a t i v e l y f l a t o r uniform s u r f a c e .  S3 has been added to the slope by the r e c e n t f a l l i n g o f blocks from overhanging w a l l s w i l l be found. I n a t i l l o t h e r p l a c e s , v e g e t a t i o n w i l l have taken  over  so s u c c e s s f u l l y t h a t o n l y d i g g i n g w i l l r e v e a l the presence o f a mantle o f d e b r i s , f u l l y clogged by m i n e r a l and organic  soil.  Moreover, even a c a s u a l l o o k w i l l show l a r g e v a r i a t i o n s i n the d e n s i t y o f the b i r d s i n any one p l a c e . I n some favoured spots,  pusilla will  reach d e n s i t i e s o f t e n b i r d s p e r square meter while i n o t h e r s , two o r three p a i r s at the most w i l l be found over wide s t r e t c h e s o f s l o p e . Some s e c t o r s which appear t o the human observer to be. e n t i r e l y s u i t a b l e f o r n e s t i n g p u r poses and s t r u c t u r a l l y i d e n t i c a l to densely populated s t r e t c h e s , w i l l  be  t o t a l l y unoccupied.  Statement o f the Problem I t i s d i f f i c u l t , not to say i m p o s s i b l e , to have access to a representative, number o f n e s t s o f A e t h i a spp. l o c a t e d i n the rock mantle. A c c e s s i b l e n e s t s a r e g e n e r a l l y marginal o r , e l s e , i n areas where rock p a r t i c l e s are s m a l l enough to be handled. T h i s makes a v a l i d comparison o f n e s t i n g h a b i t s by d i r e c t examination upon i n d i r e c t  o f n e s t - s i t e s impossible and one must r e l y  techniques.  B i r d s o f n e i t h e r s p e c i e s accumulate nest m a t e r i a l . The egg i s deposited a t the angle c r e a t e d by the contact o f two o r more b l o c k s , o r on the f l o o r o f t h e mantle, under the s h e l t e r o f jumbled boulders. I n most cases examined, d i r t , m i n e r a l o r organic d e b r i s have accumulated so that the egg i s d e p o s i t e d on a r e l a t i v e l y s t a b l e s u r f a c e . I f the spot i 3 u n d i s t u r bed and i s occupied over a p e r i o d o f s e v e r a l years, a saucer-shaped  depres-  s i o n i s l i k e l y to develop, but i t i s apparently not due to the d i r e c t v i t i e s o f the b i r d s themselves. The problem then was  :  acti-  89 l)  To determine the p r i n c i p a l f a c t o r ( s ) o r g r a d i e n t ( s ) along which s e g r e g a t i o n was  Z)  achieved.  To determine the p r i n c i p a l f a c t o r ( s ) a c t i n g i n c o n t r o l l i n g t h e d e n s i t y , i n any one area o f s l o p e , o f  A. c r i s t a t e l l a .  A, pus 13.1a. and o f both s p e c i e s combined (expressod ^cristatella/  as  ^ p u s i l l a , ' t o t a l ^* D  3) To e s t a b l i s h the r e l a t i o n s h i p between the p r i n c i p a l slope c h a r a c t e r i s t i c s and t h e v a r i a t i o n s i n r e l a t i v e abundance o f t h e two s p e c i e s ( t h i s r e l a t i v e abundance i s expressed as s  ^pusilla/cristatella  *  X  Major c o r o l l a r i e s t o these i n i t i a l questions can be formulated s 1) I f evidence f o r any form o f s t r u c t u r a l c o n t r o l o f D e n s i t y can be found, what a r e t h e l i m i t s w i t h i n which a maximum ^  d  D  cristatella * »  r  e  a  c  h  e  d  D p u s  jj2  a  ?  2) I f evidence f o r s t r u c t u r a l c o n t r o l o f D e n s i t y can be  found,  what w i l l be the importance o f t h i s f a c t o r i n accounting f o r 1 a) the m i c r o - d i s t r i b u t i o n o f the b i r d s w i t h i n the study area? b)  t h e i r m a c r o - d i s t r i b u t i o n w i t h i n t h e i r geographic range ?  Control o f Density I t must be emphasized here that D e n s i t y i s simply a measure o f abundance a t the l e v e l o f a fragment o f h a b i t a t and has no dynamic  connota-  t i o n . Therefore, the values o f D e n s i t y used i n the present context are mere census data. No i n t r i n s i c o r e x t r i n s i c f a c t o r (e.g. s u r v i v a l , p r e d a t i o n , etc.) was under study and none i a considered a t any p o i n t i n the f o l l o w i n g d i s c u s -  90 sion. The techniques d e s c r i b e d below give indeed a safe, and easy mean f o r e v a l u a t i n g the d e n s i t y o f A e t h i a i n any colony. Bat these v a l u e s , no matter how p r e c i s e , and no matter f o r which l e n g t h o f time thay are a v a i l a b l e , would have v e r y l i t t l e u s e f u l n e s s i n a broader e c o l o g i c a l p e r s p e c t i v e . A e t h i a p u s i l l a and A. c r i s t a t e l l a , . b e i n g food converters i n t e g r a t e d w i t h i n a complex marine community and, u l t i m a t e l y w i t h i n a major ecosystem, w i l l o n l y be p a r t i a l l y c o n t r o l l e d by factors; p e r t i n e n t t o t h e i r n e s t i n g h a b i t a t . U n t i l we can e x p r e s s t h e i r d e n s i t y p e r u n i t o f marine environment o r f e e d i n g h a b i t a t , we w i l l n o t be able t o draw v e r y extensive  conclusions.  Among t h e f a c t o r s t h a t c o u l d c o n t r o l d e n s i t y l o c a l l y a r e the p h y s i c a l f a c t o r s such a s p a r t i c l e s i z e , angle o f slope, t h i c k n e s s o f the mantle and so on. I t i s reasonable  t o assume t h a t w i t h i n any slope area,  there i s a f i n i t e number o f nest s i t e s : t h e d e n s i t y w i l l e v e n t u a l l y be curbed by t h e i r a v a i l a b i l i t y . T h i s seems to be g e n e r a l l y v a l i d a t the l e v e l o f the m i c r o - h a b i t a t , e s p e c i a l l y i n Kongkok where a l l the quadrats s t u d i e d seemed t o be populated a t t h e i r maximum p o t e n t i a l l e v e l s . Other f a c t o r s l i k e l y t o have an i n f l u e n c e upon D are o f a b i o l o g i c a l nature. I n the case o f the p a i r pusilla-cristatella•» b i r d s have been observed t o d i s p l a y and g e n e r a l l y l i v e amiably i n t e r m i n g l e d on the sa'ne b o u l d e r s . T h i s i s n o t t o s a y t h a t there i s no dominance o r c o n f l i c t . There i s indeed such a t r e n d and i t appears to depend l a r g e l y upon body s i z e , c r i s t a t e l l a n a t u r a l l y dominating over p u s i l l a . T h i s i s o f t e n expressed i n m i l d forms o f aggression d u r i n g which p u s i l l a c o n s i s t e n t l y withdraws. The e f f e c t o f t h i s s o t o f i n f l u e n c e s w i l l be examined l a t e r .  91 METHODS  D e s c r i p t i o n o f tho Nesting  Habitat  The l o c a t i o n o f a l l known a u k l e t c o l o n i e s on St* Lawrence I s l a n d i s given i n F i g u r e 23  t the l i s t t h e r e i n i s b e l i e v e d to be complete. T h e i r  complete absence from the south-eastern  h a l f o f the i s l a n d can be a t t r i b u t e d  to the combined e f f e c t s o f absence o f s u i t a b l e h a b i t a t i n the form o f m a r i t i me  c l i f f s and s l o p e s and,  a l s o , to the hydro graphic c o n d i t i o n s t h a t are  known t o d i f f e r s h a r p l y from the c o n d i t i o n s e x i s t i n g along the western and north-western coasts ( see p. 29).  Another f a c t i l l u s t r a t e d i n F i g u r e 23 i s  the patchy nature o f the d i s t r i b u t i o n o f A e t h i a as opposed to the l i n e a r aspect o f the d i s t r i b u t i o n o f Cyclorrhynchus. o f t h e i r habitat preferences, c l i f f s , while the o t h e r two  This i s obviously a r e f l e c t i o n  the l a t t e r being a t ease i n p r e c i p i t u o u s  species; are n e a r l y r e s t r i c t e d to t a l u s s l o p e s .  Most o f these c o l o n i e s were v i s i t e d , but o n l y two  were examined  i n any d e t a i l • these are Sevuokok and the complex and immense Eongkok colony. Photographs i l l u s t r a t i n g these c o l o n i e s are given i n F i g u r e s 2£ and  25  A t a l u s slope i s the product o f the weathering o f c l i f f s . Other names a p p l i e d to such s t r u c t u r e s are t c o n g e l i f r a c t e slopes, e b o u l i s s l o p e s , d e t r i t a l cones and s c r e e . The processes  b r i n g i n g about such a formation are :  - Frost-heaving on the c l i f f - f a c e , the rock being broken a t the l e v e l o f the j o i n t s . A h e a v i l y j o i n t e d rock w i l l break away much more q u i c k l y than massive g r a n i t e f o r i n s t a n c e . - The tumbling by g r a v i t y o f the b l o c k s so detached. - The  s e t t l i n g o f the accumulation o f d e b r i s so formed by  mass-wasting processes  slow  such as creep, s o l i f l u c t i o n , e t c .  TQIUS slopes are a c t i v e l y formed i n areas o f p e r i g l a c i a l c o n d i t i o n  92  F i g u r e 23  . L o c a t i o n o f a l l known c o l o n i e s o f Aethia p u s i l l a and A., c r i s t a t e l l a and c o n c e n t r a t i o n s o f Cyclorrhynchus p s i t t a c u l a on St. Lawrence I s l a n d , A l a s k a .  /  c A. II -III  B  II-  III CYCLORRHYNCHUS V /» -  AETHIA  A  -  SEVUOKOK  B  'i - KONGKOK ( A II " T U P U R P U K III- S I T I I L E K K  COMPLEX) C  I - KANGEE( REPORTE] ^ II - K U K U L I K III - S I N G I K P O  93 F i g u r e 24 «• View o f one s e c t o r o f the colony o f Sevuokok Mountain j n o t i c e the s l i g h t i n c r e a s e i n the angle o f repose i n the lowermost l e v e l s . The l a c k o f s o r t i n g i n p a r t i c l e s i z e with a l t i t u d e i s e v i d e n t , as w e l l as the more o r l e s s patchy nature o f the n e s t i n g h a b i t a t . A l t i t u d e .from water l e v e l to the crown i s approximately I50 m. The Parakeet a u k l e t nested i n abundance i n cracks i n the n e e d l e - l i k e p r o j e c t i o n s i n the upper center and i n the weathered ridge at the l e f t c e n t e r o f the photograph.  /  F i g u r e 25 • The g l a c i a l c i r q u e o f Kongkok along the south-wostern coast of S t . Lawrence i s l a n d . The s l o p i n g w a l l s and the moraine floor of the c i r q u e are used as nesting h a b i t a t by Aethia spp.., bat r.;>i the g e n t l y s l o p i n g ground between the beach and tho center of the f l o o r . The d i s t a n c e between the upper rims o f the c i r q u e i s ; s l i g h t l y over one km : the h i g h e s t a l t i t u d e ( on the right) i s approximately £75 m. W i t h i n the c i r q u e p e r i p h e r y , o n l y a few p a i r s o f Cyclorrhynchus were found n e s t i n g on the r i d g e s o f the r e a r w a l l . The scree s l o p e s on the extreme r i g h t are a l s o u s e d by n e s t i n g a u k l e t s .  95 F o r our purpose, i t w i l l be u s e f u l to consider two major types of  slope t a) i n l a n d slope, b) maritime s l o p e .  a) I n l a n d t a l u s s l o p e s are e x e m p l i f i e d by the Kongkok B a s i n ( F i g u r e 25). I n the p r e s e n t case, there i s no agent f o r the continuous removal o f m a t e r i a l from the base as w i l l be the case i n the next category, and the o f block-heaving  processes  and d i s i n t e g r a t i o n w i l l be given an o p p o r t u n i t y to a c t  somewhat l o n g e r on the same m a t e r i a l : t h i s w i l l g e n e r a l l y r e s u l t i n the mantle o f i n l a n d t a l u s s l o p e s having much f i n e r p a r t i c l e s . Since m a t e r i a l i s not removed from the base, the combined a c t i o n o f creep and  solifluction  w i l l u s u a l l y produce a concave-up p r o f i l e . Whatever the l i t h o l o g y be,  the  end r e s u l t w i l l p r o b a b l y be; q u i t e comparable ( F i g u r e 26,  b) Here we have to c o n s i d e r s e v e r a l minor cases s l ) The case o f massive, p o o r l y j o i n t e d rock such as i s the case i n the Sevuokok colony. Wave a c t i o n t h e r e i s moderately h i g h , but c l e a r l y  insuffi-  c i e n t to remove the l a r g e b l o c k s a t t h e f o o t o f the b l u f f , nor to a f f e c t them t t h i s g i v e s the geomorphic processes o f wedging and heaving an opport u n i t y to proceed unchecked and the t a l u s slope w i l l r e t r e a t upwards. Sea a c t i o n w i l l however, c o n t r i b u t e to the removal o f the f i n e p a r t i c l e s from the base o f the s l o p e . Because o f t h i s , a s l i g h t l y g r e a t e r angle o f repose w i l l be maintained i n the lower reaches o f the b l u f f and w i l l give i t a s l i g h t l u convex-up p r o f i l e ( F i g u r e 24 and F i g u r e 26 B ) . The lowermost p o r t i o n o f the slope w i l l , hence, be s u b j e c t to more r a p i d processes such as slump i n g and mud-flows and w i l l be n o t i c a b l y  les3 s t a b l e .  2) Wave a c t i o n (and a l s o i c e scouring) i s v e r y s t r o n g ( o r the rock i s h e a v i l y j o i n t e d ) and a l l the m a t e r i a l wedged from the c l i f f i s removed  r a p i d l y . V e r y l i t t l e o r no t a l u s a t a l l w i l l have a chance to develop.  This  i s g e n e r a l l y the case along t h e south-wast coast o f S t . Lawrence I s l a n d . Even i f a small t a l u s develops, occupies i t .  i t has never been observed t h a t Aethia,  T h i s c o n d i t i o n ( i l l u s t r a t e d i n F i g u r e 26  C) may  a l s o appear  when the d i a c l a s e s o r j o i n t s are not f a v o u r a b l y exposed to wave a c t i o n . 3) The r o c k i s s o f t and j o i n t e d and even moderate wave a c t i o n w i l l e f f e c t i v e l y remove m a t e r i a l from the base o f the t a l u s s l o p e . T h i s w i l l r e s u l t i n a somewhat h i g h e r angle o f repose and the slope i t s e l f w i l l  be  more a c t i v e , g r a v i t y p l a y i n g a dominant r o l e i n i t s m o d i f i c a t i o n . T h i s type i s ; found i n numerous; p l a c e s along the n o r t h coast o f the i s l a n d between Kukulik and Cape Myaughee. I n t h i s same area, o n l y i n s h e l t e r e d coves o r on the top o f t e r r a c e s where t a l u s formation i s not checked by removal o f m a t e r i a l by the sea, do we f i n d s u i t a b l e p l a c e s f o r A e t h i a c o l o n i e s ( F i g u r e 26  D). One  cannot ignore the d i f f e r e n c e s between the types o f b l u f f s  and the geomorphic processes t h a t l e a d to t h e i r formation. For i n s t a n c e , i n the Kukulok-Myaughee area (see Figure 6 f o r topographic l o c a t i o n ) ,  the  low t a l u s o f f e r s a t f i r s t s i g h t l o n g s t r e t c h e s o f apparently s u i t a b l e h a b i t a t f o r A e t h i a : but i t i s p o s s i b l e t h a t the absence o f a u k l e t s i s due  to the  r e l a t i v e l y h i g h degree o f a c t i v i t y o f the processes going on and the  general  t a l u s i n s t a b i l i t y . I do not however o f f e r that as a c o n c l u s i o n s i n c e much work remains to be done i n the area. A l s o , we w i l l note l a t e r t h a t the general type o f c o n d i t i o n s found i n Kongkok, a t y p i c a l i n l a n d t a l u s s l o p e , has a marked i n f l u e n c e upon the o v e r a l l p r o p o r t i o n o f the two A e t h i a found t h e r e .  species o f  97  F i g u r e 26 * P r o f i l e s o f the major types o f s l o p e s encountered rence I s l a n d , Alaska* E x p l a n a t i o n s i n the t e x t .  on St* Law-  INLAND TALUS SLOPE, NOTE CONCAVITY SKYWARDS, E X : KONGKOK BASIN  M A R I T I M E B L U F F , T Y P E B), NO T A L U S D E V E L O P M E N T , E X : SW C O A S T O F S T . L A W R E N C E I.  98 floa,drats A t o t a l o f 30 quadrats were marked out on Sevuokok Mountain (17, 1965) 14,2  and on the slopes of Kongkok Basin (13, 1966), Each quadrat was  m to a side. This dimension was selected on the follo\dng basis :  inhabited sectors of slope are often s t r i p e - l i k e i n fashion ( p a r t i c u l a r l y on Sevuokok) and a standard quadrat that would cover adequately one such stripe should not exceed 15 m; 14,2  m was selected because i t produces an  easy to handle surface value of 200 square meters. Quadrat boundaries were conspicuously painted on the boulders, Basic to the quadrat technique of study was the obtaining of v a l i d f i g u r e s on the density of birds per u n i t area. Due to the general convexity (seawards and skywards) of the slope i n Sevuokok and because of surface i r r e g u l a r i t i e s such as gulleys, pinnacles and large boulders, i t was impossible to have under inspection and , hence, to make accurate census of the birds present on any s i g n i f i c a n t area of slope unless one  occupied  a vantage p o i n t . This f a c t o r was responsible f o r the elimination of t o t a l randomness i n the s e l e c t i o n of quadrat locations. In a l l cases, the distance between the vantage point and the quadrat i t s e l f was superior to 4° m so as to minimize the possible disturbance created by the presence of an observer. Moreover, the quadrats were located so that from two to four of them could be seen from the same vantage point. In Kongkok Basin, t h i s d i f f i c u l t y was not encountered since the observer was c e n t r a l l y located with the t i l t e d walls of the cirque p l a i n l y i n view. An adequate range of v a r i a t i o n i n habitat types had also to be considered, from areas with large boulders to areas with cobble-size p a r t i cles, from areas known to be poor to areas known to be densely  populated.  