Open Collections

UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Some aspects of the ecology of lesser snow geese wintering on the Fraser River estuary Burton, Bruce Andrew 1977

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1977_A6_7 B88.pdf [ 9.01MB ]
Metadata
JSON: 831-1.0093981.json
JSON-LD: 831-1.0093981-ld.json
RDF/XML (Pretty): 831-1.0093981-rdf.xml
RDF/JSON: 831-1.0093981-rdf.json
Turtle: 831-1.0093981-turtle.txt
N-Triples: 831-1.0093981-rdf-ntriples.txt
Original Record: 831-1.0093981-source.json
Full Text
831-1.0093981-fulltext.txt
Citation
831-1.0093981.ris

Full Text

SOME ASPECTS OF THE ECOLOGY OF LESSEE SNaW GEESE WINTERING ON THE FB.ASEH BIVEB ESTUARY by BRUCE ANDREW BURTON B.Sc. (Agr.),, U n i v e r s i t y of B r i t i s h Columbia, 3 973 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF Department of GRADUATE STUDIES Animal Science He accept t h i s t h a s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BBITSH COLUMBIA A p r i l , 1977 (c? Bruce Andrew Burton, 1977 In presenting th i s thesis in pa r t i a l fu l f i lment of the requirements for an advanced degree at the Un ivers i ty of B r i t i s h Columbia, I agree that the L ibrary sha l l make it f ree ly ava i l ab le for reference and study. I further agree that permission for extensive copying of th i s thes is for scho lar ly purposes may be granted by the Head of my Department or by his representat ives. It is understood that copying or pub l i ca t ion of th is thes is for f inanc ia l gain sha l l not be allowed without my writ ten permission. Department of Q/lwdj So^KdC The Univers i ty of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1WS Date Wt*H Z/ft i i ABSTRACT A study of the winter f e e d i n g ecology of l e s s e r snow geese was conducted on the Fraser R i v e r E s t u a r y of southwestern B r i t i s h Columbia. Food h a b i t s analyses i n d i c a t e d a strong p r e f e r e n c e f o r the rhizomes of S c i r p u s americanus and S. E ^ i l d g s u s . Based on freguency o f occurrence a t l e a s t 75 percent of the d i e t i s made up of the below ground organs of these s p e c i e s . Measurements of the food supply i n d i c a t e d a t o t a l s tanding crop of 516 mt of rhizomes. Rhizome d e n s i t y v a r i e d s i g n i f i c a n t l y between each marsh u n i t from a high of 77.3 g.m - 2 on Lulu I s l a n d to a low of 30.2 g.m - 2 on Bestham I s l a n d . Rhizome d e n s i t y decreased s i g n i f i c a n t l y i n A p r i l from t h a t observed i n October and December. Standing crop was minimum i n poorly d r a i n e d depressions and along the outer reaches of the lower zone where s o i l a e r a t i o n i s l i m i t e d . Crude p r o t e i n content was s i m i l a r from rhizomes w i t h i n s i n g l e marsh u n i t s r e g a r d l e s s of v a r i a t i o n s i n water cover, m i c r o r e l i e f or season. However, s i g n i f i c a n t d i f f e r e n c e s were found to occur between l o c a t i o n s . Mean crude p r o t e i n and crude f i b e r l e v e l s were 11.8 and 22.4 percent, r e s p e c t i v e l y . P a t t e r n s of s p a t i a l and temporal d i s t r i b u t i o n were analyzed i n an attempt to determine probable c a u s a t i o n . A e r i a l photo counts and ground checks were conducted to g u a n t i f y d i s p e r s a l . M u l t i v a r i a t e Hominal Scale A n a l y s i s was used t o analyze the data. The complete model accounted f o r up to 48.4 percent of the observed v a r i a n c e . Seasonal changes i n hunting pressure, s o c i a l s t i m u l a t i o n , food supply and p a s s i v e predator avoidance s t r a t e g y were the most important f a c t o r s i n f l u e n c i n g d i s t r i b u t i o n a l p a t t e r n s . D i u r n a l a c t i v i t y p r o f i l e s were recorded between the hours of 05.00 and 24.00 from l a t e autumn to e a r l y s p r i n g to i d e n t i f y the areas of g r e a t e s t importance f o r feeding and r e s t i n g . Access to food supply, as r e g u l a t e d by changes i n t i d e height and f l o c k l o c a t i o n , was the most i n f l u e n c i a l determinant of f e e d i n g and s l e e p i n g p e r i o d i c i t y . Feeding i n t e n s i t y was g r e a t e s t at Brunswick p o i n t when water depth was between 20 cm above and 10 era below the stem base of S c i r p u s americanus and l e a s t at R e i f e l Refuge, when water depth was e i t h e r deeper than 20 cm or shallower than -10 cm at the upper and lower edges of the community, r e s p e c t i v e l y . Because of the t i d a l f l u c t u a t i o n s , a p o l y p h a s i c r h y t h m i c i t y was d i s p l a y e d by snow geese r a t h e r than the more commonly reported i l l u m i n a t i o n - c o n t r o l l e d , d i p h a s i c r o u t i n e . i i i N o cturnal f e e d i n g occurred r e g u l a r l y whether hunting season was open or c l o s e d . , The mean pr o p o r t i o n o f each day engaged in f e e d i n g was 29 percent. Feeding i n t e n s i t y by snow geese, even during p e r i o d s of o p t i m a l food a c c e s s i b i l i t y , amounted to a mean of only 52 percent of the t o t a l a c t i v i t y p r o f i l e i n d i c a t i n g a combination of r e l a t i v e l y e f f i c i e n t f e e d i n g techniques and a h i g h l y n u t r i t i o u s d i e t . A n a l y s i s of the responses of snow geese t o v a r i o u s forms of a c t i v e d i s t u r b a n c e c l e a r l y showed d i f f e r e n c e s i n s t r a t e g y and g r a d i e n t s of i n t e n s i t y of hazzard avoidance. H e l i c o p t e r s r e l e a s e d escape at the g r e a t e s t d i s t a n c e s , presumably because o f t h e i r slow, i r r a t i c f l i g h t p a t t e r n s . Small, fixed-wing wheel-planes presented the l e a s t i r r i t a t i v e image of a l l a i r c r a f t observed. B a l d e a g l e s were the most common avian predator to c r e a t e d i s t r u r b a n c e . Hunters and other humans i n the marsh produced extreme wariness and open approach was not p o s s i b l e c l o s e r than 100 m. Non-human mammals were t r e a t e d with great t o l e r a n c e . Both a i r c r a f t and eagles caused c i r c u l a r escape f l i g h t s whereas humans and gunshots produced l i n e a r f l i g h t s . The mean d u r a t i o n of normal f l i g h t was 33 seconds. F l i g h t s r e s u l t i n g from d i s t u r b a n c e were s i g n i f i c a n t l y g r e a t e r a t 85 seconds. M e t a b o l i z a b l e energy (ME) and passage r a t e were c a l c u l a t e d from experimental t r i a l s on caged snow geese. ME f o r rhizomes of S c i r p u s americanus was 1.43 k c a l / g . Mean d i g e s t i b i l i t y was 28 percent. The r a t e of passage o f the rhizome d i e t d i d not vary with a change i n the amount of food contained i n the G . I . t r a c t . Mean r e t e n t i o n time was r e l a t i v e l y constant at 120 minutes. The i n t e r n a l organ dimensions of 90 h u n t e r - k i l l e d geese were c o l l e c t e d from October t o A p r i l . A n a l y s i s showed no age or s e x - r e l a t e d d i f f e r e n c e s . G i z z a r d s i z e , s m a l l i n t e s t i n e l e n g t h and dry matter c a p a c i t y were shown to i n c r e a s e s i g n i f i c a n t l y from f i r s t a r r i v a l . The mean f u l l gut c a p a c i t y was 28.8 g dry matter. D i r e c t l a t e season measurements i n d i c a t e d a range of from 25.4 g t o a maximum of 37.7 g. A f e e d i n g s t r a t e g y was proposed to account f o r the r e l a t i v e l y s m a l l amount of time a c t u a l l y engaged i n f e e d i n g . T o t a l d a i l y energy expenditure f o r winter was c a l c u l a t e d from the a c t i v i t y budget, environmental temperatures and l e v e l s of d i s t u r b e d and undisturbed f l i g h t t o be 269 k c a l . From mean passage r a t e and alimentary t r a c t c a p a c i t y an intake of 294 g per day was estimated. At 1.43 k c a l / g t h i s l e v e l of i n t a k e r e p r e s e n t s 420 k c a l ME per day, w e l l above the c a l c u l a t e d energy expenditure. Length of e f f e c t i v e i v f eeding p e r i o d i s presented as a p o s s i b l e e x p l a n a t i o n f o r the t r a d i t i o n a l mid-winter migration which occurs during l a t e January and e a r l y February each year when, f o r s e v e r a l days, the e f f e c t i v e f e e d i n g p e r i o d f a l l s below 9 hours. D a i l y consumption per b i r d was 0.3 kg per day. The t o t a l number goose-days on the F r a s e r during winter of 1974-75 was 744,000, r e p r e s e n t i n g a removal of 167 mt, or 32 percent of the t o t a l s t a n d i n g crop. The p o p u l a t i o n s i z e f o r that year was the s m a l l e s t s i n c e 1947. a r e l a t i v e s c a l e of i developed by i n c o r p o r a t i n g me marsh plus the u s e - i n t e n s i t y a u n i t . In descending order o Brunswick P o i n t , L u l u I s l a n d , mportance f o r f e e d i n g was asurements of the s i z e of each nd feeding i n t e n s i t y at each f importance per u n i t area are Hestham I s l a n d and Sea I s l a n d . V CONTENTS 1.0 I n t r o d u c t i o n 1 2.0 The Study Area ..... ..... ............ 5 3.0 Food Habits 13 3.1 I n t r o d u c t i o n 13 3.2 Methods .............. . ..........13 3.3 Results -••> 1& 3.4 D i s s u s s i o n 18 4.0 Habitat and Food Resource 22 4.1 I n t r o d u c t i o n .22 4.2 Methods 23 4.3 Results .........................................26 4.4 D i s c u s s i o n ............31 5.0 S p a t i a l and Temporal D i s t r i b u t i o n 39 5.1 I n t r o d u c t i o n .............. ,.,.,,,.,,.,.,..,.......39 5.2 Methods 41 5.2.1 Data C o l l e c t i o n ...................,-,...,,41 5.2.2 S t a t i s t i c a l Techniques .................... 43 5.3 Re s u l t s ......45 5.4 D i s c u s s i o n .............................--.-51 5.4.1 Food Supply ..... .....53 5.4.2 Predator Avoidance ..,,....57 5.4.3 Hunting Pressure 59 5.4.4 P o p u l a t i o n S i z e ......61 5.4.5 D i f f e r e n t i a l M i g r a t i o n ..,.,...,,.,.,,.,..,63 5.4.6 T r a d i t i o n 65 6.0 D i u r n a l A c t i v i t y Budget .69 6.1 I n t r o d u c t i o n ..,....,,....,,,--..-.-,69 6.2 Methods ... .. .....72 6.3 R e s u l t s ....... ....75 6.3.1 M u l t i v a r i a t e Nominal Scale A n a l y s i s .,,..,,75 6.3.2 M u l t i p l e C l a s s i f i c a t i o n A n a l y s i s ..........79 6.4 D i s c u s s i o n 81 6.4.1 Feeding . , .......................81 6.4.1.1 T i d e Height 81 6.4.1.2 L o c a t i o n 86 6.4.1.3 Tide A c t i o n .88 6.4.1.4 Time 89 6.4.2 Res t i n g .....91 6.4.2.1 Tide Height ......................91 6.4.2.2 L o c a t i o n ...,.,...,...,..,,,,....,93 6.4.2.3 Tide A c t i o n and Time ............. 95 6.4.3 A l e r t .,.,.....,..,,..--.....,,,-.-.-,- — --95 6.4.3.1 Tide Height .96 v i 6.4.4 Preening — 98 6.4.4.1 Tide Height 98 7.0 Disturbance 101 7.1 I n t r o d u c t i o n - ....101 7.2 Methods . ......................103 7.3 Results 104 7.3.1 Avian Predators ..........................104 7.3.2 Man .. , ,.....,..,.....,,.,.,....,106 7.3.3 A i r c r a f t , ... 106 7.3.4 Water-bound V e h i c l e s .,...,....,..,..,....110 7.3.5 Land V e h i c l e s - 110 7.3.6 F l i g h t D uration ..........112 7.4 D i s c u s s i o n ..............,,.......,...----...-,..113 7.4.1 Avian Predators ..............113 7.4.2 Man .....,,,.,.............,.....,.,..-...115 7.4.3 Other Species .,,........,.-....-,.--..-..117 7.4.4 A i r c r a f t .... 117 8.0 E f f i c i e n c y of Food U t i l i z a t i o n .,.....,....-.-,--....123 8.1 I n t r o d u c t i o n .,..,---,123 8.1.1 M e t a b o l i z a b l e Energy .124 8.1.2 Passage Sate .....,.....,......,,-.....-..124 8.1.3 Gut Morphology ...........125 8.2 Methods .., - 126 8.2.1 M e t a b o l i z a b l e Energy ..,.,,,..,...,..-.-..127 8.2.2 Passage Rate , ...129 8.2.3 Gut Morphology ...........................132 8.3 Resu l t s 133 8.3.1 M e t a b o l i z a b l e Energy ......133 8.3.2 Passage Rate 135 8.3.3 Gut Morphology ....138 8.4 D i s c u s s i o n ..............139 8.4.1 M e t a b o l i z a b l e Energy 139 8.4.2 Passage Rate — ......141 8.4.3 Gut Morphology .................145 9.0 C o r r e l a t i v e D i s c u s s i o n .......,...,,,.,.-,,.,,.,,..,.148 9.1 D i g e s t i v e E f f i c i e n c y , -..148 9.2 Energy Demands ,.,.,.....,..,..,,.150 9.3 Feeding S t r a t e g y ...,,..,...,..,.,.,.,«.,...--.-152 9.4 Feeding Pressure on the Estuary ...........158 9.5 C r i t i c a l Areas .................. ...........159 10.0 L i t e r a t u r e C i t e d ...163 Appendix A 171 TABLES (I) G i z z a r d - c o n t e n t s a n a l y s i s expressed as aggregate percentage and frequency of occurence ...,,17 (II) Comparisons between d i f f e r e n t marsh u n i t s o f the t o t a l below-ground s t a n d i n g crop, rhizome s t a n d i n g crop and rhizome crude p r o t e i n l e v e l s o f S c i r e u s americanus ....,..,..,.....,.,,....,.........27 (III) Approximate s i z e , rhizome d e n s i t y and below-ground s t a n d i n g crop of each S c i r p u s americanus and S c i r p u s pa l u dps us marsh u n i t ............ ,,,,....,28 (IV) Comparisons between d i f f e r e n t months on the t o t a l below-ground s t a n d i n g crop, rhizome s t a n d i n g and rhizome crude p r o t e i n l e v e l s of S c i r f i u s americanus ............,...,...,.........,,.,,.......29 (V) Comparisons between sample s i t e s with r e s p e c t to the extent of r e l a t i v e t i d a l f l o o d i n g on the t o t a l below-ground standing crop, rhizome s t a n d i n g crop and rhizome crude p r o t e i n l e v e l s of S_cirpus americanus ................30 (VI) V a r i a b l e Response P r o f i l e s : c o e f f i c i e n t s o f the MNA model f o r d i s t r i b u t i o n ....,,..,..,.,.,,.,,,,48 (VII) C l a s s i f i c a t i o n Matrix - an a E o s t e r i o r i assignment of p r e d i c t i o n s f o r the a n a l y s i s of d i s t r i b u t i o n ........ ,,,,,.,,,,.,...,.,,..........49 (VIII) V a r i a b l e response p r o f i l e s : c o e f f i c i e n t s of the MHA model f o r snow goose d i s t r i b u t i o n with r e s p e c t to rhizome d e n s i t y 50 (IX) C l a s s i f i c a t i o n Matrix - an a p o s t e r i o r i assignment of p r e d i c t i o n s f o r the a n a l y s i s of snow goose d i s t r i b u t i o n with r e s p e c t t o rhizome d e n s i t y ..50 (X) V a r i a b l e Response P r o f i l e s - c o e f f i c i e n t s o f the MNA model f o r predominant a c t i v i t y ....77 (XT) C l a s s i f i c a t i o n Matrix - an a E o s t e r i o r i assignment of p r e d i c t i o n s f o r the a n a l y s i s o f predominant a c t i v i t y 78 (XII) MCA: p a r t i a l c o r r e l a t i o n c o e f f i c i e n t s f o r the d i u r n a l a c t i v i t y budget 78 ( X I I I ) V a r i a b l e Response P r o f i l e s : c o e f f i c i e n t s o f the MNA model f o r a i r c r a f t d i s t u r b a n c e .....108 (XIV) C l a s s i f i c a t i o n M a t r i x - an a R o s t e r i o r i assignment of p r e d i c t i o n s f o r t h e a n a l y s i s o f a i r c r a f t d i s t u r b a n c e ,....,109 (XV) N i t r o g e n - c o r r e c t e d ME v a l u e s f o r t h e r h i z o m e s °f Scirjaus americanus ..,...,,.,,...........,....,.,134 (XVI) Passage r a t e d e t e r m i n a t i o n s - Times of f i r s t passage .................135 (XVII) Passage r a t e d e t e r m i n a t i o n s - F i r s t and l a s t mean r e t e n t i o n t i m e s .,..,,.,....,...,...,,.,.,.,..,136 (XVIII) S e a s o n a l changes i n mean i n t e r n a l organ d i m e n s i o n s ,138 (XIX) F u l l gut d r y matter c a p a c i t y ....,...,.....-.-,,139 (XX) Comparison o f c a l c u l a t e d energy e x p e n d i t u r e between a 7.2 and 14 hour f e e d i n g day 151 (XXI) Feeding i n t e n s i t y , use i n t e n s i t y and r e l a t i v e i m p o r t a n c e o f each marsh u n i t f o r f e e d i n g snow geese ........................160 i x FIGURES (1) The Study Area ,. 10 (2) Mean i n t e n s i t y of snow goose a c t i v i t y a t d i f f e r e n t t i d e h e i g h t s ..............................80 (3) Cummulative percentage of Fe marker i n the fec e s of f o u r c a p t i v e snow geese .....137 (4) Estimated p o p u l a t i o n s i z e of the January snow goose f l o c k at Skagit F l a t s from 1947 to 1975 ......173 X ACKNOWLEDGEMENTS G r a t e f u l r e c o g n i t i o n i s payed t o the B r i t i s h Columbia F i s h and W i l d l i f e Branch f o r the f i n a n c i a l s u p p o r t p r o v i d e d d u r i n g t h i s s t u d y . A d d i t i o n a l a s s i s t a n c e i n terms of l a b o r a t o r y eguipement sere s u p p l i e d by the Department of Animal S c i e n c e , U.B.C. The George C. H e i f e l M i g r a t o r y B i r d S a n c t u a r y s u p p l i e d me w i t h 13 c a p t i v e snow geese f o r which I exp r e s s my a p p r e c i a t i o n . Throughout the cour s e of the s t u d y I have r e c e i v e d -supp o r t and encouragement from a l l members o f my committee, but p a r t i c u l a r a p p r e c i a t i o n i s e x p r e s s e d t o my t h e s i s s u p e r v i s o r , Dr. R.J. Hudson and to t h e chairman of the Department of P o u l t r y S c i e n c e , Dr. D a r r y l Bragg. Mr. A.E., Barnard f i r s t posed the problem and made h e l p f u l s u g g e s t i o n s at t h e b e g i n n i n g of t h e s t u d y . G r a t i t u d e i s a l s o conveyed t o the numerous concerned snow goose h u n t e r s who, i n a d d i t i o n t o s u p p l y i n g me w i t h specimens, p r o v i d e d a we a l t h of g e n e r a l i n f o r m a t i o n on the h a b i t s and r e c e n t h i s t o r y o f snow geese i n t h i s a r e a . S p e c i a l t h a n k s i n t h i s r e g a r d a re extended t o Messers P e t e r S t o r n e s s k r e s s , B i l l White, B r i a n D a v i e s , J o h n n i e G l o v e r , Bobbie K e r r , Gord Z o n a i l o and Robert Husband. I n f o r m a t i o n on the f l o c k at S k a g i t f l a t s was r e c e i v e d from Mr. Robert J e f f r e y , Washington S t a t e Game Department. Diane Sharpe made c o m p l e t i o n of t h e s t u d y p o s s i b l e by a s s i s t i n g w i t h t h e f i e l d work, t y p i n g and e d i t i n g the rough ma n u s c r i p t and r e v i e w i n g t h e f i n a l d r aught. She has been an i n t e g r a l p a r t of the p r o j e c t s i n c e i t s i n c e p t i o n and has serv e d as a p i l l a r o f moral s u p p o r t t h r o u g h o u t . My most s i n c e r e and deepest a p p r e c i a t i o n i s extended t o her f o r s h o u l d e r i n g the burden. x i ".................. the very sound of Canada, the deep tone and cadence of that name, were u t t e r e d i n the shout and r u s t l e of the autumn sky. The goose, more than any other l i v i n g c r e a t u r e , more than h i s t o r i a n , poet, musician, p a i n t e r , or o r a t o r can evoke, i n b r i e f moment of passage, a l l the c o l l e c t i v e memories o f t h i s l a n d . Our h i s t o r y from the beginning, a l l the adventures o f our f a t h e r s , the whole s t o r y of canoes, portages, and campfires long ago, the immensity, the l o n e l i n e s s and the c o l d of Canada are w r i t t e n i n our own s e c r e t alphabet, are penned i n a s i n g l e l e t t e r , the sprawling V when the geese f l y south." - by Bruce Hutchinson, In Western Windows, Longmans, Toronto. l i f i INTRODUCTION The e s t u a r i n e marshes of the Fr a s e r River D e l t a support the only w i n t e r i n g p o p u l a t i o n o f l e s s e r snow geese (Anser caerulescens) i n Canada. However, here, as eslewhere, man's i n c r e a s i n g a c t i v i t i e s t h r e a t e n t h i s unigue area and s p e c i e s . Numerous proposals f o r i n d u s t r i a l development and port expansion have been presented over the past decade. The e f f e c t on these b i r d s of h a b i t a t a t t r i t i o n i s not known, but the urgency of the problem i s i n t e n s i f i e d by the pa u c i t y of i n f o r m a t i o n . E s s e n t i a l l y no i n f o r m a t i o n on t h i s f l o c k i s p r e s e n t l y a v a i l a b l e . The Canadian W i l d l i f e S e r v i c e , P a c i f i c Region, has r e c e n t l y compiled a r e f e r e n c e l i s t of m a t e r i a l p e r t i n e n t to t h e F r a s e r River Estuary and i t s e n v i r o n s with a t o t a l of 109 c i t a t i o n s . Of these, 24 are of d i r e c t r e l e v a n c e t o the waterfowl of the fores h o r e . Only one paper c o n t a i n s any i n f o r m a t i o n concerning the w i n t e r i n g snow goose p o p u l a t i o n . The n e c e s s i t y f o r a c a r e f u l c o n t r o l of a l l development on the F r a s e r River D e l t a and the preve n t i o n o f i r r e v e r s i b l e d e s t r u c t i o n to t h i s snow goose p o p u l a t i o n c a l l s f o r d e t a i l e d documentation of the areas of g r e a t e s t importance. In response t o the immediate need of e s t a b l i s h i n g zones of c r i t i c a l importance i t i s e s s e n t i a l to understand how the geese u t i l i z e and i n t e r a c t with t h e i r w i n t e r h a b i t a t . Here 2 again, l i t t l e i n f o r m a t i o n i s a v a i l a b l e from which we can draw and reasonably adapt to the l o c a l s i t u a t i o n . , Few comprehensive f i e l d s t u d i e s of the r e l a t i o n s h i p s between w i l d geese and t h e i r h a b i t a t have yet been conducted. In southern Sweden, Gunnar Markgren c a r r i e d out an e x t e n s i v e i n v e s t i g a t i o n on the behaviour p a t t e r n s of s e v e r a l s p e c i e s of w i l d geese during winter. In 1968 Myrfyn Owen began a long-term study on the r e l a t i o n s h i p s between European w h i t e - f r o n t e d geese JAnser a l b i f r o n s ) and t h e i r h a b i t a t at S l i m b r i d g e . Both s t u d i e s have generated much in f o r m a t i o n about the w i n t e r i n g ecology of geese. However, as with most f i e l d i n v e s t i g a t i o n s of animal behaviour they f a l l somewhat s h o r t of t h e i r p o t e n t i a l because of l i m i t e d q u a n t i t a t i v e data. In North America an e x t e n s i v e data base has been e s t a b l i s h e d on m i g r a t i n g and w i n t e r i n g Canada geese, e s p e c i a l l y with r e s p e c t to t h e i r u t i l i z a t i o n of c u l t i v a t e d f i e l d s . However^ snow geese are a t y p i c a l Anseriformes. Contrary to the s i t u a t i o n f aced by other i n d i g i n o u s geese, t h e i r n a t u r a l food supply i s l o c a t e d below ground. They p r e f e r t o grub beneath the s o i l s u r f a c e f o r tubers and rhizomes. As a r e s u l t i t has been extremely d i f f i c u l t to a c c u r a t e l y measure the e s t e n t of t h e i r food s u p p l y , even w i t h i n winter ranges of known s i z e . I n v e s t i g a t i o n s d e a l i n g s p e c i f i c a l l y with l e s s e r snow geese have been r e s t r i c t e d to those conducted on t h e i r summer breeding grounds i n the 3 A r c t i c . When t h e present study was i n i t i a t e d e s s e n t i a l l y no inf o r m a t i o n was a v a i l a b l e on the ecology of w i n t e r i n g snow geese. T h i s study was conceived, t h e r e f o r e , with the dual purpose of o u t l i n i n g the e c o l o g i c a l r e l a t i o n s h i p s between l e s s e r snow geese and t h e i r n a t u r a l winter h a b i t a t , and of determining the i n t e n s i t y of u t i l i z a t i o n on the f o r e s h o r e marshes of the Fraser R i v e r D e l t a . To accomodate both o b j e c t i v e s i t was necessary t o determine p a t t e r n s of d i s t r i b u t i o n w i t h i n the h a b i t a t and measure to what extent p a r t i c u l a r environmental and s o c i a l f a c t o r s a f f e c t e d t h i s d i s t r i b u t i o n . Although every segment of the f o r e s h o r e i s u t i l i z e d to some extent c e r t a i n areas are a p p a r e n t l y of g r e a t e r importance than o t h e r s . Because of d i f f e r e n c e s i n marsh c h a r a c t e r i t was important t o d e l i n e a t e and e v a l u a t e the a b i l i t y of each marsh u n i t t o provide the geese with food and s h e l t e r . Thus g u a n t i f i c a t i o n o f d i u r n a l a c t i v i t y budgets at each l o c a t i o n was necessary. The complexity of these r e l a t i o n s h i p s suggested the use of m u l t i v a r i a t e s t a t i s t i c a l t echniques to provide g u a n t i t a t i v e e x p l a n a t i o n s f o r the observed p a t t e r n s of h a b i t a t u t i l i z a t i o n . To f u r t h e r assess the importance o f each marsh u n i t i t was necessary to e s t a b l i s h b a s i c h a b i t a t reguirements of the geese. P u b l i s h e d i n f o r m a t i o n on the d i g e s t i v e e f f i c i e n c y of snow geese on a n a t u r a l d i e t i s not a v a i l a b l e . To determine the e n e r g e t i c e f f i c i e n c y on a n a t u r a l d i e t , f i e l d s t u d i e s were augmented with c o n t r o l l e d f e e d i n g t r i a l s using c a p t i v e b i r d s . T h i s i n v e s t i g a t i o n , then* r e p r e s e n t s an i n i t i a l attempt to q u a n t i t a t i v e l y e x p l a i n observed p a t t e r n s of d i u r n a l and seas o n a l space use by w i n t e r i n g l e s s e r snow geese on the b a s i s of p h y s i o l o g i c a l , b e h a v i o u r a l and environmental parameters. F i e l d work began i n the winter of 1974-75. C o l l e c t i o n of h u n t e r - k i l l e d geese continued u n t i l the s p r i n g of 1976. Laboratory analyses were completed i n January, 1976, while s t a t i s t i c a l a nalyses were not completed u n t i l October, 1976. 5 2.0 THE STUDY AREA The Eraser R i v e r e s t u a r y l i e s approximately s i x km south-west of the c i t y of Vancouver. The study area i n c l u d e d the i n t e r t i d a l zone o f the f o r e s h o r e marsh, s t r e t c h i n g from Iona I s l a n d south t o Brunswick P o i n t . During winter t h i s p o r t i o n of the e s t u a r y supports the l a r g e s t waterfowl p o p u l a t i o n i n Canada and encompasses the e n t i r e n a t u r a l h a b i t a t of l e s s e r snow geese i n the Lower Fra s e r V a l l e y . The e n t o s o l i c muck s o i l s of the marsh are s i m i l a r to those of other e s t u a r i n e d e l t a s formed along the B r i t i s h Columbia coast.,•' S o i l t e x t u r e v a r i e s from a f i n e sandy s i l t loam to s i l t y c l a y and g e n e r a l l y occurs as a f i r m l y packed, amorphous s u b s t r a t e . According to Sprout and Holland (1955), the top two or three f e e t c o n t a i n s a moderate amount of o r g a n i c matter. On exposed f l a t s the s o i l c o n s i s t e n c e (dry) i s l o o s e because of a reduced percentage of o r g a n i c matter and may i n c l u d e t e x t u r a l c l a s s e s up to f i n e sand. S o i l s of the Fraser River estuary are i n a c o n t i n u a l s t a t e of f l u x due to the tremendous q u a n t i t i e s of suspended s i l t , estimated at 20 m i l l i o n tons, dumped an n u a l l y on the d e l t a and r e d i s t r i b u t e d over the f o r e s h o r e by the t i d e s and c r o s s c u r r e n t s of Georgia S t r a i t (Hoos and Packman, 1974). As a r e s u l t , a f r o n t , approximately 3700 m wide adjacent to 6 the main channel, i s p r e s e n t l y advancing a t a r a t e of 1.5 ra per year at the low water mark (floos and Packman, 1974). This c o n t i n u a l supply of r i c h sediments maintains the p e d o l o g i c a l and v e g e t a t i o n a l i n t e g r i t y of the marsh. The topography of the f o r e s h o r e i s determined l a r g e l y by the combined hydromorphic f o r c e s of waves, t i d e s and c u r r e n t s a c t i n g i n dynamic o p p o s i t i o n to the s o i l b i n d i n g f o r c e s of t h e marsh v e g e t a t i o n . Upper p o r t i o n s of the marsh are c h a r a c t e r i z e d by a l e v e l , or g e n t l y u n d u l a t i n g s u r f a c e cut by steep, i r r e g u l a r drainage channels. Moving seaward the landscape becomes l e s s d i s t i n c t . Rounded hummocks e n c l o s i n g shallow, w a t e r - f i l l e d depressions become more p r e v a l e n t . Below the 7 f o o t t i d e l e v e l , away from the s o l i d i f y i n g e f f e c t s of v e g e t a t i o n , the s o i l becomes e s s e n t i a l l y barren mud and sand, possessing a very gradual downward s l o p e . , Climate p l a y s a major r o l e i n the a b i l i t y of t h i s area to support l a r g e numbers of w i n t e r i n g waterfowl. The c l i m a t e of the d e l t a i s d e s c r i b e d as modified maritime (Environment Canada, 1974). Due t o the i n s u l a t i n g e f f e c t s of the Coast Mountain range and the moderating e f f e c t of the Georgia S t r a i t , winters are comparatively warm f o r t h i s l a t i t u d e . The average minimum temperature f o r January, the c o l d e s t month, i s -1°C. hs a r e s u l t w i n t e r s are seldom c o l d enough to induce f r e e z i n g i n the i n t e r t i d a l zone, even though f r e e z i n g occurs r e g u l a r l y on the adjacent uplands. 7 When the temperature drops below f r e e z i n g f o r an extended perio d of time the only source of food a v a i l a b l e to f i e l d -f e eding waterfowl i s the open water of the f o r e s h o r e marsh. These areas are of c r i t i c a l importance t o a l l waterfowl at t h i s time. Mean annual p r e c i p i t a t i o n recorded at the Vancouver I n t e r n a t i o n a l a i r p o r t on Sea I s l a n d i s 106.8 cm, most of which occurs as r a i n . Approximately 74 percent of t h i s t o t a l f a l l s d uring the 6 month p e r i o d from October to March (Department of the Environment, 1970) . Tides and c u r r e n t s are major f a c t o r s i n f l u e n c i n g the d i s t r i b u t i o n o f sediments along the f o r e s h o r e . The t i d e s of t h i s area are d e s c r i b e d as 'Mixed D i u r n a l * by the Canadian Hydrographic s e r v i c e (1975). Mixed D i u r n a l t i d e s are c h a r a c t e r i z e d by two complete t i d a l o s c i l l a t i o n s d a i l y , with marked i n e q u a l i t i e s i n both height and p e r i o d i c i t y between s u c c e s s i v e high and low waters. In a 24 hour p e r i o d the extreme low t i d e l e v e l (x = 1.25 m) e i t h e r i s f o l l o w e d by or preceeded by the extreme high t i d e (x = 4.48 m). The subsequent two t i d e s are more moderate i n t h e i r f l u c t u a t i o n s , u s u a l l y remaining between a mean low of 2.98 m and a mean high of 3.87 m. During the winter months, d i u r n a l low water occurs at n i g h t , whereas i n summer the lowest t i d e i s most common during the day. In the s p r i n g and autumn, low water occurs e i t h e r i n the e a r l y morning or l a t e afternoon* T h i s t i d a l p a t t e r n a l l o w s emergent marsh 8 v e g e t a t i o n to make maximal use of d a y l i g h t during the s p r i n g and e a r l y summer growing season. In winter i t a l s o r e s t r i c t s access to the major food item of snow geese f o r a l a r g e p a r t of the day. The i n t e r t i d a l v e g e t a t i o n of the f o r e s h o r e marshes has been d i v i d e d i n t o two broad c a t e g o r i e s (Burgess, 1970). The upper zone, which l i e s between the 3.0 and 4.6 m mean t i d e l e v e l s , c o n t a i n s e x t e n s i v e stands of Carex l i S g b e y e i with s m a l l but dense patches of Ty_£ha l a t i f o l i a and S c i r p u s acntus. Other s p e c i e s of minor importance occur i n t e r s p e r s e d among the Carex. The lower zone, l y i n g between the 2.3 to 3.4 m t i d e l e v e l s i s made up e x c l u s i v e l y of vast stands of S c i r p u s americanus^ with S c i r p u s v a l i d u s and S c i r p u s Ealudosus growing where l o c a l c o n d i t i o n s permit. The lower zone i s of g r e a t e s t importance t o snow geese. I t c o n s i s t s almost e x c l u s i v e l y of rhizome-bearing s p e c i e s . Snow geese are very g r e g a r i o u s b i r d s . During c e r t a i n p a r t s of the winter they concentrate on one or two areas, to the e x c l u s i o n of the r e s t of the f o r e s h o r e . Presumably i n response to s e a s o n a l changes i n hunting pressure, d i s t u r b a n c e and food a v a i l a b i l i t y , the geese move en masse from one p a r t of the f o r e s h o r e t o another. In t r y i n g t o e s t a b l i s h e x p l a n a t i o n s f o r these s h i f t s the study area was d i v i d e d i n t o s i x u n i t s . The boundaries were set to conform with t r a d i t i o n a l p a t t e r n s of h a b i t a t use by snow geese, r a t h e r than by the geomorphic f e a t u r e s of the 9 area. These b l o c k s of marsh. Sea Island-Iona I s l a n d , north L u l u I s l a n d , south L u l u I s l a n d , H e i f e l Refuge, the Outer I s l a n d s west o f R e i f e l Refuge, and Brunswick P o i n t were of unequal s i z e and contained s i m i l a r , but not i d e n t i c a l p l a n t a s s o c i a t i o n s ( F i g . 