On Sevuokok Mountain, auklets have been (and s t i l l are) netted f o r centuries  99 by the n a t i v e s i n t r a d i t i o n a l f o w l i n g areas. Late i n 1965,  I realized that,  u n f o r t u n a t e l y , a few quadrats had been l o c a t e d i n the midst o f such f o w l i n g grounds. Late i n the breeding season, every quadrat was re-surveyed. Among the most important c h a r a c t e r i s t i c s measured then wore : b e a r i n g t o w a t e r - l i n e , d i s t a n c e to w a t e r - l i n e , a l t i t u d e , angle o f slope, percentage o f s t o n i n e s s , percentage o f the quadrat used by the b i r d s , s p h e r i c i t y o f the p a r t i c l e s , depth o f the mantle (20 spot measurements) and p a r t i c l e  size.  The l a t t e r was measured i n the f o l l o w i n g way s a s t r i n g was s t r e t c h e d a l o n g one r i m o f the quadrat and f o r every reachable p a r t i c l e i n t e r s e c t e d by the s t r i n g , three dimensions  were obtained. The v e r y angular nature o f the  d e b r i s i n the two c o l o n i e s s t u d i e d f a c i l i t a t e d t h i s . F o r the Sevuokok s e r i e s , seven i n t e r s e c t - l i n e s were made f o r each quadrat. I n Kongkok, t h i s was r e duced t o f i v e . A c c o r d i n g to the s i z e o f the p a r t i c l e s , t h i s  produced  between 350 and 1050 measurements from which the average diameter o f t h e p a r t i c l e s and t h e i r standard d e v i a t i o n have been c a l c u l a t e d (Table 6 ) . Throughout the study, one important assumption  had to be made  concerning the v e r t i c a l homogeneity o f t h e mantle. I t i s evident t h a t f r a g ments broken o f f the boulders o f the upper mantle w i l l , by g r a v i t y , assemb l e a t the bottom and c o n s t i t u t e a lower area o f s m a l l e r p a r t i c l e s . I t can be argued however, t h a t continuous, mass-wasting processes, f r o s t and o t h e r f a c t o r s c o n t r i b u t e so much to the mixing o f the mantle m a t e r i a l t h a t i t i s not t o t a l l y v a l i d to i n f e r t h a t such a s o r t i n g by s i z e takes p l a c e . One g i g a n t i c slope slumping along a s p a r s e l y c o l o n i z e d west coast area gave support t o t h i s i d e a . The uppermost l a y e r s o f the mantle - those occupied by the b i r d s - d i d not show any s i g n o f such l a y e r i n g , and l a r g e blocks appeared with s m a l l e r ones a t any l e v e l o f the a r t i f i c i a l cut provided by  Table 6 . Corrected census figures and selected slope characteristics i n the qaadrats o f Sevuokok and Kongkok colonies. Quadrat No Sevuokok 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17  Kongkok 18 19 20 23. 22 23 24 25 26 27 28 29 30  Av. Rock Std.Dev. Diameter of Rock (dem) (dem) 7.29 7.23 6.74 5.02 10.03 6.08 4.87 3.74 6.14 9.87 6.93 6.31 9.57 4.12 4.18 4.95 5.49  5.75 5.92 4.77 3.19 7.39 4.12 3.40 2.68 4.48 6.12  3.26 3.37 3e 3.26 3.49 6.72 4*90 4*09  1.49 1.60 1.53  3.21 3.29 4.94 5.73  5.01 6.03 2.93 2.54 3.39 4.06  1.69 3.94 2»74 2.23 2.47 1,30 1.35 2c97 4.09  pusilla  total  22.31 69.42 17.99 59.72 11.39 52.08 73.07 120.00 62.68 25.02 42.48 31.38 11.73 91.04 112.03 51.51 54.45  11.28 23.35 23.10 20.83 12.37 39.93 11.52 10.00 44.61 10.50 14.84 19.72 28.18 59.70 98.61  67.95 58.21 60.87 68.23 74.31  15.81 9.38 12.55 5.17 18.03 50.17 31.45 37.86 28.87 12.63 15.69 46.82 44*36  11.97 28.47 20.53 68.53 81.69 9.25 5.26  pus/cris  D  14.02  x  100  ( r a )  % Of occupancy  29.39 60.40 54.19 69.68 79.52  115 120 90 105 40 75 105 75 55 5 5 75 15 20 20 35 30  100 80 100 80 100 100 65 80 45 65 70 100 100 1O0 100 80 55  81.13 86.12 82.91 92.96 80. 48 2.38 27.57 42.92 41*56 84.39 83.89 16.50 10.60  105 130 120 150 165 110 110 165 315 105 110 215 180  100 100 100 90 100 100 100 100 100 100 100 100 100  33.59 92.77 41.09 80.55 23.76 92.01 84.59 130.00 107.29 35.52 57.32 51.10 39.91 150.74 210.64 73.93 68.47  66.42 74.83 43.78 74.14 47.95 56.60 86.38 92.31 58.42 70.44 74.11  83.76 67.59 73.42 73.40 92.34 51.38 43.42 66.33 49.40 97.38 56.07 49.62  Altitude  Angle of slope 39|30  32i 32i  i4 35 27 33 28 16 9  i4 9 6 19117  o B fa  H o  101 the slumping.  Censusing  The technique used i n 1965 and 1966 was d e v i s e d with the h e l p o f p a r t l y q u a l i t a t i v e and p a r t l y q u a n t i t a t i v e knowledge obtained d u r i n g the f i r s t season o f f i e l d work  (1964) on  the following subjects :  1) s e a s o n a l abundance o f t h e various; age c a t e g o r i e s on the s l o p e s , 2) d a i l y v a r i a t i o n s i n attendance o f the b i r d s a t the colony, 3) determination o f the l a y i n g p e r i o d , 4) p a t t e r n s o f d a i l y v a r i a t i o n s i n the amount o f p r o s p e c t i n g f o r n e s t s i t e s and c o u r t i n g a c t i v i t y . Although  a few immature b i r d s o f both A e t h i a spp. were c o l l e c t e d  i n l a t e May each year, they do n o t appear i n numbers u n t i l about June 5 t o 10; they then i n c r e a s e i n numbers u n t i l about June 20 when they reach a maximum and make up a l a r g e but y e t undetermined percentage o f the t o t a l p o p u l a t i o n (estimated a t 25%). The peaks o f d a i l y attendance a t the colony have been i l l u s t r a t e d i n F i g u r e 1. I t must be emphasized t h a t many d i f f i c u l t i e s a r e encountered i n e s t a b l i s h i n g curves o f attendance due to s e v e r a l f a c t o r s . The b i r d s present a t the colony engage i n p r o s p e c t i n g f o r nest s i t e and i n c o u r t s h i p a c t i v i t i e s on the nest i t s e l f , so t h a t a peak i n attendance may correspond  to a l o w i f  a census i s made o f the b i r d s v i s i b l e ON the s l o p e . But one f a c t i s r e a s o nably w e l l e s t a b l i s h e d , the immature b i r d s , o r those t h a t can be recognized as such, l a n d on the n e s t i n g slopes l a t e r than the mature, and presumably experienced breeders, a t l e a s t d u r i n g the morning p e r i o d . This w s f u r t h e r a  shown i n Figure 1. As mentioned above, a l a r g e p r o p o r t i o n o f the c o u r t s h i p a c t i v i t i e s  102 take p l a c e below the s u r f a c e , o u t s i d e the o b s e r v a t i o n f i e l d . From a l o n g s e r i e s o f observations, made from permanent b l i n d s , I found that most o f the "subterranean"  a c t i v i t y was  concentrated around mid-morning  (0900 - 1100 h)  and t h a t the maximum d e n s i t y o f b i r d s ON the r o c k s could be observed  around  0500 - 0700 h. The h i g h e s t count o f breeding b i r d s t h a t i t was p o s s i b l e to o b t a i n had to be made l ) before the l a n d i n g o f the immature b i r d s and before the breeders  engaged i n "subterranean"  were conducted between  2)  a c t i v i t i e s s censuses t h e r e f o r e  0500 and 0800 h.  Furthermore, the maximum number o f observable breeders i s l i k e l y to be found j u s t p r i o r to l a y i n g when none o f the p a r t n e r s i s t i e d on the: nest by the i n c u b a t i o n d u t i e s . T h i s event was  c l o s e l y f o l l o w e d by  ovary development i n the b i r d s c o l l e c t e d f o r the study o f the food h a b i t s . L a y i n g o c c u r r e d d u r i n g the l a s t days o f June and the f i r s t 10-12  days o f  J u l y , p u s i l l a being a few days ahead o f c r i s t a t e l l a . So t h a t the l i k e l i h o o d o f o b s e r v i n g t h e most breeders o c c u r r e d j u s t p r i o r to t h i s event, i n the time p e r i o d a l l o c a t e d above. I n both s e r i e s , however, i t was the census before some l a y i n g had  impossible t o complete  occurred.  Weather d u r i n g the census p e r i o d was not uniform, but  no  c o r r e c t i o n c o u l d be c a l c u l a t e d f o r the v a r i a t i o n s i n t h i s f a c t o r that seemed to a f f e c t  attendance. Counts were, done by sweeping through the quadrat area with  b i n o c u l a r s o r s p o t t i n g scope. T a l l i e s were made every t h i r t y minutes d u r i n g the three hour p e r i o d . In the Sevuokok s e r i e s , census was  repeated i n f o u r  quadrats upon t h r e e successive days. I n h a l f o f the o t h e r s , two  series of  counts were obtained, each s e r i e s by a d i f f e r e n t observer. I n the Kongkok colony the same observer obtained t a l l i e s i n a l l the quadrats upon three successive mornings. Between f i v e and 20 t a l l i e s p e r species were a v a i l a b l e  103 f o r each quadrat. A l a s t and important problem has t o do with the meaning o f the census f i g u r e s o b t a i n e d i n the quadrats. Does, f o r i n s t a n c e , the average d e n s i t y o f 120 p u s i l l a , i n Quadrat Number 8 mean 60 p a i r s (Table 6) ? T h i s i s p r o b a b l y a f a i r l y good approximation,  but i t has n o t been adequately  e s t a b l i s h e d i n any quadrat s i n c e i t i s . next to impossible t o , e i t h e r f i n d and count a l l the eggs o r n e s t s p r e s e n t o r , e l s e , shoot a l l the b i r d s . So, i n as much a s we accept t h a t the v a l u e s o f D e n s i t y are p e r f e c t l y comparable from quadrat t o quadrat, we must f o r t h e time being c o n s i d e r the census f i g u r e s as approxiamtions o f the number o f breeding b i r d s p e r u n i t area.  Analysis  S t a t i s t i c a l procedures  employed i n comparing D e n s i t y and  P r o p o r t i o n with v a r i o u s s l o p e c h a r a c t e r i s t i c s are simple l i n e a r and c u r v i l i n e a r c o r r e l a t i o n and r e g r e s s i o n . I n t h e present a n a l y s i s , p a r t i c l e s i z e , the most important independent v a r i a b l e has been considered as f o l l o w s . I n o r d e r to avoid d i f f i c u l t i e s encountered  i n o b t a i n i n g frequency d i s t r i b u t i o n s f o r the volume o f  the p a r t i c l e s , the l i n e a r measurements o n l y were used. The measurements o f the boulders had been f a c i l i t a t e d i n the f i e l d by t h e i r low roundness and the three l i n e a r dimensions obtained were used i n the a n a l y s i s . These ware grouped i n t o 25 c l a s s e s ( w i t h an open-end c l a s s t o the r i g h t ) ; the h i g h number o f c l a s s e s was warranted  s i n c e the degree o f accuracy d e s i r e d was h i g h  and a l a r g e b u l k o f data was a t hand. The Sevuokok s e r i e s was obtained i n 1965.  After preliminary  a n a l y s i s , i t was c l e a r t h a t the data showed a h i g h v a r i a b i l i t y which d i d not q u i t e f i t the e x p e c t a t i o n s . This was a t t r i b u t e d t o the continuous usage which  i s made o f the colony by n a t i v e hunters. I n order to v e r i f y t h i s p o i n t , the o b s e r v a t i o n s were repeated i n Kongkok d u r i n g 1966 and, as w i l l be seen l a t e r , t h e i n c r e a s e i n cohesiveness o f the data i s indeed c o n s i d e r a b l e . Kongkok has been u n d i s t u r b e d by hunters f o r a t l e a s t a decade o r used o n l y s p o r a d i c a l l y d u r i n g t h a t time. F o r the above reasons, the two s e r i e s o f quadrats a r e here t r e a t e d s e p a r a t e l y .  I n t e r p r e t a t i o n o f the census- data.  The standard procedure count f o r each quadrat  adopted was t o ignore the h i g h e s t  ; the average f i g u r e s on d e n s i t y were o b t a i n e d by-  u s i n g the t h r e e h i g h e s t counts minus the h i g h e s t one.  This was necessary  because i n a few quadrats, prominent boulders p r o t r u d e d above the g e n e r a l surface and i n s e v e r a l cases i t c o u l d be observed t h a t b i r d s which d i d not indeed "belong" t o the quadrat where t h e census was being conducted  would  l a n d a f t e r a d i s t u r b a n c e on these prominent boulders and then, hop from rock to rock i n o r d e r to reach t h e i r d i s p l a y i n g grounds o u t s i d e o f the quadrat. Such a b e r r a n t census s e r i e s would l o o k l i k e t 7 5 , 33, 36, 4 0 , 28, 39. T h i s procedure  a f f o r d s a c o r r e c t i o n f o r the aberrant ones but does n o t  a f f e c t t h e normal ones. Low census f i g u r e s do not have as much importance  as the h i g h  ones s i n c e p a r t i a l o r complete d i s t u r b a n c e s were common d u r i n g the censuses : passage o f a g u l l , a f o x , e t c . \ Further Corrections In order to render values o f d e n s i t y comparable between quadrats, t h e averages had t o be c o r r e c t e d f o r u n r e l a t e d v a r i a b l e s a f f e c t i n g them. These were two t  1) Percentage  o f the quadrat occupied by the b i r d s . T h i s  e f f e c t was e l i m i n a t e d by c o r r e c t i n g to h y p o t h e t i c a l 100^ occupancy a l l the quadrat.averages  where needed ( see  Table 6 f o r o r i g i n a l values o f the % o f occupancy), 2) Thickness o f the mantle. A l l quadrats were c o r r e c t e d f o r a uniform depth o f one meter. T h i s a l s o allows us t o c o n s i d e r a u n i t o f n e s t i n g h a b i t a t e i t h e r as 200  square  meters o r as 200 c u b i c meters. The: c o r r e c t e d f i g u r e s f o r D  m s i l l a  , P  c r i s t a t  ella'  D  total  are g i v e n i n Table 6, a l o n g with s e l e c t e d s l o p e c h a r a c t e r i s t i c s .  RESULTS  Analysis o f Density  a) D  p u s  j_2i  a  • The d e n s i t y o f t h i s species i s compared to the Average Par-  t i c l e S i z e (X) i n F i g u r e 27 (Sevuokok s e r i e s ) and F i g u r e 28 (Kongkok s e r i e s ) * The r e l a t i o n s h i p f o r both s e r i e s i s o f the c u r v i l i n e a r type. But the most i n t e r e s t i n g d i f f e r e n c e between s e r i e s i s the presence o f c o a r s e r m a t e r i a l i n the Sevuokok colony accompanied by much h i g h e r d e n s i t i e s . This phenomenon, p a r t l y due t o slope conditions:, w i l l be d i s c u s s e d a t l e n g t h l a t e r . C o e f f i c i e n t s o f c o r r e l a t i o n f o r these two s e t s o f data are h i g h l y s i g n i f i cant and are presented i n Table 7. There i s a v e r y c l o s e r e l a t i o n s h i p between the Average Rock Diameter (X) and S, the t r e n d being f o r areas with l a r g e boulders to be v e r y homogeneous i n s i z e composition (Table 7 ) . This, e l i m i n a t e s the n e c e s s i t y o f d e a l i n g with the two f a c t o r s c o n j o i n t l y o r simultaneously. As a f u r t h e r  106  F i g u r e 27 • R e l a t i o n s h i p between the D e n s i t y o f Aethia p u s i l l a and the Average Rock Diameter i n the colony o f Sevuokok (see Table 7 f o r the v a l u e s o f the parameters)•  F i g u r e 28 • R e l a t i o n s h i p between the Density o f A e t h i a p u s i l l a and the Average Rock Diameter i n the colony o f Kongkok (see Table 7 f o r the v a l u e s o f t h e parameters)*,  KONGKOK SERIES F I T T E D L I N E OF PUSILLA  TYPE  = K M '  "9T0" 3.0 AVERAGE  ROCK  DIAMETER ( DECIMETERS  ) ,  T  Table 7 • Summary o f c o r r e l a t i o n and r e g r e s s i o n s t a t i s t i c s f o r t h e a n a l y s i s o f D e n s i t y (D) and R e l a t i v e Abundance ( P ) . Equation type  Relation between  1  Series(N)  Correlation  r  Signif.  of r  Explained variation(^)  Intercept  Slope  Std E r r o r of Estimate  B  Sevuokok(l7)  -.865  .001  74.8  2.52  -.139  0.164  xX  B:  Kongkok(l3)  -.993  .001  98.6  3.46  -.49  0.069  x  B  Sevuokok(l7)  -.832  .001  69.2  2.47  -.187  0.181  D  B  Kongkok(l3)  -.960  .001  92.1  2.66  -.561  0.166  D . , ,x X  -  Sevuokok(l7)  -.385  .5  14a 8  D ... xX  A  Kongkok(l3)  .908  .001  82.5  D  -  Sevuokok(l7)  A  Kongkok(l3)  .911  A  Kongkok(13)  A X S  Eai£i2-la  D  x  D D  m  X  s  pus 13 l a ... x S pusilla crl,gtat. cnstnt.  . . .x S c r i r.tqt. criot.nt.  D. . .. total  D. , n  p  total  x X xS  Eiis/£2lLl2.t; • x r  -25.97  -  19.0  -  .001  83.O  -7.10  -.768  .01  59.0  116.96  Kongkok(l3)  -.787  .001  61.9  99.66  B  Kongkok(13)  -.983  .001  96.6  3.32  A  Kongkok(l3)  -.957  .001  91.6  -.436  X  x  S  A  Kongkok( 3)  .975  .001  91.8  X  x  S  A  Sevuokok(l7)  .944  .001  89.1  X  x  S  A  Both Series(30) .958  001  91.8  n  6  -  -  12.35  -  -  6.76  6.65  -11.78  11.66  -  11.23  0.093  130.23 •-33.24 -1.21  .828  o  .169  .673  .478  847  .801  .483  —c  I C S  check on tho i n f l u e n c e o f p a r t i c l e s i z e upon Density, the r e l a t i o n between D  pusilla  f  o  r  t b a  K o n  S  l c o k  s e r i e s and S i s given i n F i g u r e 29. The r e l a t i o n ,  as expected, i s o f the same nature. But o f course, S being d e r i v e d from  X,  i t i s a much l e s s b a s i c i n t e r a c t i o n .  b) r > j t a t e l l a * '^ c r  8  iie  r e l a t i o n s h i p between the d e n s i t y o f breeding b i r d s o f  t h i s s p e c i e s and the Average P a r t i c l e S i z e (X) i a shown i n Figure 30 f o r Sevuokok and i n F i g u r e 31 f o r Kongkok. As can be seen, the s c a t t e r  diagram  f o r Sevuokok i s not v e r y e n l i g h t e n i n g . I n the case o f p u s i l l a s t u d i e d above, although the two  s e r i e s d i f f e r e d i n magnitude, the same b a s i c r e l a t i n s h i p  was born out i n both cases, i . e . , a l o g a r i t h m i c i n c r e a s e i n d e n s i t y w i t h a decrease i n average r o c k diameter. But, as has been suggested above, the p r e s e n t discordance i s a t t r i b u t e d to p r e d a t i o n by n a t i v e hunters. T h i s p r e d a t i o n , though i t p r o b a b l y does not amount to more than a few thousand  birds  p e r year (approximately nine, c r i s t a t e l l a being taken f o r every p u s i l l a ) i s a continuous and p e r s i s t e n t i n f l u e n c e , year a f t e r year. I t i s worth n o t i n g t h a t the two quadrats with the h i g h e s t p o p u l a t i o n f i g u r e s ( Q^- w i t h c r i s t a t e l l a and  w i t h 98.61  59.70  are the most remote from the settlement and  the area i s known t o be v i s i t e d o n l y s p o r a d i c a l l y . The c l u s t e r o f t h r e e p o i n t s a t the extreme r i g h t o f the diagram i s b e l i e v e d to r e p r e s e n t the f a l l i n g - o f f p o r t i o n o f the curve f o r which o n l y the l e f t hand s l o p e i s a v a i l a b l e i n the Kongkok s e r i e s ( no a r e a with so l a r g e boulders e x i s t s i n Kongkok). I n a c i r c u l a r f a s h i o n , the f a c t t h a t i n known undisturbed environments such as Kongkok, the species v a r y i n abundance according to the average diameter o f the rocks i n the mantle i n what i s c e r t a i n l y not a random f a s h i o n ( r v a l u e o f .908)  i n d i c a t e s t h a t the Sevuokok s e r i e s i s not  " n a t u r a l " . Only r e p l i c a t i o n o f these o b s e r v a t i o n s i n other undisturbed areas would allow us t o reach t h i s c o n c l u s i o n s a f e l y , but there are u n f o r t u n a t e l y  109 F i g u r e 29 • R e l a t i o n s h i p between the Density o f Aethia p u s i l l a and the Standard D e v i a t i o n o f Average Rock Diameter (s) i n the Kongkok colony (see Table 7 f o r the v a l u e s o f the parameters).  \o  \  K O N G K O K SERIES F I T T E D LINE OF T Y P E D  PUSILLA  =  K  m  S  0\ [ I LD To 3.0 STANDARD DEVIATION OF ROCK DIAMETER, S  4.  110  F i g u r e 30 • R e l a t i o n s h i p between the Average Rock Diameter (X) and the D e n s i t y of Aethia, cristatella i n the colony of Sevuokok,  Fi<nare 31 , R e l a t i o n s h i p between the Average Rock Diameter (X) and the Den° s i t y of Aethia, c r i s t a t e l l a i n the colony of Kongkok (see Table 7 for t h e v a l u e s of the parameters)•  o SEVUOKOK  SERIES  NO RELATION  o o  0  o  o 04.  o  o  o  o  r-  1  r-  5.0 7.0 _ A V E R A G E R O C K D I A M E T E R ( D E C I M E T E R S ), X  3T0  KONGKOK  90-1  <ao  SERIES  F I T T E D LINE OF T Y P E :  I D  CRISTATELLA  —  A  X  v e r y few such areas. The d i f f i c u l t y comes from the f a c t t h a t we have no way o f measuring the i n f l u e n c e o f p r e d a t i o n by man that i t s continuous  and no way o f e s t a b l i s h i n g  i n f l u e n c e c o u l d indeed b r i n g about changes o f the magni-  tude observed. The argument o f p r e d a t i o n i s p o s s i b l y not the o n l y one, b a s i c d i f f e r e n c e s i n the nature o f the mantle which passed unnoticed, e x i s t between s t a b i l i z e d and " o l d " t a l u s slopes such as Kongkok and v e l y a c t i v e slopes auch as Sevuokok. That slope c o n d i t i o n s had the d e n s i t y was  may  relati-  an e f f e c t on .  suggested above i n the case o f p u s i l l a when i t was  that t h i s undisturbed  and  found  s p e c i e s reached much h i g h e r p o p u l a t i o n l e v e l s i n  Sevuokok th^n i n Kongkok ( f i g u r e s 27 and  28).  The r e l a t i o n s h i p s between the Average Sock Diameter (X) and the D e n s i t y o f the two  s p e c i e s are combined i n F i g u r e 32 t o i l l u s t r a t e  more c l e a r l y the divergence  c) Dfo-kg^ • I  31  o f the p a t t e r n s .  "k^e p r e l i m i n a r y model drawn before the data were a c t u a l l y  obtained, a maximum d e n s i t y o f b i r d s was  expected to occur at  intermediate  v a l u e s o f the dominant f a c t o r , Average Rock Diameter. T h i s zone should c o r respond t o the zone o f o v e r l a p o f the two  s p e c i e s . This was  not v e r i f i e d ,  however, as can be seen i n F i g u r e 33. Only the Kongkok s e r i e s I s used to e s t a b l i s h this; r e l a t i o n s h i p s i n c e i t has been noted e a r l i e r t h a t the f i g u r e s f o r c r i s t a t e l l a i n Sevuokok can h a r d l y be used. T o t a l Density versus S I s shown i n Figure 34 . There i s a s l i g h t c u r v i l i n e a r trend i n the data o f F i g u r e 33, but the i n c r e a s e d amount o f e x p l a i n e d v a r i a n c e by a c u r v i l i n e a r f i t i s not s t a t i s t i c a l l y ( F = .85,  P  0.20  ). The  significant  same s i t u a t i o n occurs when one compares the T o t a l  Density with the homogeneity o f the rock m a t e r i a l (s) : the s l i g h t  curvi-  l i n e a r t r e n d i s not s t a t i s t i c a l l y s i g n i f i c a n t ( F i g u r e 34). Both r e l a t i o n shins (D w  p  v  total  with X and D  L  ^ , with S) give a r a t h e r s i m i l a r Standard E r r o r ,>  total  112 F i g u r e 32 • R e l a t i o n s h i p s between Average Rock Diameter and D e n s i t y o f the two s p e c i e s o f ftethia»The parameters o f the equations and t h e c o r r e l a t i o n s t a t i s t i c s are g i v e n i n Table 7»  113  F i g u r e 33 • R e l a t i o n s h i p between the Average Rock Diameter (X) and the T o t a l D e n s i t y (numbers o f A e t h i a c r i s t a t e l l a and A, p u s i l l a combined). See Table 7 f o r the v a l u e s o f the equation parameters and t h e c o r r e l a t i o n s t a t i s t i c s .  i 34 . R e l a t i o n s h i p between the s i z e homogeneity o f rocks (Standard D e v i a t i o n o f Rock Diameter, S) and the T o t a l Density (numbers o f A e t h i a c r i s t a t e l l a and A. p u s i l l a , combined).See Table 7 f o r the values o f the equation parameters and the c o r r e l a t i o n statistics.  but the c o e f f i c i e n t o f c o r r e l a t i o n ( r ) f o r T o t a l Density v e r s u s homogeneity (S)  i s s i g n i f i c a n t at the .001 P r o b a b i l i t y l e v e l while t h i s same c o e f f i c i e n t  f o r the r e l a t i o n between T o t a l D e n s i t y and .Average Rock Diameter (I)  i s sig-  n i f i c a n t a t the .01 l e v e l o n l y .  d) R e l a t i o n o f D e n s i t y with Other H a b i t a t C h a r a c t e r i s t i c s . No meaningful r e l a t i o n s h i p was  detected between D  ...,,» cristatella-  D  ,„„ or D , and pusiula totr.l  major h a b i t a t c h a r a c t e r i s t i c s f o r which q u a n t i t a t i v e i n f o r m a t i o n was  the  availa-  b l e . A l t i t u d e appears to have no d i r e c t e f f e c t whatsoever upon the d e n s i t y o f e i t h e r s p e c i e s , nor upon t h e i r combined d e n s i t y . T h i s i s i n c o n t r a d i c t i o n with i n f o r m a t i o n p u b l i s h e d by Fay & Cade (1959) who- have observed an  alti-  t u d i n a l segregation, p u s i l l a b e i n g claimed to occupy the h i g h e s t l e v e l s o f the t a l u s s l o p e s . T h i s r e l a t i o n , however, i s o n l y an i n d i r e c t one.  Talus  homogeneity; i s g e n e r a l l y g r e a t e r at t h e rim o r c r e s t o f t a l u s slopes » t h i s i s a p p a r e n t l y due: to the f a c t t h a t g r a v i t y and mass-wasting processes  tend  to accumulate more l a r g e p a r t i c l e s i n the lowest reaches o f the s l o p e s . But t h i s i s not the case i n a l l c o l o n i e s . A l o o k a t F i g u r e 24 f o r i n s t a n c e , which shows a s e c t o r o f the Sevuokok colony, i n d i c a t e s t h a t t h e r e i s no obvious p a t t e r n i n the d i s t r i b u t i o n o f the p a r t i c l e s o f v a r i o u s s i z e s . I t seems evident on the c o n t r a r y t h a t the p r o x i m i t y from c r e s t s o r r i d g e s o r , more g e n e r a l l y , from sources o f rock material, determines the presence o f l a r g e rock fragments. Since these c r e s t s can o c c u r i n p r a c t i c e a t any  level  on the slope, no g e n e r a l i z a t i o n can be made. I t i s g e n e r a l l y t r u e , however, f o r Kongkok and i s r e a d i l y understandable from a knowledge o f the geomcrphdc processes.  T h i s type o f • a l t i t u d i n a l s o r t i n g o f p a r t i c l e s i z e can  seen on t h e scree slope at the extreme r i g h t o f F i g u r e  be  25.  But even i n Kongkok, dense groups o f c r i s t a t e l l a . sometime dominating i n abundance over p u s i l l a . were observed up to the  south-eastern  215 rim o f t h e c i r q u e at an a l t i t u d e o f some 400 m, whenever areas o f l a r g e boulders e x i s t e d . Most, i f n o t a l l the c h a r a c t e r i s t i c s which one can observe i n such type o f h a b i t a t a r e bound to be interdependent to a l a r g e degree : angle o f s l o p e , s t a b i l i z a t i o n by v e g e t a t i o n , s i z e o f the p a r t i c l e s , e t c . are a l l interdependent c h a r a c t e r i s t i c s o f a whole and i n t e g r a t e d s t r u c t u r e . But the l a r g e amount o f e x p l a i n e d v a r i a t i o n i n the Density by the use o f a s i n g l e dominant f a c t o r , the Average Rock Diameter (X) does g i v e u s enough p r e d i c t i v e power and a f a i r enough d e s c r i p t i o n o f the n e s t i n g segregation t h a t o t h e r p o s s i b l e f a c t o r s can be n e g l e c t e d .  A n a l y s i s o f R e l a t i v e .Abundance (P)  a) P with Average Rock Diameter. As mentioned e a r l i e r , P i s a measure o f . r e l a t i v e abundance. Values o f P vary from 2 . 3 6 t o 9 2 . 9 6 (Table 6) and t h e s c a t t e r diagram  together with the r e g r e s s i o n l i n e a r e given i n F i g u r e 3 5  f o r the Kongkok s e r i e s . The dominance o f one species over the other - when P passes through the v a l u e o f 50.0 - can be c a l c u l a t e d to occur a t l e v e l s o f the independent v a r i a b l e equal to 3.8 decimeters. F i t t e d to a c u r v i l i n e a r  X r e g r e s s i o n o f the type timate i s produced  Y = k m  , a v e r y s m a l l Standard E r r o r o f the E s -  (Table 7) s the amount o f explained v a r i a t i o n i s extreme-  l y h i g h ( 9 8 . 6 $ ) and i t a f f o r d s us with a remarkable p r e d i c t i v e power. When P i s p l o t t e d a g a i n s t homogeneity ( S ) , a lower but s t i l l v e r y l a r g e amount o f the v a r i a t i o n i s explained by t h i s f a c t o r alone ( 9 1 . 6 $ : F i g u r e 3 6 ) . b) P with other F a c t o r s . As suggested e a r l i e r , there i s an observed  tendency  f o r an i n c r e a s e i n P with a l t i t u d e . T h i s was not q u a n t i f i e d , but i t was concluded to be a side e f f e c t r e s u l t i n g from the segregation o f p a r t i c l e s  116  Figure 35 • R e l a t i o n s h i p between the Average Rock Dianeter (X) and the r e l a t i v e Abundance (?) o f the two species o f A e t h i a . The v e r t i c a l broken l i n e i n d i c a t e s the value o f the independent v a r i a b l e at which the two s p e c i e s are i n equal abundance. The values o f the equation parameters and the c o r r e l a t i o n s t a t i s t i c s are g i v e n i n T a b l e 7*  F i g u r e 36  . R e l a t i o n s h i p between the Standard D e v i a t i o n o f Rock Diameter (S, o r Homogeneity) and the R e l a t i v e Abundance (?) o f the two s p e c i e s o f A e t h i a . The v e r t i c a l broken l i n e i n d i c a t e s the v a l u e s o f the independent v a r i a b l e at which the two s p e c i e s are i n equal abundance. The v a l u e s o f the equation parameters and the c o r r e l a t i o n s t a t i s t i c s are g i v e n i n Table 7.  lOOn  Il  — I  —  T—  I  3.0 4JD 5.0 AVERAGE ROCK DIAMETER ( DECIMETERS ) ,  6.0 X  lOOn  ^0  2.0 3.0 STANDARD DEVIATION OF ROCK D I A M E T E R , S  117 due  to geomorphic s o r t i n g (p. I K ) . T h i s e f f e c t , however, i s u n p r e d i c t a b l e  and i s i n e x i s t e n t i n some s l o p e s . No o t h e r f a c t o r s t u d i e d had a d e t e c t a b l e i n f l u e n c e upon the v a l u e s o f R e l a t i v e Abundance.  DISCUSSION AND CONCLUSIONS  Although there has been some unavoidable the s e l e c t i o n o f the quadrats,  subjectivity i n  i t i s b e l i e v e d t h a t the range o f v a r i a t i o n  i n D and P i s l a r g e enough to i n d i c a t e c l e a r l y the t r e n d s o f i n t e r a c t i o n , even i f o f t e n not l a r g e enough to i n d i c a t e them i n t h e i r e n t i r e t y . L e t us re-examine the major questions which were proposed i n i n t r o d u c i n g t h i s chapter and determine how c l o s e l y we have approached answers.  The  C o n t r o l o f D e n s i t y and R e l a t i v e Abundance  There can be no doubt t h a t the l o c a l d e n s i t y o f both c r i s t a t e l l a and p u s i l l a i s markedly i n f l u e n c e d by p h y s i c a l c h a r a c t e r i s t i c s • and the Average Rock Diameter i s o b v i o u s l y the p r i n c i p a l such c h a r a c t e r i s t i c ( F i g u r e s 28 and 31, Table 7 ) . As much as 98$ o f the v a r i a t i o n i n d e n s i t y o f one species ( p u s i l l a ) can be accounted f o r by t h i s f a c t o r alone. We cannot make r e l i a b l e p r e d i c t i o n s about the Density o f c r i s t g t e l l a i n the colony o f Sevuokok Mountain : as I noted e a r l i e r ,  this  seems to be due to p r e d a t i o n by man and p o s s i b l y t o p e c u l i a r slope c o n d i t i o n s * I have a l s o i n d i c a t e d t h a t p u s i l l a maintains  i n the l a t t e r colony  higher  d e n s i t i e s p e r u n i t area than i n Kongkok. Since the i n f l u e n c e o f p r e d a t i o n by man on t h i s small species i s n e g l i g i b l e , o n l y two reasons could e x p l a i n  t h i s phenomenon. The  f i r s t i s t h a t the slope c o n d i t i o n s i n Sevuokok  encourage denser aggregations, t h i s p o s s i b i l i t y . The  may  but the standardized procedures do not  support  second p o s s i b i l i t y i s t h a t the h i g h e r d e n s i t i e s o f  p u s i l l a i n Sevuokok are r e l a t e d to the decrease i n c r i s t a t e l l a . the former f i l l i n g the vacuum c r e a t e d by the d i m i n u t i o n o f the l a t t e r . What k i n d o f evidence would support  t h i s hypothesis  ?  F i r s t , , a comparison o f the r e l a t i o n s h i p between the o f the Least a u k l e t and the Average Rock Diameter i n the two (compare F i g u r e s 27 and 28)  Density  colonies  shows t h a t i n Sevuokok, the r e g r e s s i o n l i n e i s  more r e l a x e d upwards : the values o f D e n s i t y f o r intermediate v a l u e s o f the independent v a r i a b l e ( F i g u r e 27)  are more spreaded than i n the case o f  Kongkok ( F i g u r e 28). Another i n d i c a t i o n t h a t the r e d u c t i o n i n the numbers o f the C r e s t e d auklet f a v o r s the i n c r e a s e o f p u s i l l a is- found i n comparing the v a l u e s o f P f o r the two  c o l o n i e s (Figure 3?)»  The D e n s i t y o f  puslLTa/cris-ta-  t e j l l a ( R e l a t i v e Abundance) i n s t e a d o f decreasing i n a l o g a r i t h m i c f a s h i o n (as i n Kongkok) decreases according to a l i n e a r r e l a t i o n s h i p . T h i s i s p r o v i s i o n a l l y i n t e r p r e t e d as a response by p u s i l l a to the r e d u c t i o n i n numbers o f i t s l a r g e r congener (Sevuokok). B r i e f r e f e r e n c e was made e a r l i e r to the dominance o f c r i s t a t e l l a over p u s i l l a and the f a c t t h a t c o n f l i c t s , although m i l d , r e s u l t e d all  the time i n the r e t r e a t o f the s m a l l e s t s p e c i e s . Wherever c r l ^ t e l l a i s  abundant, i t stakes out a l l t h e l a r g e boulders as d i s p l a y i n g areas and seldom can one observe p u s i l l a engaged i n c o u r t s h i p i n t h e i r presence. Areas o f dense aggregations  o f c r i s t a t e l l a are a t t r a c t i v e to l a r g e numbers o f  immature i n d i v i d u a l s which engage i n c o u r t s h i p with the a d u l t b i r d s . But when a small census f i g u r e i s given f o r c r i s t a t e l l a . i t g e n e r a l l y represents a few p a i r s l i m i t e d to a small s e c t i o n o f the quadrat J small groups o f t h a t  32.9 Figure. 3 7 • Comparison_of the r e l a t i o n s h i p between the Average Rock Diameter (X) and t h e R e l a t i v e Abundance (?) o f Aethia,. ous:111a and A, c r i s t a t e l l a i n the c o l o n i e s o f Sevuokok and Kongkok. Values o f the equations parameters and c o r r e l a t i o n s t a t i s t i c s are given i n Table 7.  AVERAGE ROCK  DIAMETER ( DECIMETERS ) ,  X  120  type r a r e l y a t t r a c t immature b i r d s in. t h e i r neighbourhood, .although the r e l a t i o n s h i p could not be q u a n t i f i e d , i t seems that the amount o f  social  i n t e r a c t i o n and i n t e r f e r e n c e between c r i s t a t e l l a and p u s i l l a w i l l  increase  i n an e x p o n e n t i a l per u n i t  f a s h i o n w i t h an i n c r e a s e i n the D e n s i t y o f  cristatella  area. Although t h i s i n t e r p r e t a t i o n i s somewhat s a t i s f a c t o r y at  the p r e s e n t time, i t does not c o n s t i t u t e t o t a l evidence and  way  tho o n l y  i n which t h i s evidence can be. gained i s e i t h e r by studying the few  colonies  where c r i s t a t e l l a i s n a t u r a l l y absent o r , e l s e , by a r t i f i c i a l l y removing c r i s t a t e l l a , from experimental p l o t s and p r e v e n t i n g  t h e i r re-establishment  d u r i n g a number o f y e a r s . A d e f i n i t e t e s t to r e j e c t the h y p o t h e s i s would r e s i d e i n the p e r s i s t e n c e o f the c u r v i l i n e a r r e l a t i o n s h i p a f t e r the removal o f c r i s t a t e l l a . Evidence a g a i n s t the h y p o t h e s i s would a l s o come from the f i n d i n g o f a s i m i l a r c u r v i l i n e a r r e l a t i o n i n homogeneous c o l o n i e s o f p u s i l l a (St.  