1). Sea I s l a n d marsh i s r e l a t i v e l y narrow and c o n t a i n s dense stands of mixed S c i r E u s ai.ericanus and Scir£>us paludosus, with S c i r p u s americanus becoming more dominant as the d i s t a n c e from the dike i n c r e a s e s . C o n s t r u c t i o n of a causeway between Iona I s l a n d and Sea I s l a n d i n 1961 e l i m i n a t e d what was probably a s i g n i f i c a n t source of sediment f o r t h i s area. An a r t i f i c i a l bay was formed between the two j e t t i e s . Consequently, the n a t u r a l flow of the g y r a l c u r r e n t northward was a l t e r e d c o n s i d e r a b l y . Only very f i n e sediments have been de p o s i t e d s i n c e then (Hoos and Packman, 1974). In a d d i t i o n , the Vancouver Sewage Treatment P l a n t , s i t u a t e d on Iona I s l a n d , c o n t i n u a l l y dumps n u t r i e n t r i c h water at the head of t h i s a r t i f i c i a l bay. As a r e s u l t , the s o i l i s poorly c o n s o l i d a t e d and i s presumed to be extremely high i n o r g a n i c matter, compared to other p a r t s of the marsh. These c o n d i t i o n s favour the development of S c i r p u s paludosus, which has a competetive advantage over the more h y d r o p h i l i c S c i r p u s amerleanus. I t i s not known whether the very loose c o n s i s t e n c y of the Sea I s l a n d marsh occurs as a r e s u l t of the reduced abundance of Scirp_us 10 11 americanus or i s the cause of i t . The marsh i n f r o n t of Lulu I s l a n d i s s i m i l a r i n s t r u c t u r e and composition from north to south but i s wider than the Sea I s l a n d marsh. I t possesses an e x t e n s i v e growth °f S c i r p u s americanus along i t s lower p e r i p h e r y , which blends i n t o mixed stands with S c i r p u s paludosus as the e l e v a t i o n i n c r e a s e s . The Steveston j e t t y , c o n s t r u c t e d along the main channel a c t s to d i v e r t s i l t away from the Lulu I s l a n d s h o r e l i n e . I t i s presumed t h a t those p o r t i o n s of L u l u I s l a n d away from the middle arm of the F r a s e r are e i t h e r r e t r e a t i n g or at best remaining s t a b l e because of the reduced annual supply of sediments. The marsh i n f r o n t of the George C., R e i f e l Migratory B i r d Sanctuary was t r e a t e d as two separate e n t i t i e s . The mainland p o r t i o n possessed a lower-zone c o n s t i t u t i o n of S c i r p u s americanus i n t e r s p e r s e d with patches of S c i r p u s y a l i d u s . The Outer I s l a n d p o r t i o n , c o n s i s t e d of s i m i l a r p l a n t s p e c i e s but the s u b s t r a t a contained g r e a t e r q u a n t i t i e s of sand. From the summary o f g e o l o g i c a l r e p o r t s presented by Hoos and Packman (op. c i t . ) , the f o r e s h o r e of north westham I s l a n d appears to be advancing. I t a l s o seems l i k e l y that the back eddies caused by the A l b i o n d i k e are i n c r e a s i n g the sedimentation r a t e and, thus, are l e a d i n g to the b u i l d u p of t h i s p o r t i o n of the f o r e s h o r e . The marsh of the southern p a r t of Westham I s l a n d appeared very s i m i l a r to that i n f r o n t of R e i f e l Refuge. 12 The lower zone o f the marsh a t Brunswick P o i n t i s almost e x c l u s i v e l y S c i r p u s americanus, with the e x c e p t i o n of one l a r g e pocket o f S c i r p u s Ealudosa§ along the southern edge. C o n s t r u c t i o n of the Western Terminals causeway on Roberts Bank has r e s u l t e d i n a marked i n c r e a s e i n s i l t d e p o s i t i o n between i t s e l f and the Brunswick P o i n t marsh. I f present trends continue i t i s presumed t h a t the marsh w i l l spread southward u n t i l r e a c h i n g the Superport causeway. 13 3^0 FOOD HABITS 3. 1 I n t r o d u c t i o n The primary o b j e c t i v e i n the study of food h a b i t s i s to l e a r n which of those foods present are u t i l i z e d most e x t e n s i v e l y . Subsequent i n v e s t i g a t i o n s may i n c l u d e analyses of seasonal v a r i a b i l i t y and a v a i l a b i l i t y of important food items which can then be r e l a t e d t o d i f f e r e n c e s i n n u t r i t i o n a l g u a l i t y . Analyses of food h a b i t s are p r e r e g u i s i t e to s t u d i e s r e l a t i n g t o metabolism and h a b i t a t u t i l i z a t i o n . T h i s i n f o r m a t i o n i s e s s e n t i a l i n determining the r e l a t i o n s h i p of an organism t o i t s h a b i t a t and fundamental to h a b i t a t manipulation and c o n s e r v a t i o n . T h i s part of the study was t h e r e f o r e conducted t o a s c e r t a i n food preferences of snow geese and to e s t a b l i s h the d i v e r s i t y of t h e i r d i e t . 3.2 Methods Ninety h u n t e r - k i l l e d snow geese were c o l l e c t e d over two years. Hunters were s u p p l i e d with p l a s t i c bags, i d e n t i f i c a t i o n tags and i n s t r u c t i o n s to f r e e z e as soon as p o s s i b l e , a l l i n t e r n a l organs from the most a n t e r i o r p o r t i o n of the esophagus to the most p o s t e r i o r end of the c o l o n i n c l u d i n g the c l o a c a . One wing from each b i r d was requested f o r aging. Each hunter was asked to note the date. 1 4 l o c a t i o n , and time of day when the k i l l took p l a c e . Upon thawing measurements of organ s i z e and c a p a c i t y were recorded. The contents of each g i z z a r d were emptied i n t o a 1000 ml beaker, a g i t a t e d and s t r a i n e d through a double l a y e r o f c h e e s e c l o t h . The o r g a n i c c o n t e n t s were removed from the c h e e s e c l o t h and r e f r o z e n f o r f u r t h e r a n a l y s i s . The c l e a n g r i t which remained i n the beaker was f l u s h e d i n t o aluminum weighing d i s h e s and d r i e d t o constant weight at 100°C. G r i t samples were weighed and the p a r t i c l e s i z e d i s t r i b u t i o n was determined by p a s s i n g each sample through a s e r i e s of i n c r e a s i n g l y f i n e r meshed screens. The o r g a n i c c ontents were then thawed and placed i n a waring blender at high speed f o r 30 seconds., T h i s mixture was t r a n s f e r r e d to a 250 ml beaker and allowed to stand f o r 15 minutes. Small q u a n t i t i e s of the buoyant m a t e r i a l s f l o a t i n g on top were t r a n s f e r r e d t o p r e l a b e l l e d microscope s l i d e s . Pour or f i v e drops o f Hertwig's s o l u t i o n (a c l e a r i n g agent and p r e s e r v a t i v e ) were added and the s l i d e was placed over a bunsen burner (Baumgartner and Martin, 1939). ft few more drops of Hertwig's s o l u t i o n were added to the s l i d e as i t b o i l e d to prevent s e a r i n g . A f t e r two minutes, s l i d e s were removed from the heat. Once c o o l , cover s l i p s were placed over the medium. In cases where the esophagus or the p r o v e n t r i c u l u s c o ntained l a r g e i d e n t i f i a b l e food fragments s c r a p i n g s were taken from the epidermis. These s c r a p p i n g s were dipped i n t o 15 Hertwig's s o l u t i o n on the s l i d e and processed i n the manner d e s c r i b e d above. & s i m i l a r procedure was c a r r i e d out to produce a s e t of r e f e r e n c e s l i d e s c o n s i s t i n g of the major plant s p e c i e s found on the marsh. The s l i d e s were examined under a b i n o c u l a r microscope at 40x and 100x m a g n i f i c a t i o n . The number of i d e n t i f i a b l e c u t i c u l a r fragments observed f o r each s p e c i e s and f o r each p l a n t part was recorded. I t was not p o s s i b l e to d i f f e r e n t i a t e between the c u t i c l e r e t i c u l a t i o n s of the rhizomes of Scirjaus americanus and S c i r p u s p a l u d os us. T h e r e f o r e , these two c a t e g o r i e s were combined and expressed as a s i n g l e food item. The remaining g i z z a r d contents were s t r a i n e d through double l a y e r s of c h e e s e c l o t h , t r a n s f e r r e d to aluminum weighing d i s h e s and d r i e d over n i g h t at 100°c. Often i n d i v i d u a l food items contained w i t h i n the esophagi were r e l a t i v e l y unfragmented and e a s i l y i d e n t i f i e d , while those contained i n the g i z z a r d occurred as a tangled bo l u s , i d e n t i f i a b l e only under a microscope. Under these c o n d i t i o n s i t was not f e a s i b l e t o separate and to measure the r e l a t i v e dry weights of each food item when a g i z z a r d c o n tained more than a s i n g l e type. Dry weight of i n d i v i d u a l items can be more a c c u r a t e l y and p r e c i s e l y measured than can volume and was used i n t h i s experiment f o r that reason. Measurements of dry weight are a p p l i c a b l e when the d i e t i s made of comparatively few s p e c i e s , as was the case i n t h i s study (Yocum and K e l l e r , 16 1961). Volumetric measurements are more u s e f u l i n determining the r e l a t i v e importance of the c o n s t i t u a n t s of a complex d i e t . The frequency of occurrence (percent occurrence) was c a l c u l a t e d by d i v i d i n g t h e number of g i z z a r d s i n which a p a r t i c u l a r food item was i d e n t i f i e d by the t o t a l number of g i z z a r d s c o l l e c t e d . . Because of the s m a l l number of g i z z a r d s c o n t a i n i n g two or more d i f f e r e n t types o f food, the assumption was made t h a t samples i n which only one type of food item had been i d e n t i f i e d were con s i d e r e d t o be composed e n t i r e l y of t h a t item. Rather than t r y i n g to obtain f r a c t i o n a l e s t i m a t e s o f those samples c o n s i s t i n g of two or more s p e c i e s they were omitted from the a n a l y s i s . In each of those 13 samples omitted, S c i r p u s rhizomes c o n s t i t u t e d a major p o r t i o n of t h e i d e n t i f i a b l e fragments. 3.3 Results Most of the snow geese c o l l e c t e d f o r t h i s study were shot as they were f l y i n g i n to feed. As a r e s u l t only 12 of 90 b i r d s had s u f f i c i e n t v e g e t a t i o n i n t h e i r esophagi t o warrant a n a l y s i s of i n t a c t foods. On the other hand, 88 of 90 g i z z a r d s c o n t a i n e d an adequate amount of v e g e t a t i o n to permit i d e n t i f i c a t i o n so the a n a l y s i s of food h a b i t s was r e s t r i c t e d to g i z z a r d c o n t e n t s . The primary foods of snow geese w i n t e r i n g on the Fraser 17 De l t a were the rhizomes of S c i r p u s americanus and S c i r p u s £alu^osus (Table I) . Other v e g e t a t i o n , such as the rhizomes and shoots of Carex l y n g b y e i and t h e shoots, and i n some cases, seeds of S c i r p u s americanus were consumed i n s m a l l amounts. Table (I) - G i z z a r d contents a n a l y s i s expressed as aggragate percentage and frequency of occurrence. Pood Item Aggregate Frequency of Percentage Occurance (n=75) (n=88) 5£i£B«s Shizomes 7z» 7 americanus shoots 9 % 7 6 - 1 £*- llRlkiei rhizomes fi 7 1 7 - ° izaabyei shoots o 8.0 •^ s- Paludosus shoots n 1 . 1 S x americanus seeds 0 1 - 1 U^- H l M o s u s tubers o •? 1 * 1 U n i d e n t i f i e d 5*1 2.3 6.7 5 ^ 7 0 S c i r g u s rhizomes comprised more than 75 percent of those food items i d e n t i f i e d . Observations made while i n the f i e l d showed t h a t the m a j o r i t y of i n t e n s i v e f e e d i n g occurred w i t h i n stands of S c i r p u s americanus and, t o a l e s s e r e x t e n t , S c i r p u s paludosus. L o a f i n g and other non-feeding a c t i v i t i e s were most conspicuous i n e i t h e r the exposed hummocks of the Carex zone, or on the unvegetated mud and sand f l a t s below the seven f o o t t i d e l e v e l . No above or below-ground p o r t i o n s of other emergent s p e c i e s were recorded i n the g i z z a r d s although some f e e d i n g a c t i v i t y was observed within 18 the Tygha zone. 3.4 D i s c u s s i o n The r e s u l t s c l e a r l y i n d i c a t e that rhizomes of S c i r p u s americanus and S c i r p u s galu_dosu_s are the major food items i n the d i e t of l e s s e r snow geese on the F r a s e r River D e l t a . I t i s i n t e r e s t i n g t o c o n s i d e r the very r e s t r i c t e d d i e t of these b i r d s i n the l i g h t of an a n a l y s i s of the food h a b i t s o f snow geese shot near the Skagit River f l a t s , 160 km t o the south ( J e f f r e y , pers. comm.). In that i n v e s t i g a t i o n , which spanned seven years, only 16 of 72 g i z z a r d s c o l l e c t e d contained i d e n t i f i a b l e food items, but l a r g e d i f f e r e n c e s i n d i e t composition were noted. In a d d i t i o n t o S c i r p u s americanus and S c i r p u s paludosus, were found v a r i o u s members of the f o l l o w i n g genera: J D i s t i c h l i s , Sparganium, Rannunculus t Polygonum, flgropyron, T r i f o l i u m , Z o s t e r a , Carex and E l e o c h a r i s . although the majority of the g i z z a r d contents were e i t h e r u n i d e n t i f i a b l e or l i s t e d as " c h a f f " , i t i s c l e a r that a l a r g e d i f f e r e n c e i n d i e t composition e x i s t s between these two neighbouring f l o c k s , o f t e n assumed to represent a s i n g l e p o p u l a t i o n . I t i s i n t e r e s t i n g t o note f u r t h e r the abundance of upland v e g e t a t i o n i n the d i e t s of Skagit b i r d s and the complete absence of upland v e g e t a t i o n i n the d i e t of F r a s e r R i v e r b i r d s . T h i s d i f f e r e n c e i s probably due to the f a c t 19 that most of the snow geese collected in northwestern Washington are shot while foraging in c u l t i v a t e d f i e l d s {Jeffrey, pers. comm.). Similar field-feeding forays rarely occur with the Fraser River f l o c k . This behavioural difference, one flock f i e l d - f e e d i n g regularly, the other seldom under f i e l d feeding except under abnormal conditions, gives r i s e to questions about the support c a p a b i l i t i e s of the Skagit marsh. In other areas of low natural food supply geese u t i l i z e grain f i e l d s extensively. I t i s possible also that the geese are composed of two or more behaviourally d i s t i n c t flocks which in fact do not. mix to as great a degree as i s commonly believed. In other words they may r e t a i n t r a d i t i o n a l feeding habits even though they share their wintering grounds with a di f f e r e n t subflock. A s i m i l a r s i t u a t i o n i s found i n central C a l i f o r n i a where snow geese from many different breeding colonies intermingle f r e e l y , yet they display an extremely high l e v e l of f i d e l i t y towards members of their own flock. Elsewhere in North America, snow geese appear to be opportunistic i n their feeding habits. Where abundant, rhizomes of Scirpus americanus and Scirpus olneyi are preferred (Lynch et a l . , 1947). However in marsh areas where these plants are scarce geese w i l l make use of a variety of emergent species including Carex ly.ngbeiei, Carex rostrata, Panicurn repens, Typha a u g u s t i f o l i a , Typha 20 l a t i f o l i a , Sp_art ina patens, Sp_ar t i na a l t e r n i f l o r a , Eleocharis sp., Leptochloa sp., Salieornia rubra, and D i s t i c h l i s spicatum (Mcllhenney, 1 9 3 2 ; Soper, 1 9 4 2 ; Glazner, 1946) . Although Scjjrpjis americanus, Typha l a t i f o l i a , Carex l2fi2EY§i# S a l i c o r n i a rubra, and D i s t i c h l i s spicatumoccur in varying densities within the marshes of t h i s area they were not found in those birds submitted for gizzard content analysis. I t seems evident from these comparisons that the Fraser River flock prefers the rhizomes of Scirpus ajnericanus and Scirgus paludqsus over other marsh vegetation and that i f the Skagit and Fraser flocks do intermix freely during the winter, their food habits are determined more by location than by preference. A wide variety of food plants are p o t e n t i a l l y available on the Fraser Delta. Continentally, snow geese display a marked di v e r s i t y in diet composition. So, although a de f i n i t e preference i s demonstrated for the rhizomes of SciEP.ii§ a.§sricanus and Scirjjus £aludosus the geese may be able to a l t e r t h e i r feeding habits somewhat should these t r a d i t i o n a l foods be reduced i n supply. I t would be interesting to determine whether or not members of the Fraser River flock do f i e l d - f e e d while they are on the Skagit f l a t s . If the Fraser River geese do enter the f i e l d s (and there i s growing evidence that they are more w i l l i n g to enter f i e l d s on Westham Island and at Brunswick 21 Point) the geese c o u l d cause widespread economic damage i n a very s h o r t time. I t i s e s s e n t i a l , t h e r e f o r e , t h a t s u f f i c i e n t e s t u a r i n e marshland be preserved to a v o i d needless c o n f r o n t a t i o n s with the farming community. 22 4 • 0 H ABITAT AND POOD RESOURCES 4.1 I n t r o d u c t i o n The manner i n which a s p e c i e s i n t e r a c t s with i t s h a b i t a t depends p r i m a r i l y on i t s niche dimensions, i e . i t s requirements f o r food and space over time. When d i s c u s s i n g the u t i l i z a t i o n of an area by a p a r t i c u l a r s p e c i e s c o n s i d e r a t i o n of those f a c t o r s l i m i t i n g d i s t r i b u t i o n , i . e . those aspects of behaviour which govern how an animal s e l e c t s i t s h a b i t a t i n r e l a t i o n to i t s v a r i o u s b i o l o g i c a l needs such as f e e d i n g and thermoregulation, i s i m p e r a t i v e . For h e t e r o t r o p h s , l i k e snow geese, v e g e t a t i o n i s the ult i m a t e source of energy and as a r e s u l t , may be one of the most c r i t i c a l environmental i n f l u e n c e s {HacFadyen, 1963; Sc o t t and Olson, 1973). The major foods o f w i n t e r i n g and m i g r a t i n g maritime snow geese i n c l u d e the r o o t s t a l k s , tubers and rhizomes of numerous s p e c i e s o f emergent marsh v e g e t a t i o n (McAtee, 1910; Lynch e t a l . , 1947). P r e l i m i n a r y i n v e s t i g a t i o n s and per s o n a l correspondence with l o c a l hunters i n d i c a t e d that the rhizomes of S c i r p u s americanus were the primary food of win t e r i n g snow geese on the F r a s e r D e l t a . Because of the amount of time r e q u i r e d to p r o p e r l y sample the below-ground v e g e t a t i o n i t was decided to r e s t r i c t the i n v e s t i g a t i o n to t h i s s i n g l e s p e c i e s . 23 4.2 Methods To o b t a i n a reasonable estimate o f the s i z e of the food resource, sampling o f below-ground m a t e r i a l s was planned f o r s i x d i f f e r e n t marsh l o c a t i o n s . Each s i t e was s e l e c t e d on the b a s i s of past occurrence of geese as r e l a t e d by l o c a l hunters. The f o l l o w i n g g e o g r a p h i c a l u n i t s were chosen: Brunswick P o i n t , E e i f e l Refuge, Outer I s l a n d s , W i l l i a m s Soad, Westminster Highway and Sea I s l a n d . At each l o c a t i o n l i n e t r a n s e c t s were placed through r e p r e s e n t a t i v e p o r t i o n s of the S e i r g u s americanus zone from the highest t o the lowest occuring v e g e t a t i o n . Wooden > stakes 1 m i n length were placed a t both ends and i n the middle of each t r a n s e c t to mark the s i t e s f o r resampling. A core-sampler was used to remove f o u r c y l i n d r i c a l s o i l samples from the immediate v i c i n i t y of each stake, two being under water and two above at low t i d e . Sample cores were approximately 25 cm deep and 19 cm i n diameter and weighed about 10 kg each. For every core removed, the f o l l o w i n g was r e c o r d e d : (1) loose s i l t depth (the v e r t i c a l depth t h a t a 0.5 x 3.0 cm r e c t a n g u l a r m e t r e - s t i c k c o u l d be e a s i l y pushed i n t o the uppermost s o i l horzon without i n c u r r i n g r e s i s t a n c e ) ; (2) v i s i b l e number of stems (both l i v i n g and dead); (3) water depth over each core at low t i d e ; and (4) r e l a t i v e h e i g h t s between samples at the same s i t e . Because of time 24 l i m i t a t i o n s due to r a p i d changes i n the t i d e o n l y one t r a n s e c t could be sampled per day. Cores were placed i n t h i c k p l a s t i c bags, l a b e l l e d , and taken to the l a b o r a t o r y . There, l a b cores were weighed and f r o z e n f o r f u t u r e a n a l y s i s ^ Each t r a n s e c t was sampled once i n October, January and A p r i l during the study p e r i o d . Samples to be cleaned were placed i n a r o o t washer c o n s i s t i n g of four r o t a t i n g screen-bottomed buckets. A f o r c e d j e t of water was d i r e c t e d i n t o each bucket. As i t r o t a t e d much of the adherent s i l t was washed through the screen l e a v i n g the root mass i n t a c t . The d e n s i t y of most cores r e q u i r e d much handworking and they o f t e n were l e f t o v e r n i g h t . On the other hand, some cor e s were very s o f t and were c l e a n w i t h i n minutes. A f t e r each sample had been washed i n t h i s manner, the r o o t mass was placed i n a s m a l l p l a s t i c bag and r e f r o z e n . L a t e r , they were removed from s t o r a g e and hand-washed thoroughly over a fine-meshed s c r e e n . L i v i n g rhizomes were separated from r o o t s and from dead m a t e r i a l s . Each f r a c t i o n was d r i e d i n a forced-draught oven at 100°C t o constant weight. Dry weights of a l l clams and clam s h e l l s were a l s o recorded. Each d r i e d rhizome sample was f i n e l y ground i n a Wiley m i l l and s t o r e d . To e v a l u a t e d i f f e r e n c e s i n rhizome standing crop between areas, date of sampling, and e l e v a t i o n ( m i c r o r e l i e f ) , the data obtained from 209 sample cores were subjected t o a n a l y s i s of v a r i a n c e u s i n g S c h e f f e ' s M u l t i p l e 25 Range Test (Zar, 1 9 7 4 ) . Macro-Kjeldahls, the o f f i c i a l method of the &0&C, s e r e performed i n d u p l i c a t e to determine rhizome crude p r o t e i n l e v e l s . Samples c o l l e c t e d i n January were analyzed f o r d i f f e r e n c e s between areas and samples c o l l e c t e d from Brunswick P o i n t were analyzed f o r s e a s o n a l v a r i a t i o n . In order t o compare one core with another, a l l weights were converted t o a common core weight of 10 kg. Standing crop was then c a l c u l a t e d from the mean v e g e t a t i o n content and s u r f a c e area of each core. In e x t r a p o l a t i n g t h i s data to o b t a i n a reasonable estimate of the t o t a l rhizome content of the f o r e s h o r e marsh, the f o l l o w i n g assumptions were made: (1) core samples were of adequate s i z e and q u a n t i t y to give a r e p r e s e n t a t i v e estimate f o r each l o c a t i o n , (2) Each t r a n s e c t was placed i n a r e p r e s e n t a t i v e stand of Scirjsus americanus <3) Each l o c a t i o n had a d i s t i n c t i v e rihzome s t a n d i n g crop. Below-ground v e g e t a t i o n c o n s t i t u t e s a l a r g e , but v a r i a b l e , and o f t e n unknown percentage of the biomass of most p l a n t s . Because of the d i f f i c u l t i e s i n h e r e n t i n measuring below-ground s t a n d i n g crop techniques have been proposed to enable r a p i d e s t i m a t i o n s of below-ground v e g e t a t i o n by measuring above ground parameters., Some workers have i m p l i e d that rhizome d e n s i t i e s may be 26 c a l c u l a t e d from the number of v i s i b l e shoots (Lemieux, 1958; MacNaughton, 1966). In an attempt to develop a more r a p i d and r e l i a b l e method of e s t i m a t i n g rhizome s t a n d i n g crop from above-ground c h a r a c t e r i s t i c s , s e v e r a l o b j e c t i v e parameters, i n c l u d i n g l o o s e s i l t depth, s t a n d i n g water depth at low t i d e , v e g e t a t i o n c o n d i t i o n , v e g e t a t i o n cover and r e l a t i v e e l e v a t i o n of one s i t e to the next were measured. However, no s i g n i f i c a n t r e l a t i o n s h i p s (P>0.05) were observed between rhizome s t a n d i n g crop and any of the measured above-ground environmental parameters. The number of emergent shoots per u n i t area was another parameter found t o be not s i g n i f i c a n t l y c o r r e l a t e d with rhizome standing crop. , U.3 Results Measurements of rhizome d e n s i t y and crude p r o t e i n l e v e l were used to compare segments of the marsh on the b a s i s of t h e i r r e l a t i v e food producing c a p a b i l i t i e s . By comparing one l o c a t i o n with another, i t was p o s s i b l e to d e l i n e a t e those areas producing t h e g r e a t e s t q u a n t i t y of rhizomes and d i s t i n g u i s h them from those areas producing rhizomes of the highest p r o t e i n content (Table I I ) . 27 Table (II) - Comparisons between d i f f e r e n t marsh u n i t s of the t o t a l below-ground s t a n d i n g crop, rhizome standing crop and rhizome crude p r o t e i n l e v e l s o f S c i r p u s americanus LOCATION Bruns- fieifel Outer W i l - West Sea wick Hefuge I s l a n d s liams minster I s l a n d P o i n t Hoad Highway Shizome 40. 72 29. 9i 30. 51 74. 13 80. 4 3 56. 32 Standing Crop + 3. 17 + 3. 79 +-4.06 • 9.17 + 7. 58 * 7.50 g.m-a (35) (33) (36) (36) (35) (34) Boots 188* 2051 190* 226* 2691 131* plus Shizomes ± 2 6 . 1 +24.2 ± 2 2 . 7 ± 2 4 . 9 ± 2 3 . 0 ± 1 4 . 0 (g.m-2) (35) (33) (36) (36) (35) (34) P r o t e i n Content 13.31 12.91 9.42 8.82 7.5 2 13.31 (percent) (15) (9) (8) (9) (11) (10) * ±S.E., (n) S u p e r s c r i p t s i n d i c a t e s i g n i f i c a n t d i f f e r e n c e s (P<0.05) On the b a s i s of the dry weight of l i v i n g rhizomes per sample core, s t a n d i n g c r o p s were c a l c u l a t e d f o r each of the o r i g i n a l s i x t r a n s e c t s . Areas of the three-sguare b u l l r u s h zones at Sea I s l a n d , L u l u I s l a n d , Westham I s l a n d , and Brunswick Point were d e r i v e d from r e c e n t a e r i a l photographs (Yamanaka, 1975). Of t h e 1580 h e c t a r e s of f o r e s h o r e marsh, the three-sguare community covered approximately 981 hectares (46 percent) (Table I I I ) . 28 Table (III) - Approximate s i z e , rhizome d e n s i t y and standing crop of each S c i r p u s americanus and S c i r p u s paludosiuj; marsh u n i t L o c a t i o n Area (ha) Mean Rhizome Rhizome (Yamanaka, 1975) Density (g-m - 2) Standing Crop (m.t) Sea I s l a n d 143 56,3 2 81 Lulu I s l a n d 354 77.3* 274 Westham I s l a n d 350 30.2* 106 Brunswick P o i n t 134 40.72 55 T o t a l 981 516 S u p e r s c r i p t s i n d i c a t e s i g n i f i c a n t d i f f e r e n c e s <P<0.05) S i m i l a r i t i e s i n rhizome standing crop between areas were t e s t e d with S c h e f f e * s M u l t i p l e Range Test. On t h i s b a s i s i t was p o s s i b l e t o group the s i x o r i g i n a l l o c a t i o n s i n t o three homogeneous u n i t s . Each of these u n i t s , north and south Lulu I s l a n d , Outer T s l a n d - R e i f e l Refuge, and Sea Island-Brunswick P o i n t represented a rhizome s t a n d i n g crop which was s i g n i f i c a n t l y d i f f e r e n t (P<0.05) from the other two (Table I I I ) . The t o t a l s t a n d i n g crop of l i v i n g rhizomes on the d e l t a f o r e s h o r e was approximately 516 m e t r i c tons. Seasonal v a r i a t i o n was a major f a c t o r i n determining standing crop (Table IV). In the e a r l y s p r i n g a drop of about 12.5 g. m - 2 i n mean rhizome d e n s i t y was observed. T h i s d e c l i n e was s i g n i f i c a n t at the f i v e percent confidence l e v e l . 29 Table (IV) - Comparisons between d i f f e r e n t months on the t o t a l below-ground s t a n d i n g crop, rhizome standing crop and rhizome crude p r o t e i n l e v e l s o f S c i r g u s americanus MONTH October December A p r i l Rhizome 53.6* 56. 8 i 42. 72 Standing Crop * 4.67 + 5.29 + 4.50 (g.m-2) (65) (72) (72) Roots 247* 2211 1472 p l u s Rhizomes + 20.7 • 13.2 + 14.0 (g.m-2) (65) (72) (72) P r o t e i n Content 12.0 13.7 14. 1 (percent) (10) (12) (11) * +S.E. , (n) S u p e r s c r i p t s i n d i c a t e s i g n i f i c a n t d i f f e r e n c e s (P<0.05) The two sampling s i t e s l o c a t e d i n the upper and centre p o r t i o n s of the three-square b u l l r u s h communities at each l o c a t i o n were found to possess s i g n i f i c a n t l y g r e a t e r amounts of rhizomes than those s i t u a t e d on the lower periphery (P<0.05) (Table V). S i m i l a r l y , sample cores from water-f i l l e d d e p r e s sions contained fewer rhizomes than d i d those from stands which were s u b j e c t e d t o r e g u l a r exposure a t low t i d e (P<0.05). The average rhizome s t a n d i n g crop of samples taken from w e l l drained s i t e s was s i g n i f i c a n t l y g r e a t e r than those from w a t e r - f i l l e d d e p r e ssions (P<0.05) . S i g n i f i c a n t d i f f e r e n c e s (P<0.05) were a l s o noted between geographic l o c a t i o n s r a nging from an average maximum of 77.3 g.m - 2 on Lulu I s l a n d t o an average minimum on Westham I s l a n d of 30.2 30 g.m-2. Table <V) - Comparisons between d i f f e r e n t sample s i t e s with r e s p e c t to the extent of r e l a t i v e t i d a l f l o o d i n g on the t o t a l below-ground standing crop, rhizome s t a n d i n g crop and rhizome crude p r o t e i n l e v e l s of S c i r g u s amexicanus S i t e 1 S i t e 2 S i t e 3 ( c l o s e s t (middle of ( f u r t h e s t to dike) Scirjaus from dike] community) Rhizome 54.91 54. 91 41.12 Standing Crop + 3.79 + 5.82 + 4. 50 (g.m-2) (71) (68) (7 0) Roots 2541 2081 1 442 plus Rhizomes + 17.5 + 15.8 + 13.8 (g.m-2) (71) (68) (7 0) P r o t e i n Content 10. 8 10. 8 10.7 (percent) (22) (21) (19) * +S.E., (n) S u p e r s c r i p t s i n d i c a t e s i g n i f i c a n t d i f f e r e n c e s (P<0.05) Crude p r o t e i n content was s i m i l a r f o r rhizomes from w i t h i n s i n g l e g e o g r a p h i c a l u n i t s r e g a r d l e s s of v a r i a t i o n s i n water-cover, m i c r o r e l i e f or season. However, s i g n i f i c a n t d i f f e r e n c e s were found to occur between l o c a t i o n s (Table I ) . Rhizomes c o l l e c t e d from Sea I s l a n d , Brunswick Po i n t and R e i f e l Refuge had mean p r o t e i n l e v e l s s i g n i f i c a n t l y g r e a t e r (P<0.05) than those of north and south Lulu I s l a n d and of the Outer I s l a n d s . I n d i v i d u a l crude p r o t e i n values ranged from a low of l e s s than 6 percent on L u l u I s l a n d to a high of more than 20 percent on Sea I s l a n d . the mean l e v e l of 31 crude f i b e r c o n tained i n the rhizomes o f S c r i p u s americanus was 22 percent. Ho s i g n i f i c a n t change i n crude f i b e r content occurred between s i t e s or during the season. Combined weights of rhizomes plus r o o t s were analyzed i n the same manner as that f o r rhizomes alone. The s t a n d i n g crop of t o t a l subterranean v e g e t a t i o n was found to d i f f e r s i g n i f i c a n t l y (P<0.05) between areas (Table I I ) . I t was p o s s i b l e to s t a t i s t i c a l l y group the o r i g i n a l s i x l o c a t i o n s i n t o two homogeneous u n i t s . The e f f e c t of m i c r o r e l i e f with r e s p e c t t o the production of t o t a l below-ground v e g e t a t i o n was s i m i l a r to that observed with the production of rhizomes. Upper and middle p o r t i o n s of the three-square community produced s i g n i f i c a n t l y g r e a t e r q u a n t i t i e s (P<0.05) of below-ground m a t e r i a l s than d i d the lower edge (Table V). The q u a n t i t i e s per u n i t area of underground v e g e t a t i o n in t h i s study remained constant throughout the autumn and winter sampling periods. However, a s i g n i f i c a n t decrease (P<0.05) from the mean autumn/winter d e n s i t y to t h a t i n the s p r i n g was recorded (Table IV) . T h i s drop i n below-ground dry matter presumably occurred as a r e s u l t of the t r a n s l o c a t i o n of n u t r i e n t s i n t o the growth and development of new shoots. 