George I s l a n d i n the P r i b i l o f groupj S t . Matthew I s l a n d ) . To summarize, the degree o f s t r u c t u r a l c o n t r o l upon  D e n s i t y i s indeed remarkable. The more remarkable when one  considers a l l  p o s s i b l e sources o f e r r o r i n censusing, i n measuring the h a b i t a t and i n applying correction f a c t o r s f o r unrelated v a r i a b l e s . The l o c a l d e n s i t y o f c r i s t a t e l l a seems to be  a direct  f u n c t i o n o f the Average Rock Diameter, though the l o c a l d e n s i t y o f p u a i l l a appears to be a f u n c t i o n o f both the Average Rock Diameter and the presence o f i t s l a r g e congener. L o g i c a l l y , owing to i t s small s i z e , p u s i l l a , i s able to occupy a wider range o f n e s t i n g s i t u a t i o n s than c r i s t a t e l l a . I t has to a broader choice o f nest  access  s i t e s and there i s evidence that I t makes f u l l  use o f i t whenever p o s s i b l e . I t i s also a more v e r s a t i l e nester and  can  be  121  found i n i s o l a t e d p a i r s on p i n n a c l e s , r i d g e s o r even sheer c l i f f s i n company with cormorants, murres and p u f f i n s . T h i s l e a d s us to some o f the c o r o l l a r i e s proposed. p h y s i c a l f a c t o r s i n the n e s t i n g h a b i t a t a f f e c t the d i s t r i b u t i o n and R e l a t i v e Abundance o f the two The  Can the  species w i t h i n t h e i r geographic range ?  range o f sampled c o n d i t i o n s i s too s m a l l to a l l o w us to formulate  gene-  r a l i z a t i o n s r e g a r d i n g t h e i r p a t t e r n s o f absolute d e n s i t y . But tharo i s i n d i c a t i o n t h a t the p r o p o r t i o n o f p u s i l l a w i l l i n c r e a s e with the age o f the s l o p e . On i n l a n d talus, s l o p e s , where there i s no removal o f m a t e r i a l from below, the c l i m a t i c f a c t o r s w i l l break down the d e b r i s o f the mantle to a much f i n e r c o n d i t i o n . T h i s i s the case i n Kongkok where, on the south-western w a l l f o r i n s t a n c e , the p r o p o r t i o n o f p u s i l l a / c r i s t a t e l l a i s o f the o f 15:1  order  ( c r i s t a t e l l a i s abundant i n Kongkok, but i n l o c a l i z e d areas such as  the moraine f l o o r o f the c i r q u e and the lowest p a r t s o f the northern w a l l ) . Fay & Cade (1959) r e p o r t a r a t i o o f 20:1 gikpo Cape ( F i g u r e 23. Area C-QJ)  f o r p u s i l l a i n the colony o f S i n -  t t h i s colony is; e s t a b l i s h e d on a t e r r a c e  s l o p i n g v e r y g e n t l y and r e a c h i n g i n l a n d f o r over one k i l o m e t e r ;  slope  condi-  t i o n s there are s t i l l more " s t a b i l i z e d " than i n Kongkok. T h i s i s a l s o the case on S t . George I s l a n d i n the P r i b i l o f Archipelago.  Hopkins & E i n a r s s o n  (1966) remarked that creep and  solifluc-  t i o n dominated " f r o s t r i v i n g " s on t h i s i s l a n d , the exposed s u r f a c e s o f b a s a l t have been reduced to loode rubble d u r i n g past i n t e r v a l s o f more severe c l i m a t e . On S t . George, the main a u k l e t colony i s l o c a t e d on an i n l a n d k n o l l about one km p u s i l l a (M.  from the sea and contains. r e p u t e d l y e x c l u s i v e l y A e t h i a  Thompson, i n l i t t e r i s ) . On t h i s i s l a n d at l e a s t , cristate"? 1^  i s l i m i t e d to the base o f maritime b l u f f s (Thompson, i n l i t t e r i s ; & McAtee, 1923)  where t a l u s are s t i l l i n e a r l i e r stages o f  Preble  formation.  122 A l l the a v a i l a b l e evidence  tends to support the b a s i c  p r o p o s i t i o n t h a t p h y s i c a l f a c t o r s ( i m p l y i n g here Average Rock Diameter) determine the p r o p o r t i o n o f the two  s p e c i e s o f aethia w i t h i n the o v e r l a p -  p i n g p a r t s o f t h e i r range. A c c e p t i n g t h i s p r o p o s i t i o n as u n i v e r s a l i s not warranted, however, u n t i l q u a n t i t a t i v e observations become a v a i l a b l e from many more n e s t i n g c o l o n i e s .  Segregation i n Westing  a) Segregation between A e t h i a p u s i l l a , and A. c r i s t a t e l l a • Underlying a l l these questions was  the primary c o n s i d e r a t i o n o f segregation between the  two  s p e c i e s on the n e s t i n g s l o p e s . T h i s aspect i s summarized i n F i g u r e 33, u s i n g the Kongkok census f i g u r e s . I n t h i s f i g u r e , an extension o f the p a t t e r n i s proposed, p a r t l y based on q u a l i t a t i v e o b s e r v a t i o n s . Some remarks are a p p r o p r i a t e concerning the g r a p h i c a l model o f f e r e d i n F i g u r e 33. The l e f t p a r t o f the curve f o r  pusilla  falls  v e r y a b r u p t l y a f t e r r e a c h i n g a maximum around r o c k - s i z e diameter o f 3«0  dcm.  T h i s p a r t o f the curve has not been documented but has been drawn from qual i t a t i v e o b s e r v a t i o n s . A decrease  i n the average s i z e o f the p a r t i c l e s i s  g e n e r a l l y accompanied by a c l o g g i n g o f t h e i n t e r s t i c e s , s o i l  formation  and v e g e t a t i o n development S such c o n d i t i o n s develop r a t h e r r a p i d l y between X values o f 3 0 o  and 2.0  dcm.  At the other extreme o f the graph, i n the  domain o f c r i s t a t e l l a , there i s an. obvious l i m i t to t a l u s formation p a r t i c l e s exceeding  an average diameter o f 10.0  dcm  : i t may  with  perhaps occur'  i n some areas but i n the c o l o n i e s examined,,, such l a r g e b l o c k s accumulated at the base o f the t a l u s slope to form the "rabble". I f theso blocks are l a r g e enough, they w i l l r e s i s t removal by wave and i c e a c t i o n while  finer  p a r t i c l e s w i l l be removed from between them. At any r a t e , t h i s h a b i t a t i s  123 Figure 38  0  Generalized model showing the segregation between ?8thif> c r i s tatella; and A, p u s i l l a on the nesting slopes according to the Average Rock Diameter, The parts o f the curves shown by a broken T  l i n e are i n f e r r e d from q u a l i t a t i v e o b s e r v a t i o n s .  124 u s u a l l y occupied  by o t h e r a l c i d s such as Gepphus and, o f t e n , F r a t e r c u l a .  Furthermore, the i n c r e a s e i n p a r t i c l e s i z e above a c e r t a i n l i m i t  brings  about a d i r e c t decrease i n the p o s s i b l e number o f i n t e r s t i c e s and probably  this  accounts f o r much o f the drop t h a t occurs i n D  between cristatella.  v a l u e s o f Average Rock Diameter o f 7,0  and 10.0  dem.  the curves i n f e r r e d from q u a l i t a t i v e observations  In F i g u r e 38, p a r t s o f  are shown by a broken l i n e  That segregation occurs amidst the n e s t i n g grounds i n such a marked and p r e d i c t a b l e f a s h i o n i s merely a r e f l e c t i o n o f the l a r g e d i f f e rence i n body s i z e between the two does not precludes  s p e c i e s (proximate f a c t o r ) . T h i s , however  the e x i s t e n c e o f h a b i t a t segregation a t a b i o l o g i c a l  l e v e l ( u l t i m a t e f a c t o r s ) . D i f f e r e n c e s i n the degree o f t o l e r a n c e o f the c h i c k s to h y p o t h e t i c a l f a c t o r s o f the m i c r o - h a b i t a t may i n f l u e n c e the nest s i t e s e l e c t i o n . The two  species may  be s u b s t a n t i a l and a l s o d i f f e r In t h e i r  h a b i t s a c c o r d i n g to f a c t o r s such as substrate c o n d i t i o n o r the  differential  use thay make o f t h e f l o o r o f the mantle. There i s no claim here t h a t such preferences  have no importance s they probably r e f l e c t important  d i f f e r e n c e s which i t may,  some day,  be p o s s i b l e to  adaptive  evaluate.  I n n e s t i n g , as i n f e e d i n g , the two  species o f the genus  A e t h i a have b a s i c a l l y the same type o f requirements. In n e s t i n g , they both make use o f t a l u s slopes, but segregate i n v a r i o u s fragments o f them. I n n e s t i n g as i n f e e d i n g , the. pronounced divergence the most important f a c t o r accounting  i n body s i z e appears to  f o r segregation.  be  This i s a basic d i s -  t i n c t i o n w i t h the t h i r d a u k l e t s t u d i e d , Cyclorrhynchus p s i t t a c u l a : between the two  genera, there are d i f f e r e n c e s i n the, v e r y nature o f the r e q u i r e -  ments (see below). The question What happens when t h e r e has been complete occupancy o f a l l a v a i l a b l e nest s i t e s i s important, but cannot be answered  125 s a t i s f a c t o r i l y . A d e f i n i t e overflow appears t o be the r e s u l t : once the upper l i m i t i s reached, i t is. b e l i e v e d  that  the excess  breeders (possibly  young i n d i v i d u a l s ) s e t t l e a t the p e r i p h e r y o f the most d e n s e l y populated and most f a v o u r a b l e areas'. T h i s would account f o r the f i n d i n g o f  nests  in  i s o l a t e d c r a n n i e s , i n t u r f y slopes o r i n c r a c k s on r i d g e s . I t i s obvious t h a t the number o f such s u b s t i t u t e s i t e s i s f i n i t e as w e l l . What happens then, i f the case i s ever reached i n nature, i s r a t h e r hard  and ueiious to  document o b j e c t i v e l y . The i n c r e a s e i n the number o f "dumped" eggs i n densely populated areas, the i n c r e a s e i n the occupancy o f " s u b s t i t u t e " nest  sites  such  - a d i f f i c u l t matter t o evaluate o b j e c t i v e l y - would i n d i c a t e t h a t  a  c o n d i t i o n o f maximum d e n s i t y has occurred and t h a t o v e r f l o w i n g with unsucc e s s f u l breeding i s r e s u l t i n g .  b) The N e s t i n g o f Cyclorrhynchus » The colony o f Sevuokok Mountain i s occu-  here  p i e d by s i x s p e c i e s o f a l c i d s . Although we have been concerned  almost  e x c l u s i v e l y with A e t h i a , i t must be mentioned t h a t every one o f the f o u r other s p e c i e s i s , a t one time o r another, a s s o c i a t e d with i t .  Often,  Cepphus  w i l l n e s t i n s m a l l numbers i n areas o f t h e mantle with v e r y l a r g e p a r t i c l e s t and so do Lunda and F r a t e r c u l a . A f t e r even short f i e l d experience i t becomes p o s s i b l e t o r e c o g n i z e with f a i r accuracy those r e g i o n s where one i s l i k e l y to or  find  such  such a genus o f A l c i d a e : but the s u b t l e d i f f e r e n c e s i n h a b i t a t characte-  r i s t i c s t h a t one can l e a r n t o recognize are not easy t o d e f i n e i n o b j e c t i v e terms and s t i l l more d i f f i c u l t t o express i n q u a n t i t a t i v e  ones. In  studying  the n e s t i n g h a b i t s o f the t h i r d plankton-feeder, the Parakeet a u k l e t ,  this  d i f f i c u l t y was encountered. The l a t t e r i s g e n e r a l l y a b i r d n e s t i n g on scarp When i t nests i n the p r o x i m i t y o f t a l u s slopes, i t i s markedly  faces-  more abundant  126 on the h i g h e s t r i d g e s . I n the A l e u t i a n I s l a n d s , t h e i r h a b i t a t i s d e s c r i b e d as being " among l a r g e boulders on the beach, and  i n c r e v i c e s i n rocky  cliffs*  a l s o on s l o p e s where the rocks are p a r t l y covered  with v e g e t a t i o n " ( K u r i e ,  1959). I n the Commander I s l a n d s , Stejneger (I8S5) saw them "breeding i n steep, cracked and i n a c c e s s i b l e r o c k s . . . e s p e c i a l l y i n those p l a c e s which are c a l l e d "Nepropusk", t h a t i s , steep rocks r i s i n g s t r a i g h t out o f tho  sea,  p r o h i b i t i n g passage along the beach". On S t . Lawrence I s l a n d ,  C. psittacula  occupies  the same  type o f h a b i t a t as d e s c r i b e d by these w r i t e r s . I t i s g e n e r a l l y d i s t r i b u t e d i n the c l i f f y , areas o f the south-western at l e a s t as f a r as Boxer Bay ( F i g u r e  coast between Omwalit Mountain and  23), I t i s p r e s e n t i n v e r y small numbers  i n Kongkok B a s i n , being r e s t r i c t e d there to the r i d g e s t h a t d i s s e c t the w a l l s o f the c i r q u e . I t i s a l s o common along the n o r t h - c e n t r a l c o a s t . I n f Q l  these areas, i t I s i n company with Lunda.  Fratercula  and  Cepphus  s it  shares w i t h the l a t t e r s i m i l a r t r a i t s o f u b i q u i t o u s d i s t r i b u t i o n and moderate t o low numbers. The spacing o f these numerous forms i n such c o n d i t i o n s i s unknown and.competitive  r e l a t i o n s h i p s , i f present, have not been examined.  The Parakeet a u k l e t i s abundant on Sevuokok Mountain where i t i s concentrated along the rim o f the b l u f f i n spaces  where  p a r t i a l l y f r a c t u r e d parent rock comes to the s u r f a c e . I t i s also  the  present  throughout the slope wherever weakly weathered outcrops appear at the surface i n the form o f r i d g e s . I t does, however, also appear o c c a s i o n a l l y on  the  t a l u s slope i t s e l f where i t i s a s s o c i a t e d with l a r g e boulders p r o t r u d i n g from grassy s t r e t c h e s J i t w i l l apparently nest underneath  such boulders.  A number o f n e s t s were found also i n the rock mantle, i n company There seems t o be a set o f requirements  determining t h e i r  with  Aethia.  presence i n these  cases, but these requirements have not been s a t i s f a c t o r i l y d e t a i l e d .  227 I n f a c t , Cyclorrhynchus t a t e l l a i n n e s t i n g requirements  only barely overlaps Asthlg c r i s -  : i t i s p r i m a r i l y a scarp f a c e n e s t s r . I n a  geomorphic sense, t h i s stage proceeds t a l u s s l o p e s . 'When i t appears on t a l u s s l o p e s , i t i s always i n l a t e stages o f slope formation, i . e . on  grassy  s t r e t c h e s , o r i n areas where the s u r f a c e o f the mantle i s completely w i t h humus, although the mantle i t s e l f may  covered  offer interstices for nesting.  This stage succeeds t y p i c a l t a l u s s l o p e s . I t i s open to s p e c u l a t i o n whether i n the absence o f c r i s t a t e l l a the s p e c i e s occupies t a l u s slopes i n the  cris-  t a t e l l a manner. T h i s i s v e r y u n l i k e l y , but d i s c u s s i o n o f t h i s q u e s t i o n must be postponed u n t i l we  can d i s c u s s c o n c u r r e n t l y the b e h a v i o r a l t r a i t s t h a t  seem to make the Parakeet  auklet a more s p e c i a l i z e d s p e c i e s , r e q u i r i n g d i s -  p l a y areas o f a s p e c i a l nature. Census work i s ' d i f f i c u l t with t h i s s p e c i e s and does not produce r e s u l t s comparable to the ones obtained with .Aethia. I t does not form dense aggregations  and the l a r g e s t groups seen i n the best s e c t o r s o f  the slope were s m a l l e r than f i f t y i n d i v i d u a l s . A s m a l l s c a l e census i n t y p i c a l h a b i t a t on Sevuokok, along the rim o f the b l u f f , produced a t a l l y o f 220 b i r d s i n q. 800 x 75 m s u r f a c e , which g i v e s a low estimate o f a p p r o x i mately one b i r d p e r 200  square meters. T h i s estimate agrees v e r y w e l l with  repeated and cumulative  counts conducted i n the previous year i n slope  s e c t i o n s t h a t e v e n t u a l l y covered the wole o f Sevuokok colony. The  total  estimated number o f p s i t t a c u l a was o f 2000 b i r d s ( i n c l u d i n g a l l c a t e g o r i e s ) f o r an area o f roughly 180,000 square meters o f favourable h a b i t a t ( o r b i r d / 180  one  s. m). As a b a s i s f o r comparison,, estimates o f absolute and r e -  l a t i v e numbers o f A e t h i a i n t h i s colony have been given on pages 86-87.  128  CHAPTER I ?  THE PLANKTON-.FESDERS IN THE COMMUNITY  INTRODUCTION  The f a m i l y Alcidae i s i n t e r e s t i n g among b i r d s i n one major r e s p e c t • i t has made a s u c c e s s f u l breakthrough  and has achieved  adaptive  r a d i a t i o n i n t o a broad and d i v e r s i f i e d e c o l o g i c a l zone, the subsurface of the. ocean. Alone i n the northern hemisphere, i t has achieved t h i s Such a system should be remarkably  transition.  f r e e o f e x t e r n a l i n f l u e n c e s and should  have many o f the c h a r a c t e r i s t i c s o f a b a s i c o r elementary  community^.  R a d i a t i o n has been based mostly upon the a c q u i s i t i o n o f  specia-  l i z e d f e e d i n g h a b i t s and t h e most i n t e r e s t i n g aspect o f t h i s d i v e r s i f i c a t i o n is  that i t has l e d t o the occupancy o f two major d i s t i n c t t r o p h i c  levels,  as w e l l as t o the. development o f intermediate forms t h a t may occupy a t h i r d  them  l e v e l o f t h e i r own o r , more o f t e n , r e t a i n adaptations that a l l o w p a r t i c i p a t e i n both b a s i c l e v e l s .  Alca torda  f e e d i n g e x c l u s i v e l y on  occupies a d i s t i n c t l y d i f f e r e n t t r o p h i c l e v e l from  to  fish  Aethia. pusilla that makes  almost e x c l u s i v e u s e o f s m a l l p l a n k t o n i c grazers such as  Calanus  f$nmsrchicug»  Were i t p o s s i b l e to devise an index o r a measure o f the f e e d i n g  apparatus  t h a t would r e f l e c t the adaptations to v a r i o u s food sources, one  could "grade"  o r s o r t i n a n a t u r a l f a s h i o n the members o f t h i s i n t e r e s t i n g community and "'"Recent c o n t e n t i o n that the genus Uria needs to be removed from the Alcidao (Gysels & Rabaey, 1 9 6 4 ) , though e n t i r e l y acceptable to the author, i s ignored i n the present d i s c u s s i o n .  129 a s s i g n each s p e c i e s to i t s r e s p e c t i v e t r o p h i c p o s i t i o n . T h i s can be done s a t i s f a c t o r i l y and I w i l l attempt to develop a g r a p h i c a l model which, I f e c i , represents  the major trends o f d i v e r s i f i c a t i o n t h a t have taken p l a c e  p r o v i d e s us with a  ll  natural  ,,  and  r e p r e s e n t a t i o n o f t h i s remarkably homogeneous  communityo  The  Bill  i n Alcida?  In s e v e r a l genera, the b i l l has  acquired c h a r a c t e r i s t i c s whose  obvious purpose i s f o r c o u r t s h i p and s o c i a l behaviour ( F r a t e r c u l a . Lunda. i l e a . A e t h i a ( c r i s t a t e l l a ) . e t c . ) . These r a d i c a l m o d i f i c a t i o n s and the  fact  t h a t the b i l l i s o f t e n used f o r purposes q u i t e d i f f e r e n t from f e e d i n g , such as burrow-digging, p o i n t to c a u t i o n i n the i n t e r p r e t a t i o n o r usage o f standard measurements o f b i l l l e n g t h and b i l l depth t h a t may in  some other groups f o r the type o f comparisons  a) Feeding Adaptations  o One  the  have v a l i d i t y ,  intended.  major v a r i a b l e w i t h i n the f a m i l y which appears  to be independent o f a l i e n b i l l c h a r a c t e r i s t i c s i s the r e l a t i v e width o f the b i l l at the base. On the one hand, p r e y i n g upon s m a l l , soft-bodied organisms such as c a l a n o i d copepods has r e q u i r e d a widening o f the beak and a f l a t t e n i n g o f the p a l a t a l s u r f a c e . On the other hand, p r e y i n g on f a s t swimming, hard-bodied p e l a g i c f i s h e s has brought about a decrease i n the r e l a t i v e width o f the b i l l  i the p a l a t a l surface i s consequently much reduced and  grooves  . and r i d g e s mark i t s s u r f a c e . The mechanics i n v o l v e d i n t h i s fundamental change o f  adaptation  remain to be s t u d i e d i n d e t a i l . But the b a s i c d i f f e r e n c e between the types i s apparently the f o l l o w i n g s i n the plankton-feeders, in  the s t r e s s e s  c a p t u r i n g prey organisms are d i s t r i b u t e d i n the a n t e r i o r r e g i o n o f  bill,  o r i n the r e g i o n a n t e r i o r to the choanal s l i t ;  two  the  i n the f i s h - f e e d e r s ,  the p o i n t o f maximum s t r e s s e s moves from an a n t e r i o r p o s i t i o n to a point l o c a t e d at the l e v e l o f the a n t e r i o r end o f the  choana. The  o f the a n t e r i o r r e g i o n o f the p a l a t e i n these two  relative extent  types can be  compared by  examining Figures. 39 and £L» Mutual s i m i l a r i t i e s o f s t r u c t u r e w i t h i n group o f p l a n k t o n - f e e d e r s and w i t h i n the apparent i n these two  group o f f i s h - f e e d e r s are  readily  figures.  Other adaptations  i n the f e e d i n g apparatus can be  followed  through a g r a d i e n t from the plankton-feeders to the f i s h - f e e d e r s . In former group, one  the  the  observed a maximum development o f blade-edge, i r r e g u l a r l y  arranged horny p a p i l l a e ( h e r e a f t e r c a l l e d , d e n t i c l e s ) i n the a n t e r i o r r e g i o n o f the p a l a t e . T h i s c o n d i t i o n reaches an extreme i n P l a u t u s  (Figure 39')»  Int  the f i s h - f e e d e r s , the t o t a l number o f p a l a t a l d e n t i c l e s i s v e r y reduced : o n l y a few are p r e s e n t  i n the a n t e r i o r r e g i o n o f the p a l a t e . Their tendency  to be arranged i n r e g u l a r rows i s remarkable ( F i g u r e 4l)» to be sharp-pointed  The  d e n t i c l e s tend  when compared to those o f the f i r s t group. F i n a l l y , i n  the P u f f i n s , Rhinoceros auklet and Parakeet auklet, the above characters are intermediate  between these two  extremes. The p a l a t a l r e g i o n anterior  to the choanal s l i t i s moderately broad and the number o f d e n t i c l e s l i e s between the numbers found i n the two  b a s i c groups.  Another s e r i e s o f c h a r a c t e r i s t i c adaptations  which runs paral-  l e l to a r e d u c t i o n i n r e l a t i v e b i l l - w i d t h are shown by the tongue. In plankton-feeders,  the  t h i s organ i s v e r y broad, t h i c k and f l e s h y (Figure 3 9 ) .  T h i s i s b e l i e v e d to be i n s t r u m e n t a l i n two  ways s f i r s t , the handling of  small food p a r t i c l e s would be d i f f i c u l t , i f - n o t impossible,  with a c o r n i f x e d  and r i g i d tongue, as i s t y p i c a l o f the f i s h - f e e d e r s ; secondly, the presence o f a s u b l i n g u a l d i v e r t i c u l u m r e q u i r e s a f l e x i b l e tongue i n order to p u s h the food p a r t i c l e s at the f l o o r o f the b u c c a l c a v i t y and i n t o the  diverticula-:  Figure 39 • P r o f i l e of the b i l l p a l a t a l surface, tongue i n situ and extruded tongue i n p r o f i l e i n A) Plautus a l i o (tongue i n p r o f i l e and from below), B)Ptycoraranhup. a l e u t l c a . C) /iothie, p u s i l l a . The arrow indicates the p o s i t i o n of the commissural p o i n t . The shading on the extruded tongue shows the extent of c e r t i f i c a t i o n . Scale s approximately x2. ?  132 Figure  4.0 • Profile of the b i l l , palatal surface, tongue i n situ and extruded  tongue i n profile i n A}Cyclorrhynchus psittacula (tongue i n profile and from below), B; Pratercula cerniculata. The arrow indicates the position of the cornmis sural point. The shading on the extruded tongue shows the extent of cornificaticn» S c a l e f o r A), approximately x 2» Scale for B), approximately,  xl»  133 Figure 41 • Profile of the b i l l , palatal surface, tongue in situ and extruded tongue i n profile i n il) Brcchyromphug morraoratnia. B) Ceophv.s columba, C; Uria, aalge X e r t r u d e d tongue i n profile and from above;» The arrow indicates the position of the commissural point. The shading on the extruded tongue shows the extent of cornification. Scale for l ) , approximately x 2 : Scale for B) and C), approximately x 1 •  134 i t s e l f . At the other extreme, a long and slender tongue, enclosed to a large degree i n a r i g i d horny shield gives excellent leverage i n "locking" firmly large prey organisms against the palatal denticles. The maximum development of this condition i s reached i n UrJa aaTLge (Figure Al) but i t i s also clearly exemplified by Brachyramphus and Gepphus. Intermediate between these two types, the Puffins (Fra^crcula, and Lunda were examined) have a tongue which i s only p a r t i a l l y encased i n a horny covering i n i t s d i s t a l third : moreover, this covering does not reach the upper surface of the tongue. This region remains fleshy and this condition i s believed to be adaptive i n two ways : i t allows the successive capture of several prey items, as i s characteristic of the group, and Is also related to a definite increase i n the proportion of invertebrates making their diet (see discussion of this last point below).(Figure  4°)  Although this i s not illustrated, the two species of Aethia considered i n this study show, as expected, great similarity i n feeding adaptations s the denticles are about equally abundant and have an irregular distribution i n the anterior palatal region; tongue cornification Is of the same extent, that Is, limited to the very t i p . B i l l , palate and tongue of the third species studied, Cyclorrhynchus psittacula are shown i n Figure AO and can be compared with the same, structures i n one representative of the genus Aethia i n Figure 39 .(pusilla) : i n the former, there i s a marked reduction i n the density of palatal denticles, though the palatal surface remains relatively broad. Tongue characteristics are quite similar i n the two genera. b) A meaningful Ratio . Our aim i s to find a ratio that i s independent of body siae but reflects the major adaptive trends i n feeding. The use 01" the ratio Bill-width / Bill-length Is not satisfactory for reasons outlined  135 e a r l i e r and the r a t i o B i l l - w i d t h  / Gape (commissural p o i n t to t i p o f culmen)  was p r e f e r r e d . Some disadvantages o f t h i s r a t i o must, however, be mentioned. For s t a n d a r d i z a t i o n o f the measurements, width was measured a t the p o s t e r i o r edge o f the n o s t r i l s , as c l o s e as p o s s i b l e to the t o m i a l edge, a v o i d i n g the operculum which i n some s p e c i e s extends f u r t h e r o u t than the tomia. I n Fratercula, bill-width  t  t h i s measurement happens t o be a good approximation o f the maximum s i n c e i t i s taken c l o s e to the commissural p o i n t s i n .-Mcs, t o r d a .  the p o s t e r i o r edge o f the n o s t r i l s i s approximately a t t h e mid-point o f the d i s t a n c e between the culmen t i p and the commissural p o i n t . F o r t h i s reason, minute d i f f e r e n c e s i n the v a l u e s o f the r a t i o cannot be d i s c u s s e d i n d e t a i l i n some cases. Moreover, the measurement o f the Gape i s n o t always an adequate measurement on s k i n specimens. A way to avoid these d i f f i c u l t i e s would be t o determine t h i s r a t i o upon d i s s e c t e d m a t e r i a l by making uso o f the d i s t a n c e between the t o m i a l edges and t o determine accurately' i n t h i s way the parameterd o f width and l e n g t h % t h i s i s h a r d l y f e a s i b l e owing t o the l a c k o f m a t e r i a l in. the c o l l e c t i o n s * Measurements o f the b i l l and values o f t h i s r a t i o f o r most members o f the f a m i l y A l c i d a e are given i n Table 8.  The Model H a i r s t o n (1964.) g e n e r a l i z e s t h a t "the r e l a t i o n s h i p s t h a t f o r c e order upon n a t u r a l communities may be placed i n t o two broad c a t e g o r i e s : energy t r a n s f e r and competition".  The model proposed below combines these  two b a s i c approaches. Gradual m o d i f i c a t i o n s i n the f e e d i n g apparatus and consequent spreading o f the members o f the community a t various t r o p h i c l e v e l s , give the model i t s v e r t i c a l dimension; the increase i n body s i z e t h a t accompanies the increase i n . p r e y s i z e (from plankton  to f i s h )  imparts  an oblique, t r e n d to the grouping o f the species o f a l c i d s on the model;  Table 8 . B i l l c h a r a c t e r i s t i c s , body weight and r a t i o B i l l - w i d t h / Gape i n v a r i o u s A l c i d a e . Unless otherwise i n d i c a t e d , a l l measurements are from males i n summer plumage. The code l e t t e r r e f e r s to F i g u r e s 42 and 43. A t l a n t i c s p e c i e s are c h a r a c t e r i z e d by a c a p i t a l l e t t e r ; P a c i f i c s p e c i e s by lower case; amphi-oceanic s p e c i e s by juxtaposed l e t t e r s . U n l e s s otherwise i n d i c a t e d , a l l measurements were obtained by the author e i t h e r i n A l a s k a (body weight o f s e v e r a l species i n p a r t i c u l a r ) o r , e l s e , on specimens i n c o l l e c t i o n a t the U n i v e r s i t y o f B r i t i s h Columbia and a t the Museum o f V e r t e b r a t e Zoology, Berkeley, The o r d e r i s from P e t e r s , 1934*  Bill-length  Cods  Species 1  Pinguinus impennig  Bill-depth  8.91  A  FXautus a l l e  a  B  80.01  -  b  Bill-width  U  a  p  e  d Body-weight Cube Root o f (g) body-weight  23.13  8.74 16.73  3 „  3  107.9 5  7.6  3  Bill-width  N  Gape  166. 2*"  5.51  .378  11  -  17.0 "  .155  -  9.02  .148  733.7  4  5  C  . 35,09  U r i a lomvia^  Dd  37.24  15.41  10.54  59.85  975.5  9.91  .176  7  M a sales  Ee  47,40  15.05  10.23  63.78  980.0  9.94  .149  11  F  27.53  8.70  6.57  42,3  374.5  7.20  .155  4  g  33*33  11.28  8.O4.  43.86  502.2  7.95  .183  11  h  16.51  6.10  4.71  32.04  234.5  6.16  .147  13  B. b r e y i r q s t r e  i  10*48  5.09  4-57  27.15  237.7  Endomychura h, hypojjaxca.  j  18.85  6.07  4.72  31.28  155.9  k  19.11  5,89  4s  66  29*55  152.1  A l c a torda  Cepphus  gryJle  Gepphus columba.  6  7  marmor.uti'im  p;  T - ^-j-^y  n  1  7  8  6.19  15  5.38  6  5.34  .153  rt O  Table 8, ( C t d ) . Species  Code  Synthliboj^raphos.  I  Bill-length  Bill-depth  Bill-width  13.93  7.20  ' 5.32  Gape  Body-weight J ) b  Bill-width — Gape  N  6.15  .198  172.6*  5.57  .350  8  26.80  233.5  22.91  antiourM  Cube r o o t o f body-weight  ,9  14  m  19.09  9.31  8.01  Cyclorrhynchiis psi'ttaci^a  n  16.07  14.53  7.85  26.01  317.6  6.82  .302  14  iiajhia. crijitatelJ^  0  12.48  12.45  7.97  24.41  284.5  6.57  .326  21  A* piisi.ila  P  8.86  7.74  6.24  16. AS  86.3  4.42  .379  16  A» pyg!M£a  q  10.17  6.50  5.42  16.27  (118.0)  4.90  .333  r  34*40  17.74  10.54  44.77  11 571. 0 ^  8.30  .235  37.37  10.80  36.05  510.0  7.99  .299  9  PJyco_ramDjra?i  al^ujbica  YTI  T-'N  /*\ r"v  mono  Y**  12  "v »*l  Fr^te^-Stlla  S  axctica  Lund?, c i r r h g i a  5  t  5X©X7  43.63  10 74  39.46  652 2  8.67  .272  10  e  u  59.69  43.55  14.35  47.99  824.8  9.38  .299  12  a - e x p o s a l culmen b- maximum d e p t h s i n A e t h i a p u s i l l a ^ i n c l u d e s h e l m e t ; i n Cej orhjjic.&, i t excludes the horny p r o j e c t i o n , e- a t p o s t e r i o r edge o f n o s t r i l s , d- frora cotanvissural p o i n t t o culmen t i p 1- sample c o n t a i n s b a t h s e x e s . 2- f r o m J o h n s o n , 1935 3- f r o m d a t a i n Coues, 1863. ,  0  95- f r o m B e l o p o l ' s k i i , 1957. 1 \ 6 - two s p e c i m e n s o n l y , m a n d j x l l , Bering S t r a i t region. 7- Three measurements o n l y , f r o m 11Sww, t . Lawrence I s l a n d.. From w e i g h t s g i v e n o n l a b e l s o f 8s p e c i m e n s examined a t B e r k e l e y . E» hv^oj^ouca, N - 7 Us. c r a y e r i . N s 8 :  f r o m T h o r e s e n , 3.964 f r o m F e i n s t c i r . , 1959.l.'eight e s t i m a t e d from r o g r e a a i o n line. M i d - p o i n t o f cxtrcmer; g i v e n i n K o s l o v a , 1957. < I  finally,  c o n s i d e r a t i o n s o f competition and e c o l o g i c a l u n s t a b i l i t y w i l l d e t e r -  mine rhe breadth o f the e c o l o g i c a l zone t h a t w i l l be occupied i n the model. One must impose r e s t r i c t i o n s over H a i r s t o n s g e n e r a l i z a t i o n 8  quoted above. I t i g n o r e s the r o l e that s e v e r a l other f a c t o r s may have p l a y e d i n shaping the community i n i t s present form. The h i s t o r i c a l f a c t o r i s one o f them f o r i n s t a n c e . -As we l o o k a t the f a m i l y A l c i d a e now, we can o n l y s p e c u l a t e about the r o l e o f competition i n i n f l u e n c i n g the radiation, i n f e e d i n h a b i t s t o the degree t h a t we can observe  today. I n a few cases which I s h a l l  d i s c u s s l a t e r , i t seems p l a u s i b l e to i n f e r t h a t divergence i n a d a p t a t i o n i s , o r has been emphasized as a mean o f a l l e v i a t i n g competition f o r food between c l o s e l y r e l a t e d forms s but t h i s i s c e r t a i n l y not alvrays the case. I wanted t o make c l e a r by t h i s d i g r e s s i o n t h a t I do n o t deny the r o l e o f o t h e r f a c t o r s than those mentioned by H a i r s t o n i n i n f l u e n c i n g community s t r u c t u r e . But the model presented below has a f f i n i t i e s  with  taxonomic o r p h y l o g e n e t i c models : i t d e l i b e r a t e l y grades o r organises s e r i e s o f animals according to d i f f e r e n c e s i n one major character ( i n the present case, f e e d i n g adaptations) even though no taxonomer w i l l b e l i e v e t h a t t h i s c h a r a c t e r c o n s t i t u t e s r e a l l y t h e o n l y a x i s along which the p a r t i c u l a r group he examines has evolved. I t must be emphasized again t h a t the community s t u d i e d here i s t a x o n o m i c a l l y homogeneous.. Moreover, the hunting s t r a t e g y i s v e r y s i m i l a r i n a l l s p e c i e s : a l l are b a s i c a l l y s o l i t a r y feeders who propulse themselves under water with t h e i r p a r t l y opened wings and who pursue r e l a t i v e l y small prey organisms; a l l pursue and capture i n d i v i d u a l prey organisms i n p e l a g i c environments and swallow them one by one under water. S t o r e r (194-5) suggested  t h a t Endomychura i s the most p r i m i t i v e  member o f the f a m i l y a s i n d i c a t e d by i t s two eggs, small, " p r i m i t i v e "  bill,  small body s i z e and absence o f d i f f e r e n c e between summer and winter plumages.  