4.4 D i s c u s s i o n 32 Data on the p r o d u c t i v i t y and s t a n d i n g crop of below-ground v e g e t a t i o n are n o t o r i o u s l y d i f f i c u l t t o c o l l e c t and are s u b j e c t to numerous e r r o r s . N e v e r t h e l e s s , t h i s survey did generate p r e v i o u s l y u n a v a i l a b l e i n f o r m a t i o n r e g a r d i n g the approximate below-ground s t a n d i n g crop of three-square b u l l r u s h . The core sampling technique used i n t h i s study was c r i t i c i z e d by Westlake (1963) and Keefe (1972) as they f e l t i t overestimated the below-ground s t a n d i n g crop, compared with l a r g e r s c a l e r o o t e x c a v a t i o n technigues which tended towards underestimation. However, the b i a s a s s o c i a t e d with a l a r g e circumference to s u r f a c e area r a t i o was reduced by the use of a core sampler 19 cm i n diameter, r a t h e r than the more common s i z e s of l e s s than 10 cm. Although the exact mechanism i s not known, rhizome and seed production tend to be i n v e r s e l y r e l a t e d (HacNaughton, 1966). Since seed p r o d u c t i o n of emergent v e g e t a t i o n i n g e n e r a l , and three-square b u l l r u s h i n p a r t i c u l a r , has been repor t e d t o decrease with an i n c r e a s e i n t i d a l water cover (Burgess, 1970) i t was expected t h a t a p r o p o r t i o n a l i n c r e a s e i n rhizome d e n s i t y would have occurred i n those s i t e s p r o g r e s s i v e l y f u r t h e r away from the d i k e s . However, data c o l l e c t e d i n t h i s study d i d not support t h i s c o n t e n t i o n . In f a c t , the lower p o r t i o n of the three-square zone was shown to possess a s i g n i f i c a n t l y s m a l l e r q u a n t i t y of rhizomes per square meter than e i t h e r the middle or upper p o r t i o n s . An e x p l a n a t i o n f o r t h i s anomaly does not appear t o l i e 33 i n the presumption t h a t an i n c r e a s e in t i d a l cover reduced the number of i n d i v i d u a l p l a n t s . , The number of shoots per sample showed no tendency to decrease as t i d a l i n undation i n c r e a s e d . However, s t u d i e s have been performed on other s p e c i e s which demonstrate a more d i r e c t dependence of r o o t and rhizome p r o l i f e r a t i o n on r o o t a e r a t i o n and s o i l type. Dean (1933) demonstrated that T y p h a - l a t i f o l i a • g r o w n i n muck s o i l s produced rhizomes approximately t h r e e times the l e n g t h of those grown i n sand. I f S c i r p u s americanus responded i n l i k e f a s h i o n the low rhizome d e n s i t i e s observed wit h i n the lower reaches of the three-sguare zone may be r e l a t e d to s i l t depth. U n f o r t u n a t e l y no accurate measurements of s i l t depth were recorded but o b s e r v a t i o n s i n d i c a t e d t h a t s i l t depth decreased as the d i s t a n c e from the d i k e s i n c r e a s e d . Data c o l l e c t e d by Yamanaka (1975) supports t h i s o b s e r v a t i o n by demonstrating that s o i l o r g a n i c matter along the l e n g t h of the f o r e s h o r e decreased as t h e d i s t a n c e from the dikes i n c r e a s e d . In some areas three-sguare b u l l r u s h was growing i n only 10 to 15 cm of s i l t on top of almost pure sand. The sand acted e s s e n t i a l l y as a pan and p e n e t r a t i o n by t h e r o o t mass was minimal. Weaver and Himmel (1930) s t a t e d t h a t p l a n t s growing n a t u r a l l y i n poorly drained and aerated c o n d i t i o n s , such as those found i n marshes, are l e s s s e n s i t i v e to e i t h e r the composition or t o t a l absence of a s o i l atmosphere than those in n a t u r a l l y w e l l drained s o i l s . However, i t was subsequently demonstrated that an i n c r e a s e i n a e r a t i o n measurably i n c r e a s e d the l e n g t h , diameter and presumably, dry weight of the r o o t s and rhizomes of another hydrophyte, Typha l a t i f o l i a (Dean, 1933). Notwithstanding the f a c t that S c i r p u s americanus i s a h y d r o p h i l i c s p e c i e s , the l i m i t e d degree of s o i l a e r a t i o n a v a i l a b l e to p l a n t s growing i n w a t e r - f i l l e d depressions may have been r e s p o n s i b l e f o r the s i g n i f i c a n t l y s m a l l e r rhizome d e n s i t y observed t h e r e i n . L i t t l e i s known r e g a r d i n g r e l a t i o n s h i p s between s i t e f e r t i l i t y parameters and s t a n d i n g crop. However, i t has been e s t a b l i s h e d that the n u t r i e n t composition of a p a r t i c u l a r s p e c i e s may vary c o n s i d e r a b l y between s i t e s (Boyd and Hess, 1970). In the present study crude p r o t e i n , d i d not d i f f e r s i g n i f i c a n t l y with r e s p e c t to date, amount of water cover or r e l a t i v e height of sampling w i t h i n each marsh u n i t . However, s i g n i f i c a n t d i f f e r e n c e s were recorded between areas. Working with Typha l a t i f o l i a , Boyd and Hess (1970) found no c o r r e l a t i o n between n i t r o g e n content and the standing crop of a e r i a l v e g e t a t i o n . However, they d i d i n d i c a t e t h a t t i s s u e c o n c e n t r a t i o n s of v a r i o u s n u t r i e n t s were higher i n p r o d u c t i v e p o p u l a t i o n s than i n unproductive ones. On the F r a s e r Delta the most productive stands, or a t l e a s t those with the l a r g e s t s t a n d i n g crops, maintained the lowest l e v e l s of crude p r o t e i n , while stands with the highest percentage o f crude p r o t e i n were only of average 35 standing crop. There would appear to be no simple r e l a t i o n s h i p between the a r e a l d i s t r i b u t i o n of crude p r o t e i n and rhizome standing crop. Crude f i b e r l e v e l s i n t h i s study were demonstrated to remain r e l a t i v e l y constant over time. S i m i l a r l y , Boyd (1968) noted that there d i d not appear t o be the same age-r e l a t e d i n c r e a s e i n l i g n i n and other crude f i b e r components with emergent v e g e t a t i o n as there was with t e r r e s t r i a l v e g e t a t i o n . As a r u l e , rhizomes and r o o t s c o n t a i n lower c o n c e n t r a t i o n s o f p r o t e i n and higher c o n c e n t r a t i o n s of carbohydrate than do l e a v e s . However, growing c o n d i t i o n s have been shown to a f f e c t t h i s balance. I f grown i n very p r o d u c t i v e c o n d i t i o n s , the below-ground p a r t s of Carex b i g e l o w i i show a marked i n c r e a s e i n n u t r i e n t l e v e l s while those of the l e a v e s remain r e l a t i v e l y constant (Hadley and B l i s s , 1964). Because rhizomes act both as v e h i c l e s f o r v e g e t a t i v e r e p r o d u c t i o n and as storage organs, i t would be expected t h a t an i n c r e a s e i n the q u a n t i t y of n u t r i e n t s produced by the p l a n t would be r e f l e c t e d i n the n u t r i e n t l e v e l s of the rhizomes. Although the r e l a t i o n s h i p s are not c l e a r , the n u t r i e n t composition of c e r t a i n a q u a t i c p l a n t s has been r e p o r t e d t o i n c r e a s e with an i n c r e a s e i n the l e v e l s of environmental n u t r i e n t s (Boyd and Hess, 1970). But i t i s c o i n c i d e n t a l t h at those areas r e c e i v i n g the l a r g e s t annual increment of f r e s h s i l t d e p o s i t s (Sea I s l a n d , R e i f e l Refuge 36 and Brunswick Point) are a l s o the areas of h i g h e s t rhizome crude p r o t e i n . Below-ground:above-ground r a t i o s have been recorded f o r a wide v a r i e t y of plant s p e c i e s however, the f i g u r e s are extremely v a r i a b l e , even among members of the same s p e c i e s , e s p e c i a l l y when the pl a n t s are subjected to d i s s i m i l a r micro-environments. Rootrshoot r a t i o s v a r i e d from l e s s than one percent i n a c o r n f i e l d t o over 90 percent i n a p r a i r i e g r a s s l a n d (Ovington e t a l . , 1963). P e a r s a l l and Gorham (1956) s t a t e d that 40 to 50 percent of the t o t a l p l a n t biomass was l o c a t e d below ground while Westlake (196 3) f e l t t h a t from 50 to 85 percent would be more a c c u r a t e . Other workers have recorded r o o t : shoot r a t i o s d i f f e r i n g by more than 100 percent (MacNaughton, 1966). In f a c t . Bray (1963) l i s t e d r o o t to shoot values which ranged from 0.15 to 5.50. I t must be remembered t h a t i n the case of p e r e n n i a l s p e c i e s , such as emergent marsh p l a n t s , the peak standing crop of a e r i a l v e g e t a t i o n occurs when the below-ground ve g e t a t i o n i s e i t h e r at or near i t s lowest l e v e l and that peak underground standing crop o f t e n occurs when there are few, i f any, l i v i n g shoots. S i n g l e measurements of standing crop, i n these i n s t a n c e s a r e , t h e r e f o r e , of l i t t l e value when used to r e l a t e the r e l a t i v e p r o p o r t i o n s of above-ground to below-ground v e g e t a t i o n . The annual c y c l e of below-ground p r o d u c t i v i t y of Sc i r p u s americanus presumably f o l l o w s that o u t l i n e d by 37 Bernard (1973) f o r two monocots, Carex r o s t r a t a and Poa ££§.tensis. A f t e r a decrease i n e a r l y s p r i n g , due mainly to the m o b i l i z a t i o n of n u t r i e n t s f o r shoot growth, the below-ground s t a n d i n g crop i s at i t s y e a r l y minimum. I t s t a y s at t h i s low l e v e l u n t i l the growth of a e r i a l shoots and i n f l o u r e s c e n c e development has ceased; g e n e r a l l y around June f o r emergents at t h i s l a t i t u d e . Subsequently rhizome growth and p r o l i f e r a t i o n i s a c c e l e r a t e d as a l l products of p h o t o s y n t h e s i s are s t o r e d . P r o d u c t i o n and s t o r a g e of these m a t e r i a l s may continue u n t i l a l l a e r i a l v e g e t a t i o n d i e s , which i n the case of three-square b u l l r u s h , may not occur u n t i l e a r l y to mid autumn. The standing crop of below-ground v e g e t a t i o n then remains at or near i t s maximal l e v e l u n t i l shoot e r u p t i o n occurs once more duri n g the f o l l o w i n g s p r i n g . In communities where the s t a n d i n g crop of below-ground v e g e t a t i o n remains e s s e n t i a l l y c onstant from year to year annual production roughly equals annual l o s s . Head (1971) repor t e d that estimates of below-ground p r o d u c t i v i t y of grasslands vary between 25 and 50 percent of the t o t a l below-ground s t a n d i n g crop (Semezov e t a l . , 1963; D a l i a n and Kucera, 1965)and w i l l change depending upon the season of sampling. No estimates of p r o d u c t i v i t y were conducted during t h i s study. However, such i n f o r m a t i o n would be of value to assess the r e s i l i e n c y of three-sguare b u l l r u s h to damage by e x c e s s i v e l y l a r g e c o n c e n t r a t i o n s of snow geese. 38 Based on the mean rhizome standing crop of 516 met r i c tons a rough e s t i m a t e of the p r o d u c t i v e c a p a c i t y of below-ground s t r u c t u r e s would range from 129 to 258 metric tons of rhizomes per year. Comparisons o f p r o d u c t i v i t y and/or standing crop between d i f f e r e n t s p e c i e s at d i f f e r e n t geographic l o c a t i o n s are d i f f i c u l t t o i n t e r p r e t because of the inherent v a r i a t i o n between s i t e s . E c o t y p i c v a r i a t i o n w i t h i n Typha l a t i f o l i a was d i s c u s s e d at l e n g t h by MacNaughton (1966) who concluded that northern v a r i e t i e s produce g r e a t e r q u a n t i t i e s of below-ground v e g e t a t i o n than do t h e i r southern c o u n t e r p a r t s . However, even among c o n s p e c i f i c s a t the same l o c a t i o n tremendous v a r i a t i o n between s i t e s may e x i s t . In t h i s study mean sta n d i n g crop of t o t a l below-ground v e g e t a t i o n t o depth of 25 cm ranged from a low of 130 g.m - 2 to a high of 270 g.m~2. Yet the i n d i v i d u a l samples v a r i e d from l e s s than 4 g.m~2 t o more than 705 g.m - 2. I t i s t h e r e f o r e i m p e r a t i v e to ensure adequate sample s i z e s p r i o r to making d e f i n i t i v e statements on the standing crop and p r o d u c t i v i t y of a s p e c i e s . Without s t a n d a r d i z e d techniques and e x p l i c i t l y s t a t e d o b j e c t i v e s comparisons between s t u d i e s of biomass and p r o d u c t i v i t y of d i f f e r e n t l o c a t i o n s must be conducted with c a u t i o n . 39 5-.0 SPATIAL AND TEMPORAL DISTRIBUTION 5.1 I n t r o d u c t i o n The degree to which v a r i o u s environmental a t t r i b u t e s i n f l u e n c e the s p a t i a l and temporal d i s t r i b u t i o n of organisms i s not c l e a r l y understood. However, i t i s s a f e to assume that these a t t r i b u t e s s e t the f u n c t i o n a l boundaries of a given h a b i t a t . I t f o l l o w s t h a t any attempt to e x p l a i n the r e l a t i o n s h i p between an organism and i t s h a b i t a t must i n c o r p o r a t e r e c o r d s and i n t e r p r e t a t i o n s of s p a t i a l d i s t r i b u t i o n over time. The d i s t r i b u t i o n o f animals i s b a s i c a l l y the r e s u l t of an i n t e r a c t i o n between the b i o l o g i c a l demands of e i t h e r an i n d i v i d u a l or p o p u l a t i o n and the a b i l i t y of the h a b i t a t to s a t i s f y t h e s e demands. A s y n t h e s i s o f the l i t e r a t u r e i n d i c a t e s t h a t both s o c i a l ( v o c a l i z a t i o n s , presence of other geese, a c t i v i t y of neighbours) and n o n - s o c i a l (food a v a l i a b l i t y , marsh s t r u c t u r e , v e g e t a t i o n c h a r a c t e r i s t i c s ) a t t r a c t a n t s i n t e r a c t with v a r i o u s r e g u l a t o r y f a c t o r s ( d i s t u r b a n c e , t r a d i t i o n , weather) d u r i n g a l l l e v e l s of h a b i t a t s e l e c t i o n . However, the p r e c i s e s t i m u l i and t r i g g e r mechanisms i n v o l v e d have not been e l u c i d a t e d . Information from l o c a l observers i n d i c a t e s d e f i n i t e annual p a t t e r n s of u t i l i z a t i o n by the Fr a s e r R i v e r f l o c k . Obviously the s t r e n g t h and d u r a b l i l i t y o f these h a b i t s are no d i f f i c u l t t o measure. However, past o c c u p a t i o n a l p a t t e r n s c o n s t i t u t e a meaningful s t i m u l u s i n f l u e n c i n g h a b i t a t use (Klopfer and Hailman, 1965) and attempts t o d e f i n e h a b i t a t q u a l i t y must take them i n t o account. Metabolic and s o c i a l needs of the geese may change g u i c k l y depending on changes i n food a v a l a i b i l i t y , extremes of weather, and e x c e s s i v e harrassment. Under c o n d i t i o n s where f r e e h a b i t a t s e l e c t i o n i s p o s s i b l e geese may be expected to d i s t r i b u t e themselves i n a p a r t i c u l a r manner d i c t a t e d by s u b l i m i n a l attempts to maximize b e n e f i t s from the energy expended. However, under c o n d i t i o n s where f r e e s i t e c h o i ce i s not p o s s i b l e d i s t r i b u t i o n may be determined by one or more environmental f a c t o r s , not otherwise of conseguence. In other words, changes i n the p e r c e i v e d environment may l e a d to changes i n a r e a l d i s t r i b u t i o n . An understanding of the r o l e played by v a r i o u s f e a t u r e s of the environment i n d i s t r i b u t i n g snow geese throughout the f o r e s h o r e i s t h e r e f o r e an e s s e n t i a l step i n a s s e s s i n g the r e l a t i o n s h i p between the b i r d s and each marsh u n i t . When geese can r a p i d l y d i s t i n g u i s h between a p p r o p r i a t e and i n a p p r o p r i a t e h a b i t a t s , or p a r t s t h e r e o f , random s e a r c h i n g i s minimized and e f f i c i e n c y of u t i l i z a t i o n i s enhanced. A n a l y s i s of the processes l e a d i n g to a non-random d i s t r i b u t i o n may have p r a c t i c a l management i m p l i c a t i o n s . By measuring the s p a t i a l d i s t r i b u t i o n of geese on the e s t u a r y and r e l a t i n g the observed p a t t e r n s to changes i n 41 environmental f e a t u r e s i t may be p o s s i b l e t o d e l i n e a t e c r i t i c a l f e e d i n g and l o a f i n g areas. Concurrent monitoring of p o p u l a t i o n s i z e may then permit estimates of the feeding i n t e n s i t y e x e r t e d w i t h i n each marsh u n i t . Because of t h e i r i n t e n s i v e method o f f e e d i n g and high degree of aggregation snow geese have been known to destroy l a r g e t r a c t s of t h e i r Gulf Coast winter h a b i t a t (Lynch e t a l . , 1947). Knowledge of l o c a l h a b i t a t '.requirements during winter may provide the in f o r m a t i o n necessary to prevent s i m i l a r problems from oc c u r i n g on the F r a s e r River e s t u a r y . 5.2 Methods 5.2.1 Data C o l l e c t i o n In an attempt to measure changes i n p o p u l a t i o n s i z e and d i s p e r s a l a s e r i e s of 23 a e r i a l censuses were conducted each week from October 24, 1974 t o A p r i l 20, 1975, using a Cessna 185, fixed-wing f l o a t plane. As of t e n as p o s s i b l e each census was conducted when the t i d e was between 3 and 4 m (9 and 12 f t ) above sea l e v e l and the c l o u d c e i l i n g was g r e a t e r than 250 m. Under these c o n d i t i o n s the geese were u s u a l l y concentrated along the water's edge in two or th r e e l a r g e , compact f l o c k s . L i g h t c o n d i t i o n s were g e n e r a l l y b r i g h t enough to o b t a i n s a t i s f a c t o r y photographs. The a i r s p e e d and a l t i t u d e of each f l i g h t depended p r i m a r i l y on l i g h t c o n d i t i o n s , the degree o f f l o c k compactness and the wariness 42 of the b i r d s but averaged approximately 100 knots at 150 to 300 m. Standard 35 mm black and white photographs were taken using e i t h e r I l f o r d Pan F (50 ASA) under b r i g h t s k i e s or I l f o r d FP4 (125 AS A) under o v e r c a s t c o n d i t i o n s . Enlargements (15x20 cm) were p r i n t e d on Ilf a b r o m Semi-matt No. 3 paper which provided moderately high c o n t r a s t with s u f f i c i e n t l y f i n e d e t a i l at the d e s i r e d s c a l e . P r i n t s were d i v i d e d i n t o g r i d s and geese were counted under a 10x power b i n o c u l a r d i s s e c t i n g microscope. A s m a l l hole was punched through each goose as i t was counted to prevent d u p l i c a t i o n . Counts were t a l l i e d f o r each census and f l o c k l o c a t i o n s were recorded during each f l i g h t . More o f t e n than not a sequence of photographs was r e q u i r e d because geese were spread out along the marsh to such an extent that i t was not p o s s i b l e to i n c l u d e the whole f l o c k i n a s i n g l e frame. Daytime d i s t r i b u t i o n was a l s o o btained from the ground during the a c t i v i t y budget f i e l d s t u d i e s . F l i g h t s of geese to and from a l l p a r t s of the f o r e s h o r e were e a s i l y observed with a s p o t t i n g scope. In order to o b t a i n a measure of goose d i s t r i b u t i o n over 24 hours, each marsh u n i t was v i s i t e d at d i f f e r e n t times between sunset and s u n r i s e to a s c e r t a i n the presence or absence of geese i n that area. I t was decided t h a t a f l o c k c o n s i s t i n g of 100 or more i n d i v i d u a l s r e p r e s e n t e d presence i n an area and fewer than t h i s amount represented absence. Because of the g r e g a r i o u s 43 nature of snow geese they were r a r e l y observed on any of the s i x marsh u n i t s i n f l o c k s of l e s s than 100 i n d i v i d u a l s . Data c o l l e c t e d i n t h i s manner, augmented by the use of a n i g h t - v i s i o n scope i n the l a t t e r part of the study, was i n s u f f i c i e n t t o develop p r e c i s e p a t t e r n s of n o c t u r n a l movement but general trends were i n d i c a t e d . Because of l i m i t a t i o n s i n the range of the scope, i t was not p o s s i b l e to get a c c u r a t e n o c t u r n a l counts a t each l o c a t i o n . , However, estimates of g e n e r a l f l o c k d i s t r i b u t i o n were recorded. Data on those parameters which appeared t o exert some c o n t r o l on the s p a t i a l d i s t r i b u t i o n o f geese over the f o r e s h o r e were c o l l e c t e d . These i n c l u d e d l e v e l of d a y l i g h t , t o t a l number of b i r d s on the f o r e s h o r e , q u a n t i t y and crude p r o t e i n l e v e l s of the food r e s o u r c e , minimum d a i l y temperature and time of year (expressed i n terms of one month i n t e r v a l s ) . The a b i l i t y o f hunting t o modify d i s p e r s a l p a t t e r n s of waterfowl i s widely known but i s p o o r l y documented (Winner, 1951; Owen, 1972). Because hunting c o n s t i t u t e s a major environmental f e a t u r e on the F r a s e r e s t u a r y an attempt was a l s o made t o q u a n t i f y i t s e f f e c t s on the geese by r e c o r d i n g whether the hunting season was open or c l o s e d . 5.2.2 S t a t i s t i c a l Techniques The nominally s c a l e d s t r u c t u r e of most d i s t r i b u t i o n data precludes a n a l y s i s by the c o n v e n t i o n a l s t a t i s t i c a l methods of m u l t i p l e r e g r e s s i o n and a n a l y s i s of v a r i a n c e and 44 c o v a r i a n c e . An approach b e t t e r s u i t e d to the a n a l y s i s of such f a c t o r s was t h a t based upon m u l t i v a r i a t e s t a t i s t i c s . M u l t i v a r i a t e a n a l y s i s lends i t s e l f to use by e c o l o g i s t s because i t provides a means of e x p r e s s i n g , i n terms of v e c t o r q u a n t i t i e s , those of a l l p o s s i b l e combinations of f a c t o r s which are most c l o s e l y a s s o c i a t e d with the v a r i a t i o n s i n the q u a n t i t i e s observed (MacFadyen, 1963). In r e c e n t years the number of mathematical tec h n i q u e s have i n c r e a s e d tremendously and a v a r i e t y of m u l t i v a r i a t e s t a t i s t i c a l programs are p r e s e n t l y a v a i l a b l e . One such technique, M u l t i p l e C l a s s i f i c a t i o n A n a l y s i s (MCA) o f f e r s the advantage t h a t independent v a r i a b l e s need not be measured as i n t e r v a l s c a l e s and that r e l a t i o n s h i p s between the dependent and independent v a r i a b l e s need not be l i n e a r (Andrews et a l . , 1967). However, MCA assumes that the dependent v a r i a b l e s are measured only as i n t e r v a l s c a l e s . Not a l l e c o l o g i c a l s i t u a t i o n s can be reasonably recorded i n t h i s manner., In 1973 a new m u l t i v a r i a t e procedure, M u l t i v a r i a t e Nominal Scale A n a l y s i s (MNA), was developed to handle s i t u a t i o n s where the dependent v a r i a b l e i s a s e t of mutually e x c l u s i v e n o m i n a l l y - s c a l e d c a t e g o r i e s and where the independent v a r i a b l e s may be recorded at any l e v e l of measurement (nominal, o r d i n a l or i n t e r v a l s c a l e s ) . MNA has the f l e x i b i l i t y to i d e n t i f y any form or p a t t e r n of r e l a t i o n s h i p t h a t may e x i s t e i t h e r between any independent 45 v a r i a b l e and the dependent v a r i a b l e or between any p a i r of independent v a r i a b l e s (Andrews and Messenger, 1973). Because the dependent and independent ! v a r i a b l e s i n the d i s t r i b u t i o n a l data were n o m i n a l l y - s c a l e d , MNA was chosen as the a p p r o p r i a t e s t a t i s t i c a l procedure f o r a n a l y z i n g predominant a c t i v i t y . 5.3 Results Snow geese were present on the F r a s e r D e l t a f o r 142 days during the 1974-1975 season. Each day was d i v i d e d , f o r the purposes of data c o l l e c t i o n , i n t o day and n i g h t - t i m e viewing i n t e r v a l s . Of the p o s s i b l e 284 o b s e r v a t i o n p e r i o d s , data was c o l l e c t e d during 94, of which 75 percent were gathered during the day. Snow geese d i s p l a y e d an a f f i n i t y f o r the refuge marsh d u r i n g the d a y l i g h t hours of the f i r s t h a l f of hunting season. Conversely, they d i s p l a y e d a strong tendency to l o c a t e on areas o u t s i d e of the refuge when hunting pressure was absent. The Outer I s l a n d s , though seldom frequented by snow geese, were most important during the evenings of November and December. When hunting pressure was absent they r e s t r i c t e d t h e i r movements almost e n t i r e l y t o the marshes of Brunswick P o i n t and L u l u I s l a n d , i g n o r i n g R e i f e l Refuge completely. S e v e r a l s t a t i s t i c s are generated by the MNA program. However, i n the i n t e r e s t s of c l a r i t y , I have only presented 46 t h o s e most r e l e v a n t to the s t u d y . A r e l a t i v e l y l a r g e p r o p o r t i o n o f t h e v a r i a n c e i n h a b i t a t s e l e c t i o n was accounted f o r by t h e e n v i r o n m e n t a l v a r i a b l e s measured. G e n e r a l i z e d R 2 i s the m u l t i p l e c o r r e l a t i o n c o e f f i c i e n t and r e p r e s e n t s t h e p r o p o r t i o n o f t h e observed v a r i a n c e e x p l a i n e d by the complete modal. G e n e r a l i z e d R 2 r e v e a l e d t h a t the complete model accounted f o r 49.0 p e r c e n t of t h e v a r i a n c e observed between l o c a t i o n s ( T a b l e VI) . G e n e r a l i z e d E t a 2 performs t h e same f u n c t i o n i n a b i v a r i a t e s i t u a t i o n as G e n e r a l i z e d R 2 does i n a m u l t i v a r i a t e s i t u a t i o n . G e n e r a l i z e d E t a 2 r e p r e s e n t s the p r o p o r t i o n o f t h e observed v a r i a n c e e x p l a i n e d by each o f t h e f o u r independent v a r i a b l e s and ranged from a low o f 0.039 (Darkness) t o a h i g h of 0.3058 (Month). Hu n t i n g p r e s s u r e was the second most i m p o r t a n t f a c t o r a f f e c t i n g d i s t r i b u t i o n f o l l o w e d c l o s e l y by p o p u l a t i o n s i z e . C o e f f i c i e n t s o f the MNA model can be i n t e r r p r e t e d d i r e c t l y as t h e g a i n o r l o s s i n l i k e l i h o o d of geese b e i n g p r e s e n t at each l o c a t i o n under s t a t e d c o n d i t i o n s o f d a t e , i l l u m i n a t i o n , p o p u l a t i o n s i z e , t i d a l s t a t u s , and h u n t i n g season. A l a r g e p o s i t i v e c o e f f i c i e n t would i n d i c a t e s t r o n g a f f i n i t y and a l a r g e n e g a t i v e c o e f f i c i e n t i n d i c a t e s s t r o n g a v o i d a n c e . A d e f i n i t e p r e f e r e n c e f o r Brunswick P o i n t was noted a t p o p u l a t i o n l e v e l s up t o 5,000 geese. With an i n c r e a s e above t h i s number L u l u I s l a n d became more i n t e n s i v e l y u t i l i z e d and t h e t o t a l p o p u l a t i o n was s p l i t 47 between t h e s e two a r e a s . P o p u l a t i o n s i z e does not appear t o have been a major f a c t o r i n f l u e n c i n g use o f t h e Outer I s l a n d s . Of t h e t o t a l t i m e on t h e f o r e s h o r e 63.2 p e r c e n t was spent on Brunswick P o i n t and L u l u I s l a n d . O u t s i d e of h u n t i n g season t h i s p r o p o r t i o n i n c r e a s e d t o a p p r o x i m a t e l y 94 p e r c e n t . I t f o l l o w s t h a t Brunswick P o i n t and L u l u I s l a n d a r e a r e a s of s p e c i a l a t t r a c t i o n f o r the geese and appear t o be o f c r i t i c a l i m p o r t a n c e . 48 Table (VI) - V a r i a b l e Response P r o f i l e s : c o e f f i c i e n t s of the MNA model f o r d i s t r i b u t i o n PREDICTORS CATEGORIES LOCATION Brunswick R e i f e l Outer L u l u Sea Poin t Refuge I s l a n d I s l a n d I s l a n d Date November 17. 49 17.96 3. 02 -13. 75 -24.72 (. 3058) December 23. 49 14. 19 - 1. 18 -15.51 -20. 99 January 16. 66 8.29 1. 44 -13. 51 -12.88 March -37. 75 -18.04 -2. 14 20. 97 36. 97 A p r i l -11. 38 -12.95 -0. 10 12.91 11.53 I l l u m i n a t i o n l i g h t -7. 67 12. 54 -5. 28 -0.27 0.68 (.0390) dark 23. 00 -37.62 15. 84 0.82 -2.04 P o p u l a t i o n 0-1.50 — — — — — — S i z e 1.50-3.00 26. 47 -16.78 - 1. 21 -24. 40 15.92 (1,000 3.00-4.50 32. 29 -10.26 -2. 30 -33. 03 13.29 geese) 4.50-7.00 -16. 20 5. 98 1. 01 8.53 0.68 (.2149) >7.00 1. 08 0. 57 -0. 05 8.35 -9.95 T i d e low d u r i n g S t a t u s d a y l i g h t -3. 27 -4.76 0. 83 6.54 0.67 (.0961) low at nig h t 5. 81 8. 46 - 1. 48 -11.60 -1.19 Hunting open -29. 3 3 2 9.47 3. 32 -20. 31 16. 86 Season c l o s e d 20. 53 -20.63 -2. 32 14. 22 -11. 80 (.2206) (Ge n e r a l i z e d E t a 2 ) G e n e r a l i z e d R*=.4904 49 Table (VII) - C l a s s i f i c a t i o n Matrix - an a p o s t e r i o r i assignment of p r e d i c t i o n s f o r the a n a l y s i s of d i s t r i b u t i o n PREDICTORS Brunswick R e i f e l Outer Lulu Sea T o t a l P o i n t Refuge I s l a n d s I s l a n d I s l a n d Brunswick Poi n t 81.03 5. 17 0.0 13.79 0.0 58 R e i f e l Refuge 5.88 94.12 0.0 0.0 0.0 34 ACTUAL Outer I s l a n d s 62.50 37.50 0.0 0.0 0.0 8 Lulu I s l a n d 42.86 0.0 0.0 57.14 0.0 28 Sea I s l a n d 12.50 0.0 0.0 62.50 25.00 8 T o t a l 67 38 0 29 2 136 50 Table (VIII) - V a r i a b l e Response P r o f i l e s : c o e f f i c i e n t s of the MNA model f o r snow goose d i s t r i b u t i o n with r e s p e c t t o rhizome d e n s i t y PREDICTOR CATEGORIES RHIZOME DENSITY (g. VARIABLES 0-150 150-300 >300 Date November 20. 98 7.23 -13.75 (.3611) December 13. 01 2.50 -15.51 January 9. 74 3.78 -13.51 March -20. 18 -0.78 20.97 A p r i l -13. 05 0. 14 12.91 I l l u m i n a t i o n l i g h t 7. 26 -6.98 -0.27 (.0048) dark -21. 77 20.95 0.82 P o p u l a t i o n S i z e 1.50-3.00 -17. 99 43.39 -24.40 (1,000 geese) 3.0 0-4.50 -12. 55 45.5 8 -33.03 (.2771) 4.50-7.00 6. 99 - 15.52 8.53 >7.00 0. 51 -8.87 8.35 Tide Status low during (. 1327) d a y l i g h t -3. 93 -2.60 6.54 low at nig h t 6. 98 4.62 -11.60 Hunting Season open 3 2. 78 -12.47 -20.31 (.3 266) c l o s e d -22. 95 8.73 14.22 (G e n e r a l i z e d E t a 2 ) G e n e r a l i z e d R 2=.5112 Table (IX) - C l a s s i f i c a t i o n Matrix - an a p o s t e r i o r i assignment of p r e d i c t i o n s f o r the a n a l y s i s of snow goose d i s t r i b u t i o n with r e s p e c t to rhizome d e n s i t y ACTUAL PREDICTED <150 150-300 >300 T o t a l <150 100.0 0.0 0.0 42 150-300 18. 18 63.64 18.18 66 >300 0.0 46. 43 53. 57 28 T o t a l 54 55 27 136 51 5.4 DISCUSSION Habitat s e l e c t i o n i s a process by which animals r e s t r i c t t h e i r a c t i v i t i e s t o p a r t i c u l a r areas i n an attempt to maximize t h e i r o p p o r t u n i t i e s f o r s u r v i v a l . D i s t r i b u t i o n of i n d i v i d u a l s w i t h i n a given h a b i t a t i s i n f l u e n c e d by f a c t o r s s i m i l a r to those i n v o l v e d i n h a b i t a t s e l e c t i o n and may be c o n s i d e r e d a b e h a v i o u r a l phenomenon i n v o l v i n g s t i m u l i and responses. Although the s t i m u l i d i r e c t l y i n f l u e n c i n g h a b i t a t c h o i c e may be only i n d i r e c t l y c o r r e l a t e d with h a b i t a t s u i t a b i l i t y , i t i s the s u i t a b i l i t y i t s e l f which i s the b a s i c determinant of s p a c i a l occupation* Thus, the r e l a t i v e s u i t a b i l i t i e s o f d i f f e r e n t h a b i t a t s give r i s e to h a b i t a t s e l e c t i o n pressures which, u l t i m a t e l y , determine d i s t r i b u t i o n w i t h i n the h a b i t a t ( F r e t w e l l and Lucas, 1970). The mechanisms by which r e c o g n i t i o n of a s u i t a b l e h a b i t a t and d i s p e r s a l w i t h i n i t are accomplished d i f f e r markedly between s p e c i e s . However, i t i s g e n e r a l l y agreed that d i s t r i b u t i o n i s a s t o c h a s t i c f u n c t i o n of the i n t e r a c t i o n s between the u l t i m a t e and proximate f a c t o r s i n f l u e n c i n g h a b i t a t s e l e c t i o n . In g e n e r a l , u l t i m a t e determinants of behaviour are those f a c t o r s f a v o u r i n g n a t u r a l s e l e c t i o n o f a p a r t i c u l a r response. In the case of d i s p e r s a l throughout the winter h a b i t a t , the problem of food a c q u i s i t i o n may assume t h i s r o l e . Proximate determinants are those which d i r e c t l y e l i c i t the d i s c r i m i n a t o r y 52 behaviour. In t h i s study they would i n c l u d e t r a d i t i o n , s o c i a l i n t e r a c t i o n s , predator and hunter avoidance and p r o t e c t i o n from extremes of weather. As a r u l e occupied h a b i t a t s c o n t a i n an ample supply of food {Andrewartha and B i r c h , 1954). When food i s i n abundance proximate f a c t o r s may e x e r t the s t r o n g e s t i n f l u e n c e on d i s p e r s a l . In a d d i t i o n , they may impose immediate c o n s t r a i n t s by a c t i n g as p e r i p h e r a l sensory f i l t e r s . As such, they may e i t h e r l i m i t or enhance the p e r c e p t i o n of c e r t a i n environmental s t i m u l i , thereby a l t e r i n g the p r o b a b i l i t y and manner i n which those s t i m u l i w i l l be p e r c e i v e d ( K l o p f e r and Hailman, 1 965) i Under these c o n d i t i o n s , the r o l e of food abundance would not be of primary importance. However, when environmental c o n d i t i o n s begin to l i m i t the a b i l i t y o f b i r d s to o b t a i n s u f f i c i e n t q u a n t i t i e s of food e i t h e r through d i s e a s e (Burton, 1960), unseasonably high t i d e s ( E i n a r s e n , 1955), snow cover (G. Markgren, 1963; Owen, 1972), or overcrowding (Andrewartha, 1963), food a c q u i s i t i o n i t s e l f w i l l s t i m u l a t e and d i c t a t e d i s p e r s a l p a t t e r n s . Food s u p p l i e s then become of c r i t i c a l importance. I t i s w e l l documented that when faced with unfavourable f e e d i n q c o n d i t i o n s snow qeese w i l l d e s e r t an area completely (Howard, 1940; Lynch et a l . , 1947; Dzubin, 1965). D i s t r i b u t i o n w i t h i n the winter h a b i t a t may thus be c o n s i d e r e d a product of the food supply, augmented by the 53 dynamic i n t e r a c t i o n s of s o c i a l s t i m u l a t i o n ; predator and hunter avoidance, t r a d i t i o n and p r o t e c t i o n from extremes of weather. 5.4.1 Food Supply. The importance of food abundance i n determining the s p a t i a l o r i e n t a t i o n of waterfowl w i t h i n a given h a b i t a t has been c l e a r l y i l l u s t r a t e d i n the l i t e r a t u r e , abnormal f o r a y s i n t o upland p a s t u r e s by otherwise a g u a p h i l i c European and P a c i f i c brant during p e r i o d s of food shortages exemplify the short term response (Burton, 196 1; E i n a r s e n , 1965). Black duck d i s t r i b u t i o n along the shores of the Pendobscot e s t u a r y has been d i r e c t l y r e l a t e d to amphipod abundance d e s p i t e c l o s e proximity to b u i l d i n g s and roads, and the absence of p r o t e c t i o n from extreme weather c o n d i t i o n s (Hartman, 1963). D i s t r i b u t i o n of snow geese i n L o u i s i a n a and eas t e r n Texas was r e p o r t e d l y governed by l o c a l s u p p l i e s of p r e f e r r e d food p l a n t s (Lynch et a l . , 1947). U n f o r t u n a t e l y , the absolute abundance of a p a r t i c u l a r food item does not o r d i n a r i l y r e f l e c t i t s importance to the b i r d s . I t i n d i c a t e s nothing about the n u t r i t i o n a l q u a l i t y nor does i t imply a l e v e l of a v a i l a b i l i t y . In many cases, e s p e c i a l l y when the d i e t i s h i g h l y v a r i e d and the b i r d s are able t o switch r a p i d l y from one food to another, the absolute q u a n t i t y of any s i n g l e food does not p r o v i d e much u s e f u l i n f o r m a t i o n a t a l l . However, i t was found t h a t the d i e t o f snow geese on 54 the F r a s e r D e l t a c o n s i s t e d almost e n t i r e l y of the rhizomes of S c i r p u s americanus and S c i r p u s paludosus. Because of t h e i r monophagus h a b i t s , the importance of t h i s f o o d item may be s a f e l y assumed high. In t h i s s i t u a t i o n where a s i n g l e food i s p r e f e r r e d to a i l o t h e r s i t s r e l a t i v e d e n s i t y may i n f l u e n c e d i s t r i b u t i o n throughout an otherwise uniform h a b i t a t . N u t r i t i o n a l g u a l i t y i s a d i f f i c u l t parameter both to measure and d e f i n e and w i l l be d e a l t with i n more d e t a i l i n a subsequent s e c t i o n . S u f f i c e i t to say that snow goose d i s t r i b u t i o n was analyzed with r e s p e c t to rhizome crude p r o t e i n l e v e l s . The weak r e l a t i o n s h i p s obtained i n d i c a t e d that rhizome crude p r o t e i n l e v e l s were not a major f a c t o r c o n t r i b u t i n g t o the d i s p e r s a l of snow geese over the estuary. Rhizome a v a i l a b i l i t y i s a complex product of absolute d e n s i t y , water depth, absence of d i s t u r b a n c e , s o i l c o n s i s t e n c y and the anatomical and p h y s i o l o g i c a l c a p a b i l i t i e s of the geese. Because of the nature of the area, changes i n water depth and s u b s t r a t e c h a r a c t e r i s t i c s are e s s e n t i a l l y uniform over the f o r e s h o r e and the grubbing a b i l i t i e s of snow geese are u n l i k e l y t o d i f f e r from one part of the marsh to another. Rhizome d e n s i t y , t h e r e f o r e , being the only measurable v a r i a b l e to change, was assumed r e p r e s e n t a t i v e of the e f f e c t i v e food supply a t each l o c a t i o n . 55 The main p o i n t to be considered i n a n a l y z i n g d i s t r i b u t i o n i s t h a t of o u t l i n i n g h a b i t a t s u i t a b i l i t y . To f u l l y understand t h i s aspect o f snow goose ecology i t may be necessary to know how and t o what degree environmental a t t r i b u t e s are p e r c e i v e d by the geese ( K l o p f e r and Hailman, 1965). T h i s type of a n a l y s i s would r e q u i r e d e t a i l e d p h y s i o l o g i c a l s t u d i e s on snow goose sensory c a p a b i l i t i e s . E x tensive e t h o l o g i c a l i n v e s t i g a t i o n s of p r e c i s e , b e h a v i o u r a l responses t o p a r t i c u l a r s t i m u l i would a l s o be needed. This approach would i n v o l v e work f a r beyond the scope o f the present study. I t was f e l t that a more pragmatic g a t h e r i n g of u s e f u l i n f o r m a t i o n c o u l d be accomplished by a t t a c k i n g the problem at a d i f f e r e n t l e v e l . Snow goose d i s t r i b u t i o n was recorded and analyzed with r e s p e c t to s e v e r a l environmental parameters. From these, causes of p a r t i c u l a r d i s p e r s a l p a t t e r n s were i n f e r r e d . During winter d i s p e r s a l p a t t e r n s were recorded under c o n d i t i o n s of both r e s t r i c t e d and f r e e s i t e c h o i c e . When compelled to remain w i t h i n the boundaries of the r e f u g e , f e e d i n g i n t e n s i t y was low. Whereas, when geese were f r e e to s e l e c t any p o r t i o n of the f o r e s h o r e , d i s p e r s a l r a p i d l y ensued to those areas having the g r e a t e s t recorded f e e d i n g i n t e n s i t i e s . C o n s i d e r i n g that feeding a c t i v i t y was g r e a t e s t at Brunswick P o i n t and L u l u I s l a n d (Section 6.3) i t i s 56 reasonable t o assume that the u n d e r l y i n g f a c t o r l e a d i n g to the s e l e c t i o n of these areas was the r e l a t i v e d i f f e r e n c e s i n food a c q u i s i t i o n e f f i c i e n c y as r e f l e c t e d by v a r i a t i o n s i n rhizome d e n s i t y between marsh u n i t s . To approach the problem from a l e s s o b l i q u e angle d i s t r i b u t i o n p a t t e r n s of the geese were analyzed d i r e c t l y with r e s p e c t to a b s o l u t e rhizome d e n s i t y . The r e s u l t s of the MNA a n a l y s i s i n d i c a t e d a more pronounced s h i f t away from areas of low food abundance when f r e e s i t e c h o i c e was permitted. Regardless of the proximate s t i m u l i i n v o l v e d , i t i s b e l i e v e d t h a t the d i s p e r s a l and the r e s u l t a n t d i s t r i b u t i o n p a t t e r n of snow geese was an i n d i r e c t response to more fa v o u r a b l e f e e d i n g c o n d i t i o n s . Support f o r the proposed s u b l i m i n a l r e g u l a t i o n of d i s t r i b u t i o n by food s u p p l i e s comes from the f a c t t h a t rhizomes are e s s e n t i a l l y i n v i s i b l e . N either rhizome d e n s i t y nor f e e d i n g e f f i c i e n c y can be p e r c e i v e d by v i s u a l i n s p e c t i o n of the marsh alone. Proximate f a c t o r s must t h e r e f o r e i n i t i a l l y d i c t a t e d i s p e r s a l p a t t e r n s before any knowledge of the present s t a t u s of the food resource can be detected. Only subsequent to f e e d i n q experience by at l e a s t a few members of the f l o c k can food supply per se i n f l u e n c e d i s t r i b u t i o n . T h i s behaviour may a l s o help t o e x p l a i n the apparent r e t i c e n c e of the geese to enter c u l t i v a t e d f i e l d s . Presumably once they are f o r c e d i n t o the these f i e l d s , e i t h e r from d i s t u r b a n c e , h a b i t a t 57 a t t r i t i o n or d i s p e r s a l of s m a l l groups, i s i s p o s s i b l e that new behaviour p a t t e r n s may be formed which w i l l i n c r e a s e the number of geese f l i g h t i n g i n t o neighbouring p a s t u r e s . F i e l d - f e e d i n g , with i t s a s s o c i a t e d problems, may then be expected t o i n c r e a s e each year as more and more b i r d s l e a r n the d e s i r a b i l i t y of feeding on c u l t i v a t e d crops. When the r e s t of the h a b i t a t h a b i t a t i s e s s e n t i a l l y uniform i n most measurable a t t r i b u t e s and proximate f a c t o r s are not i n v o l v e d , d i s p e r s a l w i t h i n the h a b i t a t i s i n f l u e n c e d p r i m a r i l y by those v a r i a b l e s d i r e c t l y r e l a t e d to food a c q u i s i t i o n , of which the d e n s i t y of three-square b u l l r u s h rhizomes appears t o be a t l e a s t p a r t i a l l y r e s p o n s i b l e . 5.4.2 Predator Avoidance Roostinq s i t e s have never been i m p l i c a t e d as l i m i t i n g f a c t o r s f o r w i n t e r i n g waterfowl ( A l l a n , 1956). However, the s e l e c t i o n of a s a f e r e s t i n g area appears to i n f l u e n c e d i s p e r s a l p a t t e r n s w i t h i n the h a b i t a t . Although i t has been recorded t h a t snow geese w i l l r e g u l a r l y f l y up t o 30 m i l e s (48 km) per day to l o c a t e s u i t a b l e f e e d i n g grounds (Glazner, 1946) i t was observed by Bossenaaier and M a r s h a l l (1958) that geese i n g e n e r a l feed as c l o s e to t h e i r r o o s t i n g s i t e as p o s s i b l e . In t h i s l i g h t i t i s understandable why the geese ceased to u t i l i z e R e i f e l Refuge subsequent t o the c l o s u r e of huntinq season. Snow geese r e q u i r e open areas with unhindered v i s i b i l i t y i n a l l d i r e c t i o n s , as do most s p e c i e s of geese. 58 Optimal r e s t i n g s i t e s are provided at the d i u r n a l low t i d e by every marsh u n i t . Movements between marshes are thus minimized a f t e r the c l o s e of hunting season and a more even balance between f e e d i n g and s l e e p i n g i n t e n s i t y i s e s t a b l i s h e d at each. P r o t e c t i o n from predators may then assume a higher s u r v i v a l value than s h e l t e r from the p r e v a i l i n g weather c o n d i t i o n s encountered on the barren mud and sand f l a t s . S i n c e s u i t a b l e r o o s t i n g s i t e s are a v a i l a b l e at a l l marsh u n i t s , the e f f e c t of predator avoidance may have a major d i u r n a l e f f e c t on goose d i s t r i b u t i o n . Both R e i f e l Refuge and the open waters of Georgia S t r a i t a f f o r d adequate p r o t e c t i o n d u r i n g hunting season. The observance t h a t snow geese p r e f e r the refuge to open water may support the b e l i e f t h a t p r o t e c t i o n from land-bound predators i s not of great importance i n the seasonal d i s t r i b u t i o n of snow geese. On the other hand, t h i s p a s s i v e predator avoidance technique may s t r o n g l y r e g u l a t e d i u r n a l d i s t r i b u t i o n . Once a r e s t i n g s i t e has been chosen, e i t h e r on land or open water, the geese form very l a r g e , c l o s e l y spaced f l o c k s . The c r e a t i o n of l a r g e f l o c k s i n open areas i s presumably an evolved mechanism t o provide adequate p a s s i v e p r o t e c t i o n from t h e i r n a t u r a l enemies. F l o c k i n g behaviour i s a common predator avoidance mechanism of b i r d s , p a r t i c u l a r l y of g r e g a r i o u s s p e c i e s such as snow geese, and may f u n c t i o n s u c c e s s f u l l y i n both the 59 a c t i v e and p a s s i v e defence o f the f l o c k . S i m i l a r crowding mechanisms are s u c c e s s f u l l y u t i l i z e d by c e r t a i n s p e c i e s of f i s h and by many of the l a r g e ungulates of the A f r i c a n savanahs (Kruuk, 1972). The success o f f l o c k i n g behaviour was emphasized by Ospenski (1963) who re p o r t e d t h a t p r e d a t i o n was only a f a c t o r at the outer edges of the l a r g e c o l o n i e s and i n the s m a l l e r s u b f l o c k s of breeding snow geese on Wrangel I s l a n d . I t has been r e p o r t e d elsewhere that geese p r e f e r to f l y to open water f o r r e s t and escape (Howard, 1940; G. Harkgren, 1963). P r i o r t o the establishment of R e i f e l Refuge i n 1967, snow geese t r a d i t i o n a l l y gathered i n l a r g e r a f t s f a r o f f s h o r e d u r i n g d a y l i g h t (Racey, 1924). Since then the geese have g r a d u a l l y become aware of the refuge and at present they respond to hunting pressure by seeking asylum w i t h i n i t s p r o t e c t e d marshes. Some r a f t i n g up s t i l l does occur, e s p e c i a l l y d u r i n g the l a t t e r part of December and e a r l y January. In response to the c l o s e of goose hunting and maintenance o f duck hunting snow geese formrd t i g h t o f f - s h o r e f l o c k s between Brunswick P o i n t and the superport j e t t y . U n f o r t u n a t e l y , the s m a l l number of o b s e r v a t i o n s made under these c o n d i t i o n s p r e c l u d e s f u r t h e r s p e c u l a t i o n . 5.4.3 Hunting Pressure Just as hunters e l i c i t from snow geese d i f f e r e n t a c t i v e escape responses from those caused by n a t u r a l p r e d a t o r s , so 60 t h e i r a d a p t a t i o n s f o r p a s s i v e hunter avoidance d i f f e r from those of p a s s i v e predator avoidance. Because of the h i g h l y alarming image presented by hunters ( s e c t i o n 7.3) a d i f f e r e n t , more s p e c i a l i z e d form of p a s s i v e avoidance i s u t i l i z e d . With r e s p e c t to hunters and hunting p r e s s u r e , not a l l marshes provide equal p r o t e c t i o n . The r e f u g e a f f o r d e d almost complete i s o l a t i o n from hunters while the p o t e n t i a l f o r harassment by hunters was present at a l l other segments of the f o r e s h o r e . Hunting p r e s s u r e by i t s e l f was the second most important v a r i a b l e of those measured i n f l u e n c i n g snow goose d i s t r i b u t i o n . I t was r e s p o n s i b l e f o r e x p l a i n i n g more than 22 percent of the observed v a r i a n c e . Although L u l u I s l a n d and Brunswick P o i n t were c l e a r l y p r e f e r r e d i n a f r e e - c h o i c e s i t u a t i o n , hunting pressure prevented geese from u t i l i z i n g these areas and c o n c e n t r a t e d them on the refuge, an area of comparatively l i t t l e value f o r f e e d i n g . Proximate f a c t o r s u s u a l l y a f f e c t b e h a v i o u r a l responses i n d i r e c t l y by a l t e r i n g the p e r c e p t i o n of other environmental s t i m u l i ( K l o p f e r and Hailman, 1965). However, hunting pressure may f u n c t i o n by a l t e r i n g b e h a v i o u r a l responses d i r e c t l y r a t h e r than changing the p e r c e p t i o n of other s t i m u l i because geese s t i l l attempt t o u t i l i z e favoured areas d u r i n g hunting season. Once hunting i s removed they may r e t u r n almost immediately. 61 I t may be advantageous f o r geese to maintain a c l e a r p e r c e p t i o n of the areas from which they are being kept to ensure a more r a p i d and e f f i c i e n t r e - i n v a s i o n of f a v o u r a b l e areas once hunting has ceased. T r a d i t i o n would appear to play a r o l e i n such cases. Hunting pressure, t h e r e f o r e , may be more p r o p e r l y c o n s i d e r e d a b e h a v i o u r a l response f i l t e r than a sensory f i l t e r . In the absence of hunting pressure geese were able to e x e r c i s e t h e i r i n a t e p r e f e r e n c e s and d i s t r i b u t e themselves a c c o r d i n g l y . T h e r e f o r e , a c l e a r e r p i c t u r e of the i n f l u e n c e of the other proximate f a c t o r s was o b t a i n e d when the season was c l o s e d . 5.4.4 P o p u l a t i o n s i z e R e s u l t s from the a n a l y s i s i n d i c a t e d that a change i n p o p u l a t i o n s i z e was the t h i r d most important f a c t o r a f f e c t i n g snow goose d i s t r i b u t i o n . I t i s not obvious on f i r s t i n s p e c t i o n how p o p u l a t i o n s i z e may a f f e c t space u t i l i z a t i o n but the f o l l o w i n g e x p l a n a t i o n i n v o l v i n g the s o c i a l i n t e r a c t i o n s and t r a d i t i o n s o f d i f f e r e n t groups w i t h i n the t o t a l f l o c k may be v a l i d . Snow geese are extremely g r e g a r i o u s b i r d s . They are known to e x h i b i t s t r o n g s o c i a l t i e s to a p a r t i c u l a r group of b i r d s by m a i n t a i n i n g t i g h t l y k n i t a s s o c i a t i o n s above that of the f a m i l y u n i t . T h i s s u b - f l o c k or group t e n a c i t y has been documented f o r members of the genus L a r i d a e . In response to 62 colony d i s r u p t i o n t e r n s were shown t o re - n e s t i n a d i f f e r e n t area adjacent to the same neighbours t h a t they had possessed p r i o r t o the d i s t u r b a n c e ( M c N i c o l l , 1975). S i m i l a r group adherence responses may e x p l a i n the f i d e l i t y of geese to s p e c i f i c breeding s u b - f l o c k s even though e x t e n s i v e mixing occurs on the w i n t e r i n g grounds. From neck-banding s t u d i e s conducted i n the USSR i t i s now c l e a r t h a t a l l of the snow geese w i n t e r i n g on the Fraser Delta come from Mrangel I s l a n d (Sladen, p e r s . comm.). Rapid changes i n the po p u l a t i o n s i z e on the fo r e s h o r e i n d i c a t e c o n t i n u a l inward and outward movments of l a r g e groups of b i r d s at one time. I t i s , t h e r e f o r e , f e a s i b l e to expect that s u b - f l o c k a l l e g e n c e s are maintained on the wi n t e r i n g grounds and t h a t each s u b - f l o c k i s exposed to somewhat d i f f e r e n t e x p e r i e n c e s . As a r e s u l t c o n d i t i o n e d responses to p a r t i c u l a r segments o f the marsh are l i k e l y to d i f f e r between s u b - f l o c k s , l e a d i n g t o the establishment of d i s t i n c t p a t t e r n s of f o r e s h o r e u t i l i z a t i o n . The p r e ference of c e r t a i n areas over o t h e r s by d i f f e r e n t s u b - f l o c k s may e x p l a i n the observed s e g r e g a t i o n of the p o p u l a t i o n i n t o two separate f l o c k s during March and A p r i l . Again, the maintenance of s t r i c t , g r o u p - s p e c i f i c bonds may shed some l i g h t on the r e g u l a t o r y e f f e c t that changes i n p o p u l a t i o n s i z e may have on d i s p e r s a l p a t t e r n s . It i s p o s s i b l e t h a t any one of the s u b - f l o c k s c o n s i s t i n g of approximately 5,000 i n d i v i d u a l s may c o n s t i t u t e the main 63 f l o c k of winter r e s i d e n t s on the Fraser D e l t a . An i n c r e a s e above t h i s number may i n d i c a t e the i n f l u x of a d i f f e r e n t s u b - f l o c k , which, s u b j e c t to separate e x p e r i e n c e s and t r a d i t i o n s , u t i l i z e s a d i f f e r e n t segment of the f o r e s h o r e . T h i s e x p l a n a t i o n i s supported only by very l i m i t e d neck-band data but i s presented here i n l i e u of more r i g o u r o u s i n v e s t i g a t i o n s . 5.4.5 D i f f e r e n t i a l m i g r a t i o n The presence or absence of members of the same s p e c i e s c o n s t i t u t e s a meaningful f e a t u r e of the environment. For many t e r r i t o r i a l s p e c i e s , t h e presence o f c o n s p e c i f i c s l e a d s to a r e d u c t i o n i n l o c a l d e n s i t i e s , whereas with g r e g a r i o u s s p e c i e s such as sea ducks ( N i l s s o n , 1972) and g u l l s (Frings et a l . , 1955) t h e i r presence i n c r e a s e s the a t t r a c t i v e n e s s of a p a r t i c u l a r area. In f a c t , K l o p f e r and Hailman (1965) reported t h a t t h e most evident s i n g l e f a c t o r r e s p o n s i b l e f o r a t t r a c t i n g a g u l l t o i t s c o r r e c t h a b i t a t i s the presence of other g u l l s . Laughing g u l l s u t i l i z e only a s m a l l p o r t i o n of t h e i r h a b i t a t f o r n e s t i n g each year, even though nearby s i t e s appear i d e n t i c a l l y s u i t e d . These s i t e s may have been used e i t h e r p r e v i o u s to or subseguent t o the present s i t e without a p r e d i c t a b l e p a t t e r n of r e p e t i t i o n . I t was found t h a t only one of the a v a i l a b l e colony s i t e s i s occupied because the choice i s determined by those b i r d s e a r l i e s t to a r r i v e on the breeding grounds (Frings e t a l . , 1955). The presence of 64 these b i r d s then a t t r a c t s l a t e r a r r i v a l s . A s i m i l a r s i t u a t i o n i s proposed f o r t h e e x c l u s i v e use of Brunswick Point by snow geese during the evenings of October, November and December. D i f f e r e n t i a l m i g r a t i o n s are r e p o r t e d to occur with snow geese (White and Lewis, 1937). F i r s t a r r i v a l s i n October are u s u a l l y s i n g l e a d u l t s and p a i r s without young. The wariness of a d u l t geese with no young t o care f o r i s l e s s than among a d u i t s with a f a m i l y (Owen, 1972). F i r s t a r r i v a l s are i n c l i n e d to s e t t l e i n areas known to be o f high q u a l i t y from past experience. Since unmated a d u l t s do not have the same d r i v e s to migrate north i n s p r i n g they are o f t e n the l a s t to l e a v e i n A p r i l and, t h e r e f o r e , would l i k e l y have spent at l e a s t the l a s t few days at Brunswick P o i n t . Since mated a d u l t s with young are o f t e n found to migrate l a t e r i n t h e year than do non-breeding a d u l t s those without young would be f i r s t to a r r i v e on the F r a s e r . Upon t h e i r a r r i v a l i n autumn, i t i s probable t h a t they would r e t u r n i n i t i a l l y t o a f a m i l i a r segment of the f o r e s h o r e , i f only f o r a s h o r t time. Hunting pressure d u r i n g the day f o r c e s the geese away from Brunswick P o i n t . However, fe e d i n g success may r e i n f o r c e a d e s i r e to r e t u r n at n i g h t . Rapidly a t r e n d would be e s t a b l i s h e d . T h i s f l i g h t p a t t e r n may then be passed on to new a r r i v a l s through empathic l e a r n i n g . T h e r e f o r e , the s e l e c t i o n of f e e d i n g and r o o s t i n g s i t e s would be based on the s u c c e s s f u l (and p o s s i b l y 65 t r a d i t i o n a l ) experiences of the f i r s t geese to a r r i v e on the d e l t a . S o c i a l s t i m u l a t i o n may, t h e r e f o r e , a t l e a s t p a r t i a l l y e x p l a i n the apparent preference of Brunswick P o i n t over L u l u I s l a n d with r e s p e c t t o n o c t u r n a l f e e d i n g f l i g h t s d u r i n g the hunting season. 5.4.6 T r a d i t i o n T r a d i t i o n i s a term used to express the continued b e h a v i o u r a l responses t o p r e v i o u s l y encountered s t i m u l i , although d i f f i c u l t to q u a n t i f y , t r a d i t i o n has been i m p l i c a t e d as a c r i t i c a l i n f l u e n c e i n h a b i t a t s e l e c t i o n by b i r d s , e s p e c i a l l y Anseriformes (Cooch, 1958; F r e t w e l l and Lucas, 1970). K l o p f e r and Hailman (1965) s t a t e d that experience i s a major f a c t o r i n the s e l e c t i o n of s u i t a b l e feeding areas by g u l l s . Wild geese show a s t r o n g tendency to r e t u r n year a f t e r year to the same breeding and w i n t e r i n g grounds (Boyd, 1955; Dzubin, 1974). That snow geese r e t u r n each year t o the r e l a t i v e l y s m a l l e s t u a r i n e marshes on the Fr a s e r R i v e r f o r e s h o r e i l l u s t r a t e s the str o n g t r a d i t i o n a l t i e s formed i n response to f a v o u r a b l e c o n d i t i o n s . T r a d i t i o n i n c l u d e s both s h o r t term c o n d i t i o n i n g , such as that i n v o l v e d i n e s t a b l i s h i n g the above-mentioned n o c t u r n a l f l i g h t s between Brunswick P o i n t and R e i f e l Refuge, and long term h a b i t f o r m a t i o n , such as breeding-ground f i d e l i t y . Long term t r a d i t i o n s of h a b i t a t u t i l i z a t i o n may be c r e a t e d i n response to environmental c o n d i t i o n s of a 66 previous time. They may be maintained f o r many ye a r s , even a f t e r those s t i m u l i o r i g i n a l l y evoking the responses have long s i n c e disappeared. An example would be the repeated f l i g h t s of snow geese to Iona I s l a n d . P r i o r t o the f i l l i n g i n o f the l o n a I s l a n d -Sea I s l a n d causeway i n 196 1 and c o n s t r u c t i o n of the Iona I s l a n d j e t t y snow geese made e x t e n s i v e use of t h i s segment of the f o r e s h o r e (Barnard, pers. comm.). Over the past decade geese have been observed t o f l y r e g u l a r l y from other p a r t s of the marsh towards Iona I s l a n d . Upon r e a c h i n g the now diked and f i l l e d - i n beaches of the i s l a n d they would break formation, f l y i n a l l d i r e c t i o n s , and f i n a l l y r e t u r n southward a f t e r f u t i l e attempts to l a n d . T h i s h a b i t had been observed r e p e a t e d l y up u n t i l the l a s t few y e a r s . C o n s i d e r i n g the expected l o n g e v i t y of snow geese (up to 17 years i n c a p t i v i t y ) i t i s presumed t h a t the t r a d i t i o n s were maintained i n the e l d e s t members of the f l o c k u n t i l e i t h e r these t r a d i t i o n s had been superseded by other c o n d i t i o n e d responses or the i n d i v i d u a l s m a i n t a i n i n g these t r a d i t i o n s had died. I t i s w e l l known t h a t ducks w i l l attempt to land i n apparently u n s u i t a b l e f i e l d s i n response to the a e r i a l p e r c e p t i o n of o l d water courses l o n g - s i n c e f i l l e d i n . However, no such a t t r a c t i n g s t i m u l i are present a t Iona I s l a n d . An e x p l a n a t i o n other than t r a d i t i o n i s d i f f i c u l t to formulate. 67 The g e n e r a l e f f e c t of t r a d i t i o n , e s p e c i a l l y i n l o n g -l i v e d migratory s p e c i e s such as geese, would appear t o have d e f i n i t e s u r v i v a l advantage- T r a d i t i o n i t s e l f may have been most u s e f u l i n t h e r e c o g n i t i o n of p r e v i o u s l y l e a r n e d landmarks, thus ensuring proper migratory pathways. In a d d i t i o n , c o n d i t i o n e d a t t r a c t i o n to areas a s s o c i a t e d with rewarding experiences and avoidance of those areas evoking f e a r or unrewarding experiences i n c r e a s e s h a b i t a t s e l e c t i o n e f f i c i e n c y . T h i s aspect i s of g r e a t e s t importance upon a r r i v a l at the n e s t i n g grounds where n e s t s i t e s e l e c t i o n must be completed soon a f t e r a r r i v a l . I t i s t h e r e f o r e l i k e l y that t r a d i t i o n i s a l s o important in d i s t r i b u t i n g geese throughout t h e i r w i n t e r i n g grounds. Each year i n e i t h e r mid-January o r e a r l y February the e n t i r e snow goose p o p u l a t i o n leaves the F r a s e r , only to re t u r n i n l a t e February, e a r l y March. The reason f o r t h i s r e g u l a r l a t e - s e a s o n m i n i - m i g r a t i o n i s not known but has been a t t r i b u t e d v a r i o u s l y to low environmental temperatures and ex c e s s i v e hunting pressure. N i l s s o n (1972) found that although the highest d i v i n g duck feeding i n t e n s i t i e s were recorded i n the c o l d e s t months, minimum d a i l y temperature d i d not appear to e x e r t an e f f e c t . The poor c o r r e l a t i o n between minimum d a i l y temperature and goose d i s t r i b u t i o n i n the present study i n d i c a t e s the absence of a d i r e c t temperature e f f e c t . Because hunting pressure i s at l e a s t as 68 i n t e n s e , i f not more, during November and e a r l y December when l a r g e numbers o f b i r d s are concentrated on the refuge, i t i s e q u a l l y d i f f i c u l t to accept t h a t e x c e s s i v e hunter caused harrassment i s the primary i n s t i g a t o r of departure. The cause of t h i s l a t e winter m i g r a t i o n unknown. The d e s t i n a t i o n of these geese i s thought t o be Skagit f l a t s because i t i s the only other snow goose f l o c k known to winter north of C a l i f o r n i a . However, i t has been o f t e n observed by members of the Hashington State game department that decreases i n the s i z e of the F r a s e r f l o c k have not been met with compensatory i n c r e a s e s i n the S k a g i t f l o c k and v i c e versa ( J e f f r e y , pers. comm.). F o r t u n a t e l y , the neck-banding program i n i t i a t e d on Wrangel I s l a n d i n i n 1974 has solved the problem. P a r t i c u l a r neck banded geese have been observed both on the S k a g i t and F r a s e r marshes, c o n f i r m i n g that at l e a s t some members of these two f l o c k s are indeed of a d i s c r e t e p o p u l a t i o n (Sladen, pers. comm.). Assuming t h a t the d i s c r e p e n c i e s i n estimated p o p u l a t i o n s i z e are caused by the almost t o t a l absence o f r e g u l a r counts on the Fraser Delta i t i s most l i k e l y that a l l of the b i r d s do form a s i n g l e , l a r g e f l o c k with much int e r c h a n g e between the two areas. 69 6^0 DIORNAL ACTIVITY BUDGETS 6.1 I n t r o d u c t i o n In the absence of a c t i v e d i s t u r b a n c e the d i u r n a l r o u t i n e of w i l d a n a t i n i d s g e n e r a l l y c o n s i s t s of a more or l e s s r e g u l a r p a t t e r n of f e e d i n g and r e s t i n g behaviour i r r e g u l a r l y i n t e r s p e r s e d with l e s s f r e g u e n t d i s p l a y s of preening, f l i g h t and a l e r t n e s s . D e v i a t i o n s from the normal a c t i v i t y budget may profoundly a f f e c t energy uptake and expenditure, e s p e c i a l l y during c o l d weather. Because maintenance of p a r i t y between energy input and output i s c r i t i c a l f o r s u r v i v a l , measurements of changes i n a c t i v i t y p a t t e r n s may be u s e f u l i n d i c e s f o r monitoring the extent and e f f i c i e n c y of food resource u t i l i z a t i o n . S i m i l a r l y , a l t e r a t i o n s of the d i u r n a l rhythm may be u s e f u l i n d i c a t o r s of b e h a v i o u r a l a d a p t a t i o n s to changes i n e i t h e r h a b i t a t composition or s t r u c t u r e . Before a c l e a r statement of the r e l a t i o n s h i p between snow geese and t h e i r winter h a b i t a t can be proposed, i t i s necessary to i d e n t i f y the e f f e c t o f each environmental a t t r i b u t e on the manner i n which each marsh u n i t i s u t i l i z e d . The amount of time engaged i n o b t a i n i n g food and the l o c a t i o n s where f e e d i n g i s most i n t e n s e may be de r i v e d from r e c o r d s of the d i u r n a l a c t i v i t y p r o f i l e of f r e e - r a n g i n g geese under n a t u r a l c o n t i d i o n s . 