139 In the present model, Endomychura i s considered a specialist - which Is more or less a contradictory interpretation. Storer further says that the Alcidae, rather than showing adaptive radiation, show a series of "parallel trends". He then continues  trends toward deepening and lateral  compression (of the b i l l ) are to be found i n SynthD-iboramphus and the auklets, auks and puffins". Storer i s neglecting the fact that the b i l l , i n this family i n particular, i s not exclusively a food-getting tool, biro i s also used extensively as a social -releaser (sensu Tinbergen) and i s , hence, subject to many different types of selective pressures. When considered as a social releaser, the b i l l i n the family does show "parallel trends", but when considered as a feeding apparatus, we observe rather a continuum or a gradation which is. equivalent to adaptive radiation. But the model does not allow us to determine which i s the most primitive type and i t i s independent of taxonomic considerations. The graphical representation of the ratio Bill-Width / Gape versus Body-size for most members of the family i s given i n Figure 4 2 . Needless to say, the horizontal clusters representing the various trophic levels have been determined afterwards, upon our knowledge of the feeding habits of the key-species. This knowledge i s at best fragmentary for a number of species included i n the graph. What we know of the diet of such forms as Synthliboramphus or Endomychura i s v i r t u a l l y n i l , but the interesting point about the model i s that i t allows us. to make predictions as to the ecological position of such forms i n the community. Two basic trophic levels are represented i the plankton-feeding l e v e l (Carnivore I i n the traditional vocabulary) and the fish-feeding level (Carnivore I I ) . Representatives of the f i r s t level are /.ethia, and Pla^tua^ of the second, Uria and Alca. However, an intermediate level can thecretical.. , ;  be distinguished i n marine environments : there exists a number of carni-  •vorous planktonic organisms such as pelagic amphipods, fish larva~, arrowworms, polychaetes, etc* so that the predator specializing i n these prey organisms can occupy a third more or less distinct l e v e l that would require us to reassign the fish-feeders to the level of Carnivores III,, In practice, this l e v e l i s rather an element of a web rather than a l i n k i n a chain. But, as i t happens, i t i s indeed occupied by one species, Cyclorrhynchus psittacula which has a diet including the above l i s t e d forms of marine invertebrates i n a large proportion (Chapter I I I ) . This shift to a higher trophic level (accompanied by a sharp reduction i n abundance) i s believed to constitute the major difference i n feeding ecology between this species and i t s possible competitor, Aethia cristatella. In the model, the Parakeet auklet i s associated with the puffins because i t s ratio of Bill-width / Gape i s smaller than i n the true plankton-feeders (Aetnaa, Plautus, Ptycoraraohus). even though i t posseses i n common with the l a t t e r , a fleshy tongue and a sublingual diverticulum. The Fraterculinae (Fratercula, Lunda,, Cerorhinca.) make up an intermediate l e v e l between Plautus and Uria. They do share adaptations that characterize the two adjacent levels, such as a moderately wide b i l l at the base, a fleshy tongue i n surface and a moderate, increase i n the density of . palatal denticles when compared to the fish-feeders (Figure AO). They are known to participate i n fact to these two levels : a l l species bring exclusively f i s h to their nestling but do a large amount of their own feeding upon crustaceans ( see Swartz  (1966)  for Lund?: Belopol'skii (1957) for Prgtftrcxila,  arctica ). For graphical reasons, they are here represented as belonging to a distinct level, but biologically they are better considered as intermediates. Another characteristic of the model i s that i t bears out the relative increase i n body size with an increase i n prey size (and trophic level). This i s i n agreement with Eltonian concepts of predator-prey systems  141 Figure 42 « The relationship between Body-weight (cubic root) and the ratio Bill-width / Gape i n Alcidae. Explanations i n the text. The l e t t e r code i s given i n Table 8.  142 a n d ' w i l l not be developped  any f u r t h e r here.  The model can be expanded as i s attempted i n F i g u r e 43. There are obvious l i m i t s to the h o r i z o n t a l spreading a t any l e v e l . A plankton f e e d e r must not exceed a c e r t a i n body s i z e o r i t q u i c k l y becomes uneconomical and t h e energetic, balance soon becomes unfavourable. I n the sa-ne manner, too b i g a r e d u c t i o n i n s i z e f o r a plankton feeder, though i t c o u l d t h e o r e t i c a l l y open the p o s s i b i l i t y o f e x p l o i t i n g a v e r y r i c h food source made up by the microplankton  (Pseudocalanus,  c r e a t e such an unfavourable  copepod n a u p l i i , e t c ) i s i m p o s s i b l e f o r i t would  surface to volume r a t i o . However, i t i s not  u n t h i n k a b l e on t h e o r e t i c a l grounds t h a t a l a r g e plankton f e e d e r c o u l d develop but t h i s would r e q u i r e s p e c i a l i z e d adaptations t o render economical the c o l l e c t i o n o f small food p a r t i c l e s . This could be achieved by the a c q u i s i t i o n o f a s p e c i a l s t r a i n i n g apparatus,  such as modified r i c t a l f e a t h e r s . T h i s  would a t t h e same time open up a t o t a l l y new e c o l o g i c a l zone i n t o which f a r t h e r d i v e r s i f i c a t i o n c o u l d occur. I n t h e same way, there i s an optimum s i z e f o r f e e d i n g on f i s h e s . I t i s a l s o apparent t h a t w i t h i n the f a m i l y , there i s an upper l i m i t to body s i z e i the a c q u i s i t i o n n o f d i v i n g h a b i t s has meant s t r u c t u r a l m o d i f i c a t i o n s which c o n s i s t above a l l i n marked strengtherbLng o f the s k e l e t o n ; the l a r g e s t f i s h - f e e d e r s are already c l o s e t o a c r i t i c a l t h r e s h o l d o f body-weight compatible  w i t h the power o f a e r i a l and submarine f l i g h t , and any f u r t h e r  i n c r e a s e above t h a t t h r e s h o l d could not be made without the l o s s o f one o r the other a t t r i b u t e ( S t o r e r ,  I960).  In the model ( F i g u r e 43), the shaded area represents the zone o f e c o l o g i c a l u n s t a b i l i t y , the i n v a s i o n o f which must be accompanied by the development o f s p e c i a l i z e d adaptations. As i s shown i n Figure 43, s e v e r a l species are i s o l a t e d i n t h i s shaded area. At the l e v e l o f the f i s h - f e e d e r s , the breakthrough  i n the zone o f e c o l o g i c a l u n s t a b i l i t y was achieved by P i n -  143 F i g u r e A3*  Breadth o f the e c o l o g i c a l f i e l d occupied by the A l c i d a e . 2 x p i a n a t i o n s i n the t e x t . The l e t t e r code i s given i n Table 8.  144 guinus imponnis and was  accompanied by what can ba considered a s p e c i a l  adaptation, namely the l o s s o f a e r i a l f l i g h t . The M u r r e l e t group which appears as s m a l l body-sized f i s h feeders i n F i g u r e 43, must be considered s p e c i a l l y adapted and t h i s appears indeed to be the case. Sndorcychura, and Synthliboramphus have reached body s i z e (and,, consequently,  such a small  b i l l - s i z e ) t h a t i t i s d o u b t f a l i f they feed at  a l l on f i s h e s ( H o w e l l , 1917), and whether they could catch and c a r r y f i s h to the developping n e s t l i n g . T h i s l a t t e r f a c t c r e a t e s a s p e c i a l problem s the t r u e plankton-feeders  have evolved a s p e c i a l s t r u c t u r e - the neck-pouch -  to render e f f i c i e n t the t r a n s p o r t o f a s a t i s f a c t o r y volume o f p a r t i c u l a t e food to the n e s t . Svnthliboramphus and Bndomyehura. l a c k i n g such a s t r u c t u r e are f a c e d w i t h the a l t e r n a t i v e o f e i t h e r making a v e r y  energy-absorbing  s h u t t l e between the o f t e n d i s t a n t feeoling grounds and the nest, o r , e l s e , to shorten and even e l i m i n a t e the n e s t l i n g stage. This e l i m i n a t i o n o f 'the n e s t l i n g stage has indeed occurred o r i s l i m i t e d to one o r two days d u r i n g which, as f a r as is- known, the c h i c k i s not f e d (Howell, 1917). T h i s again must be considered s p e c i a l adaptation. The case o f Brachyramphus i s not documented enough, but t h e r e , the parents o f at l e a s t one  s p e c i e s , ma.rmoratura.  are known to c a r r y f i s h - m a t e r i a l to the n e s t . Moreover, the evidence  reviewed  by Drent and Guiguet (1961) seems to I n d i c a t e t h a t t h e chick l e a v e s the nest before the a c q u i s i t i o n o f the power o f f l i g h t and t h e r e could w e l l be a tendency f o r a shortening o f t h i s stage. V i r t u a l l y nothing i s known o f b r e v i r o s t r e , although a recent nest d i s c o v e r y r e v e a l e d the presence o f a p a r t l y grown c h i c k (Williamson e t . a l . , 1966) to what i t i s i n mam  and the p a t t e r n i s probably  similar  ora turn.  Information on M u r r e l e t s i s scanty : but we know t h a t they are s s t r i c t e d to c o a s t a l waters (except S y n t h l i boramphus); some forms arc known  res  to pursue schools o f s m a l l f i s h e s (mamoratum : G x i n n e l l , quoted i n 3ent, 1921). But as a whole, they probably depend much upon marine i n v e r t e b r a t e s of  the c o a s t a l o r l i t t o r a l zone ( b r e v i r o s t r e s K i s c h i n s k i i , 1965). Worms,  gammarids, mollusks and other hard-bodied p r e y probably make up a s u b s t a n t i a l p a r t o f t h e i r d i e t . But they b a s i c a l l y stem from the f i s h - f e e d e r s l e v e l  and  do share a d a p t a t i o n s o f t h i s group ( F i g u r e 4 l ) . Shortening o f the n c c t l i n g stage, r e s t r i c t i o n to l i t t o r a l waters ( w i t h the exception o f Synthlibor^mphus which i s a shallow, o c e a n i c d i v e r ) must be considered s p e c i a l adaptations t h a t have p e r m i t t e d a breakthrough  i n the zone o f e c o l o g i c a l u n s t a b i l i t y .  I n the model ( F i g u r e 43),  the area o f e c o l o g i c a l u n s t a b i l i t y i s  extended between l e v e l s and communication between them i s p o s s i b l e o n l y for  intermediate forms. F o r any one l e v e l , b a r r i n g s p e c i a l adaptations,  there i s an optimum body s i z e at which energy conversion i s maximum. I t i s v e r y u n l i k e l y f o r i n s t a n c e t h a t an h y p o t h e t i c a l Lunda could, i n a v e r y r a p i d l y changing environment adapt to a lower l e v e l and r e v e r t to e x c l u s i v e depen• dence upon p e l a g i c i n v e r t e b r a t e s without f i r s t - i f at a l l p o s s i b l e r e d u c i n g I t s body s i z e c o n s i d e r a b l y . This minimizes the area o f exchange between l e v e l s . There i s some evidence a v a i l a b l e , supporting the above reasoning. I n the North P a c i f i c and the B e r i n g Sea, the p l a n k t o n - f e e d i n g niche i s f i l l e d by f i v e species whose ranges o v e r l a p ( o r overlapped d i s t u r b a n c e by man)  before  i n p a r t s o f the A l e u t i a n chain. I t i s i n t e r e s t i n g to note  t h a t i n the North A t l a n t i c , o n l y one form f i l l s the e q u i v a l e n t niche, namely P l a u t u s (see Bateson, 1961;  Witherby e t . a l . , 1944;  Salomonsen, 1951;  Kar-  taschew, I960 f o r i n f o r m a t i o n on f o o d - h a b i t s ) . I n the Eastern North P a c i f i c , Ptycoramphus alone occupies the niche i n the s u b a r c t i c and b o r e a l waters from the A l a s k a P e n i n s u l a to Baja C a l i f o r n i a . Both s p e c i e s , alone i n t h e i r niche, are o f intermediate body s i z e .  Similarly, Fratercula arctica. the only Ivorth Atlantic representant o f the intermediate l e v e l as well as Cerorhinc?, the only member o f the group i n the subarctic and boreal waters o f the eastern P a c i f i c are also of intermediate body size. (Recently Schoener (1967), i n a study of the anol i n e l i z z a r d s i n the Caribbeans, remarked that most species o f Are^is, which occur without congeners are about the same absolute size from island to island.) At the l a s t l e v e l , no representative has a non-overlapping  dis-  tribution with either o f i t s close relatives : .iCI.cq torda and U r i a aalge are to be considered the most t y p i c a l icthyophagous species (see Eolopol'skii, 1957) and the theoretical optimum body size could a r b i t r a r i l y be placed between the two. Finally, upon the basis of the preceding considerations, the model i s expanded and generalized i n Figure 44* The sorting at various levels i s merely a duplication of the case described and analysed above, the family Alcidae. Elements or species can move i n the model - through long-term d i f f e r e n t i a t i o n and t h i s p o s s i b i l i t y for s h i f t i n g i s indicated by two components J a large horizontal one and a smaller v e r t i c a l one! The former implies long term character displacement, niche partitioning by morphological d i f f e r e n t i a t i o n . The l a t t e r implies modifications of feeding adaptations and is. probably a more d i f f i c u l t route of segregation.  Rqtio of Character Difference  KacArthur and Levins (I96A) generalized that there exists two extreme types o f niches : i n one, the animal s remain adaptable but a r e able to coexist because of specific behavioural differences that keep them i n the right place : i n the other type o f niche, the different species l i v i n g a t  147 Figure 44- • Generalised model based upon the data contained i n Figures 42 and 4-3• The model considers one taxonomically homogeneous group that has diversified at more than one trophic level. The sorting along the vertical axis i s an expression of regular variation i n feeding adaptations taken as linear measurements or as ratios describing the feeding apparatus 5 the sorting along the horizont a l axis i s based upon variations i n body size that accompany a change i n trophic position or a change i n the size o f the prey .items consumed by a predator at any level (this change i s expressed i n a linear fashion, v.g. by the logarithm or the cubic root o f the body weight). The vertically shaded area constitutes the zone of ecological unstability and to invade i t , any element or taxonomic entity considered i n the ecological f i e l d depicted by the model (white area) must develop specialized adaptations that render the breakthrough a biological f e a s i b i l i t y . The diagonal line of Optimum Body Size predicts the size o f a predator when i t i s alone to occupy a niche i n a broad geographical area. Further explanations i n the t e x t .  the same t r o p h i c l e v e l can have b r o a d l y o v e r l a p p i n g b e h a v i o u r a l  responses  to  the environment, but they u s u a l l y d i f f e r i n s i z e and t h i s d i f f e r e n c e i s  of  the o r d e r o f 130:100. T h i s alone f o r c e s o b l i g a t e f e e d i n g upon f i f f e r e n t  p o r t i o n s o f the food r e s o u r c e s . The r a t i o was  f i r s t proposed by  Hutchinson  (1959) and the o r i g i n a l p r o p o s i t i o n a l s o h e l d that a d i f f e r e n c e o f t h i s nature i n the t r o p h i c apparatus alone need not be accompanied by an equivale d i f f e r e n c e i n body s i z e : i n p r a c t i c e , however, th© l a t t e r w i l l c f t e n f o l l o w Schoener (1965) determined t h i s r a t i o o f "character d i f f e r e n c e " for  l a r g e numbers o f congeneric  r a t e f a m i l i e s o f b i r d s . The for  species o f t r o p i c a l , s u b t r o p i c a l and tempe-  technique, however d i d not prove s a t i s f a c t o r y  a l l cases s i n c e , as Bowman ( I 9 6 l ) p o i n t e d out and as Schoener recognises  b i l l - s h a p e i n c e r t a i n cases i s as important  I n accounting f o r segregation  as the dimension o f l e n g t h used i n e s t a b l i s h i n g the r a t i o . Johnson (1966). a l s o p o i n t e d out t h e exaggerated importance attached to b i l l l e n g t h i n e s t a b l i s h i n g t h i s r a t i o . T h i s i s true i n the present case where the ve width o f the b i l l at the base was  found to be j u s t as important  relatia charac-  t e r i s t i c as the l e n g t h o f the b i l l i t s e l f (see the case o f U r i a d i s c u s s e d below). With t h i s r e s t r i c t i o n i n mind, the r a t i o o f c h a r a c t e r d i f f e r e n c e was  c a l c u l a t e d f o r some s p e c i e s p a i r s . Aethia c r i s t a t e l l a . and A»  do d i f f e r i n culmen l e n g t h i n the p r o p o r t i o n o f 141:100 and,  pusilla  superimposed  upon t h i s d i f f e r e n c e , there has also been a marked segregation i n body s i z e . The evidence  c o l l e c t e d on f o o d - h a b i t s (Chapter II) indicates c l e a r l y t h a t  both s p e c i e s belong to the same t r o p h i c l e v e l and that they do also e x h i b i t a c o n s i d e r a b l e degree o f overlap i n h a b i t s and i n behavioural r e a c t i o n s to the environment. The case o f the t r i o Aethia c r i s t a t e l l a , A. pygmge^ and A, pu,?ij  i s much l e s s c l e a r due  to l a c k o f i n f o r m a t i o n . But the fragments we have  do f i t w e l l the e x p e c t a t i o n s . I n the A l e u t i a n I s l a n d s , pygmaea i s with i t s two  sympatric  congeners and a l l r e p o r t s concur i n e s t a b l i s h i n g i t as a scarce  and s p a r i n g l y d i s t r i b u t e d b i r d throughout t h i s t e r r i t o r y ( K u r i e , 1959;  Ga-  b r i e l s o n & L i n c o l n , 1959). I n the K u r i l e chain, on the contrary, Gizenko (1955) c o n s i d e r s pygroaea, as b e i n g very abundant throughout the c h a i n and makes frequent mention o f " l a r g e f l o c k s everywhere". In the l a t t e r area, p u s i l l a I s absent and i t i s not i m p o s s i b l e t h a t the absence o f a close competitor  allows  pygmaea, to be more g e n e r a l l y d i s t r i b u t e d w i t h i n i t s range and t o be a l s o more abundant. The r a t i o o f c h a r a c t e r d i f f e r e n c e f o r the two  s p e c i e s o f the  p a i r pygnaea x p u s i l l a i s b a r e l y 114:100. The  case o f Brachyramphus i s a l s o i n t e r e s t i n g . Both s p e c i e s  o v e r l a p b r o a d l y i n south-eastern  Alaska % 'they o f t e n occur together i n i n l e t s  and i n the neighbourhood o f g l a c i e r s . The two  s p e c i e s do not d i f f e r appre-  c i a b l y i n body s i z e , but the r a t i o o f the culmen l e n g t h o f marmo^r-forr. to b r e v i r o s t r e i s o f 157:100 and i t i s almost c e r t a i n that t h i s d i f f e r e n c e alone r e s t r i c t s the two  species to v e r y d i f f e r e n t p o r t i o n s o f the a v a i l a b l e food  1 resources  . The  case o f U r i a spp. i s more d i f f i c u l t . Both species are o f recen-t  o r i g i n , lomvia having most l i k e l y evolved on the margins o f the P o l a r Basin d u r i n g one o f the g l a c i a l , p e r i o d s . Both species have now  widely  overlapping  d i s t r i b u t i o n s i n the s u b a r c t i c waters o f the North A t l a n t i c and o f the North ? a c i f i c ( s e e Tuck, I960). The case i s f u r t h e r complicated  i n The North A t l a n t i c  by the presence o f a t h i r d c l o s e l y r e l a t e d ' s p e c i e s ( e c o l o g i c a l l y ) , Ale?, 1  This r a t i o was determined on specimens coming mostly from the zone o f o v e r l a p . I do not know I f i t changes when one compares a l l o p a t r i c popul a t i o n s o f the two s p e c i e s .  150 torda. The p l a s t i c i t y o f U r i a renders the a n a l y s i s or the  comparison  d i f f i c u l t s i n c e t h i s p l a s t i c i t y does not always' operate i n the f a s h i o n expected and i n at l e a s t one the two  geographic area (the P r i b i l o f I s l a n d s , Southern A l a s k a ) ,  s p e c i e s have v e r y s i m i l a r b i l l lengths (sea S t o r e r  (1952)  who  48.80 mm  as the Average B i l l Length f o r males s a i g a i n Southern Alaska  45.26 mm  as Average B i l l l e n g t h f o r males 2pm~t.% t r a t i o o f  gives and  character  d i f f e r e n c e , 108:100). I t must be mentioned that lomvx^ has v e r t e b r a t e s than aalge : from Swartz's a n a l y s i s  a tendency to use more i n -  (1966)  the percentage o f  stomachs' c o n t a i n i n g f i s h remains and i n v e r t e b r a t e remains was r e s p e c t i v e l y for  l e w i a , 34 and 63; f o r aalge, 6 and 95.The value o f the B i l l - w i d t h / Gape  r a t i o i s l a r g e r i n lorn v i a  than i n aalge (.176  a g a i n s t .149;  Table 8), but  as  I mentioned e a r l i e r i t i s d i f f i c u l t to compare s m a l l d i f f e r e n c e s i n t h i s r a t i o owing to the inadequacy o f the Gape measurement and a l s o , i n the case, owing to the f a c t t h a t i t was o f sympatric  impossible  present  to e s t a b l i s h i t on specimens  r a c e s . However, examination o f s e v e r a l specimens o f the two  spe-  c i e s r e v e a l e d c o n s i s t e n t d i f f e r e n c e s i n f e e d i n g adaptations t h a t i - e f l e c t t h i s t r e n d i n a widening o f the b i l l a t the base i n lomvia.  In the l a t t e r ,  tongue i s much wider and f l e s h y throughout i t s e n t i r e upper surface;  the the  extent o f i t s c o r n i f i c a t i o n below and on the s i d e s i s much reduced when compared to aalge. Moreover, there i s a s u b s t a n t i a l increase i n the number o f p a l a t a l d e n t i c l e s , e s p e c i a l l y i n the a n t e r i o r p o r t i o n o f the p a l a t e . As  we  have discussed e a r l i e r , t h i s t r a i t i s a s s o c i a t e d with an increase i n the p r o p o r t i o n o f i n v e r t e b r a t e s i n the d i e t . The  case o f the U r i a s p e c i e s - p a i r  would c o n s t i t u t e a case o f segregation along the v e r t i c a l component i n d i c a t e d  xn  Figure 44. The  e l u c i d a t i o n o f these r e l a t i o n s would c o n s t i t u t e a most  promising subject of investigation. A most interesting fact i n this connection Is the concordance of the reports of observers who have mentioned large oscillations i n the relative abundance of the two species from year to year (Preble & KcAtee, 1923 for the P r i b i l o f Islands; Fay & Cade, 1959 for St, Lawrence Island). Unfortunately, no quantitative observations are available on this* phenomenon. These fragmentary observations, together ^ i t h the cAu;rsering of -the three icthyophagous forms i n the same area cf the model point to a rather "unstabilised" system, possibly i n view of i t s recent formation. These three species could profitably be studied from this angle s such a study could contribute to increase or, better, precise our knwledge of community s t a b i l i t y which i s s t i l l quite obscure. As Sloboolan (1963) suggested, i t may turn out that community "stability  11  i s i n "some sense proportional  to food-wob complexity".(See also Hutchinson, 1959). The model also illustrates the- tendency for having more small species than large ones. This tendency, most apparent at the fish-feeders level (Figures A2 and A 3 ) , has been known for some time (Eensch, I960) and recently Hutchinson & MacArthur have attempted with partial success to give this phenomenon a mathematical formulation (1959).  CONCLUSIONS  " . . . a l l models leave out a l o t and are i n that sense false, incomplete, inadequate"(Levins, 1966). This author then continues : The 11  validation of a model Is not that i t i s "true" but that i t generates good, testable hypotheses relevant to important problems. A model nay be discarded i n favour of a more powerful one, bat i t i s usually simply outgrown when  the l i v e i s s u e s are not any l o n g e r those f o r which i t was designed!.' H a i r s t o n (1959) i n s i s t e d upon the n e c e s s i t y o f knowing not c n i y the s p a t i a l d i s t r i b u t i o n but a l s o the numerical abundance o f a l l species before we c o u l d reach an understanding o f community o r g a n i s a t i o n . I n view •of o u r p r e s e n t i n a b i l i t y t o d e v i s e meaningful  e g r e s s i o n s o f biomass o r  abundance f o r any one s p e c i e s o f the f a m i l y , t h i s aspect cannot be i n t e g r a ted i n the model presented above. Q u a l i t a t i v e remarks o r i n f e r e n c e s concerning the r e l a t i v e abundance o f some s p e c i e s have been made i n the d i s c u s s i o n , but we cannot go any f u r t h e r a t t h e p r e s e n t time. T h i s f a i l u r e to i n t e g r a t e the most fundamental element o f abundance does not, however, i n my opinion,, i n v a l i d a t e s the d e r i v a t i o n o f p a t t e r n s such as, segregation a t v a r i o u s t r o p h i c l e v e l s , the concepts o f s p e c i a l adaptation, gradual change i n f e e d i n g adaptations, optimum body s i z e at any l e v e l , l i m i t e d zones o f interchange, e t c . Another c r i t i c i s m t h a t could be formulated, i s the f a c t t h a t l a r g e l y a l l o p a t r i c forms b e l o n g i n g to d i s t i n c t communities are grouped simultaneously. T h i s was done, however, p u r e l y f o r g r a p h i c a l reasons and i n order to p l a c e emphasis upon some p a r t i c u l a r r e l a t i o n s such as the intermediate body-size o f i s o l a t e d s p e c i e s . I t would be wrong to expect the model t o provide us with an o b j e c t i v e and t o t a l l y accurate p i c t u r e o f the immensely complex r e l a t i o n s h i p s t h a t c h a r a c t e r i z e any community. But, the model given above i n t e g r a t e s some o f the b a s i c r e l a t i o n s o f f e e d i n g and competition among the v a r i o u s members o f the f a m i l y . Moreover, i t allows us to make p r e l i m i n a r y p r e d i c t i o n s , i . e . hypotheses,  as t o the areas o f u n s t a b i l i t y w i t h i n the community. For instance,  U r i a p o p u l a t i o n s i n zones o f a l i o p a t r y are more s t a b l e ( i . e . t h e i r biomass i s subject to o s c i l l a t i o n s o f l e s s e r amplitude)  specific  than i n areas o f  overlap. I t permits us to formulate hypothesis such as the f o l l o w i n g :  •Ob  taking for granted that marine productivity and food-resources diversity are comparable In areas of the North Atlantic and cf the Bering Sea ( a very reasonable  assumption),  Piautus alle occupies i n the absence of ecological  relatives a broader niche that must be roughly equivalent to tho combined niches occupied by Aethia cristatella and A , pusilla. Within areas of comparable productivity, the total average but  certainly less  than  the  biomass  combined bicmass  of  of Piautus i s nearly equivaler cristatella one ru?i"lc.  The two l a t t e r can be considered specialists, hence, more efficient energy converters. The type of documentation necessary to test "these postulates i s d i f f i c u l t to obtain at the moment for the lack of suitable censusing techniques and the perennial d i f f i c u l t y of evaluating primary productivity. But, yet, this remains a testable hypothesis. The model allows us to propose hypotheses about the species-pairs When the difference i n bill-length i s vide enough, such as i n the pair c r i s tatella x pusill a. or- the two species of Brachyramphus. the difference i s preserved i n zones of allopatry. When the value of the ratio of character difference i s "small" i n zones of sympatry, the difference may disappear i n zones of allopatry • moreover, coexistence in the zone of overlap does not give rise to a stable system. The degree of mutual interdependence, basic to community concepts Is here given some qualitative evaluation. Our understanding v a i l be greatly improved when we can present these evaluations i n quantitative terras. I t Is not known at the moment how applicable this model could be to other groups (Figure 4 4 } . Seldom dees one encounter i n terrestrial ccamunities such a  simple  taxonomic  entity that lias diversified so broadly at  severtd levels i n the food web. Possibly, some Crustaceans would be appro-  priate to verify the generality of the model : the d i f f i c u l t y might reside i n establishing ratios of the dimensions of the feeding apparatus that vdl segregate the various forms i n a regular pattern.  Sul^lARX  AND  CONCLUSIONS  1) The study was an attempt to determine the modalities of segregation i n feeding and nesting among three species o f plankton-feeding Alcidae (Aethia c r i s t a t e l l a , . A* p u s i l l a and Cyclorrhynchus psittecuta)» The study ras carried out on St. Lawrence Island, Alaska, during the summers of 196A to 1966. 2) The main aspects of the breeding biology o f the Crested, Least and Parakee auklets are summarized i n as much as they have a relevance -bo the problems of ecology and segregation discussed i n the major chapters. The two spec i e s of Aethia have overlapping d a i l y schedules : the birds have a b i modal rhythm of a c t i v i t y on the nesting colonies (morning and evening) and a biraodal rhythm o f feeding ( e a r l y afternoon and e a r l y morning). C. p s i t t a c u l a lands on the colony l a t e r than aethia i n the morning and leaves f o r the sea s l i g h t l y l a t e r i n the afternoon. I t does not come on the colony i n the evening and presumably consacrates t h i s time to feeding. There i s p a r t i a l overlap between molt and breeding a c t i v i t i e s i n Aethia, but none i n Cyclorrhynchus. 3) The two species o f Aethia exhibit rather similar patterns o f dependence upon the food source; both show during early summer a d i v e r s i f i e d diet consisting o f mysids, hyporiids, gammarids, etc. but r e s t r i c t themselves l a r g e l y to one p r i n c i p a l prey during the chick-rearing period. Then, A. r u s i j l s , eats mostly Calanus firasrch.icus while A. c r i s t a t e l l a eats Thvsanoessa spp.  U) This sharp r e v e r s a l to monophagy during the chick-rearing period appar e n t l y r e f l e c t s a sudden increase i n the a v a i l a b i l i t y of these prey items i n the surrounding waters. Available evidence indicates that the food carried to the chick does not d i f f e r from the food used by the adult birds themselves. In a l l years, hatching coincided c l o s e l y with the appearance of these prey items i n the environment and i t i s believed that the breeding season has been adjusted to t h e i r c y c l i c a l abundance. 5) Cyclorrhynchus p s i t t a c u l a occupies a s l i g h t l y higher p o s i t i o n i n the trophic pyramid. This i s indicated by i t s eating a higher proportion of carnivorous zooplankton (such as hyperiids, f i s h , pteropods, cephalopoda, etc.  ) than e i t h e r species of Aethia.  6) Although the sampling i s l e s s adequate i n the case of C. psittacula,, there i s no sign that the birds o f t h i s species revert to one p r i n c i p a l type of prey during the period of rearing of t h e i r chick. They seam rather to present a preference f o r numerous types of prey during that period. 7) Feeding segregation between A, p u s i l l a and A. c r i s t a t e l l a i s achieved by differences i n b i l l - s i z e . Within a common feeding area, the two species obtain very d i f f e r e n t foods. The difference i n b i l l length between the two species (ratio of the l a r g e s t to the smallest) i s of the order of l.A:1.0. This f i n d i n g agrees with Hutchinson's generalization that In orde to coexist at the same trophic l e v e l , two species of animals must d i f f e r i n the size of t h e i r trophic apparatus by a r a t i o of approximately  1.3  to 1.0 : t h i s alone, imposes obligatory feeding upon d i f f e r e n t resources. 8) There i s no i n d i c a t i o n that the shape of the b i l l i n C. psitta^xol? i s a specialized feeding adaptation. This species was, at least during  the  157  three summers of observation, a more d i v e r s i f i e d feeder than Aethia c r i s tateAla. Indirect evidence suggests that these possible competitors are exposed to the same food spectrum by feeding i n the same areas and feeding within the same depth range. 9)  Furthermore, C. psittacula d i f f e r s from A. c r i s t a t e l l a i n spending more time on the feeding grounds, i n spacing i t s e l f more widely over the l a t t e r and i n moving to and from these feeding grounds i n more s o l i t a r y movements. I t i s suggested temporarily that structural factors such as the shape of the b i l l , , under-water manoeuvrability, etc. are responsible for differences i n the diet. The way i n which this segregation i s achieved i s s t i l l obscure but the expression of these structural differences would be i n d i f f e r e n t i a l feeding efficiency upon different basic prey-types. Feeding preferences and feeding efficiency can be quantified and this hypothesis can be submitted to experimental tests.  10) im. increase i n the importance of gammarids during the pre-laying period r e f l e c t s a f a i l u r e i n the supply of preferred pelagic prey organisms. During the pre-laying period, Aethia devotes only a limited amount of time to feeding, owing to the primary importance of social behaviour on the colonies during that period. In absence of pelagic prey, the birds turn to the ever-present benthic gammarids 1 but because of the low n u t r i tive value of these prey items, this can lead to c r i t i c a l physiological conditions i n the females and, possibly, affect their breeding success. At other times of the year, when the pressures of social and sexual behaviour are reduced, there i s no reason why gammarids could not constitute an adequate food source.  11) The l o c a l density of the two species of Aethia, i s clearly affected by a single, p r i n c i p a l factor, the Average Rock Diameter on the talus slopes used as nesting habitat. This factor seems to operate i n a direct fashion, i . e . by simply regulating the number of interstices usable as nest-sites. Although there w i l l eventually be an upper c e i l i n g to the maximum number of birds that can nest i n a given geographic sector or area, the evidence that such a maximum has been reached could not easily be  gathered.  12) Segregation on the nesting grounds between Aethia pusilla, and A. c r i s t a t e l la, i s achieved In the following way J pusilla, dominates i n areas where the average rock size i s small and c r i s t a t e l l a i s almost the only one represented i n areas where the slope i s made of large cobbles and boulders*, But p u s i l l a becomes less abundant than i t should with the increasing Average Rock Diameter and'this i s attributed to the presence of i t s large congener. In other words, c r i s t a t e l l a seems to respond d i r e c t l y to the increasing rock size by increasing i t s density i the increase i n the density of p u s i l l a w i l l depend not only on this physical factor but also on the density of i t s congener. 13)There i s some evidence that the size of the rock debris on talus slopes w i l l determine the relative abundance of the two species of Average Rock Diameter.diminishes  ABtbls.  The  with increased s t a b i l i t y of slope, or  age (frost being given a chance to act longer on the same material i n the absence of removal agents at the base) : this would account for the dominance of Aethia p u s i l l a on inland talus slopes. IA)Cyclorrhyncfaus psittacula nests i n l ) semi-decomposed or shattered pinnacles or ridges or c l i f f s and 2) i n vegetation-covered talus slopes.  159 Both situations are, i n a geomorphic sense, adjacent to talus slopes and represent stages which are ( l ) ) anterior, or (2)) posterior to the habitat used by Aethia, spp. There i s very l i t t l e overlap i n nesting requirements between the two genera. 