70 The b a l a n c e between the a b i l i t y t o i n g e s t l a r g e q u a n t i t i e s o f food and t o s e l e c t a r e l a t i v e l y n u t r i t i o u s d i e t i s v e r y i m p o r t a n t w i t h b i r d s such as geese which, as a group, possess i n e f f i c i e n t d i g e s t i v e systems ( M a t t o c k s , 1971). D a i l y procurement o f t h i s d i e t i s most o f t e n r e g u l a t e d by t h e degree of i l l u m i n a t i o n (Bossenmaier and M a r s h a l l , 1958). However, o t h e r f a c t o r s such as a c t i v e d i s t u r b a n c e and r e g u l a r changes i n f o o d a v a i l a b i l i t y may a l t e r t h e d a i l y f e e d i n g r o u t i n e markedly., One c r i t i c a l f a c t o r c o n t r o l l i n g t h e l e v e l o f energy i n t a k e i s the e f f i c i e n c y of f e e d i n g i n r e l a t i o n to t h e amount of time a v a i l a b l e . T h i s " e f f e c t i v e f e e d i n g p e r i o d " , i n t u r n , i s d i r e c t l y r e l a t e d t o the s i z e , q u a l i t y , and a c c e s s i b i l i t y of the food r e s o u r c e . By m o n i t o r i n g d a i l y p a t t e r n s o f a c t i v i t y w i t h i n t h e c o n f i n e s o f a g i v e n h a b i t a t , i t may be p o s s i b l e to r e l a t e both d i u r n a l and s e a s o n a l v a r i a t i o n s i n t h e l e v e l of a c t i v i t y t o e i t h e r changes i n food a v a i l a b i l i t y , changes i n the b i o l o g i c a l demands of an organism i t s e l f , o r p o s s i b l y t o changes i n o t h e r parameters which may i n f l u e n c e t h e l e v e l of energy i n t a k e . Energy o u t p u t i s r e l a t e d t o the l e v e l of d a i l y a c t i v i t y , which . i n c l u d e s t h e energy used f o r s t a n d i n g , w a l k i n g , swimming, p r e e n i n g , f e e d i n g and f l y i n g and t o the maintenance of homeothermy. Of t h e s e a c t i v i t i e s f l i g h t i s the most energy i n t e n s i v e . I t has been c a l c u l a t e d t h a t the energy c o s t of b i r d f l i g h t ranges from 5 t o 14 times 71 Standard M e t a b o l i c Rate ( O t t e r , and LeFebvre, 1970). Ther e f o r e , to o b t a i n a reasonable estimate of the amount of energy expended i n a day i t i s necessary to q u a n t i f y the l e v e l of both " u n d i s t u r b e d " and " d i s t u r b e d " f l i g h t a c t i v i t y . In a d d i t i o n to measuring the amount of time per day a c t i v e l y engaged i n o b t a i n i n g food, i t i s e s s e n t i a l that those areas most i n t e n s i v e l y u t i l i z e d f o r feeding be determined. A g e n e r a l i z e d waterfowl winter range u s u a l l y i n c l u d e s at l e a s t two f u n c t i o n a l l y d i s t i n c t p a r t s , a f e e d i n g s i t e and a r o o s t i n g or l o a f i n g s i t e , and may a l s o have separate d r i n k i n g and g r i t - t a k i n g areas (Glazner, 1946). Because of the high m o b i l i t y of waterfowl there i s no n e c e s s i t y f o r these p o r t i o n s of the h a b i t a t t o be continuous. More o f t e n than not the winter range i s d i s j o i n t e d . Although the f o r e s h o r e marshes of the Fraser Delta may appear s t r u c t u r a l l y and v e g e t a t i o n a l l y s i m i l a r , the environment as perceived by the geese, the "Umwelt" of K l o p f e r and Hailman (1965), i s not n e c e s s a r i l y constant. I t f o l l o w s t h a t d i f f e r e n t p o r t i o n s of the f o r e s h o r e may be used more i n t e n s i v e l y f o r one a c t i v i t y than f o r o t h e r s . D e l i n e a t i o n of these areas may be f a c i l i t a t e d by r e c o r d i n g s of s p a t i a l l y and temporally d i s t i n c t group-a c t i v i t y p r o f i l e s . In other words, measurements of the dominant a c t i v i t y w i t h i n each p o r t i o n of the f o r e s h o r e may i n d i c a t e the r e l a t i v e importance of d i f f e r e n t segments of the h a b i t a t with r e s p e c t to i t s a b i l i t y to provide food. 72 s h e l t e r , g r i t and s a n c t i t y at d i f f e r e n t times of the year. 6.2 Methods Observations o f snow goose a c t i v i t y were c a r r i e d out during the p e r i o d from mid-November, 1974, to m i d - A p r i l , 1975. Data were c o l l e c t e d between the hours of 05:00 and 24:00 over 27 days. Regular o b s e r v a t i o n s were conducted using a s p o t t i n g Scope with a 20x40 power zoom o c u l a r . Counts of the number of b i r d s engaged i n each of the four major a c t i v i t i e s , r e s t i n g , f e e d i n g , preening, or a l e r t n e s s were recorded at ha l f - h o u r i n t e r v a l s . Each count c o n s i s t e d of 200 b i r d s . These sample groups were s e l e c t e d from four d i f f e r e n t segments of the f l o c k i n order to b e t t e r r e p r e s e n t the o v e r a l l a c t i v i t y p a t t e r n at that time. In order to o b t a i n a measure of a c t i v i t y during the evening, each marsh u n i t was v i s i t e d at d i f f e r e n t times between sunset and s u n r i s e . I t was p o s s i b l e , with the a i d of a n i g h t - v i s i o n scope, to i d e n t i f y the a c t i v i t y of those b i r d s w i t h i n about 25 to 50 m depending on the weather, the s c a t t e r i n g of the b i r d s and the a b i l i t y of the observer to remain hidden. A r e l a t i v e l y s m a l l amount of data on the night-ti m e a c t i v i t y of the geese thus was obtained. U n f o r t u n a t e l y , the n i g h t - v i s i o n scope was not a v a i l a b l e b e f o r e mid-December, so i n f o r m a t i o n on s p e c i f i c n o c t u r n a l 73 a c t i v i t y , was l i m i t e d f o r the most part to the second h a l f of the winter. Other data were recorded i n c l u d i n g estimates of f l o c k s i z e , l o c a l d i s t r i b u t i o n of the f l o c k , number of b i r d s a r r i v i n g and d e p a r t i n g and the number of s i n g l e and p a i r e d a d u l t s observed i n f l i g h t . Records were maintained regarding weather c o n d i t i o n s and g e n e r a l f l o c k behaviour i n response to v a r i o u s s t i m u l i . Approximate t i d e l e v e l s were c a l c u l a t e d f o r the c l o s e s t port of r e f e r e n c e (Sand Heads) from the Tables o f Tides and C u r r e n t s p u b l i s h e d by the Canadian Hydrographic S e r v i c e . For each a c t i v i t y p r o f i l e a l i s t of s i x environmental a t t r i b u t e s was recorded. A s s o c i a t i o n s between the major a c t i v i t y and each of these parameters were compared. Because problems of c o - l i n e a r i t y were encountered among c e r t a i n independent v a r i a b l e s , o n l y those r e p r e s e n t i n g t i d e h e i g h t , t i d a l a c t i o n and l o c a t i o n were u t i l i z e d i n the a n a l y s i s . A l l a n a l y t i c a l c a l c u l a t i o n s were performed using MNA and MCA from the O s i r i s I I I s t a t i s t i c a l package (Andrews and Messenger, 1 9 7 3 ) . MNA and MCA evaluated s i m i l a r , but not i d e n t i c a l a s p e c t s of the d i u r n a l a c t i v i t y p r o f i l e s . MNA was u t i l i z e d to t e s t f o r d i f f e r e n c e s i n the predominant group a c t i v i t y . Since behaviour was s u b j e c t to numerous extraneous i n f l u e n c e s not measured i n the present study, t h e l e v e l of v a r i a n c e was h i g h . I t was f e l t that an a n a l y s i s of 74 predominant a c t i v i t y would minimize these d e v i a t i o n s and thus improve the p r e d i c t a b i l i t y of the model. In a d d i t i o n to reducing v a r i a n c e t h i s method a l l o w s a c l e a r e r e x p r e s s i o n of the c o n t r o l s exerted by independent v a r i a b l e s on the two major a c t i v i t i e s , f e e d i n g and r e s t i n g . At the same time the c o n t r o l s exerted on preening and a l e r t behaviour were masked because of the s m a l l number of times when each c o n s t i t u t e d the predominant a c t i v i t y . In order t o c o n s t r u c t a more p r e c i s e model of a l l c a t e g o r i e s of goose a c t i v i t y i t was necessary to analyze the data using a d i f f e r e n t program. MCA was s e l e c t e d because i t accepted data f o r the dependent v a r i a b l e i n an i n t e r v a l l y s c a l e d format, while independent v a r i a b l e s were accepted a t a l l l e v e l s of measurement. I t enabled i d e n t i f i c a t i o n of the r e l a t i v e a b i l i t i e s of the p r e d i c t o r v a r i a b l e s to e x p l a i n the v a r i a n c e of a l l f o u r a c t i v i t y c a t e g o r i e s , not j u s t the predominent ones. Because the program does not assume o r t h o g o n a l i t y of i t s p r e d i c t o r s ( i e . , that no r e l a t i o n s h i p e x i s t s between any of the independent v a r i a b l e s ) i t was p o s s i b l e to i n c l u d e an a d d i t i o n a l p r e d i c t o r , which had been d e l e t e d from the MNA a n a l y s i s . The s t a t i s t i c s generated by these two programs not only r e f l e c t e d the a c t u a l e x p l a n a t i o n of a c t i v i t y p a t t e r n s but a l s o i n d i c a t e d the success with which the environment had been d e s c r i b e d by the observer i n terms r e l e v a n t t o snow geese. For a complete d e s c r i p t i o n of the s t a t i s t i c s the 75 reader i s r e f e r r e d to Andrews and Messenger (1973) and Andrews et a l . (1967). 6.3 Results Snow geese were engaged i n f e e d i n g an average of 7.2 hoars each day. R e s t i n g accounted f o r j u s t over 50 percent of d i u r n a l a c t i v i t y budget occupying approximately 12.4 hours. Preening and A l e r t n e s s were of s h o r t e r d u r a t i o n amounting to 1.4 and 2.8 hours r e s p e c t i v e l y . The time spent i n f l i g h t , both d i s t u r b e d and undisturbed, was estimated to be at l e a s t 0.25 hours. However, du r i n g p e r i o d s of e x c e s s i v e wind or harrassment t h i s l e v e l c ould e a s i l y t r e b l e . 6.3.1 MNA A n a l y s i s Resting and Feeding a c t i v i t y were c l o s e l y c o r r e l a t e d with t i d e l e v e l s and l o c a t i o n . The d i r e c t i o n of t i d a l movements had only a minor e f f e c t on goose a c t i v i t y . Feeding predominated under c o n d i t i o n s where the t i d e was between 2.1 and 3.4 m and was most i n t e n s i v e on Brunswick P o i n t , Lulu I s l a n d and Sea I s l a n d . Although some fe e d i n g was observed on R e i f e l Refuge i t seldom predominated. Geese c l e a r l y demonstrated an i n c l i n a t i o n to feed elsewhere than on the refuge whenever p o s i b l e . Resting was most p r e v a l e n t when t i d e l e v e l s were e i t h e r below 2.1 m or above 3.4 m. Res t i n g occured most f r e q u e n t l y 76 at R e i f e l Refuge and l e a s t f r e q u e n t l y at Brunswick P o i n t . Other p a r t s of the f o r e s h o r e were l e s s c l e a r l y dichotomized but l e v e l s of r e s t i n g behaviour were not as high as on the refuge. The complete model accounted f o r 21.9 percent of the v a r i a n c e between d i f f e r e n t c a t e g o r i e s of goose a c t i v i t y . E v a l u a t i o n of the l e v e l of f e e d i n g behaviour showed that l o c a t i o n e x p l a i n e d l e s s than 25 percent of the v a r i a n c e e x p l a i n e d by T i d e Height (Table X). L o c a t i o n may i n d i r e c t l y i n f l u e n c e f e e d i n g i n t e n s i t y through i n t e r a c t i o n s with other f a c t o r s such as food a v a i l a b i l i t y . By t a k i n g i n t o account these r e l a t i o n s h i p s i t was p o s s i b l e t o i l l u s t r a t e the e f f e c t s of t i d e h e i g h t , d i r e c t i o n of t i d a l movement and f l o c k l o c a t i o n with r e s p e c t to the l i k e l i h o o d of c o r r e c t l y p r e d i c t i n g the predominant a c t i v i t y (Table XI). An a-p o s t e r i o r i a p p l i c a t i o n o f the model generated 397 c o r r e c t l y c l a s s e d p r e d i c t i o n s of the 427 o b s e r v a t i o n s , r e p r e s e n t i n g an i n c r e a s e i n the p r e d i c t i v e power over and above that s u p p l i e d by the mode. Of the independent v a r i a b l e s used i n c o n s t r u c t i o n of the model t i d e height and l o c a t i o n were r e s p o n s i b l e f o r e x p l a i n i n g the l a r g e s t p r o p o r t i o n of the variance while the d i r e c t i o n o f t i d a l movement c o n t r i b u t e d e s s e n t i a l l y no a d d i t i o n a l i n f o r m a t i o n (Table X). Of the four a c t i v i t y c a t e g o r i e s R e s t i n g was most o f t e n c l a s s i f i e d c o r r e c t l y , followed c l o s e l y by Feeding. Since Preening and A l e r t r a r e l y c o n s t i t u t e d the predominant f l o c k a c t i v i t y , the 77 Table (X) - V a r i a b l e Response P r o f i l e s : c o e f f i c i e n t s of the MNA model f o r predominant a c t i v i t y PREDICTOR CATEGORIES ACTIVITY VARIABLES Resting A l e r t Feeding Preening Time 03- 06 13. 53 -1. 27 -10. 16 -2. 11 (hr) 06- 09 -10. 55 0. 01 9. 48 1. 06 (.0514) 09- 12 1. 21 -0. 28 2. 22 -0. 73 12- 15 2. 45 -0. 11 -4. 14 1. 80 15- 18 10. 59 0. 98 -9. 75 -1. 8 3 18- 21 -2 2. 40 -2. 13 25. 29 -0. 76 21- 24 -2. 39 0. 3 9 4. 53 -2, 53 T i d e A c t i o n r i s i n g 3. 95 0. 76 -3. 72 -0. 99 (.0024) f a l l i n g -2. 94 -0. 56 2. 76 0. 74 Tide Height 2.0- 3. 9 36. 17 -0. 71 -35. 83 0. 38 (. 1049) 4.0-5.9 19. 0 -1. 80 -16. 66 -0. 54 6.0-7.9 10. 29 -0. 95 -7. 94 -1. 39 8.0- 9.9 -15. 39 2. 71 12. 85 -0. 17 10.0- 11.9 -12. 16 0. 85 11. 54 -0. 23 12.0- 13.9 7. 71 -1. 3 4 -7. 57 1. 21 14.0- 15.9 27. 00 -0. 86 23. 55 -2- 60 Loca t i o n Brunswick -32. 08 7. 37 26. 57 -1. 85 (. 1248) R e i f e l 15. 13 -0. 63 -15. 70 1. 21 Outer I s . 1. 81 -1. 91 5. 47 -1. 75 Lul u I s . 8. 86 -1. 77 10. 93 -0. 29 Sea I s . , -6. 64 3. 79 4. 52 -1. 67 (Gene r a l i z e d Eta 2) G e n e r a l i z e d R 2=.2188 78 Table (XI) - C l a s s i f i c a t i o n Matrix - an a p o s t e r i o r i assignment of p r e d i c t i o n s f o r the a n a l y s i s of predominant a c t i v i t y PREDICTED Resting A l e r t Feeding Preening T o t a l Resting 80.99 0.0 19.01 0.0 263 ACTUAL A l e r t 16.67 0.0 83.33 0.0 6 Feeding 38.67 0.0 61.33 0.0 150 Preening 75.00 0.0 25.00 0.0 8 T o t a l 278 0 149 0 4 27 Table (XII) MCA: p a r t i a l c o r r e l a t i o n c o e f f i c i e n t s f o r the d i u r n a l a c t i v i t y budget A c t i v i t y Resting A l e r t Feeding Preening Time 1. 58 0. 77 1. 46 2. 65 Hunting Pressure 2. 14 0. 17 2. 53 0. 2 5 Tide A c t i o n 0. 73 0. 20 0. 71 0. 19 Tide Height 16. 57 3 • 18 11. 43 6. 28 L o c a t i o n 3. 74 5. 95 2. 51 0. 60 P a r t i a l R* 24. 76 10. 27 18. 64 9. 9 7 M u l t i p l e R 2 33. 79 17. 47 38. 49 11. 62 D i f f e r e n c e 9. 03 7. 20 19. 85 21. 59 79 frequency of c o r r e c t p r e d i c t i o n s i s u n d e r s t a n d i b l y zero. 6.3.2 MCA a n a l y s i s Tide height was c l e a r l y the most important v a r i a b l e of those measured i n f l u e n c i n g i n d i v i d u a l l e v e l s of R e s t i n g , Feeding and Preening (Table X I I ) . Goose l o c a t i o n , a major f a c t o r i n determining predominant f l o c k a c t i v i t y , was of c o n s i d e r a b l y reduced importance i n e x p l a i n i n g the observed v a r i a n c e of the i n d i v i d u a l a c t i v i e s with the e x c e p t i o n of A l e r t n e s s . M u l t i p l e c o r r e l a t i o n c o e f f i c i e n t s v a r i e d from a high of 38.5 percent f o r Feeding to a low of 11.0 percent f o r Preening. I t i s i n t e r e s t i n g t o note d i f f e r e n c e s between the sums of p a r t i a l c o r r e l a t i o n c o e f f i c i e n t s and m u l t i p l e c o r r e l a t i o n c o e f f i c i e n t s . The r e s i d u a l , or i n t e r a c t i o n e f f e c t amounted to between 7.2 and 21.6 percent of the t o t a l e x p l a i n e d v a r i a n c e f o r each category. The r e l a t i o n s h i p s between mean a c t i v i t y and mean t i d e l e v e l s are r e a d i l y apparent even as they are portrayed i n the s t a t i s t i c a l a n a l y s e s . However, the r e l a t i v e l y weak r e l a t i o n s h i p s between t i d e height and the remaining a c t i v i t y c a t e g o r i e s can be i d e n t i f i e d more e a s i l y with the a i d of a graph ( F i g . 2). Mean l e v e l s of a l e r t n e s s g r a d u a l l y i n c r e a s e d with t i d e height t o a maximum at approximately 4.0 m (13 f t ) , a f t e r w h i c h occured a s m a l l d e c l i n e . The p l o t of mean preening a c t i v i t y shows t h a t the l e v e l of preening Figure 2' Mean Intensity of Snow Goose Activities Tide Height (feet) 81 behaviour i n c r e a s e d g r a d u a l l y with water depth up to a maximum of 13 percent of the f l o c k at the 3.7 m (12 f t ) t i d e l e v e l . Preening dropped s h a r p l y a f t e r r e a c h i n g t h i s peak to l e s s than 2 percent at 4.6 m (15 f t ) . 6.4 D i s c u s s i o n 6.4.1 Feeding 6.4. 1. 1 T i d e Height Water l e v e l s are of major conseguence to the d a i l y a c t i v i t i e s of many s p e c i e s of waterfowl, i n c l u d i n g snow geese, through a d i r e c t e f f e c t on food a v a i l a b i l i t y ( N i l s s o n , 1972). When water depth i s f a v o u r a b l e f e e d i n g behaviour i s s t i m u l a t e d ; when e i t h e r too low or too high, f e e d i n g i s i n h i b i t e d . Wintering snow geese p r e f e r to fe e d in water from 2 to 15 cm i n depth (Mcllhenney, 1932; Soper, 1942). The r e s u l t s of the present study show that approximately 83 percent of a l l f e e d i n g a c t i v i t y took p l a c e between the 2.0 and 3.7 m t i d e l e v e l s . S c i r p u s americanus and S c i r p u s paludosus» the primary food p l a n t s of snow geese, grow between 2.1 and 3.5 m (Burgess, 1970) i n d i c a t i n g t h a t most feeding occurs, on the average, when the water l e v e l i s between 10 cm below the minimum and 20 cm above the maximum e l e v a t i o n a l ranges of these p l a n t s . I f the water i s deeper than 20 cm i t i s not p o s s i b l e 82 f o r geese to p r o p e r l y brace themselves and e x e r t the f o r c e s needed to excavate and e x t r a c t the embedded rhizomes. I f , on the other hand the water i s too shallow i t i s d i f f i c u l t f o r the geese to remove adhering s i l t and f i b r o u s r o o t s before swallowing. These r e s u l t supports the food h a b i t s a n a l y s i s which demonstrated that snow geese while f e e d i n g on the e s t u a r y r e l y almost e x c l u s i v e l y on S c i r p u s americanus and S c i r p u s paludosus. an i n c r e a s e i n f e e d i n g i n t e n s i t y occurred when the t i d e was between 2.0 and 2-2 m. T h i s delayed a c t i v i t y i s almost e n t i r e l y r e s t r i c t e d to the s i d e s of w a t e r - f i l l e d d e p r e s s i o n s . Feeding was p o s s i b l e f o r a short time a f t e r l e v e l p o r t i o n s o f the S c i r g u s zone had been exposed because of the abundance of w a t e r - f i l l e d depressions. However, the rhizome d e n s i t i e s i n the bottom of these d e p r e s s i o n s are s i g n i f i c a n t l y lower than i n w e l l exposed stands. In a d d i t i o n , l a r g e p o r t i o n s of the f l o c k g e n e r a l l y l e a v e the f e e d i n g areas below a t i d e of 2.0 ra so the s o c i a l inducement to l e a v e the f e e d i n g grounds i s very high. S e v e r a l s t u d i e s have e s t a b l i s h e d the importance of water depth i n r e g u l a t i n g d i u r n a l f e e d i n g behaviour of waterfowl i n h a b i t a t i n g t i d a l a reas. Hartman (1963) demonstrated that t h e f e e d i n g of black ducks on c r i t i c a l i c e - f r e e p a r t s of the Penobscot estuary i n Maine i s l i m i t e d to a s h o r t p e r i o d immediately before and a f t e r low t i d e . T ides were a l s o shown to impede f e e d i n g on e e l g r a s s by black 83 brant. During p e r i o d s o f e x c e s s i v e l y high water they were f o r c e d to c l o s e l y f o l l o w d i v i n g ducks which i n s e a r c h i n g f o r molluscs and c r u s t a c e a n s brought up fronds of e e l g r a s s otherwise u n a v a i l a b l e to the brant (Einarsen, 1955). T i d a l o s c i l l a t i o n s i n the F i r t h of Forth c o n t r o l l e d d a i l y changes i n I x d r o b i a a v a i l a b i l i t y , which i n t u r n , i n f l u e n c e d the p a t t e r n of f e e d i n g a c t i v i t y by shelducks (Tadorna tadorna) (Bryant and Leng, 1976). F l u c t u a t i n g water l e v e l s were b e l i e v e d r e s p o n s i b l e f o r changes i n the w i n t e r i n g l o c a t i o n s of g r e a t e r snow geese along the east c o a s t of the United S t a t e s . Howard (1940) recorded that snow geese d i d not h e s i t a t e to change t h e i r feeding grounds i n response to unfavourable c o n d i t i o n s created by e i t h e r storms or abnormally h i g h t i d e s . Dzubin (1965) i m p l i c a t e d e x c e s s i v e f l o o d i n g of previous f e e d i n g areas as a c o n t r i b u t o r y f a c t o r i n c a u s i n g s h i f t s i n the t i m i n g of the southward departure of m i g r a t i n g snow geese. In southeastern Texas snow geese responded to e x c e s s i v e f l o o d i n g of t h e i r f e e d i n g marshes by e i t h e r a l t e r i n g t h e i r d i e t or moving to areas with a more fa v o u r a b l e water regime (Lynch et a l . , 1947). In the same study i t was noted that the geese avoided otherwise e x c e l l e n t f e e d i n g areas u n t i l they had been inundated with a shallow c o v e r i n g of water. Because food a v a i l a b i l i t y i s dependent on water depth and the l e v e l of f e e d i n g behaviour i s c l o s e l y t i e d to changes i n food a v a i l a b i l i t y , i t f o l l o w s t h a t f e e d i n g 84 a c t i v i t y i s c o n t r o l l e d , f o r the most p a r t , by t i d a l f l u c t u a t i o n s . As a r e s u l t l i g h t i n t e n s i t y , u s u a l l y a f a c t o r of primary importance i n waterfowl, may a f f e c t f e e d i n g p e r i o d i c i t y very l i t t l e . Information on d i u r n a l a c t i v i t y p a t t e r n s t r a d i t i o n a l l y c o n s i s t s of data c o l l e c t e d only d u r i n g d a y l i g h t . Prom such o b s e r v a t i o n s many authors i m p l i e d a more or l e s s r i g i d , d i p h a s i c p a t t e r n of a c t i v i t y f o r most s p e c i e s of b i r d s , with peak f e e d i n g l e v e l s o c c u r i n g i n the e a r l y morning and the l a t e a f t e r n o o n (Palmgren, 1949; Bossenmaier and M a r s h a l l , 1958; Winner, 1959). Many workers have i n f e r r e d t h at the extent of n i g h t - t i m e f e e d i n g , except under abnormal circumstances, i s n e g l i g i b l e . However, i n d i r e c t records i n the l i t e r a t u r e i n d i c a t e that n o c t u r n a l f e e d i n g may, i n some cases, c o n s t i t u t e a l a r g e p o r t i o n of the normal d i u r n a l rhythm of b i r d s , e s p e c i a l l y when b i r d s r o o s t on the f e e d i n g grounds. Nocturnal f e e d i n g a c t i v i t y has been recorded f o r s e v e r a l s p e c i e s of geese, under c o n d i t i o n s when e i t h e r the b i r d s were h i g h l y v i s i b l e , such as on moonlit n i g h t s (Howard, 1940; Boyd, 1955; M a r i o t t , 1970, Owen, 1972) or when movements of l a r g e numbers of b i r d s at one time would be most conspicuous, such as during p e r i o d s of e x c e s s i v e hunting pressure (Racey, 1924; Mcllhenney, 1932; Glazner, 1946). This segment of the study c l e a r l y e s t a b l i s h e d t h a t snow geese do i n f a c t feed at a l l hours, r e g a r d l e s s of the degree .85 of i l l u m i n a t i o n . Nocturnal f e e d i n g occurred whether hunting season was open or c l o s e d , f u r t h e r i n d i c a t i n g that f l u c t u a t i n g food a v a i l a b i l i t y {due to changing t i d e l e v e l s ) and not hunter harrassment e x e r t s the s t r o n g e s t i n f l u e n c e on feeding p e r i o d i c i t y . Few d i r e c t accounts of r e g u l a r , n o c t u r n a l f e e d i n g behaviour i n w i n t e r i n g a n a t i n i d s are p r e s e n t l y a v a i l a b l e . However, some s u p p o r t i n g , c i r c u m s t a n t i a l evidence has been p u b l i s h e d . M a r i o t t {1970) d i d not observe f r e e - r a n g i n g Cape Barren geese f e e d i n g a t night (except under moonlight when b i r d s , i f they were f e e d i n g a t n i g h t , would be most v i s i b l e ) . However, during experimental t r i a l s on caged b i r d s he noted that at l e a s t o n e - t h i r d o f the t o t a l d a i l y i n t a k e was consumed d u r i n g the hours of darkness. Owen (1970) found t h a t i n the absence of d i s t u r b a n c e , caged blue wing t e a l were a t l e a s t as a c t i v e a t night as they were during t h e day. U t i l i z i n g image i n t e n s i f i c a t i o n equipment, Swanson and Sargent (1972) observed a d u l t and immature ducks (of s e v e r a l s p e c i e s ) f e e d i n g i n t e n s i v e l y between the hours of 21:00 and 04:00 during the summer. The major f a c t o r i n f l u e n c i n g the n o c t u r n a l h a b i t s of these b i r d s was the abundance of midges (Chirpnomidae) and m a y f l i e s ( Epheneroptera). Feeding a c t i v i t y responded to per i o d s of gre a t e s t food a v a i l a b i l i t y , r a t h e r than to l i g h t i n t e n s i t y . assuming t h a t feeding i n t e n s i t y i s c o n t r o l l e d to a l a r g e extent by t i d e height i t i s p o s s i b l e to c a l c u l a t e the 86 l e n g t h and r h y t h m i c i t y of the e f f e c t i v e f e e d i n g p e r i o d s over the winter. From the end of October to the middle of A p r i l the average length o f time when the t i d e was between 2.0 and 3.7 m was 14 hours per day. Although s h o r t e r d a i l y f e e d i n g periods d i d occur i n December and January the average was s t i l l 12 hours of f a v o u r a b l e feeding c o n d i t i o n s per day during these months. Between the 2.0 and 3.7 m t i d e l e v e l s f e e d i n g accounted f o r an average of only 29 percent of the t o t a l a c t i v i t y . I t was c a l c u l a t e d t h a t the mean pr o p o r t i o n of the 24 hour day spent f e e d i n g amounted to only 30 percent of the t o t a l a c t i v i t y budget. T h i s f i g u r e i s r e l a t i v e l y low compared to the mean l e v e l of d i u r n a l f e e d i n g estimated f o r European wh i t e - f r o n t e d geese which fed f o r a mean period of 9.4 hours of a p o s s i b l e 10 on two o b s e r v a t i o n days (Owen, 1972) . Since n o c t u r n a l f e e d i n g was known not to have occured among the w h i t e - f r o n t s , 39 percent of the 24 hour day was spent f e e d i n g . 6.4.1.2 L o c a t i o n Measurements of rhizome q u a n t i t y were made which demonstrated that R e i f e l Refuge, along with the Outer I s l a n d s , possessed the lowest rhizome d e n s i t i e s on the fore s h o r e . I t i s p o s i b l e that geese were able to detect the d i f f e r e n c e s i n rhizome d e n s i t y between the v a r i o u s marsh u n i t s a f t e r a r e l a t i v e l y s h o r t p e r i o d of time and respond a c c o r d i n g l y . Although t r u e preferences Of these h a b i t a t f a c t o r s may 87 be masked by d i f f e r e n c e s i n p e r c e p t i o n between geese and observer, i t was apparent that p r e f e r r e d f e e d i n g areas along the f o r e s h o r e were those with comparatively high rhizome d e n s i t i e s . C e r t a i n s p e c i e s of A l l t i n i d a e s e l e c t f e e d i n g areas by r e c o g n i z i n g and compensating f o r changes i n food a v a i l a b i l i t y . Bossenmaier and M a r s h a l l (1958) s t a t e d t h a t f e e d i n g s i t e p r e f e r e n c e s of waterfowl are based p r i m a r i l y on food d e n s i t y and a c c e s s i b i l i t y , i n c l u d i n g water l e v e l s i n the f i e l d s . In the same study i t was recorded that b i r d s p r e f e r r e d t o use those a c c e p t a b l e f i e l d s nearest t h e i r r o o s t s . Once an a c c e p t a b l e f e e d i n g s i t e was s e l e c t e d the b i r d s , with r a r e e x c e p t i o n , returned to the same p l a c e s each day. C e r t a i n l y other h a b i t a t f a c t o r s such as the s t r u c t u r a l and chemical c h a r a c t e r i s t i c s of the v e g e t a t i o n , r o o t to rhizome r a t i o s , r e l a t i v e amounts of pothole and channel edge, and ease of e x t r a c t i o n , combined with environmental f a c t o r s l i k e wind, p r e c i p i t a t i o n , and temperature must i n f l u e n c e l e v e l s o f f e e d i n g d i f f e r e n t l y at d i f f e r e n t l o c a t i o n s . But, i t i s d i f f i c u l t t o adequately measure these f e a t u r e s as they may be p e r c e i v e d by the geese. I n t e r e s t i n g l y , Lulu and Sea I s l a n d s outwardly appear at l e a s t as s u i t a b l e f o r f e e d i n g as Brunswick P o i n t with r e s p e c t t o rhizome d e n s i t i e s . However, snow geese were not observed t o u t i l i z e these areas at a l l d u r i n g November and 88 December. T h i s anomalous s i t u a t i o n may be e x p l a i n e d by the e f f e c t s of empathic or i n f e c t i o u s l e a r n i n g . I t was observed t h a t those geese l a t e s t to migrate north i n s p r i n g were i n v a r i a b l y found at Brunswick P o i n t and t h a t e a r l y autumn migrants f i r s t s e t t l e d there October. This marsh was used both day and n i g h t f o r a short time subsequent to a r r i v a l . Hunting pressure d u r i n g the day soon f o r c e d them onto the refuge. Because s u i t a b l e c o n d i t i o n s were encountered at Brunswick a f e e d i n g f l i g h t p a t t e r n was e s t a b l i s h e d which appa r e n t l y committed them to r e t u r n each n i g h t . Reinforced by s u c c e s s f u l f o r a g i n g geese maintained t h i s r e g u l a r f l i g h t p a t t e r n u n t i l January when a l l the b i r d s departed f o r Skagit F l a t s . Upon t h e i r r e t u r n to the F r a s e r D e l t a i n March, i t appeared t h a t Brunswick P o i n t and Sea I s l a n d were again chosen by the f i r s t a r r i v a l s . However, at t h i s time hunting pressure was absent, thus a l l o w i n g a f u l l e r e x p r e s s i o n of i n a t e f e e d i n g s i t e p r e f e r e n c e s . 6.4.1.3 T i d e Action R e s u l t s from both analyses i n d i c a t e that the d i r e c t i o n of t i d a l movements e x e r t s l i t t l e , i f any, c o n t r o l on the f e e d i n g i n t e n s i t y and p e r i o d i c i t y of snow geese. This c o n c l u s i o n i s supported by data from White and Lewis (1937) who r e p o r t e d that g r e a t e r snow geese, under c o n d i t i o n s very s i m i l a r to those of the F r a s e r D e l t a , fed with egual frequency on r i s i n g and f a l l i n g t i d e s . 89 Some s p e c i e s of waterfowl do feed p r e f e r e n t i a l l y on e i t h e r r i s i n g or f a l l i n g t i d e s , u s u a l l y as i t a f f e c t s t h e i r food supply. Tide a c t i o n was demonstrated t o play a l a r g e r o l e i n the fe e d i n g behaviour of shelducks who p r e f e r r e d to feed as the t i d e dropped (Bryant and Leng, 1976). S o v i e t workers mentioned t h a t l e s s e r snow geese p r e f e r r e d to feed on an incoming t i d e as i t f l o o d e d the feed i n g grounds (Telpov and Shevareva, 1963). L o c a l hunters, on the other hand, suggested t h a t f e e d i n g i s most common on a f a l l i n g t i d e . T h i s assumption i s based on the f a c t t h a t most geese are shot as they f l y i n to feed. During hunting season t i d a l c o n d i t i o n s a re such that minimum low t i d e occurs at night and feeding by geese on f a l l i n g t i d e s u s u a l l y occurs twice d u r i n g d a y l i g h t . F l i g h t a c t i v i t y g e n e r a l l y i n c r e a s e s with an i n c r e a s e i n f e e d i n g a c t i v i t y t h e r e f o r e geese are more v u l n e r a b l e to hunters. Feeding on f a l l i n g t i d e s would thus be observed most f r e q u e n t l y . The deductions of the hunters would not n e c e s s a r i l y be i n c o r r e c t but would i n s t e a d be somewhat incomplete. From n i g h t - t i m e and post-hunting season data i t i s now c l e a r that a b s o l u t e t i d e height r a t h e r than i t s movement i s most important i n r e g u l a t i n g f e e d i n g a c t i v i t y . 6.4.1.4 Time Time of day was of s u r p r i s i n g l y minor i n f l u e n c e i n the r e g u l a t i o n of d i u r n a l f e e d i n g l e v e l s . The f e e d i n g behaviour 9 0 of many other b i r d s p e c i e s are d i r e c t l y c o n t r o l l e d by l i g h t i n t e n s i t y ( S i e b e r t , 1951; A s c h o f f , 1966) and d i p h a s i c f e e d i n g f l i g h t s have been recorded f o r most s p e c i e s of waterfowl, i n c l u d i n g snow geese, when food a v a i l a b i l i t y i s s t a b l e . The present study has demonstrated t h a t a p o l y p h a s i c feeding rhythm does e x i s t w i t h i n the l o c a l snow goose p o p u l a t i o n and t h a t i t may be caused by changes i n food a v a i l a b i l i t y with a l l other f a c t o r s being of secondary importance. S e v e r a l authors a l l u d e to the e x i s t e n c e of an i n h e r i t e d , endogenous 24 hour metabolic rhythm. G. Markgren (1963) s t a t e d that t h i s rhythm i n bean geese determines the p a t t e r n of t h e i r d a i l y a c t i v i t i e s . He a l s o suggested t h a t l i g h t i n t e n s i t y , as i t a f f e c t s v i s i b i l i t y and other environmental f a c t o r s such as temperature and food a v a i l a b i l i t y , r e g u l a t e s the e x p r e s s i o n of t h i s rhythm i n the form of the d i u r n a l a c t i v i t y p r o f i l e . Other s t u d i e s point out that n o c t u r n a l behaviour i n waterfowl i s common and that the 24 hour rhythm o f most b i r d s may a c t u a l l y c o n s i s t of s e v e r a l s m a l l e r c y c l e s (Harker, 1958; Swanson and Sargent, 1972). S i e g f r i e d (1974) proposes j u s t such a p o l y p h a s i c r h y t h m i c i t y f o r mated female scaup. Without f o l l o w i n g the a c t i v i t i e s of e i t h e r s i n g l e b i r d s or f a m i l i e s , i t i s d i f f i c u l t to i d e n t i f y these i n d i v i d u a l behaviour c y c l e s e s p e c i a l l y i n s p e c i e s l e s s g r e g a r i o u s than 91 snow geese. However, i f s i m i l a r p o l y p h a s i c b e h a v i o u r does oc c u r i n snow geese i t may h e l p e x p l a i n how they are a b l e t o t a k e f u l l advantage o f such an a l t e r n a t i n g l y a v a i l a b l e food s o u r c e . 6.4.2 R e s t i n g 6.4.2.1 T i d e H e i g h t The d a i l y a c t i v i t y p a t t e r n of snow geese i s dominated by two f u n c t i o n s , f e e d i n g and r e s t i n g . R e s t i n g c o n s t i t u t e d a major p o r t i o n of f l o c k a c t i v i t y at a l l t i m e s , o c c u p y i n g an e s t i m a t e d 52 p e r c e n t o f each 24 hour day. S i n c e snow geese a r e observed t o s l e e p w i t h e g u a l f a c i l i t y on l a n d and water i t i s l i k e l y t h a t t i d e h e i g h t r e g u l a t e s r e s t i n g b e h a v i o u r i n d i r e c t l y t h r ough i t s e f f e c t on food a v a i l a b i l i t y . D e f i n i t e maximum and minimum l e v e l s o f r e s t i n g a c t i v i t y were r e c o r d e d under s p e c i f i c t i d a l c o n d i t i o n s . However, c o n t r o l o f r e s t i n g b e h a v i o u r by f l u c t u a t i o n s i n t i d e h e i g h t i s not a b s o l u t e . a l a r g e p e r c e n t a g e o f geese were found a s l e e p a t a l l t i m e s . D u r i n g p e r i o d s when rhizomes were r e a d i l y a v a i l a b l e an u n e x p e c t e d l y h i g h amount o f s l e e p i n g a c t i v i t y was r e c o r d e d . I t may be t h a t t h e geese had consumed s u f f i c i e n t g u a n t i t i e s of f o o d t o c o m p l e t e l y f i l l t h e i r g a s t r o - i n t e s t i n a l t r a c t s . C o n s i d e r i n g t h a t an average of 29 p e r c e n t o f t h e f l o c k was a s l e e p between the 2.0 and 3.6 m t i d e l e v e l s a h i g h degree of f e e d i n g e f f i c i e n c y i s i n d i c a t e d . Even among t h e more n e a r l y d i p h a s i c bean geese, which u s u a l l y s l e p t a t n i g h t and f e d d u r i n g t h e day, t h e r e 92 were always a r e l a t i v e l y l a r g e number of b i r d s r e s t i n g at any one time (G. Markgren, 1963). During winter, the hi g h r e l a t i v e humidity plus the low ambient temperature a m p l i f i e d by the almost constant winds, along the f o r e s h o r e , emphasize t h e need to conserve body heat. Under normal c o n d i t i o n s s l e e p i n g may be induced by a completion of the other e s s e n t i a l a c t i v i t i e s , f e e d i n g and preening, combined with a need to conserve body heat. However, duri n g extreme weather c o n d i t i o n s and p e r i o d s of r e s t r i c t e d food a v a i l a b i l i t y the r e g u l a r d i u r n a l f e e d i n g h a b i t s of waterfowl may be abandoned completely i n order to maintain body i n s u l a t i o n . Bean geese d i s p l a y e d prolonged bouts of daytime r e s t i n g i n response to unseasonably c o l d weather and a l i g h t snow cover on the f e e d i n g grounds (G. Markgren, 1963). Although the snow d i d not p h y s i c a l l y prevent f e e d i n g , the e f f i c i e n c y of e x t r a c t i o n may have been reduced t o a p o i n t where i t would not have been economical to f e e d . Markgren reported that when a b i r d assumed a s l e e p i n g p o s i t i o n with the b i l l tucked under one wing, metabolic a c t i v i t y dropped 50 to 60 percent below t h a t when sta n d i n g with the head h e l d e r e c t . I f the p o s s i b i l i t i e s of o b t a i n i n g food are s m a l l , the low metabolic r a t e and decreased p h y s i o l o g i c a l a c t i v i t y a s s o c i a t e d with ; s l e e p may be one way of c o u n t e r a c t i n g the s i t u a t i o n . I t would appear that the bouts of r e s t i n g a c t i v i t y 93 e x h i b i t e d by snow geese are c o n t r o l l e d , to a l a r g e e x t e n t , by food a v a i l a b i l i t y and the r a t e of food consumption which, i n t u r n , are r e g u l a t e d by changes in t i d e height. 