15) When compared to Aethia, Cyclorrhynchus  depends upon nest sites which are  much less available, has much less gregarious habits and eats p r i n c i p a l l y prey organisms which are less abundant and not subject to wide o s c i l l a t i o n s i n a v a i l a b i l i t y . These three characteristics seem to be related to a lowering of i t s biomass o r i t s lower density per unit area than Aethia. 16) As a whole, the amount of overlap i n feeding and nesting between the three species studied i s very small. I t i s suggested that these differences w i l l persist whenever, for one reason or another, one or two of the three species i s absent from a particular l o c a l i t y . This needs extensive v e r i f i c a t i o n from f i e l d observations i n selected areas. 17) A simple graphical model i s proposed to integrate the plankton-feeders within the community. The model i s independent of taxonomic considerations and deals with the entire family Alcidae. The model i s constructed around the fundamental change i n feeding adaptation that accompany a s h i f t from plankton-feeding to fish-feeding. In the plankton-feeding species, the b i l l i s broad at the base and this modification i s essential for feeding on small particulate food organisms. In the fish-feeding species^ the b i l l i s narrow at the base and acts as pincers for catching swift and slippery prey (other modifications i n palatal structures, tongue shape id tongue cornification accompany this fundamental adaptation). This an edification i n feeding adaptation i s expressed as a ratio and rives the moc  model i t s vertical dimension. The increase i n body size that accompanies the increase i n prey size (from planlcton to fish) imparts an oblique trend to the grouping of the Alcidae species on the model. Finally, considerations of competition and ecological unstability v a i l determine the breadth of the ecological zone that v a i l be occupied i n the model. IS)Along the ordinate, segregation i s made at two basic trophic levels 5 the plankton-feeders and the fish-feeders. The f i r s t l e v e l i s characterized by such'forms as Aethia and Plautus. the second by TJria and Alca. An intermediate level Is characterized by forms such as Fratercula* Cerorhrnca and Lund a which are known to take part i n both trophic levels and to have feeding adaptations intermediate to the two basic levels. 19) Among the plankton-feeders, those genera that are alone i n a broad oceanic area are of intermediate body size (Plautus. Ptycoramphus). The same i s true for the intermediate level where Fratercula arctica and Cerorhinca are such examples. No case i s available for the category of fish-feeders. 20) The model allows us to recognize and define special adaptations with respect to the other members of the family : i t allows, us to recognize the main trends i n evolution of body size and feeding adaptations within the family Alcidae. And i t has some value i n anabling us to predict l i k e l y zones of ecological unstability i n various segments of the community. 21) The system depicted by the model has had a long evolutionary history i f compared to younger families or orders such as the Passerines for instance, and most of i t s elements are ecologically well-defined. On the basis of the model, i t i s inferred that competition for food has played a role, i n conjunction with long-term ecological differentiation, isolation and  adaptive radiation, i n structuring the community to the degree of complexity that ve can observe today. But the role competition for food has had i s not always clear, even i n comparing elements of recent formation. Between the Crested, Least and Parakeet auklets, there has been found no evidence of actual competition for food or for nesting space and the overlap i n ecological requirements i s very small.  162  LITERATURE CITED Aron, W. 1962. 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Holt, Rinehart & Winston, New York. Stejneger, L. 1885. Results of ornithological explorations In the Commander Islands and Kamchatka. B u l l . U. S. Nat. Mus., 29; 7-362. Storer, R.  W. 1945. The systematic position of the Murrelet genus Sndomychura. Condor, 47; 154-160.  Storer, R.  W. 1952. A comparison of variation, behavior and evolution i n the sea b i r d genera Uria, and Ceophus. Univ. C a l i f . Publ. Zool., 52; 121-222.  Storer, R.  W. I960. Evolution i n the diving birds. Proc. XII Intern. Orn. Congr., Helsinki 1953. p. 694-707.  Swarth, K. 3. 1934. Birds of Nunivak Island, Alaska. Pac. Coast. A v i f . , 22; 1-64.  Swartz, L. G. 1966. S e a - c l i f f birds. Chapter 23, p. 611-673 i n : ::. J . Wilimowsky and J . N. Wolfe, eds, Environment of the Cape Thompson region, Alaska. U. 3. Atomic Energy Commission, Division of Technical Information. Thompson, M. J . A J . H. Mines & F. 3. 1. Williamson 1966. Discovery of the downy young o f K i t t l i t z ' s Aurrelet. Auk, S3; 349-351. Thoresen, A. C. 1964. The breeding behavior of the Cassin Auklet. Condor,  66; 456-476.  Tuck, L . M. I960. The Kurres. Their d i s t r i b u t i o n , populations and biology. Canadian Wildlife Series; Ho 1, Ottawa. !  Tuck, L. M. & H. J . Squires 1955. Food and feeding habits of 3runrdch s Murre (Uria lonvia lomvAa) on Akpatok Island. J . Fish. Res. Bd. Canada, 12; 781-792. Udvardy, M. D. F. 1963. Zoo geographical study of the Pacific Alcidao. p. 85-111 i n : -J. L. Gressitt, ed. Pacific Basin Bio geography, a Symposium. Honolulu. Vinogradov, A. P. 1953. The elementary chemical composition of marine organisms. Mem. No. 2, Sears Foundation for Marine Research, 647 p. Wagner, F. H. & C. D. Besadny & C. Kabat 1965. Population ecology and management of Wisconsin Pheasants. Wisconsin Conservation Department, Technical Bulletin N o . 3 4 > 163 p. Walford, L. A. 1953. Living resources of the sea; opportunities for research and expansion. Ronald Press, New York. WItherby, H. F. & F. C. R. Jourdain & N. F. Ticehurst & B. W. Tucker 1941* The handbook of B r i t i s h Birds. Vol V*. London, Withorby. Zenkevitch, L. 1963. Biology of the seas of the USSR. George Allen & Unwin, London.  Donal weight changes i n a d u l t ac and A. p u s i l l a . d u r i n g 1 9 6 4 , 1965 and 1966. B i r d s removed from c a l c u l a t i o n s are "Known" and "Suspected Tmm; veignts are correc ced f o r the presence o f f o o d i n the g u l l e t o r neck-pouch and female weight I s g i v e n minus the egg-weight when f u l l y s h e l l e d i n the o v i d u c t . .Aethia c r i s t a t e l l a » males  Period M  2  X  1964  May 21-31 3 293.9 6 303.1 <iune i-10 6 283. A June 11-20 313.8 June 21-30 7 J u l y 1-10 17 306.3 J u l y 11-20 3 289.8 1 1 291.9 J u l y 21-31 August 1-10 A 2SZ},« 2 276.1 12 August 11-20 8 263.2 August 21-30 September 1-10 A 276.4  )•] •  19.57  11  12.84  A3  4 4  16.72  9 0  14-*  13.27  294.0 283.9  21.05  -  299.9  18.60  3 2 6  13.62  3  269*9 279*5  18.04  4  -  15.62 —  14.61  266.2  —  2S3.1  19.39 9.73 15.47  Aethia c r i s t a t e l l a , May 21-31 June 1-10  0 5  June 21-30 J u l y 1-10 J u l y 11-20 J u l y 21-31 August 1-10 August 11-20 August 21-31 September 1-10  4 304.2  June 1 1 - 2 0 .  — 293.8  6  283.2  9  294.9 266.9 255.9  5  7 9  12 6 7  —-  15.95 " 17.28 6.72 24.88 16.65 17.48 15.49 9.78 7.97  269.3 258.5 252.5 255.6  15 4 6 11 0 4 4 9  7  8  290.4  6 21  310.4 295.4 289.3  5 11  293.1 290.1  12  •4-  t  s  22.35  20.31 19.74 14.85  18.44  -  5  265.6 262.7 290.1  3 267.3  5.63 12.62  5 4  275.5 274-* 4-  14.01  299.6 237. £ 2o3» 8  19.53 26.94 13 0 80  282.3 273. 5  20.35 22.17  281.9  40.44  263.1 273.0 259.8 260.7  19.79 16.59 12 93  2  /  8.11  16.03  females  14.88  271.9 292.5 267.7 — 294.0  24.7t>  308.9 270.1 265o8 271.2  32.64  5 254.4  N  S  31.15 27.18  295.8  21.05  I  313»4 297.8  2  12.83 15.52  _ 1966  1965  I  23.94  12 7 0  23.31  -  38.30  J-jLa 14-  12 » 22 16.96 9.69  18 3 0 7 10 9 8  -  0  10.23  A e t h i a p u s i l l a * males May 21-31 June 1-10 June 11-20 June 21-30 J u l y 1-10 J u l y 11-20 J u l y 21-31 August 1-10 August 11-20 August 21-31 September 1-10  4 10  102.6  7  91.6  6  90.1  22 7 7  94.7  10 16 6  3  3.97  90.2  7.23  37.6 36.2  5.27 6.65 7.89 7.73 9.81 5.20  84.7  3.07  91.1  .  86.4  83.8  1.44  19 12  98.7 89.7  9.24 6.23  9 15 0 0  88.5 86.3 _  3.85 4» 28  8 3  95.5 87.6  3.70  /•  " 0 5 3  —  — —  87.1 86.6  5.51 2.53 3.91  86.3  5.74  13 15 17 9  99.6 94.5 36,9  4.69  13 3 3 0 6 8 0  93*1  3.96 4.12  109.3  37.^24.7  84.9  81.1  5.19 So 22 2.43 3° 22 5.34  4.00  170  •Appendix I , Ctd,  Aethia, pusilla. females May 21-31 5 June 1-10 9 June 11-20 2 June 21-30 5 10 J u l y 1-10 J u l y 11-20 o 7 J u l y 21-31 August 1-10 3 August 11-20 6 August 21-30 6 September 1-10  95oS 90.9 86.6 92.3 95.6 88.4 95.5 77.9 81. A3 S0 3 83.5 o  4.42 4»S1  -  8.22 10.747.79 8 02 3.36 5.94 5.16 o  -  13 o 5 10 0 0 2 5 3 8 •3  90.8 87.8 99.8 oo.5  5.67 4»3o 5.53 6.12  —  —  —•  —  99.2 •83.3 81.6 84.9 80.6  —  5.70 5.90 2.63 6.36  14 >,  10 2 20 2 3 7  '7 7 7  96.0 ICO. 3 UU,(C  /.  ~  OsXy'  6.4-3 5.90  OO .'  —  87.7  7.35  97.1 37.6 33«5 84.9 83.0  10.77 3.21 3»43 2.33 2.06  —  im AP?3i>JDTZ IT  Relative importance of various food items i n numbers f o r the early summer period ("A", A r r i v a l to hatching time; food i n gullets) and the chick-rearing period ( " 3 " ,  from early August to early September; food i n neck-  pouches) i n Aethia pusilla•> A , c r i s t a t e l l a and Cyclorrhynchus  psittaculg.  Data f o r both sexes and the years of 1964 to 1966 combined. The index f o r conversion to volume (see text) i s shown i n the l a s t column, (number of items to one cubic centimeter). Size categories are : I, 0-7.0 mm; I I , 7.1-15*0 mm; III, 15.1 mm and over. A l l Calanus cristatus and Bucalanus bungii were grouped i n Size I I though small numbers of the f i r s t and about h a l f of the second were indeed of Size I. Some samples were halved when size was marginal to two size categories. The phylogenetic order Is not followed. Very p a r t i a l gullets (less than 30 prey organisms ) are included i n C. psittacula, period "A", but not i n other compilations.  A8THIA CRISTATELLA "A"  (N = 145) Relative T o t a l jujportance Numbers in Numbers (5?) Col^"US Tip* " " T ^ i Qixs 1  6395 229  o 300 ^ c a l g p u n Uj>.\li Porotber.\isto liAoeAJai a f l 837 ' " Ti ' ' u ,11 295 u II I I I 13 3 2 Thysgnq. u onsna spp», I 101 n ,11 III 5 4 ' 1302 Gammc-ridea , it , JLl 411 " ,111 10 7 Mysidacea, I " , II 36A « , III 9 Caridea , I 2592  39.2 1.3 1.7 4.8 1.7 0.1 0.6  x  ir  , xx T  T  Decapoda , I 11  ,II  Cumace3/', I Chaoiognatho. Fit'bI " II " III  3279 82 0 26 26 285 322 137 1 0  2.3  «B" CN = 124) Relative Importance Numbers in Number s(£>) Total  77903 1444 169 1637 332 83 2ZA  1924  157 319 209  5  0  2.1 ILZj-o 7  IS. 6 05 o  1.6 1.8  X»  1  151 12 743 2046 17  38.9 1.6  0.2 1.9  0.4 0.1 0.3 0.2 0.4 0.2  0.2 0.8  2.3  2 0  148 6  0.2  0  0 20 6  0.7 1.7  "A" (N c 107) Total  Relative  Importance Numbers in Numbers{%)  157 143 1 215 1830 74 0 69 642 2587 3348 11 45 2592 396 35 38 27 20 33 94 16 0 0 2 8  "3" (N = 135)  Relative , Importance Numbers Numbers in Total  T  X® 3 X* X  6023 1463  28,7 7.0 —  1.7  82 298 137  0.4  -*  14.8 0.6 0.5  5.2  20.9 27.0 0.1 o4 0  20.9  7  0  332 10857 0  0.4  924 1  0.7  0.1  0 0 2 5 0  0 0  ...  —  94  0.3 0.2  0.3  —  4© 2. 51.8  —  63 1  0.2  0.6  4 0 0  3,2  0.3  1.4  47  —  _  0.3 — 4« 4 —  -— -  0.2  <! o  2 5  p., CD O c+  o  189 23 40  175 14.4 4.7 150 70 3.3 75 3.8 7.5  150 64 10  235 135 235 135 90 41  250 150 200 28 3.5  -173  C YGaOPul . YN GN 0 3FSiTTAGJLA "A" (N = 85 ) CN = 12 only; see text) Total Numbers  Calanus flnmarchicus  0  Calanus cristatus  0  Eucalanus bungii  0  1  Parathj^is/to 2 I liballula t 11 II ii  III  3  Thysanoessa  spp.  tt  a Kysidacea, i  ti  >  n  Carictea , it  y  tl  3  7  Cumacea I!  , 3  tt  3 3  H" O  397  Ho 2  139  2477  30.9  23  0  -  AO  0.1  102  4-6.3  371  4.6  14.4  10  4*5  1028  12.8  4.7  0  I  0  -  -  0  350 1562 0  4-* A19.5  -  0  III  0  -  I  0  0  2  -  32  0.4  60  0.7  III  1  I  0  -  II  0  —  III  0  I  0  -  II  0  —  0  79 0  I  0  II  0  III  0  (III)  o o X <r-  7  0  II •  \—{  10.0  III  Polychaetes,, I I I Clione  -  Numbers  Relative Importance in Number s(&  22  0  Cephalopoda (III)  11  -  I II  Limacina Pish ,  _  Total  ' II  Gammaridea^, t!  T  Relative Importance in Number s(%)  5 1  —  -  35.9  -  2.2  -  175  150 70 8.8 150  439  5.5  64  294  3.7  10 75 13 7.5  -  235  180  2.2  134  22  0.3  0  •> o do.  0  -  38  0.5  250  12  0.1  2  0  0 • 35  -  90 41  200  0.4  192 17 8  0.2  1.4 2  174  Anpendix I I ,  Gtd.  Notes to the Tables :  M o s t l y Gopepodite Stage V 2  3  Contains a l s o s m a l l numbers o f Parathemisto p a c i f i c ^ ( i n the case o f A. p u s i l l a ) a n d H y p e r i a medusqrum ( i n the case o f C . p s i t t a c u l a ) * Two s p e c i e s o f Thysanoessa were r e c o g n i z e d and were p r e s e n t i n about e q u a l abundance i T. i n e r m i s and T. r a s c h i i .  ^ See Appendix I I I f o r d e t a i l s on the r e p r e s e n t a t i o n o f y a r i o u s  genera.  i n c l u d e s l a t e Zoea stages o f one dominant u n i d e n t i f i e d s p e c i e s : T r i b e C a r i d e a , Grangonidae(?)• ^ "Decapoda" i n c l u d e s o n l y Megalopa stages o f P a g u r i d a a and Brachyura. ^ One s p e c i e s dominates the sample i n a p r o p o r t i o n o f 95% '* D i a s t y l i s bident a t a . O n l y one o t h e r form was r e c o g n i z e d , Lamprops s p .  175  &PPE1-ID1X  III  Relative importance of various genera of Gammaridea i n the diet of ^..ykia PJlliAA-A and A. cristatella,. The samples used represent a part only of a l l the tracts containing Gammaridea : the ones pooled i n the following table were randomly selected and come from various years. They include samples i n which gammarids dominated and others i n which they were represented by a very few individuals. For the purpose of comparison, the data for two plankton hauls are shown. Both hauls were deep water hauls during which the net scraped the bottom accidentally once, during the ten-minutes period, i s i s apparent i n comparing the two hauls, variations were observed i n the dominance of one gammarid genus over a l l the others t i n haul Number 7, Orchomenella made the bulk of the sample, while i n haul If umber 22, Monoculodes zernovi had the largest representation. This was also commonly observed i n dredge samples which were obtained throughout the area. No doubt, fifferences i n sampling depth, nature of the sediments, and other similar factors account for much of this variation. Atylus bruggeni i s the most important gammarid i n the diet of the two species of Aethia • but i t i s represented by samll numbers only i n the two hauls for which tabulation i s given and never appeared as a dominant species i n any of the dredge samples obtained. Its dominance i n the birds' diet can be due to the fact that the dredge samples simply missed concentrations of i t or, else, i t i s due to a high preference of aethia spp. for that particular form. The available information on the abundance of Jtylus i n the environment i s not sufficient to warrant the determination of electivity Indices for that prey. I t i s worth mentioning, however, that this gammarid was frequently encountered i n small numbers i n mid-water and even surface hauls nd a  i t s peculiar habits may explain the discrepancy between i t s appearance i n the habitat sampling and the birds' digestive tract. Species were i d e n t i f i e d by comparison to a reference collection f o r which determinations were kindly provided by Dr. L. E. Bousfield of the National Museum of Canada.  Notes to the Table of page 177. aenenovi  Gurj.?  obtusifrons 1 At least two species of this genus were present. dentata ? At least three species of t h i s g v u s were present j megacheir Boeck, anguipes (?) apd serratus (?J. 10 minute horizontal haul with y conical closing net. May 28, 19&5. Time, 1450-17+60. Depth of tow, 15-18 m i n 20 m depth. Location, 7 kra SSW of Garabell. Mesh opening, .0173». m  10 minute horizontal haul with jr m conical closing net. 6 August, 1965* Time, 117+0-1150. Depth of tow, 25-28 m i n 30 m depth. Location, 5 km "NN¥ of Garabell. Mesh opening, .0178'.  .77 o  Relative  vO 9  o  cn  I  Total  o  o  o  o  a a a© r|0 C V H  o  CV  u Importance (&)  o  -t -t  O O  U A s Q "CO N O tC V rt UA  o  o vO -<j-  Importance($) o  Total  OA  o  o  t> O ON o o o  O  to C-  OA rt  ON  WA O  N O  to o!  rt OA  to C-  OA  H o  OA  Relative  C - CV  Importance (/o,  a);  ro  OA OA «  «  O  OA ON  r-i  -3-  O  0  CV  OA  V O  o  Frequency o f  O  N O  O  UA CV  OA  O N  OA  N O  rt vO  o  r-  O N  OA  CV  UA  VA O  O  C V O O O A  C-  rt  rt  O 0 N  0  Q  O  OA  tQ.0AOA£  O g >  UA (  rt  -tf rt 1-1 UA tO rt CV  O O CV  O  0  0  » N O  C V N O  O  © rt oft  N O  O  O  2>  O  $  O  OA  CV  O  to  O  o  o.  rt  t^O  O N  rt  CV  O  c-  CV  ON  CV  to  °5!  o  CV  N O  3  Numbers  rt! rt!  N O  vO  N O  rt  to  Numbers Relative  CV  o  CV  o  e  $ 3  Occurrence^)  05'  •HI  U  o  Total  rt  Numbers  UA OA 11  •  cv  ort  Relative  o  Importance  O  A  C  V  O  N  0 ** 0 ^  O A  ota  O  {%)  rt  ^* rt <D•  -  C A N O  N  O  ^  T  CV rt  OA  to  t>to  O  C-  rtvO  vO  ^>  O A  vO C-  !25  Frequency o f  otg  o  N  O  O  A  O  ^  ^  53  o  o  rtvo  o  o  o  £ ^  Gccurence($) Total  I  oto  o  cn«oo  rt.  O A  N O C V  O ,0  Numbers  1  •n  -Pi CO  2 .1 • H  ©  .... : o tH  Ci  c  •Hi  o  ol  olti  W 4*1 - H  UN © K?  ®  •3  o!  <D  «  O  •H  y o  o r• H  4 °  -qrts  [3 o  6-i  Oj  O  o!  ji "a, ui •^ r  M B l c M to Sirt  (2  CO  COJ  rt  Pi a  et o d  ,51  as o  CX J. S  O f-ijHjl  l-i  !  i I  O -P W CD  o  

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