6.4.2.2 L o c a t i o n During hunting season the refuge provides the only safe land-base a v a i l a b l e to snow geese. T i d a l c o n d i t i o n s a t t h i s time of year l i m i t the amount of daytime f e e d i n g . Since rhizome d e n s i t i e s i n t h i s marsh are s i g n i f i c a n t l y lower than i n other p a r t s of the f o r e s h o r e , f e e d i n g would appear to be i n e f f i c i e n t . With a drop in f e e d i n g i n t e n s i t y s l e e p i n g would i n c r e a s e . A f t e r hunting p r e s s u r e i s removed i n a t e r o o s t i n g s i t e p r e f e r e n c e s may then be e x e r c i s e d and the geese are f r e e t o make use of other segments of the for e s h o r e during d a y l i g h t . The p r e c i s e environmental c h a r a c t e r i s t i c s a s s o c i a t e d with r o o s t - s i t e q u a l i t y have not been e x t e n s i v e l y s t u d i e d . However, i t i s known th a t geese, i n g e n e r a l , d i s p l a y a preference f o r areas p r o v i d i n g unhindered v i s i b i l i t y i n a l l d i r e c t i o n s (G. Markgren, 1963). In t h i s l i g h t , open water s u r f a c e s and barren shore l i n e s are s t r o n g l y a t t r a c t i v e . Even though the lower reaches of the Outer I s l a n d s , Brunswick Po i n t and Lulu I s l a n d o f f e r l i t t l e p r o t e c t i o n from the weather, they do provide an unobstructed panoramic view. R e i f e l Refuge, on the other hand, i s r e l a t i v e l y w e l l s h e l t e r e d from wind but i s l o c a t e d i n the center of a complex of i n t e r t i d a l i s l a n d s . At high t i d e these i s l a n d s 94 are covered with water. However, when the i s l a n d s are exposed by the f a l l i n g t i d e , geese are l e f t e s s e n t i a l l y surrounded by land. F l i g h t s t o more open areas, the Outer I s l a n d s and Brunswick P o i n t , may be then r e l e a s e d . S l e e p i n g geese when p r o p e r l y groomed are o s t e n s i b l y wind-proof. T h e r e f o r e , the g r e a t e r degree of p r o t e c t i o n a g a i n s t p r e d a t o r s and other land-bound dangers f u r n i s h e d by unhindered v i s i b i l i t y on the sand f l a t s may be of g r e a t e r s u r v i v a l value than p r o t e c t i o n from normal weather c o n d i t i o n s . Once, during a s t r o n g west wind, geese were observed to remain w i t h i n dense stands of c a t t a i l even when c l o s e l y pressed by two hunters. So while t h e i r d i s t r i b u t i o n does not appear to be a f f e c t e d by normal weather, they do respond to extreme c o n d i t i o n s . Glazner (1946) reported that snow geese r e a d i l y flew up to 30 miles (48 km) from t h e i r r o o s t s to feed. However, a p r o p e n s i t y to remain c l o s e to the fee d i n g grounds was c l e a r l y demonstrated by the l o c a l snow geese. While hunting season was open geese u t i l i z e d R e i f e l Refuge e x t e n s i v e l y f o r s l e e p i n g during t h e day. A f t e r hunting ceased they p r e f e r r e d to r e s t along the open s h o r e l i n e s of the marshes i n which they had j u s t completed f e e d i n g , r a t h e r than r e t u r n to the refug e . T h e r e f o r e , i t appears t h a t r o o s t i n g s i t e s u i t a b i l i t y i s determined by a combination of u n r e s t r i c t e d v i s i b i l i t y and 95 p r o x i m i t y to the f e e d i n g grounds. 6.4.2.3 Ti d e A c t i o n and Time Neit h e r t i d a l a c t i o n nor time of day were shown to i n f l u e n c e the l e v e l and p e r i o d i c i t y of r e s t i n g behaviour. Due to the dependence of f e e d i n g on t i d e height no r e g u l a r mid-day s l e e p i n g behaviour was observed as had been recorded f o r snow geese w i n t e r i n g i n L o u i s i a n a (HcAtee, 1910; Mcllhenney, 1932). On the F r a s e r e s t u a r y r e s t i n g c o n s t i t u t e s a major p o r t i o n of f l o c k a c t i v i t y at a l l times of the day with no d i s c e r n a b l e t i m e - r e l a t e d peaks. Although l i g h t i n t e n s i t y may r e g u l a t e the d u r a t i o n and t i m i n g of n o c t u r n a l s l e e p i n many b i r d s p e c i e s , r e s t i n g a c t i v i t y i n the present study was most c l o s e l y c o r r e l a t e d with food a v a i l a b i l i t y . I t i s p o s s i b l e t h a t most b i r d s show an i n h e r i t e d tendency towards d i s p h a s i c s l e e p (Palmgren, 1949; A s c h o f f , 1966) but i t would appear t h a t snow geese, and presumably most waterfowl are q u i t e capable of a d j u s t i n g to a p o l y p h a s i c rhythm, depending upon food a v a i l a b i l i t y , r a t h e r than on l i g h t i n t e n s i t y (Swanson and Sargent, 1972; S i e g f r i e d , 1974). 6.4.3 A l e r t A l e r t behaviour i s a p u r p o s e f u l l y broad term encompassing a l l a c t i v i t i e s other than f e e d i n g , r e s t i n g , 96 preening and f l y i n g . I t i n c l u d e s the ''non-essential'' a c t i v i t i e s of walking, swimming, f i g h t i n g and s t a n d i n g . A c t i v i t i e s c o n s i d e r e d w i t h i n t h i s category p r i m a r i l y execute the f u n c t i o n of enumerating i n d i v i d u a l s not engaged i n the other main a c t i v i t i e s . T h e r e f o r e i n c l u s i o n of t h i s category i n the a n a l y s i s was j u s t i f i e d . No c o r r e l a t i o n was e s t a b l i s h e d between e i t h e r time of day, hunting season or d i r e c t i o n o f t i d a l movement and the l e v e l of a l e r t behaviour. These r e s u l t s are c o n s i s t a n t with those of Owen (1972) who c o u l d demonstrate no r e l a t i o n between the l e v e l of a l e r t n e s s i n undisturbed f l o c k s and time of day. 6.4.3. 1 T i d e Height Minimum l e v e l s of a l e r t behaviour were a s s o c i a t e d with maximum l e v e l s o f r e s t i n g . As water depth i n c r e a s e d from below 1.2 m (4.0 feet) s l e e p i n g geese were f o r c e d t o e i t h e r walk to higher ground, or to f l o a t i n with the t i d e . When r a f t s of geese began to form on the incoming t i d e many were observed to swim towards shore, e s p e c i a l l y a f t e r those on shore had begun i n t e n s e v e feeding. Presumably, most geese feed u n t i l t h e i r alimentary t r a c t s become f u l l . As a p p e t i t e s become s a t i s f i e d , l e s s emphasis i s focused on f e e d i n g and more time i s devoted t o i n t e r a c t i o n s with other geese and t o " a i m l e s s " walking. Maximum A l e r t l e v e l s occur immediately f o l l o w i n g the h i g h - t i d e drop i n f e e d i n g a c t i v i t y . Above 3.7 m (12 feet) 97 there e x i s t few exposed s u r f a c e s on which they are a b l e to stand. Under these c o n d i t i o n s many geese f l o a t c l o s e to the s h o r e l i n e and go to s l e e p , thus the apparent drop i n a l e r t n e s s . However, proxim i t y to t a l l v e g e t a t i o n i n s t i l l s a high degree of wariness i n the b i r d s . At these times a l e r t behaviour i s maintained above the l e v e l s observed when geese r e s t i n more open and t h e r e f o r e secure areas at low t i d e . A l e r t behaviour was most f r e g u e n t l y observed among i n d i v i d u a l s and groups that had stopped i n t e n s i v e f e e d i n g while f e e d i n g c o n d i t i o n s were s t i l l f a v o u r a b l e . Owen (1972) recorded t h a t d u r i n g d a y l i g h t , approximately 3.0 percent of the f l o c k was a l e r t d u r i n g p e r i o d s of i n t e n s i v e f e e d i n g . In the present study a l e r t behaviour amounted to approximately 11.5 percent of the a c t i v i t y p r o f i l e d u r i n g s i m i l a r p e r i o d s of maximum f e e d i n g i n t e n s i t y . T h i s d i s c r e p e n c y may, i n p a r t , r e f l e c t the r e l a t i v e amount of f o r a g i n g time r e q u i r e d to o b t a i n an adequate d i e t . In a d d i t i o n , the w h i t e - f r o n t s had an e f f e c t i v e f e e d i n g p e r i o d of between 8 and 10.5 hours whereas S c i r p u s rhizomes were a v a i l a b l e to snow geese an average of 14.0 hours per day. C o n s i d e r i n g the r e l a t i v e l y l a r g e p r o p o r t i o n of the snow goose f l o c k engaged i n a c t i v e , non-feeding behaviour during p e r i o d s of optimum food a v a i l a b i l i t y , f e e d i n g e f f i c i e n c y of snow geese may be assumed high. G. Markgren (1963) observed a marked i n c r e a s e i n n o c t u r n a l a c t i v i t y i n r o o s t i n g bean geese, which l a r g e l y 98 c o n s i s t e d of i n t e r a c t i o n s between b i r d s . The r e g u l a r i t y of such non-feeding a c t i v i t i e s lends support to the concept of po l y p h a s i c r h y t h m i c i t y i n geese, apa r t from t h a t d i c t a t e d by changes i n food a v a i l a b i l i t y . 6.4.4 Preening Included w i t h i n the preening category were a l l o f the comfort movements r e l a t e d to c l e a n i n g and grooming l i s t e d by HacKinney (1965). Neither time of day, d i r e c t i o n of t i d a l movement, hunting season nor l o c a t i o n were of consequence i n e x p l a i n i n g the l e v e l and p e r i o d i c i t y of preening behaviour. 6.4.4.1 T i d e Height I t seems reas o n a b l e t o expect t h a t changes i n preening a c t i v i t y are m a n i f e s t a t i o n s of the synchronized r e p a i r of r u f f l e d and d i s a r r a n g e d f e a t h e r s caused by the d i s t i n c t i v e s u b t e r r a n i a n f e e d i n g methods of snow geese. R e s u l t s i n d i c a t e then that preening i s d i r e c t l y r e l a t e d to f e e d i n g i n t e n s i t y and, t h e r e f o r e , to food a v a i l a b i l i t y . In the present study, i t was estimated that snow geese spend approximately 6.0 percent of each 24 hour day engaged i n preening. The l e v e l of preening a c t i v i t y may be expected to vary with weather, f e e d i n g c o n d i t i o n s , season and the degree of harassment experienced i n d i f f e r e n t l o c a t i o n s . These r e s u l t s are c o n s i s t e n t with the statements of S i e g f r i e d (1974) and MacKinney (1965) who c l a i m t h a t preening behaviour i n waterfowl most f r e q u e n t l y occurs subsequent to f l i g h t s and bouts of i n t e n s i v e f e e d i n g and 99 p r i o r to s l e e p i n g . Preening i s e s s e n t i a l l y the maintenance of a w e l l -i n s u l a t e d , water-proof body c o v e r i n g and must be repeated s e v e r a l times d u r i n g the day. Few s t u d i e s have been conducted on the amount of preening performed by f r e e -ranging b i r d s . White-fronted geese were r e p o r t e d to spend an average of 2.4 percent of an 8 hour day i n a c t i v e preening (Owen, 1972). Lesser scaup spent from 1.3 t o 3.5 percent of the d a y l i g h t hours i n v o l v e d i n preening and bathing ( S i e g f r i e d , 1974). In t h e a r c t i c , K i t t i w a k e g u l l s spent from 2.4 to 6.9 percent of 7 hour days i n the act of preening. I n these s t u d i e s no estimates were made of the p o s s i b l e l e v e l s of n o c t u r n a l preening. A r e c o r d of the number of preening bouts per day performed by each goose was not c o l l e c t e d i n the present study but MacKinney (1965) r e p o r t e d that a s i n g l e c a p t i v e , blue-phase snow goose preened s i x times and bathed twice during a 13 hour, dawn-til-dusk o b s e r v a t i o n day i n March. Since each preening sequence l a s t s an average of f o u r minutes, a c c o r d i n g t o MacKinney, these data r e p r e s e n t very roughly 24 minutes of preening. I f preening occurs as f r e q u e n t l y a t n i g h t as i t does during d a y l i g h t , another f i v e bouts may be expected, g i v i n g a t o t a l amount of time spent a c t i v e l y preening of 44 minutes, which i s s t i l l h a l f t h a t estimated i n the f i e l d . Presumably the r i g o u r s of f l i g h t , wind and i n t e n s i v e f e e d i n g would e x p l a i n the higher l e v e l s 100 of preening observed i n f r e e - r a n g i n g snow geese and account f o r the d i s c r e p e n c y . 101 7^0 P i s t u r b a n c e 7. 1 I n t r o d u c t i o n Although s e v e r a l workers have grappled with the problem of t r y i n g t o analyze the e f f e c t of hunting pressure and how i t a f f e c t s waterfowl d i s t r i b u t i o n (Craighead and Stockstad, 1956; R a v e l i n g , 1969), very few have attempted to q u a n t i t a t i v e l y assess the e f f e c t s of other forms of dis t u r b a n c e . Owen (1971) i n st u d y i n g f e e d i n g s i t e s e l e c t i o n and food i n t a k e of European w h i t e - f r o n t e d geese noted that d i s t u r b a n c e s c o u l d be co n s i d e r e d e i t h e r d i r e c t i o n a l o r non-d i r e c t i o n a l . In a n a l y z i n g the many p o t e n t i a l types of harassment encountered on the estuary i t i s u s e f u l to d i f f e r e n t i a t e between a c t i v e and passive forms. The v a r i o u s types of d i s t u r b a n c e then may be c a t e g o r i z e d as e i t h e r p a s s i v e - n o n d i r e c t i o n a l , p a s s i v e - d i r e c t i o n a 1 , a c t i v e -n o n d i r e c t i o n a l or a c t i v e - d i r e c t i o n a l . P a s s i v e - n o n d i r e c t i o n a l f a c t o r s , such as hunting seasons, do not evoke tendencies t o f l e e an area* Instead they may have long term e f f e c t s l e a d i n g t o changes i n d i u r n a l and se a s o n a l p a t t e r n s of h a b i t a t use. Pa s s i v e -d i r e c t i o n a l d i s t u r b a n c e f a c t o r s such as d i k e s , j e t t i e s , b l i n d s and t h i c k v e g e t a t i o n o f t e n e x e r t only a l i m i t e d c o n t r o l on d i s t u r b e d behaviour. A c t i v e - n o n d i r e c t i o n a l 1 0 2 f a c t o r s such as r e a c t i o n s to the d i s t u r b a n c e of other members of the f l o c k are very d i f f i c u l t t o i s o l a t e . Loud noises such as those emanating from heavy machinery may o f t e n be considered a c t i v e , yet n o n - d i r e c t i o n a l . However, a u d i t o r y s t i m u l i i n general appear to e l i c i t l e s s e r responses than do v i s u a l s t i m u l i . The most conspicuous forms of d i s t u r b a n c e are those which are both a c t i v e and d i r e c t i o n a l . although the consequences of human a c t i v i t y , a i r c r a f t and predators appear s t r a i g h t - f o r e w a r d assessment of the long and s h o r t term e f f e c t s of these f a c t o r s have been n e g l e c t e d . E x c e s s i v e l e v e l s of harassment may a d v e r s e l y a f f e c t geese i n s e v e r a l ways such as reducing the l e n g t h o f the e f f e c t i v e f e e d i n g p e r i o d , p r e v e n t i n g a c c e s s t o p r e f e r r e d areas, f o r c i n g c o n c e n t r a t i o n on poor areas and i n c r e a s i n g energy expenditure by i n c r e a s i n g f l i g h t a c t i v i t y . Disturbance may u l t i m a t e l y f o r c e the geese t o abandon an area e n t i r e l y . With the expanding human po p u l a t i o n of the adjacent back-up lands l e v e l s of d i s t u r b a n c e along the f o r e s h o r e have i n c r e a s e d d r a s t i c a l l y over the past few ye a r s . Recent submissions by developers to f i l l and r e c l a i m l a r g e segments of the e s t u a r y o u t s i d e o f the e x i s t i n g d i kes i n d i c a t e that these pressures w i l l c o n t i n u e to mount. N e i t h e r the e f f e c t , nor the extent of the v a r i o u s forms o f d i s t u r b a n c e with re s p e c t to the l o c a l snow goose p o p u l a t i o n are known, yet 103 t h i s i n f o r m a t i o n i s e s s e n t i a l to the e v a l u a t i o n of h a b i t a t d e s t r u c t i o n by these encroaching developments. The purpose of t h i s part of the study was t o e s t a b l i s h the l e v e l of a c t i v e - d i r e c t i o n a l d i s t u r b a n c e and to monitor the e f f e c t s of such harassments., 7.2 Methods D i u r n a l a c t i v i t y p r o f i l e s were recorded a t h a l f - h o u r i n t e r v a l s . Measurments of f l i g h t behaviour were recorded during the i n t e r i m . During these twenty minute i n t e r v a l s e i g h t counts were conducted of the number of b i r d s i n i t i a t i n g normal f l i g h t i n one minute. At t h a t time the dura t i o n of undisturbed f l i g h t by groups and i n d i v i d u a l s were monitored from i n i t i a t i o n to t e r m i n a t i o n . By r e l a t i n g these f i g u r e s t o the most recent photographic counts i t was p o s s i b l e t o c a l c u l a t e the average percent of the f l o c k i n i t i a t i n g undisturbed f l i g h t each minute. Information concerning d i s t u r b a n c e was c o l l e c t e d whenever p o t e n t i a l hazards came w i t h i n range. Two separate sheets were used to t a b u l a t e the i n f o r m a t i o n . Recorded on the f i r s t sheet were (1) the responses t o a l l forms of a c t i v e - d i r e c t i o n a l d i s t u r b a n c e , (2) the time when geese f i r s t became a l e r t , (3) the time when they i n i t i a t e d f l i g h t , (4) the time when 50 percent of the f l o c k had terminated f l i g h t and (5) the time when 50 percent of the f l o c k resumed 104 undisturbed a c t i v i t i e s . The cause of the d i s t u r b a n c e , i t s e f f e c t and the estimated percentage of the f l o c k so a f f e c t e d a l s o were d e s c r i b e d . The l a r g e number of d i s t u r b a n c e s caused by a i r c r a f t emphasized the need f o r a d e t a i l e d a n a l y s i s of the e f f e c t s of aeroplanes and h e l i c o p t e r s . T h e r e f o r e , a second sheet s t r i c t l y r e l a t e d t o a i r c r a f t d i s t u r b a n c e s was prepared. On i t were recorded <1) the s i z e and type of a i r c r a f t , (2) i t s d i r e c t i o n of f l i g h t , (3) the d i s t a n c e from the observer to the c e n t r e of the goose f l o c k , (4) the d i s t a n c e from the observer to the a i r c r a f t and (5) the angle between them. I t was then a simple matter to c a l c u l a t e the f l u s h i n g d i s t a n c e between the approaching a i r c r a f t and the geese with r e l a t i v e accuracy. The f l i g h t path of the plane was recorded as passing on e i t h e r the landward s i d e , the seaward s i d e or d i r e c t l y over the f l o c k . These data were c o l l e c t e d f o r a l l a i r c r a f t f l y i n g near the geese, whether or not they evoked aa alarmed response. Distances were o b t a i n e d by use of a hand-held, m i l i t a r y - t y p e r a n g e - f i n d e r . S t a t i s t i c a l analyses were performed using M H A . 7.3 R e s u l t s 7.3.1 Avian Predators Although r e c o r d e d elsewhere as o c c a s i o n a l predators of 105 geese, p e r e g r i n e f a l c o n s (Falco p e r e g r i n u s ) , g r y f a l c o n s ( Fal c o E M s t i c o l u s ) , and marsh hawks ( C i r c u s cyaneus) were commonly observed f l y i n g low over the geese without producing alarm. Every approaching bald eagle ( H a l i a e e t u s l e u c o c e p h a l u s ) , on the other hand was watched c l o s e l y . I f i t f s d i r e c t i o n o f f l i g h t c a r r i e d i t d i r e c t l y towards the f l o c k the nearest geese would take f l i g h t as soon as the eagle passed within> a c r i t i c a l f l u s h i n g d i s t a n c e . . Most o f t e n the whole f l o c k would immediately f o l l o w s u i t . As the eagle passed over, geese would f l y ahead and away from i t s f l i g h t path i n a l a r g e a r c and f i n a l l y c i r c l e around behind. They o f t e n landed near t h e i r o r i g i n a l s i t e of t a k e - o f f but u s u a l l y were c l o s e r to the s h o r e l i n e away from the t a l l e r marsh v e g e t a t i o n ; C i r c u l a r escape f l i g h t s were recorded i n a l l cases of eagle-caused d i s t u r b a n c e s except one. In t h i s case a l l of the geese were i n r e l a t i v e l y deep v e g e t a t i o n , as the eagle approached, the geese made a s h o r t , d i r e c t f l i g h t towards the open s h o r e l i n e . However, l i n e a r escape f l i g h t s were r a r e and the g r e a t e s t number o f the d i s t u r b a n c e s r e s u l t e d i n the more common c i r c u l a r f l i g h t s . Escape t a c t i c s such as r a p i d i r r a t i c f l i g h t or folded-wing f r e e - f a l l o f t e n are d i s p l a y e d by ducks ( e s p e c i a l l y t e a l ) when c l o s e l y pressed by avian p r e d a t o r s . However, these s t r a t e g i e s were never employed by snow geese even though they appear capable o f doing so. In 25 of the 28 recorded i n s t a n c e s o f eagle-caused 106 escape f l i g h t the geese landed away from marsh v e g e t a t i o n , along the s h o r e l i n e i n one or two compact f l o c k s . The other three d i s t u r b a n c e s produced a s p l i t i n the f l o c k , each p o r t i o n l a n d i n g elsewhere on the f o r e s h o r e . 7.3.2 Han Humans appeared to e l i c i t a more dramatic response than did avian p r e d a t o r s . E i g h t of nine recorded i n t e r a c t i o n s between humans and snow geese produced d i r e c t and immediate f l i g h t s away from the v i s i b l e t h r e a t while only one c i r c u l a r f l i g h t was observed. T h i s group o f b i r d s c i r c l e d but d i d not attempt to l a n d near t h e i r o r i g i n a l s i t e . On the F r a s e r Delta " l o c a t i o n " appeared to e x e r t only a l i m i t e d c o n t r o l on the l e v e l of d i s t u r b e d f l i g h t . Except f o r Brunswick P o i n t , which had a r e l a t i v e l y s m a l l number of recorded d i s t u r b a n c e s (10 out of 189), the l e v e l of escape f l i g h t was e s s e n t i a l l y the same f o r a l l l o c a t i o n s along the f o r e s h o r e , i n c l u d i n g Sea I s l a n d . 7.3.3 A i r c r a f t H e l i c o p t e r s were by f a r the most d i s t u r b i n g a i r c r a f t type, encountered (Table X I I I ) . Large wheel-planes were appa r e n t l y the second most d i s t u r b i n g type of a i r c r a f t . However, s i n c e only t h r e e o b s e r v a t i o n s of large-wheel planes were recorded, t h i s c o n c l u s i o n must be i n t e r p r e t e d with c a u t i o n . Small and medium f l o a t planes evoked a moderate response, whereas, sma l l and medium wheel planes had very l i t t l e e f f e c t on the geese. 107 3\s the planes approached the geese, the i r r i t a t i v e e f f e c t i n c r e a s e d . However, because of the extreme s e n s i t i v i t y to h e l i c o p t e r s geese were o f t e n put t o f l i g h t at d i s t a n c e s g r e a t e r than 750 m. As a r e s u l t c o e f f i c i e n t s r e p r e s e n t i n g a d i s t a n c e of more than 750 m were more i n d i c a t i v e of a s p e c i a l i z e d long-range type of d i s t u r b a n c e . I f the e f f e c t s o f h e l i c o p t e r s were removed from the a n a l y s i s no geese would have been d i s t u r b e d by a i r c r a f t at these d i s t a n c e s . D i r e c t i o n of plane f l i g h t , approach and l o c a t i o n di d not i n f l u e n c e the l e v e l of a c t i v e d i s t u r b a n c e . G e n e r a l i z e d R 2 showed t h a t the MNA model accounted f o r approximately 33 percent of the observed v a r i a n c e (Table X I I I ) . An a p o s t e r i o r i a p p l i c a t i o n of the model generated 146 c o r r e c t l y c l a s s e d p r e d i c t i o n s of the 189 o b s e r v a t i o n s (Table XIV), an i n c r e a s e i n p r e d i c t i v e power of 24.3 percent over and above t h a t s u p p l i e d by the mode. Of the f i v e independent v a r i a b l e s employed to develop the model, plane type and d i s t a n c e to the geese e x p l a i n e d the g r e a t e s t p r o p o r t i o n of the v a r i a n c e , as shown by t h e i r r e s p e c t i v e g e n e r a l i z e d E t a 2 v a l u e s . Of l e s s importance were the v a r i a b l e s r e p r e s e n t i n g l o c a t i o n , approach and d i r e c t i o n of plane f l i g h t . 108 Table (XIII) - V a r i b l e Response P r o f i l e s : c o e f f i c i e n t s of the a NA model f o r a i r c r a f t d i s t u r b a n c e PREDICTOR CATEGORIES EFFECT VARIABLES Released Escape No E f f e c t F l i g h t D i s t a n c e 0-150 36.72 -36.72 (m) 151-300 7.52 -7.52 (-0925) 301-450 -8.53 8.53 451-700 -14.50 14.50 >701 0.66 -0.66 D i r e c t i o n north 2. 57 -2.57 (.0143) south -0.05 0.05 e a s t 4.09 -4.09 west 10. 97 -10.97 southeast -12. 13 12.13 northwest 7. 08 -7.08 southwest -4.03 4.03 nor t h e a s t -10.50 10.50 A i r c r a f t Type sm a l l wheel plane -25.72 25.72 (.2183) medium wheel plane -32.28 32.28 l a r g e wheel plane 13. 12 -13.12 s m a l l f l o a t plane -5.36 5.36 medium f l o a t plane -0.42 0.42 l a r g e f l o a t plane -17.61 17.61 h e l i c o p t e r 46. 97 -46.97 Approach l a n d s i d e -4. 12 4. 12 (.0192) waterside 2. 95 -2.95 over 1. 15 -1. 15 L o c a t i o n R e i f e l Refuge -5. 89 5.89 (,0579) Brunswick P o i n t 48. 15 -48.15 Lulu I s l a n d -2.05 2.05 Sea I s l a n d 4.85 -4.85 (G e n e r a l i z e d E t a 2 ) G e n e r a l i z e d R2=.3301 1 0 9 T a b l e (XIV) - C l a s s i f i c a t i o n M a trix - an a p o s t e r i o r i assignment of p r e d i c t i o n s f o r the a n a l y s i s of a i r c r a f t d i s t u r b a n c e PREDICTED Released Escape Ho E f f e c t T o t a l F l i g h t Released Escape F l i g h t 76.00 24.00 100 ACTUAL No E f f e c t 21.35 78.65 89 T o t a l 95 94 189 110 7.3.4 Water-bound V e h i c l e s Very l i t t l e maritime t r a f f i c was observed during the study. Of the f o u r s m a l l boats observed t o pass beside the geese only two r e l e a s e d escape f l i g h t . Escape was not u s u a l l y r e l e a s e d u n t i l the boat was very c l o s e to the f l o c k . In one i n s t a n c e the boat a c t u a l l y had passed a l a r g e segment of the f l o c k before the geese f l u s h e d . S i m i l a r delayed r e a c t i o n s by bean geese were recorded i n Sweden (G. Markgren, 1963). The us u a l response of the geese was to c i r c l e and l a n d at approximately the same s i t e . Although a c o a s t guard Hovercraft was observed in the immediate v i c i n i t y of the geese once d u r i n g the study, many i n t e r e s t e d observers have s t a t e d t h a t the H o v e r c r a f t was r e s p o n s i b l e f o r an; extremely high l e v e l of i n t e n t i o n a l harassment i n previous years. While i n the area, the Ho v e r c r a f t was c l o s e l y watched by a l l members of the f l o c k i n s i l e n c e . I t made s e v e r a l passes i n f r o n t of the marsh though no f l u s h i n g occurred, presumably because i t d i d not attempt t o land. 7.3.5 Land V e h i c l e s Wild geese, l i k e a majority of other w i l d animals, d i s p l a y c o n s i d e r a b l e c o n f i d e n c e with r e s p e c t to v a r i o u s types of land-bound v e h i c l e s . I t i s presumed t h a t they do not d i r e c t l y a s s o c i a t e the appearance of t r u c k s , c a r s and even motorcycles with man. Aside from the f a c t t h a t hunting from a motor v e h i c l e i s almost impossible on the f o r e s h o r e . 111 i t i s p r o h i b i t e d by law which, e i t h e r by l e a r n i n g or t r a d i t i o n , c e r t a i n l y may be one reason f o r the perc e i v e d harmlessness of such o b j e c t s . S t a t i o n a r y v e h i c l e s are regarded with l e s s s u s p i c i o n than those which are moving. However, i f a moving v e h i c l e stop a b r u p t l y i t i s immediately regarded with o v e r t s u s p i c i o n . One i n s t a n c e of escape f l i g h t was produced by slow l y approaching the geese i n f r o n t of Sea I s l a n d during pre-dawn i n a v e h i c l e with the h e a d l i g h t s out. When the v e h i c l e h a l t e d those b i r d s c l o s e s t to the dike took f l i g h t . On t h i s occasion the wariness of the geese may have been i n c r e a s e d by the darkness. During d a y l i g h t the same v e h i c l e was g e n e r a l l y ignored and approach was p o s s i b l e t o l e s s than 25 m i n some cases. A human l e a v i n g the v e h i c l e on the other hand, produced an escape f l i g h t at d i s t a n c e s g r e a t e r than 100 m. 7.3.6 F l i g h t Duration By d i v i d i n g the mean number o f b i r d s i n i t i a t i n g undisturbed f l i g h t per minute by the s i z e of the f l o c k under o b s e r v a t i o n i t was p o s s i b l e to c a l c u l a t e the mean percentage of the p o p u l a t i o n i n i t i a t i n g f l i g h t each day. Approximately 0.64 percent of the f l o c k p o p u l a t i o n i n i t i a t e undisturbed f l i g h t each minute. I f e x t r a p o l a t e d over 24 hours, every b i r d i n the p o p u l a t i o n would take f l i g h t an average o f 9.2 times per day. The mean l e n g t h o f time between the i n i t i a t i o n and 112 t e r m i n a t i o n of 1,223 recorded undisturbed f l i g h t s was s i g n i f i c a n t l y s h o r t e r , at 33 +0.77 (SE) seconds, than the mean f o r 136 f l i g h t s i n s t i g a t e d by a i r c r a f t harassment, which l a s t e d an average of 87 + 5.12 (SE) seconds (P<0.001). Assuming t h a t the p a t t e r n o f f l i g h t a c t i v i t y p a r a l l e l e d t h a t of f e e d i n g a c t i v i t y the l e v e l of undisturbed f l i g h t would be c o n s i s t a n t over 24 hours. Therefore, an average of 5.1 minutes of each day i s spent i n normal, undisturbed f l i g h t . D i sturbed f l i g h t v a r i e d tremendously from one day to the next, but over the season, averaged 58.7 seconds of f l i g h t per hour. Aggravated f l i g h t caused by a i r c r a f t was not observed at n i g h t , although i l l e g a l , a f t e r - h o u r s hunting was observed to r e l e a s e a high l e v e l of escape a c t i v i t y . With a mean daylength o f 10 hours d i s t u r b e d f l i g h t a c t i v i t y would then account f o r approximately 10 minutes of ex t r a f l i g h t each day. V i s u a l s t i m u l i are apparently more important to the geese i n i d e n t i f y i n g danger than are a u d i t o r y s t i m u l i . On one o c c a s s i o n when the cloud c e i l i n g was approximately 100 m a h e l i c o p t e r was c l e a r l y heard f o r 34 seconds b e f o r e i t became v i s i b l e . During t h i s time geese showed no response. Once the h e l i c o p t e r dropped through the cloud at a d i s t a n c e of approximately 250 m, w e l l i n s i d e the normal f l u s h i n g d i s t a n c e , the geese immediately took f l i g h t . S e v e r a l other i n s t a n c e s were recorded where h e l i c o p t e r s t a k i n g o f f from 113 the Vancouver I n t e r n a t i o n a l A i r p o r t , ( l e s s than 1.5 km away but hidden behind the L u l u I s l a n d dike) could be heard w e l l before the geese r e a c t e d t o t h e i r v i s u a l presence. 7.4 D i s c u s s i o n I t i s g e n e r a l l y accepted that snow geese, and i n f a c t most waterfowl s p e c i e s , have few s i g n i f i c a n t p r e d a t o r s on t h e i r w i n t e r i n g grounds other than man. Notwithstanding, geese remain extremely s e n s i t i v e to p a r t i c u l a r d i s t u r b a n c e s t i m u l i . So, although predators and man-induced d i s t u r b a n c e s do not p l a y a major r o l e i n the p o p u l a t i o n dynamics of w i n t e r i n g snow geese, the e t h o l o g i c a l a s p e c t s of these r e l a t i o n s h i p s are of i n t e r e s t i n the context of monitoring the i n c r e a s e d l e v e l s of energy expenditure, changes i n d i s t r i b u t i o n p a t t e r n s and u l t i m a t e l y o f the e c o l o g i c a l r e l a t i o n s h i p of snow geese to t h e i r e s t u a r i n e h a b i t a t . 7.4.1 Avian Predators Of those r a p t o r s o c c u r r i n g on the F r a s e r D e l t a , the bal d eagle i s the most important s p e c i e s t h r e a t e n i n g snow geese. Although none of the snow geese under o b s e r v a t i o n were captured or even a c t i v e l y pursued by eagles, 28 i n s t a n c e s of f l u s h i n g were recorded i n 32 days of o b s e r v a t i o n . Hacllhenney (1932) and Howard (1940) r e p o r t e d eagle p r e d a t i o n on snow and blue geese i n the southern 114 United S t a t e s . According t o M. Markgren (1960) the wing movements and " s h o r t neck" o f the s i l o u e t t e of a b i r d are o f such importance i n the r e c o g n i t i o n of avian predators that o f t e n harmless b i r d s with e a g l e - l i k e wing beats produce d i s t u r b e d behaviour. In the present study great blue herons (Ardea herodias) passed over the geese r e g u l a r l y i n v a r i a b l y c a u s i n g an i n c r e a s e i n the l e v e l o f n o i s e and a l e r t n e s s . However, the f l o c k was observed to take f l i g h t i n response to a f l y i n g heron only once d u r i n g the e n t i r e study period i n d i c a t i n g t h at geese were able to d i s t i n g u i s h between herons and e a g l e s t o some degree. The c i r c u l a r escape f l i g h t s employed by snow geese to avoi d eagles i s almost i d e n t i c a l t o the s t r a t e g y recorded by M. Markgren (1963) f o r s e v e r a l s p e c i e s of ducks. C i r c u l a r escape f l i g h t s are advantageous i n that the eagle i s always held i n s i g h t by the b i r d s and they can e i t h e r respond to changes i n i t s hunting behaviour or g u i c k l y r e t u r n to t h e i r previous l o c a t i o n . I t would seem reasonable that a f t e r being f r i g h t e n e d , snow geese would maintain a higher l e v e l of a l e r t n e s s immediately a f t e r s e t t l i n g down. One obvious reason f o r l a n d i n g near the s h o r e l i n e would be t o i n c r e a s e the a b i l i t y to view the surrondings. However, i t was o f t e n observed that w i t h i n minutes of l a n d i n g i n the open the geese would re t u r n i n s m a l l groups to resume f e e d i n g . A l e r t behaviour 115 d i d not remain at e l e v a t e d l e v e l s f o r very long. Escape f l i g h t s along with the observed crowding behaviour would appear to a f f o r d h e a lthy snow geese a s u c c e s s f u l means o f minimizing p r e d a t i o n by e a g l e s . Conversely, i n j u r e d or otherwise unhealthy geese are much more obvious on the marsh by themselves and t h e r e f o r e would be s u b j e c t to a much higher l e v e l of m o r t a l i t y from r a p t o r s . Avian predators are not a d i r e c t t h r e a t to the geese but may i n f l u e n c e t h e i r energy balance by i n c r e a s i n g energy expenditure and r e d u c i n g the e f f e c t i v e f e e d i n g p e r i o d . 7.4.2 Man M. Markgren (1960) i n d i c a t e d t h a t l i n e a r f l i g h t i s a t y p i c a l escape t a c t i c o f c e r t a i n heavy-bodied b i r d s , i n c l u d i n g members of the genus Anser. L i n e a r escape f l i g h t was d i s p l a y e d by snow geese only r a r e l y but most f r e q u e n t l y occurred when d i s t u r b e d by e i t h e r a human i n the marsh or by a gunshot. F l i g h t was d i r e c t l y away from the t h r e a t and the geese showed no apparent i n t e n t i o n s to r e t u r n . Thorpe (1951) s t a t e d t h a t wariness becomes r e a d i l y attached to man as a r e s u l t of experience of the p a r e n t s . From subsequent s t u d i e s i t seems f a i r to assume t h a t hunters are one phenomenon t r a d i t i o n a l l y considered as something to be avoided. Duck and goose hunting i s permitted along the f o r e s h o r e during a l a r g e p o r t i o n o f the time when snow geese are present. The e f f e c t of hunting season has been demonstrated to e x e r t c o n t r o l on t h e i r s e a s o n a l and d i u r n a l 116 d i s t r i b u t i o n . I t i s l i k e l y t h a t humans may be a s s o c i a t e d with the r e p o r t of a gun; the f a l l i n g of f l o c k members, an unknown item i n an otherwise known environment and p o s s i b l y the pain a s s o c i a t e d with shot p e n e t r a t i o n . The avoidance of humans may thus be a combination of e x p e r i e n c e o f the parents and l e a r n i n g by the young. a d d i t i o n a l l y , hunting or e x c e s s i v e d i s t u r b a n c e s on the breeding grounds by humans may predispose both a d u l t and immature geese to acute avoidance of man even p r i o r t o rea c h i n g the w i n t e r i n g grounds. Repeated egg c o l l e c t i n g (Uspenski, 1963} and neck banding o p e r a t i o n s (Sladen, per. comm., 1975) on Wrangel I s l a n d i n a d d i t i o n to s p r i n g hunting (Telpov and Shevareva, 1959) may c o n d i t i o n these b i r d s to " f e a r " humans w e l l before they a r r i v e on the F r a s e r D e l t a . As with other phenomena, the d i s t a n c e between humans and the geese as w e l l as the type of a c t i v i t i e s engaged i n were important i n determining the l e v e l of avoidance. For i n s t a n c e , when present i n the marsh where hunters were normally found, a l l humans evoked d i s t u r b e d r e a c t i o n s . However, people i n f u l l view walking along the d i k e p a r a l l e l to the s h o r e l i n e were e s s e n t i a l l y ignored even though at times they were only 70 t o 80 m f u r t h e r away. while the hunting season was open i t was d i f f i c u l t to approach snow geese c l o s e r than 150 m. However, a f t e r c l o s u r e , the observer twice walked to w i t h i n 100 ra of the f l o c k before r e l e a s i n g s h o r t escape f l i g h t s . From these 117 l a t t e r o b s e r v a t i o n s no c o n c l u s i o n s can be drawn. However, i t i s p o s s i b l e t h a t s e n s i t i v i t y t o human d i s t u r b a n c e i n the marsh i s r e l a t e d to the hunting season. A f t e r c l o s u r e the number of humans i n the marsh became n e g l i g i b l e 7.4.3 Other Species The r e a c t i o n s of geese t o dogs {Canis f a m i l i a r i s ) appears to be c h a r a c t e r i z e d by great r e s t r a i n t . S u r p r i s i n g t o l e r a n c e t o two I r i s h s e t t e r s was d i s p l a y e d by the geese at Brunswick P o i n t . The r a p i d l y approaching dogs e l i c i t e d much neck s t r e t c h i n g and e v e n t u a l l y r e l e a s e d s h o r t escape f l i g h t s by the c l o s e s t geese. However, those b i r d s along the outer periphery of the f l o c k remained a s l e e p . Prowling foxes and dogs i n Sweden are t r e a t e d by bean geese with s i m i l a r d i s r e g r a d and r a r e l y r e l e a s e escape u n t i l the behaviour and d i r e c t i o n of movement appear t o be a g g r e s s i v e (G. Markgren, 1963) . The only other p o s s i b l e mammalian i n t r u d e r s on the e s t u a r y were muskrats. Geese would watch an approaching muskrat on l y i f i t was c l o s e r than about three meters. I f i t was heading d i r e c t l y towards some i n d i v i d u a l s they would slo w l y swim out of i t s path. No a c t i v e avoidance of muskrats was observed. 7.4.4 A i r c r a f t Although i t i s g e n e r a l l y assumed t h a t most s p e c i e s of waterfowl take wing when a i r c r a f t pass over i t has been observed t h a t t h i s r u l e i s not without exception* The 1 18 present study has demonstrated the importance of plane s i z e and type, l o c a t i o n and d i s t a n c e between the f l o c k and the plane i n determining the extent of a i r c r a f t d i s t u r b a n c e . C o n f l i c t i n g r e p o r t s on the degree of escape f l i g h t e l i c i t e d by v a r i o u s types o f a i r c r a f t have been only s p a r s e l y recorded and as a r e s u l t very l i t t l e q u a n t i t a t i v e i n f o r m a t i o n p r e s e n t l y i s a v a i l a b l e . Tinbergen (1957) recorded t h a t goose f l o c k s took wing whenever an aeroplane flew overhead. T h i s o b s e r v a t i o n was supported by G. Markgren (1963) who s t a t e d t h a t white-f r o n t e d geese almost without e x c e p t i o n , took f l i g h t i n response to planes. However, he r e p o r t e d t h a t bean geese under i d e n t i c a l circumstances o f t e n remained on the ground. S u r p r i s i n g l y , a i r c r a f t , i n c l u d i n g h e l i c o p t e r s , were mostly ignored by shelducks i n B r i t a i n (Bryant and Leng, 1975). G. Markgren (1963) s t a t e d that a i r c r a f t type was of minor importance i n e l i c i t i n g d i s t u r b e d f l i g h t from white-f r o n t e d and bean geese. T h i s i d e a was not supported by the present study. On the c o n t r a r y a i r c r a f t type was the f a c t o r of g r e a t e s t importance i n determining the l e v e l of d i s t u r b a n c e . In a d i f f e r e n t study M. Markgren (1960) i n f e r r e d t h a t the b i r d - l i k e body shape of most a i r c r a f t played a l a r g e r o l e i n r e l e a s i n g escape behaviour. He i m p l i e d a l s o that planes may be p e r c e i v e d as " l a r g e predatory b i r d s . " However, at the same time he noted t h a t a s m a l l j e t plane 119 with a d o u b l e - s t r u t e d t a i l ("vampire" type) which was the l e a s t b i r d - l i k e of a l l planes i n t h a t study, caused t o t a l escape r e l e a s e . In the present study, h e l i c o p t e r s , the l e a s t b i r d l i k e of a l l a i r c r a f t on the F r a s e r D e l t a caused the mose dramatic escape behabiour. Snow geese may be so s e n s i t i v e to h e l i c o p t e r s because of t h e i r apparent slow a i r s p e e d and u n p r e d i c t a b l e f l i g h t behaviour compared to other a i r c r a f t . P lanes, on the other hand, may be l e s s menacing because they appear as d i s i n t e r e s t e d passers-by. Planes g e n e r a l l y move a t higher speeds and i n a s t r a i g h t l i n e whereas h e l i c o p t e r s g e n e r a l l y move i n a slow, e r r a t i c f a s h i o n . Tinbergen (1963) s t a t e d that the impression of s i z e or "heaviness" of an aeroplane and t h e r e f o r e i t s i r r i t a t i v e e f f e c t would be g r e a t e r i n a s l o w - f l y i n g o b j e c t . In t h i s l i g h t , i t i s i n t e r e s t i n g t o note that while r e s i d i n g on t h e Sea I s l a n d marsh, the freguent l a n d i n g and ta k i n g o f f of medium to l a r g e j e t planes caused no escape f l i g h t whatsoever. In f a c t , these planes were completely ignored. Even the l a r g e , slow-moving s i l h o u e t t e of a Boeing 747 caused no r e a c t i o n . However, when a Boeing 747 made an abnormal f l i g h t over a d i f f e r e n t p a r t of the f o r e s h o r e , even though at an e x c e p t i o n a l l y high a l t i t u d e , the whole f l o c k took f l i g h t . The presence of l a r g e numbers of a i r c r a f t may help to d e - s e n s i t i z e the b i r d s t o t h i s form of d i s t u r b a n c e . Support 120 f o r t h i s i d e a was, claimed by noting d i f f e r e n c e s i n a i r c r a f t s e n s i t i v i t y by geese i n d i f f e r e n t l o c a t i o n s . Although geese always f l u s h with the d i r e c t approach of a h e l i c o p t e r , t h e i r s e n s i t i v i t y t o t h i s phenomenon i n winter appears t o be much l e s s than what i t i s d u r i n g the autumn. In the Canadian a r c t i c , snow geese have been observed to take f l i g h t i n response t o an approaching h e l i c o p t e r a t d i s t a n c e s of up to 5 km (Barnard, p e r s . comm.). However, on the F r a s e r D e l t a , h e l i c o p t e r s may be t o l e r a t e d at d i s t a n c e s as c l o s e as 750 m before f l u s h i n g . A i r c r a f t wariness thus may be i n v e r s e l y r e l a t e d t o the amount of a i r t r a f f i c i n the area, or i n other words the " n o r m a l i t y of occurrence" attached to a l l components of the environment. D i f f e r e n t l e v e l s of a i r c r a f t d i s t u r b a n c e a l s o were recorded between the two major w i n t e r i n g grounds of the c e n t r a l west co a s t of North America. J e f f r e y (pers. comm.) found i t extremely d i f f i c u l t t o obtain a e r i a l photos of s t a t i o n a r y snow geese at S k a g i t F l a t s because they would take f l i g h t whenever a s i n g l e - e n g i n e d f l o a t plane came within 1.5 to 2 km. On the other hand, geese on the Fraser Delta would, i n many cases, permit a s i m i l a r f l o a t plane to pass d i r e c t l y overhead at h e i g h t s of only 150 m. These anomalous s i t u a t i o n s demonstrate the apparent d i f f e r e n t i a l wariness of snow geese from one part of t h e i r h a b i t a t to another not only between the summer and winter h a b i t a t s but a l s o between d i f f e r e n t segments of t h e i r winter h a b i t a t . 121 Observed d i f f e r e n c e s i n the a b i l i t y of geese to d i s t i n g u i s h between p o t e n t i a l l y harmful and harmless phenomena may be r e l a t e d to f l i g h t path p r e d i c t a b i l i t y i n a d d i t i o n to wing movements and body shape. I f t h i s i s so, the d i f f e r e n c e s between eagles and planes and between planes and h e l i c o p t e r s and the s i m i l a r i t i e s between h e l i c o p t e r s and eagles may be e x p l a i n e d by the l e s s p r e d i c t a b l e , n o n - l i n e a r f l i g h t paths of eagles and h e l i c o p t e r s . I t would seem p o s s i b l e then t h a t o b j e c t s moving i n an i r r a t i c f a s h i o n would more resemble an a c t i v e l y pursuing predator than would one with p r e d i c t a b l e motion and t h e r e f o r e would maintain a higher e s c a p e - r e l e a s i n g p o t e n t i a l even a f t e r repeated passes with no a c t i v e p u r s u i t . Although the d i r e c t i o n of plane f l i g h t has been l i s t e d as an important d i s t u r b a n c e f a c t o r elsewhere (G. Markgren, 1960), i t was not s i g n i f i c a n t i n r e l e a s i n g escape by snow geese. However, the d i s t a n c e between geese and the approaching plane, which i n c o r p o r a t e d both v e r t i c a l and h o r i z o n t a l componants, was p r e d i c t a b l y very important. As the d i s t a n c e decreased the l e v e l of d i s t u r b e d f l i g h t i n c r e a s e d . T h i s s i t u a t i o n may be expected i n that most o b j e c t s appear more t h r e a t e n i n g as they get c l o s e r . I t i s d i f f i c u l t to decide to what extent a u d i t o r y s t i m u l i i n f l u e n c e escape behaviour. On s e v e r a l o c c a s sions extremely noisy planes were observed to pass over the f l o c k 122 at low a l t i t u d e s with no apparent e f f e c t while r e l a t i v e l y g u i e t planes under s i m i l a r circumstances caused f l u s h i n g . I t has been s p e c u l a t e d t h a t the throbbing sounds produced by h e l i c o p t e r s act to enchance t h e i r t h r e a t e n i n g posture. However, the r e s u l t s of t h i s p a r t of the study l e a d to the c o n c l u s i o n t h a t the v i s u a l i d e n t i f i c a t i o n of an a i r c r a f t evokes a higher l e v e l of d i s t u r b a n c e than does i t s a s s o c i a t e d n o i s e s . In almost a l l recorded cases of a i r c r a f t d i s t u r b a n c e geese escaped using the same c i r c u l a r - f l i g h t t a c t i c as used to av o i d e a g l e s . However, l e s s time appeared to be spent r e c o v e r i n g from the shock before f l y i n g back i n t o the marsh. 123 liO_JI£ICIENCYjOF_FOOD_U 8.1 I n t r o d u c t i o n Though d i f f i c u l t t o q u a n t i f y d i r e c t l y , energy flow through the components of a given ecosystem r e p r e s e n t s an important step i n the a n a l y s i s of t r o p h i c s t r u c t u r e . To p r o p e r l y understand the f u n c t i o n i n g of a p o p u l a t i o n under a p a r t i c u l a r s e t o f environmental c o n d i t i o n s i t i s imperative to know how e f f i c i e n t l y i n d i v i d u a l s are a b l e to u t i l i z e t h e i r food r e s o u r c e . R e g u l a t i o n of v a r i o u s a c t i v i t i e s and d i s t r i b u t i o n throughout the h a b i t a t then may be r e l a t e d to the a v a i l a b l e energy. Compared to the domestic fowl l i t t l e i s known about the n u t r i t i o n o f w i l d b i r d s . Because of t h i s d i s p a r i t y many workers have a p p l i e d the r e s u l t s obtained on p o u l t r y to grouse, q u a i l and pheasant. However, snow geese d i f f e r a n a t o m i c a l l y and p h y s i o l o g i c a l l y from g a l l i n a c e o u s s p e c i e s and r e s u l t s obtained on p o u l t r y are not d i r e c t l y a p p l i c a b l e . Over the years there has been a tremendous amount of work conducted on the food h a b i t s of f r e e - r a n g i n g waterfowl. However, emphasis has been on d i e t composition r a t h e r than on d i e t q u a n t i t y and q u a l i t y . Those which had endeavoured to monitor the more s a l i e n t f e a t u r e s of waterfowl n u t r i t i o n were r e s t r i c t e d to the a n a l y s i s of a r t i f i c i a l d i e t s on young growing b i r d s (Penney and B a i l e y , 1970; Sugden, 1971). Very 124 l i t t l e work had been d i r e c t e d towards determining the n u t r i t i o n a l q u a l i t y of n a t u r a l foods using a d u l t waterfowl. 8.1.1 M e t a b o l i z a b l e energy M e t a b o l i z a b l e energy {ME) i s c o n s i d e r e d to be the most meaningful e x p r e s s i o n of d i e t a r y energy content. I t r e p r e s e n t s the gross energy of a food substance i n k c a l per g consumed minus the t o t a l amount of energy voided i n f e c a l and u r i n a r y e x c r e t i o n s a t zero n i t r o g e n balance. In a d d i t i o n to being the most meaningful e x p r e s s i o n of a v a i l a b l e food energy, e s p e c i a l l y f o r an animal i n a c o l d environment, i t i s e s s e n t i a l l y u n a f f e c t e d by age, sex or l e v e l of food i n t a k e (above 30 percent of ad l i b i t u m i ntake) and can be measured with r e l a t i v e accuracy. 8.1.2 Passage Rate In order to e v a l u a t e the a b i l i t y of an organism to e f f e c t i v e l y u t i l i z e i t s food r e s o u r c e i t i s necessary to o b t a i n an estimate of d i g e s t i v e e f f i c e n c y . D i g e s t i v e e f f i c i e n c y i s p r o p o r t i o n a l to the p e r i o d of time during which a given food sample remains i n the gut. T h e r e f o r e , knowledge of the passage r a t e , and the manner i n which i t i s a f f e c t e d by the amount of food contained w i t h i n the gut, may be o f s i g n i f i c a n c e when c o n s i d e r i n g t h e balance between the b i o l o g i c a l demands of the b i r d s and the amount o f time a v a i l a b l e i n which to s a t i s f y them. Because t i d a l o s c i l l a t i o n s a l t e r n a t e l y cover and expose p o r t i o n s of the three-sguare zone, f e e d i n g c o n d i t i o n s on the 125 f o r e s h o r e are i d e a l f o r only s h o r t p e r i o d s d u r i n g the day. In the absence of a s t o r a g e organ f u n c t i o n a l l y analagous to the crop and assuming a low d i g e s t i v e e f f i c i e n c y , geese must process l a r g e volumes of food during these s h o r t p e r i o d s . I t t h i s p o i n t the a b i l i t y t o a l t e r the passage r a t e i n response to changes i n f e e d i n g i n t e n s i t y becomes r e l e v a n t to the study of h a b i t a t u t i l i z a t i o n . 8.1.3 Gut Morphology Over the l a s t 25 years, d i e t q u a l i t y i n terms of f i b e r content has been shown to a f f e c t the i n t e r n a l morphology of c e r t a i n a vian s p e c i e s . Consumption o f a d i e t high i n crude f i b e r r e s u l t s i n a g r e a t e r a b s o r p t i v e s u r f a c e w i t h i n the gut due to i n c r e a s e s i n the dimensions and weight of the d i g e s t i v e organs (Leopold, 1953; Moss, 1974; Pendergast and Boag, 1973). Lewin (1963) observed i n c r e a s e s i n the length and p r o l i f e r a t i o n of i n t e s t i n a l mucosal v i l l i with an i n c r e a s e d f i b e r content i n the d i e t of C a l i f o r n i a Q u a i l . D i g e s t i v e e f f i c i e n c y i s c o n t r o l l e d to a l a r g e degree by the a b i l i t y of a s p e c i e s to adapt s u c c e s s f u l l y to changes i n d i e t q u a l i t y . L i t t l e work has been conducted on the a b i l i t y of f r e e - r a n g i n g waterfowl to p h y s i c a l l y modify d i g e s t i v e c a p a b i l i t i e s i n response to these changes. M o r p h o l o g i c a l adaptations to changes i n d i e t q u a l i t y are of p a r t i c u l a r importance d u r i n q the major seasonal changes i n food h a b i t s a s s o c i a t e d with m i g r a t i o n . U n t i l r e c e n t l y , a l l work d e a l i n g with changes i n gut morphology was r e s t r i c t e d to t h a t on 126 g a l l i n a c e o u s b i r d s and was o f t e n i n c i d e n t a l to the study of c e l l u l o s e d i g e s t i o n . At present, no records of the len g t h and c a p a c i t y of the d i g e s t i v e organs of f r e e - r a n g i n g snow geese are a v i a l a b l e . Except f o r M i l l e r (1975) who demonstrated that high l e v e l s of d i e t a r y f i b e r produced r a p i d i n c r e a s e s i n the d i g e s t i v e organ s i z e of young mallards, work conducted on w i l d waterfowl has been l i m i t e d . The purpose o f t h i s p o r t i o n of the study was t o e s t a b l i s h the mean g a s t r o -i n t e s t i n a l c a p a c i t y o f w i l d snow geese and to monitor seasonal changes, i f any, r e s u l t i n g from an i n c r e a s e i n the d i e t a r y l e v e l s o f crude f i b e r . 8.2 Methods When t e s t i n g f o r d i g e s t i v e e f f i c i e n c y , i t i s important that the d i e t be as s i m i l a r to t h a t s e l e c t e d by f r e e - r a n g i n g b i r d s i n terms of p h y s i c a l form, composition and p r o p o r t i o n . I d e a l l y , s u b j e c t s should be maintained under s i m i l a r c o n d i t i o n s with r e s p e c t to ambient temperature, humidity and photoperiod as those found i n the n a t u r a l s i t u a t i o n . A c t i v i t y and energy expenditure should a l s o approach normal l e v e l s . Although i t was not p o s s i b l e t o allow freedom of movement i t was p o s s i b l e t o place c a p t i v e snow geese under semi - n a t u r a l environmental c o n d i t i o n s and to supply them with a r e p r e s e n t a t i v e d i e t . 127 I t has been demonstrated that l e s s e r snow geese may s u b s i s t almost e x c l u s i v e l y on a d i e t of the rhizomes of three-sguare b u l l r u s h w h ile w i n t e r i n g on the F r a s e r D e l t a . I f so, i t may be assumed t h a t the rhizomes provide a complete balanced d i e t * A t e s t d i e t c o n s i s t i n g e n t i r e l y of three-sguare rhizomes may then be r e p r e s e n t a t i v e of a n a t u r a l d i e t s e l e c t e d by f r e e - r a n g i n g geese. 8.2.1 M e t a b o l i z a b l e Energy Ten l e s s e r snow geese were obtained from the George C. R e i f e l Migratory B i r d Sanctuary i n l a t e March, 1975. Cages were c o n s t r u c t e d of 2.5 cm mesh 92 cm l o n g by 31 cm wide by 62 cm high, a f f o r d i n g the geese adequate but minimal f r e e space. G r i t was s u p p l i e d ad l i b i t u m i n s i d e the water c o n t a i n e r s . Strong p l a s t i c food baskets were wired i n t o each cage. They were deep enough to minimize s p i l l a g e and so r e q u i r e d a concave l i p c u t i n t o the f r o n t - f a c i n g s i d e p e r m i t t i n g access to the food. A continuous flow of water was s u p p l i e d to each cage* Angled, sheet metal, c o l l e c t i n g t r a y s were placed under each cage so that a l l droppings and s p i l l e d rhizomes c o u l d be c o l l e c t e d without l o s s . Geese were placed i n the cages and f e d commercial duck p e l l e t s . Of t h e ten geese, two f a i l e d to a d j u s t to these c o n d i t i o n s and were returned t o the r e f u g e . These b i r d s were r e p l a c e d with three which had been r a i s e d from one day o l d on the u n i v e r s i t y campus, two of which adapted w e l l to the cages. A l l b i r d s were i n good h e a l t h d u r i n g the t r i a l s 128 and became d o c i l e r a p i d l y . Esohogeal samples from the h u n t e r - k i l l e d geese demonstrated t h a t the rhizome s i z e i n the gut v a r i e d from 2 to 5 cm i n l e n g t h . The long rhizomes were s e c t i o n e d i n t o p i e c e s of t h i s s i z e . When presented to the geese i n t h i s form, only one goose re f u s e d to e a t . I t was then necessary to c o l l e c t enough rhizomes f o r s i x days, a three day a c c l i m a t i o n p e r i o d plus a three day f e e d i n g t r i a l . Rhizomes (20 kg) were c o l l e c t e d from the Sea I s l a n d marsh over a p e r i o d of f o u r days. a f t e r each day the rhizomes were washed and r e f r i g e r a t e d whole. Once a s u f f i c i e n t amount had been c o l l e c t e d they were s e c t i o n e d and s t o r e d o v e r n i g h t i n a i r - t i g h t p l a s t i c bags. During the f o u r days p r i o r to the t r i a l the commercial p e l l e t e d r a t i o n was r e p l a c e d with 300 g of rhizomes per day.. On the morning the t r i a l was to begin, the geese were removed from t h e i r cages and placed o u t s i d e . The c o l l e c t i n g pans were scraped c l e a n and washed thoroughly with detergent and water and f r e s h g r i t and water were provided . Samples of rhizome p i e c e s were weighed and placed i n s m a l l p r e l a b e l l e d p l a s t i c bags two hours before f e e d i n g . Samples were removed randomly at each f e e d i n g d u r i n g the t r i a l and fro z e n f o r l a t e r a n l a y s i s . Each goose was given a preweighed sample a t the beginning of the t r i a l . The geese were f e d twice d a i l y at 10:00 and 20:00 f o r three days. On the morning of day f o u r , a l l the geese were t r a n s f e r r e d from the cages to communal 129 h o l d i n g pens. S p i l l e d rhizomes were separated from the f e c e s . Each water pan was emptied through double l a y e r s of ch e e s e c l o t h to c o l l e c t any suspended m a t e r i a l s . Feces, uneaten rhizomes and s p i l l e d rhizomes were f r o z e n f o r subsequent a n a l y s i s . The experiment was repeated two weeks l a t e r on the same group of b i r d s . In the l a b o r a t o r y , rhizome and f e c a l samples were d r i e d at 80°C to constant weight. Gross energy (GE) determinations of each sample were performed on a Gallenkamp a d i a b a t i c bomb c a l o r i m e t e r . Nitrogen l e v e l s were determined by raacro-Kjeldahl. M e t a b o l i z a b l e energy values c o r r e c t e d f o r d e v i a t i o n from n i t r o g e n balance. Computations are adjusted to a c o n d i t i o n of zero n i t r o g e n r e t e n t i o n by adding the energy content of u r i c a c i d (8.22 kcal/gm) e q u i v a l e n t to the amount of n i t r o g e n r e t a i n e d per gram of feed consumed. The c a l c u l a t i o n s f o l l o w e d those of S c o t t et a l . , (1969, p. 491). 8.2.2 Passage Rate Passage r a t e i s a nebulous term which has been a p p l i e d to s e v e r a l d i f f e r e n t measurements by v a r i o u s authors. In g e n e r a l , t h e r e are three methods used t o estimate passage r a t e : (1) " i n i t i a l through-put-time" ( a f t e r Mattocks, 1970) (herein r e f e r e d to as time of f i r s t passage) — time between the f i r s t f e e d i n g and the f i r s t d e f e c a t i o n caused by t h a t f eeding. 130 (2) " f i r s t and l a s t mean r e t e n t i o n time" ( a f t e r Biondo, 1953) — the average of the time p e r i o d s between f i r s t consumption and f i r s t d e f e c a t i o n and f i r s t consumption and l a s t d e f e c a t i o n . (3) "cumulative mean r e t e n t i o n time" ( a f t e r C a s t l e , 1956) — the average of the r e t e n t i o n times c a l c u l a t e d a f t e r the e x c r e t i o n o f 5%, 15%, 25%..., 95% of e i t h e r the e n t i r e meal or of an i n e r t marker substance placed i n the feed. Although e s t i m a t e s of passage r a t e have been obtained with domestic geese f ed a r t i f i c i a l l y prepared d i e t s , very l i t t l e i n f o r m a t i o n e x i s t s r e g a r d i n g wild geese on n a t u r a l d i e t s . The a v a i l a b l e data tends to be r a t h e r vague and o f t e n i s not accompanied by any r e f e r e n c e t o technigue. This l a c k of a standard technique makes comparisons with other s t u d i e s d i f f i c u l t . To f a c i l i t a t e i n c o r p o r a t i o n of the r e s u l t s from r e l a t e d s t u d i e s , i t was necessary t o perform a l l three methods. The desiqn of the experiment was such t h a t i t permitted the t e s t i n g of passage r a t e a t two d i f f e r e n t l e v e l s of s a t i e t y . E i g h t b i r d s were t e s t e d when t h e i r guts were empty and f o u r were t e s t e d t wice each when t h e i r guts were approximately 30 percent f u l l . Fresh rhizomes were c o l l e c t e d from the Sea I s l a n d marsh. The rhizomes were washed, s e c t i o n e d and r e f r i g e r a t e d o v e r n i g h t . The next day 500 g of s e c t i o n e d rhizomes were 131 d i v i d e d i n t o e i g h t a l l o t m e n t s of 50 to 60 g each. The remaining 750 g were d i v i d e d i n t o e i g h t p o r t i o n s of 75 t o 80 grams each. To four of the samples were added 0.05 g of f e r r i c oxide and to the remaining samples were added 0.05 g of chromic oxide. Each of these samples were mixed thoroughly. The s u r f a c e moisture caused the marker substances to adhere to the o u t s i d e of the rhizomes. E i g h t of the geese used i n the m e t a b o l i z a b l e energy t r i a l s were used i n t h i s experiment and were maintained i n the same cages. Food was removed the evening b e f o r e the experiment commenced. The next morning a l l f e c a l m a t e r i a l was removed from each of the c o l l e c t i n g t r a y s . a t 11:10 the e i g h t geese were given 50 g of unmarked rhizomes.. At s u c c e s s i v e ten minute i n t e r v a l s the cages were checked f o r the presence of f e c a l output. As f e c e s were encountered they were placed i n s m a l l c o n t a i n e r s p r e v i o u s l y l a b e l l e d with the goose i d e n t i f i c a t i o n number and the time of c o l l e c t i o n . Four of the e i g h t geese consumed rhizomes without h e s i t a t i o n . These b i r d s subsequently r e c e i v e d the rhizomes marked with f e r r i c oxide. The same geese then were presented with the chromic o x i d e - t r e a t e d rhizomes. C o l l e c t i o n of f e c e s proceeded c o n t i n u o u s l y f o r seven and one-half hours. The c o l l e c t e d f e c e s then were f r o z e n . A recheck of the t r a y s l a t e r that evening r e v e a l e d no f u r t h e r d e f e c a t i o n s c o n t a i n i n g rhizomatous m a t e r i a l . 132 Each f e c a l sample was placed i n a f o r c e d draught drying oven at 100°C overnight- A f t e r weighing, the samples were ashed at 600°C f o r 6 hours. Where q u a n t i t i e s permitted, ash samples of 0.05 g were placed i n 15 ml beakers t o which was added approximately 10 ml of an equal s o l u t i o n of 3N HCl and 4N HN03. T h i s mixture was b o i l e d f o r f i v e minutes, then f i l t e r e d through Whatman No. 4 paper i n t o p r e l a b e l l e d 30 ml g l a s s s c i n t i l l a t i o n v i a l s . Each 10 ml beaker was washed with 5 ml d i s t i l l e d water through the f i l t e r paper so t h a t each sample was d i s s o l v e d i n 15 ml o f s o l u t i o n s Samples were then analyzed f o r Fe and Cr on an atomic a b s o r p t i o n spectrophotometer. 8.2.3 Gut Morphology Measurements were c a r r i e d out on n i n e t y h u n t e r - k i l l e d snow geese to determine the average d i g e s t i v e organ dimensions and to e s t a b l i s h whether or not adaptive morphological changes had occurred d u r i n g the p e r i o d from when the b i r d s f i r s t a r r i v e d on the F r a s e r D e l t a i n mid-October u n t i l t h e i r departure i n l a t e A p r i l . To f a c i l i t a t e s e p a r a t i o n of the morphological changes o c c u r r i n g over time i t was decided t o d i v i d e the data i n t o : (1) new a r r i v a l s only-{those b i r d s shot i n O c t o b e r ) , (2) a mixture of l a t e and e a r l y a r r i v a l s - ( t h o s e b i r d s shot i n November and December), (3) geese exposed to a d i e t of three-square rhizomes 133 e x c l u s i v e l y f o r more than one month-(those b i r d s shot i n March) . The c o l l e c t i o n of snow goose GI t r a c t s has been d e s c r i b e d i n S e c t i o n 4.0. P r i o r t o removal of gut contents measurements were taken, i n c l u d i n g the l e n g t h and, whenever p o s s i b l e , the volume of the esophagus, p r o v e n t r i c u i u s , g i z z a r d , s m a l l i n t e s t i n e , l a r g e i n t e s t i n e and ceca. The l e n g t h , depth and width of each g i z z a r d was recorded as was the weight. The date of each k i l l was recorded e n a b l i n g a seasonal d i s t r i b u t i o n of the i n t e r n a l organ measurements to be made. I t was a l s o p o s s i b l e t o separate each b i r d on the b a s i s of sex and age (adult or immature) and thereby r e l a t e each of these parameters to the s i z e and weight of the v a r i o u s p o r t i o n s of the GI t r a c t . Records were kept of the dry weights of i n g e s t a found i n each p o r t i o n of the gut. From t h i s data the mean dry weight c a p a c i t y of the ali m e n t a r y t r a c t was c a l c u l a t e d . 8.3 Results 8.3.1 M e t a b o l i z a b l e Energy The average m e t a b o l i z a b l e energy (ME) value of three-sguare b u l l r u s h , rhizomes was 1.43 k c a l per g (dry matter) (Table XV). A n a l y s i s of the data showed no s i g n i f i c a n t d i f f e r e n c e (P< 0.05) between the mean values o b t a i n e d i n the 134 f i r s t and second t r i a l s although d i f f e r e n c e s between i n d i v i d u a l s were apparent. Table (XV) - N i t r o g e n - c o r r e c t e d ME va l u e s f o r the rhizomes of S c i r p u s americanus Gross Excreta N cor- ME S.E. Energy Energy r e c t i o n (kcal/g) (kcal/g) (kcal/g) (kcal/g) T r i a l 1 3.96 2. 49 0.020 1.45 0.043 T r i a l 2 4.05 2.63 0.0 15 1.41 0.053 Mean 4.01 2. 56 0.017 1. 43 Because the mean value of the two b i r d s best adapted to c a p t i v e c o n d i t i o n s was 1.60 k c a l per g the a c t u a l ME a v a i l a b l e to f r e e - r a n g i n g snow geese may be somewhat higher than the mean presented here. However, with the s m a l l s i z e of the t r i a l group and the s u c c e s s f u l r e p r o d u c t i o n o f the same mean values over two t r i a l s , i t i s l i k e l y t h a t 1.43 k c a l per g i s a reasonable minimum e s t i m a t e of the ME contained i n three-sguare rhizomes. C o r r e c t i o n s f o r the energy l o s s e s due t o the normal e x c r e t i o n of u r i c a c i d i n the f e c e s were s m a l l . In a l l cases the amount of n i t r o g e n e i t h e r r e t a i n e d or l o s t was l e s s than 6 mg per g of d i e t consumed. Of the f i f t e e n geese u t i l i z e d i n the two t r i a l s only one was i n negative n i t r o g e n balance. The average c o r r e c t i o n f o r n i t r o g e n e x c r e t i o n was 0.017 k c a l per g of d i e t consumed (Table XV). T h i s s i t u a t i o n , o f e s s e n t i a l l y zero n i t r o g e n l o s s , i n d i c a t e s that three-sguare rhizomes may 135 have s u f f i c i e n t l y high l e v e l s o f m e t a b o l i z a b l e p r o t e i n to meet the d a i l y reguirements of the geese even at the a r t i f i c i a l l y low l e v e l s of v o l u n t a r y i n t a k e . Dry matter i n t a k e v a r i e d from a low o f 66.0 g to a high of 136.5 g. Mean d i g e s t i b i l i t y was 28 percent. Average dry matter content was low, approximately 18 percent, d e s p i t e the r e l a t i v e l y high crude f i b e r content of 21.9 p e r c e n t . 8.3.2 Passage Rate The time of f i r s t passage d i s p l a y e d no tendency to change as the amount of food i n the gut changed (Table XVI). Although the mean remained cons t a n t , the v a r i a t i o n between in the i n d i v i d u a l r a t e s i n c r e a s e d n o t i c a b l y as food comsumption i n c r e a s e d . Though not c o n c l u s i v e , the data i n d i c a t e t h at passage r a t e , may not be g r e a t l y a f f e c t e d by changes i n the amount of food contained i n the g a s t r o i n t e s t i n a l t r a c t . Table (XVI) - Passage r a t e d e t e r m i n a t i o n s - Times of f i r s t passage (minutes) Goose Number 01 03 05 06 07 08 09 Mean No marker 60 50 60 60 60 60 60 57.5 Fe marker 50 40 90 50 57.5 Cr marker 55 35 75 65 57.5 Mean 55 4 2 75 58 57.5 The mean r e t e n t i o n time f i r s t and l a s t d e f e c a t i o n rhizomes was 42.5 minutes (n based on of those = 4; SD the p e r i o d between the geese f e d the unmarked = 5.0) . This very 136 r a p i d r a t e of passage may be due, i n p a r t , to the small q u a n t i t i e s of food i n g e s t e d . These b i r d s d i d not consume a l l of the o f f e r e d rhizomes w i t h i n t h i r t y minutes f o l l o w i n g p r e s e n t a t i o n and, as a r e s u l t , were not given any marked rhizomes. Measurements of the f i r s t and l a s t occurrences of e i t h e r f e r r i c or chromic oxide gave a much l o n g e r and presumably more r e p r e s e n t a t i v e r e t e n t i o n time of approximately 134 minutes (Table XVII). As with the time of f i r s t passages, variance i n c r e a s e d g r e a t l y with an i n c r e a s e i n gut c o n t e n t s . Table (XVII) - Passage r a t e determinations - F i r s t and l a s t mean r e t e n t i o n times (minutes) Goose Number 01 04 08 09 Mean Fe marker 150 140 100 170 1 40 Cr marker 130 150 110 120 128 Mean 140 145 105 145 134 The cumulative mean r e t e n t i o n times were s l i g h t l y more r a p i d than those estimated by the " f i r s t and l a s t " method* The c a l c u l a t e d v a l u e using f e r r i c oxide was 119 minutes while that using chromic oxide was 121 minutes, g i v i n g a mean cumulative r e t e n t i o n time of 120 minutes. Because these are cumulative f i g u r e s i t was not reasonable to c a l c u l a t e standard d e v i a t i o n s . However, the data i n d i c a t e a l a r g e amount of v a r i a n c e a s s o c i a t e d with those e s t i m a t e s obtained by u s i n g the marked rhizomes. 137 F i g u r e 3 ; Cummulat ive Percen tage of Fe Marker Recovered in the Feces of Four C a p t i v e Snow Geese over Time Time ( m inutes ) 138 8.3-3 Gut Morphology I t was found that the mean s m a l l i n t e s t i n e length i n c r e a s e d s i g n i f i c a n t l y (P<0.05) from October t o March (Table XVIII) . An i n c r e a s e was a l s o noted from the time of f i r s t a r r i v a l to mid-November and December. However, i t was not s i g n i f i c a n t . G i z z a r d s i z e i n c r e a s e d s i g n i f i c a n t l y (P<0.01) from mid-autumn to l a t e w i n t e r . No s i g n i f i c a n t changes i n l e n g t h were observed i n e i t h e r the p r o v e n t r i c u l u s , l a r g e i n t e s t i n e or ceca. Table (XVIII) - Seasonal changes i n mean i n t e r n a l organ dimensions Organ Date of C o l l e c t i o n October November/ March (n) December (n) (n) Small I n t e s t i n e l e n g t h (cm) 177 (29) * 185 (26) i 196 (22) 2 Large I n t e s t i n e l e n g t h (cm) 14.0 (26) 14. 2 (26) 14.0 (22) T o t a l C e c a l l e n g t h (cm) 55.2 (29) 57. 4 (24) 57. 1 (19) G i z z a r d weight (g) 122 (29)» 146 (25) 2 142 (22) 2 Small I n t e s t i n e c a p a c i t y (g/cm) 0.89 (11)* 1.02 (13) 2 1.37 (11 ) 3 A s i g n i f i c a n t l y l a r g e r (P<0.05) dry matter c a p a c i t y of the s m a l l i n t e s t i n e was observed i n well-adapted i n d i v i d u a l s as compared to unadapted ones., U n f o r t u n a t e l y , the smal l q u a n t i t y of food found i n the upper p o r t i o n s o f the gut i n b i r d s s u p p l i e d by hunters precluded meaningful s t a t i s t i c a l analyses of changes i n the f u l l c a p a c i t y o f other p a r t s of 139 the GI t r a c t (Table XIX) . S i m i l a r l y , esophagi most f r e q u e n t l y were severed w e l l below the b u c c a l o r i f i c e , reducing the number of a c c u r a t e q u l l e t l e n g t h measurements. No s i g n i f i c a n t age or s e x - r e l a t e d d i f f e r e n c e s were found. Table (XIX) - F u l l - g u t dry matter c a p a c i t y Organ Mean Length n Mean Cap- Mean (cm) a c i t y (g/cm) C a p a c i t y Esophagus 27.0 13 0.27 7.3 P r o v e n t r i c u l u s 4.3 76 0.25 1. 1 Small I n t e s t i n e 186 81 0.12 16.8 Large I n t e s t i n e 14.0 78 0.13 1.8 T o t a l 28.8 U t i l i z i n g mean values f o r le n g t h and c a p a c i t y (Table XIX) the average amount of food c o n t a i n e d in a f u l l gut was c a l c u l a t e d to be approximately 28.8 g dry matter. T h i s value agrees c l o s e l y with that obtained by d i r e c t measurements of geese whose GI t r a c t s were e s s e n t i a l l y f u l l . D i r e c t measurements v a r i e d from a minimum of 25.4 g to a maximum of 37.7 g, with a mean of 30.2 g. 8.4 D i s c u s s i o n 8.4.1 M e t a b o l i z a b l e Energy To mantain body weight during the winter i n South Dakota, c a p t i v e s h a r p - t a i l e d grouse were f o r c e d to i n c r e a s e t h e i r d a i l y ME consumption to 35 percent above standard 140 metabolic r a t e (SMR) {Evans and D i e t z , 1 974). Since ambient winter temperatures measured on the U.B.C. campus during the ME t r i a l s averaged 9°C and were much warmer than those presumably encountered i n a South Dakota winter, a f i g u r e of 35 percent may be c o n s i d e r e d a maximum i n c r e a s e i n the d a i l y energy demands of caged snow geese. For non-passerine b i r d s SMR i s c a l c u l a t e d as SMR=74.3 ( B ) 0 . 7 * * where W i s the body weight i n kg and SMR i s the s t a n d a r d metabolic r a t e expressed i n terms of k c a l per day ( S t u r k i e , 1965). SMR f o r a 2.5 kg snow goose i s approximately 147 k c a l per day. A 35 percent i n c r e a s e would mean the geese would have to consume 198 k c a l per day. At 1.43 k c a l per g t h i s requirement would represent about 138 g of rhizomes per day. To ob t a i n at l e a s t 30 percent of the p r o j e c t e d ad l i b i t u m i n t a k e , the geese r e g u i r e about 40 g of rhizomes each day. E i g h t of the 10 c a p t i v e geese over the perio d of the two t r i a l s consumed greater than 40 g per day and t h e r e f o r e were considered v a l i d s u b j e c t s f o r ME d e t e r m i n a t i o n s . ME content o f the rhizomes appear t o be r e l a t i v e l y low compared to the values of most c u l t i v a t e d g r a i n s . Wheat and b a r l e y , f o r example, possess ME l e v e l s f o r p o u l t r y upwards of 3.20 k c a l per g (N a t i o n a l Academy of S c i e n c e s , 1971). Even though the passage r a t e of waterfowl i s much g r e a t e r than i n p o u l t r y , mallards obtained the same ME l e v e l s from these g r a i n s as d i d chickens (Sugden, 1971). The amount of food i n g e s t e d by b i r d s depends p r i m a r i l y 1 4 1 on the energy demands of each i n d i v i d u a l . When a d i e t i s adequately balanced i n the l e v e l s of a l l n u t r i e n t s , b i r d s w i l l consume a d i e t to o b t a i n a constant i n t a k e of ME each day (Scott et a l . , 1969). E x i s t e n c e energy i s d e f i n e d as the amount of HE i n t a k e r e q u i r e d t o maintain body weight f o r an extended p e r i o d of time (Kendeigh, 1970). At 0°C e x i s t e n c e energy may be c a l c u l a t e d by the formula log m = 0.6372 +0.5300 l o g w, where m i s the energy expenditure i n k c a l per b i r d per day and w i s the weight of the b i r d i n g. Because of the high humidity and constant wind along the fore s h o r e i t was f e l t t h a t e x i s t e n c e energy c a l c u l a t e d f o r a mean temperature of 0°C would more c l o s e l y r e p r e s e n t the maximum d a i l y energy expenditure of f r e e - r a n g i n g snow geese than would SMR even though the mean temperature from November 1974 to March 1975 was 4°G (Environment Canada, 1975). From t h i s equation the e x i s t e n c e energy of a 2.5 kg goose i s 274 k c a l per day. 8.4.2 Passage Hate Although the mean length of time snow geese r e t a i n e d three-sguare rhizomes i n t h e i r a l i m e n t a r y t r a c t was only two hours, the r e s u l t s of other s t u d i e s i n d i c a t e t h a t the passage r a t e s of other s p e c i e s of geese are much more r a p i d . Because of the incomplete and o f t e n vague r e p o r t i n g of experimental technique and d i e t composition i t i s d i f f i c u l t to assess and compare mean r e t e n t i o n time r e s u l t s from other s t u d i e s on Anatinidae. However, e a r l y s t u d i e s have been 142 conducted on domestic geese (Anser- anser) which can be r e l a t e d t o times of f i r s t passage. Workers using dyed c l o t h and c h a r c o a l as markers repo r t e d times of f i r s t passages i n domestic geese of up to Workers using dyed c l o t h and c h a r c o a l as markers reported times of f i r s t passages in domestic geese of up to 240 minutes (Mariott and Forbes, 1 970). Dorozunska (1963) presented f i g u r e s r a n g i n g from 76 to 270 minutes f o r o l d e r and younger b i r d s r e s p e c t i v e l y when f e d a "green" d i e t (but found no c o r r e l a t i o n between passage r a t e and body s i z e ) . More r e c e n t l y , i n experiments with domestic geese the time of f i r s t passage v a r i e d from an average of 44 minutes on a d i e t of meal, to 71 minutes on a d i e t of grass (Mattocks, 1970). Very few passage r a t e s t u d i e s have been conducted on w i l d waterfowl. Ranwell and Downing (1959) reported t h a t food passed through black brant (Branta b e r n i c l a n i g r i c a n s ) i n l e s s than 120 minutes. However, f e c e s were c o l l e c t e d only i n two hour i n t e r v a l s , meaning that the i n i t i a l d e f e c a t i o n may have occ u r r e d at any time duri n g the f i r s t two hours. The mean i n i t i a l through-put times i n mallards (Anus platyrhnchus) v a r i e d from 48 to 165 minutes depending on the nature of the food i n g e s t e d (Malone, 1965). In the present study the average time r e q u i r e d f o r f i r s t appearance of f e c e s a f t e r f e e d i n g from a s t a r v e d c o n d i t i o n was the same as t h a t when the gut contained 143 approximately 10 g o f rhizomes. S i n c e the mean gut c a p a c i t y of snow geese i s 28.8 g the alimentary t r a c t s of the geese were about o n e - t h i r d f i l l e d during the f e e d i n g s of Fe and Cr l a b e l l e d rhizomes. Although t h e r e were d i f f e r e n c e s between i n d i v i d u a l s , the mean times of f i r s t passage were the same f o r both l e v e l s of s a t i e t y . The a n a l y s i s of t h i s part of the study i n d i c a t e s that the r a t e of passage f o r a s i n g l e type of food i s constant and not i n f l u e n c e d s i g n i f i c a n t l y by the g u a n t i t y o f food a l r e a d y p r e s e n t . Tuckey et a l . (1958) s t a t e d that p r o v i d i n g feed to young c h i c k s d i d not a f f e c t the r a t e of passage of food a l r e a d y consumed. I t would appear reasonable t o accept the value of 58 minutes as the maximum passage r a t e f o r r e s t i n g snow geese on a d i e t of three-sguare b u l l r u s h rhizomes. However, time of f i r s t passage i s only an estimate of the maximal a b i l i t y o f the b i r d t o process a s m a l l g u a n t i t y of food. Other than to demonstrate r e l a t i v e d i f f e r e n c e s and s i m i l a r i t i e s between i n d i v i d u a l s , i t s i n t e r p r e t a t i o n as e i t h e r a v a l i d measure of i n g e s t a passage r a t e or an index of d i g e s t i v e a b i l i t y i s q u e s t i o n a b l e . Mean r e t e n t i o n time may prove to be a more u s e f u l measure of passage r a t e because i t takes i n t o account two or more p o i n t s on the e x c r e t i o n curve and i s a c l o s e approximation of the average l e n g t h of time a g i v e n amount of food remains i n the a l i m e n t a r y t r a c t . 144 Measurements of mean r e t e n t i o n time provide meaningful comparisons between members of d i f f e r e n t s p e c i e s on the same d i e t and between c o n s p e c i f i c s on d i f f e r e n t d i e t s . Tuckey et a l . (1958) found that while the f i r s t t r a c e s of Cr marker were observed i n the fec e s o f young c h i c k s w i t h i n one hour of feeding mean r e t e n t i o n time was between f o u r and s i x hours. Snow geese had the same time o f f i r s t passage of one hour but mean r e t e n t i o n time was only two hours. D i f f e r e n c e s i n anatomical s t r u c t u r e would no doubt e x p l a i n much of the v a r i a t i o n but i t i s c l e a r t h a t mean r e t e n t i o n time i s a more r e p r e s e n t a t i v e index of passage r a t e than time of f i r s t passage. The r e s u l t s i n d i c a t e a " f i r s t and l a s t " mean r e t e n t i o n time of approximately 134 minutes. The cumulative mean r e t e n t i o n time i s somewhat l e s s at 120 minutes. However, the two values were encouragingly c l o s e . ft passage r a t e o f between 120 and 134 minutes i s very r a p i d compared to th a t of herbivorous mammals and g a l l i n a c e o u s b i r d s . Long p e r i o d s of food r e t e n t i o n are a s s o c i a t e d with m i c r o b i a l breakdown of c e l l u l o s e and other poorly d i g e s t e d f r a c t i o n s . The r a p i d passage of food through the al i m e n t a r y t r a c t of geese reduces the p o s s i b i l i t y of c e l l u l o l y t i c a c t i v i t y . T h e r e f o r e , i t i s u n l i k e l y t h a t c e l l u l o s e i s of much n u t r i t i o n a l b e n e f i t to geese. 145 Rapid d i g e s t i o n of d i e t a r y p r o t e i n and non-rfibrous carbohydrate has been demonstrated i n geese. Because of t h e i r r a p i d passage r a t e and i n a b i l i t y t o d i g e s t crude f i b r e i t i s i m p e r a t i v e t h a t snow geese have a l a r g e supply of food high i n p r o t e i n and d i g e s t i b l e carbohydrate. Although e a r l i e r p o s t u l a t e d that d i e t a r y crude f i b e r had a depressing e f f e c t on passage r a t e , the p h y s i c a l s t r u c t u r e of the food e x e r t s the g r e a t e s t i n f l u e n c e (Malone, 1965). He found that food items having the lowest water content and those most s t r u c t u r a l l y r e s i s t a n t t o g r i n d i n g (corn, oats) were r e t a i n e d i n the gut up to t h r e e times as long as were s o f t e r foods (Elodea, c r a y f i s h ) . Crude f i b e r l e v e l s may, t h e r e f o r e , a f f e c t the d i g e s t i b i l i t y of c e r t a i n foods once i n the duodenum but water content and p h y s i c a l s t r u c t u r e are most i n f l u e n t i a l i n r e g u l a t i n g passage r a t e . 8.4.3 Gut Morphology Increases i n d i e t a r y l e v e l s of crude f i b e r produce changes i n the gross anatomy of the g a s t r o i n t e s t i n a l t r a c t s of g a l l i n a c e o u s b i r d s (Savoury and Gentle, 1976). A l a r g e p o r t i o n of t h i s i n c r e a s e i n v o l v e s an i n c r e a s e i n c e c a l volume. The ceca of s e v e r a l s p e c i e s of g a l l i f o r m e s harbours po p u l a t i o n s of c e l l u l o l y t i c b a c t e r i a (Moss, 1974). Th e r e f o r e , much i n t e r e s t has centered around the extent of m i c r o b i a l d i g e s t i o n of c e l l u l o s e . Once the grouse had adpated m o r p h o l o g i c a l l y to high f i b e r d i e t s , they were ab l e to u t i l i z e c e l l u l o s e with comparative e f f i c i e n c y . In f a c t . 146 male spruce grouse a t t a i n t h e i r maximum annual weight i n e a r l y winter on a d i e t composed e n t i r e l y of low q u a l i t y c o n i f e r browse (Pendergast and Boag, 1973)., Recently, M i l l e r (1974) demonstrated s i m i l a r anatomical adaptations to high l e v e l s of d i e t a r y f i b e r i n mallards. Ceca s i z e i n c r e a s e d s i g n i f i c a n t l y with an i n c r e a s e i n crude f i b e r . Although evidence e x i s t s t o show that some i n t e s t i n a l contents of mallards nay be d i v e r t e d i n t o the ceca (Malone, 1965) the c o r r e l a t i o n between d i g e s t i b i l i t y and ceca enlargement i n waterfowl remains u n c e r t a i n . whatever the case i n ducks, c e l l u l o s e d i g e s t i o n w i t h i n the ceca of geese i s u n l i k e l y . M a r r i o t t (1970) found that d i e t a r y markers were not d i v e r t e d i n t o the ceca of s a c r i f i c e d Cape Barren geese. Mattocks (197 2) c o u l d not i s o l a t e e i t h e r c e l l u l o l y t i c b a c t e r i a or protozoa i n the c e c a l contents of domestic geese. C o n f l i c t i n g r e p o r t s on c e l l u l o s e degradation i n geese have been presented (Mariott and Forbes, 1970). However, no c e l l u l o l y t i c b a c t e r i a have yet been i s o l a t e d from e i t h e r the i n t e s t i n e s or ceca of waterfowl as they have from s e v e r a l s p e c i e s of grouse (Moss, 1974). In the present study, no s i g n i f i c a n t change i n t o t a l ceca l e n g t h of snow geese was observed from the time of f i r s t a r r i v a l i n October u n t i l departure i n A p r i l . I t appears that the ceca of snow geese are n e i t h e r concerned with nor a f f e c t e d by changes i n the l e v e l s of crude f i b e r as encountered i n the normal course o f s w i t c h i n g from a low 147 f i b e r summer d i e t to a high f i b e r winter d i e t . Because c e l l u l o l y t i c a c t i v i t y i s low i n geese and apparently does not i n c r e a s e with l e v e l s of d i e t a r y f i b e r , i t i s proposed that the observed i n c r e a s e s i n s m a l l i n t e s t i n e and g i z z a r d s i z e are mechanical ada p t i o n s to a r e d u c t i o n i n d i e t q u a l i t y , r a t h e r than a p h y s i o l o g i c a l response to i n c r e a s e d m i c r o b i a l p o p u l a t i o n s . Feeding e f f i c i e n c y The mean s m a l l i n t e s t i n e volume rose from an i n i t i a l c a p a c i t y of 15.4 g t o over 27.0 g a f t e r a l l geese had become f u l l y adapted to a d i e t of three-sguare rhizomes. T h i s doubling of i n t e s t i n a l volume may act t o r e t a r d the passage r a t e , thus p e r m i t t i n g an improved d i g e s t i o n of the food consumed. Larger g i z z a r d s i z e presumably i n c r e a s e s the r a t e of food p r o c e s s i n g . These gr o s s morphological changes may be of s u r v i v a l advantage t o snow geese i n that they may be able t o improve the u t i l i z a t i o n e f f i c i e n c y of a food source r e l a t i v e l y high i n crude f i b e r but otherwise of good q u a l i t y . 1U8 9^0 C o r r e l a t i v e D i s c u s s i o n The o b j e c t i v e of t h i s study was to i d e n t i f y the r e l a t i o n s h i p s between l e s s e r snow geese and t h e i r n a t u r a l maritime winter h a b i t a t i n an attempt to u l t i m a t e l y determine the r e l a t i v e importance and support c a p a b i l i t y of each segment o f the estuary. The i n f o r m a t i o n generated by the i n v e s t i g a t i o n i s c o l l a t e d i n the f o l l o w i n g d i s c u s s i o n . 9.1 Feeding e f f i c i e n c y By i n f l u e n c i n g the amount of time spent f e e d i n g passage r a t e may s i g n i f i c a n t l y a f f e c t the a b i l i t y of snow geese to e f f i c i e n t l y u t i l i z e t h e i r food resource. I f r a t e of i n t a k e i s more r a p i d than r a t e of output geese would be a b l e to f i l l t h e i r guts q u i c k l y . Once the esophagus i s f u l l , f e e ding must stop even though c o n d i t i o n s may s t i l l be fa v o u r a b l e . During the most f a v o u r a b l e t i d a l c o n d i t i o n s f e e d i n g accounted f o r a mean of only 52 percent o f the a c t i v i t y p r o f i l e ( Section 4.1). T h i s s t r o n g l y suggests that snow geese were able to s a t i s f y t h e i r food requirements w i t h i n a very s h o r t p e r i o d . The mean r e t e n t i o n time of snow geese e a t i n g t hree-sguare rhizomes was 120 minutes. These rhizomes had a high moisture content (80 percent) and although crude f i b e r l e v e l s were approximately 21.5 percent, rhizome s t r u c t u r e 149 provided no r e t a r d i n g i n f l u e n c e on passage r a t e . T h i s r a t e was 40 minutes slower than t h a t r e p o r t e d f o r Cape Barren geese on a much coars e r d i e t o f l u c e r n e c h a f f ( M a r i o t t and Forbes, 1970). Although they are about twice as heavy as snow geese, t h e i r alimentary t r a c t s are about the same l e n g t h . D i f f e r e n c e s i n d e f e c a t i o n r a t e s between s p e c i e s may r e f l e c t d i f f e r e n c e s i n r a t e s of passage as w e l l . White-f r o n t e d geese defecated on the average once every 3.5 minutes while f e e d i n g (Owen, 1972). A s m a l l number of ob s e r v a t i o n s (16) i n d i c a t e d t h a t the d e f e c a t i o n r a t e i n u n r e s t r a i n e d snow geese was much lower; one every 7 t o 8 minutes. During t r i a l s r a r e l y were more than one or two d e f e c a t i o n s noted at each t en minute c o l l e c t i o n i n t e r v a l . Obviously, more work i s r e q u i r e d but i t appears t h a t snow geese may possess a slower passage r a t e than t h a t normally encountered i n other wild geese. A slow passage r a t e may be advantageous f o r snow geese. T h e i r a b i l i t y to grub i n the s o i l and e x t r a c t below-ground v e g e t a t i o n r e g u i r e s a l a r g e expenditure of energy. However, the n u t r i t i o n a l g u a l i t y o f rhizomes and tubers i s r e l a t i v e l y high compared t o above-ground marsh v e g e t a t i o n e s p e c i a l l y during winter. A slow passage r a t e would permit a more complete d i g e s t i o n of the food already consumed and would a l s o reduce the l e v e l of energy expenditure due to a r e d u c t i o n i n f e e d i n g a c t i v i t y . 150 Although i n t h i s study i t was not measured at d i f f e r e n t times during the winter, mean r e t e n t i o n time may be expected to remain e s s e n t i a l l y constant. From measurements of seasonal v a r i a t i o n s i n gut dimensions g i z z a r d s i z e was shown to i n c r e a s e s i g n i f i c a n t l y over the winter. The c a p a b i l i t y of the g i z z a r d to process food l i m i t s the passage r a t e of i n g e s t a (Owen, 1972). T h e r e f o r e , as g i z z a r d s i z e i n c r e a s e s , so shoud i t s a b i l i t y to process food. However, duodenal c a p a c i t y a l s o i n c r e a s e d s i g n i f i c a n t l y over the winter. R y b i c k i (1965) demonstrated the r e t a r d i n g i n f l u e n c e of greater i n t e s t i n a l l e n g t h on the passage r a t e of geese. T h e r e f o r e , an i n c r e a s e i n the a b i l i t y of the g i z z a r d to process food would be countered by an i n c r e a s e i n the t o t a l i n t e s t i n a l volume and passage r a t e may be expected e i t h e r to remain constant or t o decrease s l i g h t l y over the winter. 9.2 Energy Demands To get an approximate value of the energy expenditure per day based on the d i u r n a l a c t i v i t y p r o f i l e i t was assumed that the energy demands o f a l e r t and preening behaviour were as represented by the e x i s t e n c e energy {Kendeigh, 1969). Sleeping reduces t h i s demand by at l e a s t 50 percent (G. Markgren, 1963). The energy cost of f l i g h t i s approximately 12 times SMR (Utter and Lefebvre, 1970), I f the cost of fe e d i n g i s assumed to be one quarter of the c o s t of f l i g h t , then the t o t a l energy expended by snow geese i n an average 151 w i n t e r day would be 269 k c a l ( T a b l e XX). T a b l e (XX) - Comparison o f c a l c u l a t e d energy e x p e n d i t u r e between a 7 . 2 and 14 hour f e e d i n g day 7.2 Hour Feeding Day 14 Hour Feeding Day A c t i v i t y Time Energy T o t a l (hr) Expended Energy per hr Cost ( k c a l / day) Time Energy T o t a l (hr) Expended Energy per hr C o s t ( k c a l / day) Feeding A l e r t P r e e n i n g F l y i n g S l e e p i n g T o t a l 7.2 18. 3 132 14.0 18. 3 256 2.8 11.4 32 2. 8 11.4 32 1.4 11.4 16 1. 4 11. 4 16 0.25 73.5 18 0. 25 73.5 18 12.4 5.7 71 5.6 5.7 32 269 354 Because of t h e p a r t i c u l a r manner i n which snow geese feed i t was not p o s s i b l e t o measure d i r e c t l y the r a t e of rhizome consumption., An i n d i r e c t method o f c a l c u l a t i n g i n t a k e , found t o be r e l i a b l e w i t h o t h e r w i l d geese (Owen, 1972), i s a t t a i n e d by measuring f e c a l o u t p u t and c a l c u l a t i n g the amount consumed from knowledge o f the d i g e s t i b i l i t y of the d i e t . T h i s t e c h n i q u e was attempted on p i n i o n e d snow geese at R e i f e l Refuge ( B u r t o n , unpub.). The i n t e r v a l between d e f e c a t i o n v a r i e d from 2.25 t o 17 minutes i n 16 o b s e r v a t i o n s . S i n c e f e e d i n g regime and d i e t c o m p o s i t i o n were e n t i r e l y d i f f e r e n t from the w i l d snow geese on the f o r e s h o r e , t h i s t e c h n i q u e was abandoned i n f a v o u r o f one c a l c u l a t e d from qut c a p a c i t y and passage r a t e . I 152 By combining mean r e t e n t i o n time with gut c a p a c i t y i t was p o s s i b l e t o c a l c u l a t e the approximate r a t e of de f e c a t i o n - The mean c a p a c i t y of the esophagus and v e n t r i c u l u s was 10.2 g o f undigested rhizomes while t h a t f o r the s m a l l and l a r g e i n t e s t i n e was 18.6 g of di g e s t e d rhizomes. C o n s i d e r i n g t h a t a l a r g e p r o p o r t i o n o f the d i g e s t i o n had occur r e d by the time the i n g e s t a had passed through the duodenum, the amount of ex c r e t a represented i n the alimentary t r a c t of a snow goose was 25.9 g. The mean leng t h of time any one p o r t i o n o f food remained i n the gut was 120 minutes. In other words, the r a t e o f d e f e c a t i o n was 25.9 g i n two hours or approximately 13.0 g per hour. at a d i g e s t i b i l i t y o f 28 percent these f i g u r e s r e p r e s e n t an average l e v e l of i n t a k e of 17 g per hour dry matter. 9.3 Feeding Str a t e g y From the d i u r n a l a c t i v i t y p r o f i l e s i t can be seen t h a t f e e d i n g i n t e n s i t y i s f a r below that p o s s i b l e during f a v o u r a b l e t i d a l c o n d i t i o n s . I f feeding d i d indeed occur c o n t i n u o u s l y f o r the c a l c u l a t e d amount o f time spent f e e d i n g on an average day (7.2 hours), the e f f e c t i v e d i g e s t i o n p e r i o d would be only 8.5 hours. At t h i s r a t e the t o t a l d a i l y p r oduction o f feces would be 111 g r e p r e s e n t i n g an in t a k e of 153 g of rhizomes or 219 k c a l . T h i s value i s f a r below that c a l c u l a t e d f o r mean d a i l y energy expenditure. However, by a l t e r i n g t h e i r f e e d i n g s t r a t e g y snow geese may 1 5 3 be able to make more e f f i c i e n t use of t h e i r i n t e r m i t t a n t l y a v a i l a b l e food supply. In order to o b t a i n enough BE to balance energy output i t i s necessary f o r the geese t o o p t i m i z e the use of f a v o u r a b l e f e e d i n g c o n d i t i o n s . The vigourous method of feeding common to snow geese r e q u i r e s l a r g e p h y s i c a l e x e r t i o n . Displacement of f e a t h e r s during the process a l s o may c o n t r i b u t e towards much heat l o s s . In mammals e x c e s s i v e muscular work reduces blood flow to the v i s c e r a . The same c o n d i t i o n l i k e l y occurs i n b i r d s . Passage r a t e may then be expected to decrease under c o n d i t i o n s of i n t e n s i v e f e e d i n g l e a d i n g t o a r a p i d f i l l i n g of the gut. Instead of f e e d i n g i n one or two continuous s t r e t c h e s , i t may be more e f f i c i e n t f o r each goose to f i l l i t s g u l l e t r a p i d l y , s l e e p u n t i l i t s v e n t r i c u l u s i s empty, then q u i c k l y f i l l up t h e esophagus again and s l e e p and so f o r t h . T h i s r e p e t i t i o n of i n t e n s i v e bouts of f e e d i n g and s l e e p i n g may minimize the energy expenditure a s s o c i a t e d with f e e d i n g , while at the same time maximize the u t i l i z a t i o n o f the already i n g e s t e d food by i n c r e a s i n g d i g e s t i b i l i t y . S i m i l a r bouts of s l e e p i n g and f e e d i n g have been recorded f o r l e s s e r scaup ( S i e g f r i e d , 1974). The primary advantage of s l e e p i n g between feed i n g bouts i s energy c o n s e r v a t i o n . An i n c r e a s e i n the amount of s l e e p i n g reduces metabolic demands. G. Harkgren (1963) reported t h a t the m e t a b o l i c r a t e of a goose drops at l e a s t 154 50 percent from a s t a n d i n g a l e r t p o s i t i o n to s l e e p i n g with the b i l l under the wing. In proposing such a f e e d i n g s t r a t e g y i t i s i m p e r r a t i v e to know when f e e d i n g resumes. The p r e c i s e p h y s i o l o g i c a l mechanisms which i n i t i a t e f e e d i n g behaviour i n b i r d s i s p o o r l y understood. However, th r e e f a c t o r s known to s t i m u l a t e f e e d i n g i n c h i c k e n s are a c o l d environment, v i s u a l i d e n t i f i c a t i o n of food and the c o n t r a c t i o n of an empty stomach ( S t u r k i e , 1965). Snow geese i n winter are c o n t i n u a l l y exposed to a c o l d environment so the low temperature e f f e c t may be present at a l l times. However, other f a c t o r s such as e i t h e r a f u l l gut or e x c e s s i v e harassment may a l t e r the response. In b i r d s as gregarious as snow geese f e e d i n g may be v i s u a l l y s t i m u l a t e d by other members of the f l o c k so engaged. Under f a v o u r a b l e c o n d i t i o n s some f e e d i n g i s always o c c u r i n g . The l o u d g a b b l i n g , c h a r a c t e r i s t i c of f e e d i n g snow geese, may augment the v i s u a l e f f e c t and i n c r e a s e the d e s i r e to f e e d . However, here again a l l b i r d s would be s u b j e c t to a s i m i l a r l e v e l of s t i m u l a t i o n . C o n s i d e r i n g a l l of the p o s s i b l e s t i m u l i the only v a r i b l e d i f f e r e n t f o r each i n d i v i d u a l i s the amount of food c o n t a i n e d i n t h e f o r e g u t . Presumably a goose must stop f e e d i n g when i t s g u l l e t i s completely f i l l e d . Measurements of esophogeal and v e n t r i c u l a r c a p a c i t y i n d i c a t e that 35 percent of the t o t a l gut contents are found a n t e r i o r to the duodenum. As a 155 r e s u l t i t may take approximately 42 minutes (120 min.(mean r e t e n t i o n time)x 0.35) from the c e s s a t i o n of f e e d i n g to empty the g i z z a r d . Movement of the empty stomach i n a s s o c i a t i o n with low environmental temperatures and the observance of other n o i s i l y f e e d i n g geese may then r e l e a s e feeding behaviour at t h i s time. In s t a r v e d snow geese i t t a k e s approximately 13 minutes fo r consumed food to reach the duodenum ( R y b i c k i , 1965). From the c e s s a t i o n o f f e e d i n g u n t i l the i n i t i a t i o n of the next bout of f e e d i n g 29 minutes have e l a p s e d d u r i n g which geese were able to drop t h e i r metabolic r a t e at l e a s t 50 percent below the e x i s t e n c e energy l e v e l . T h e r e f o r e , 30 minutes of s l e e p i s obtained f o r each bout of f e e d i n g . A f t e r the f i n a l c e s s a t i o n of f e e d i n g due t o u n s u i t a b l e t i d a l c o n d i t i o n s , food remains w i t h i n the s m a l l i n t e s t i n e an average of 100 minutes ( R y b i c k i , 1965). The s m a l l i n t e s t i n e may t h e r e f o r e remain e s s e n t i a l l y f i l l e d d uring the whole p e r i o d when rhizomes are a v a i l a b l e and up t o 90 minutes subsequent to each f a v o u r a b l e t i d e even though fee d i n g a c t i v i t y may only occur s p o r a d i c a l l y f o r a mean o f 7.2 hours per day. Using t h i s s t r a t e g y , snow geese are a b l e to begin p r o c e s s i n g food c o n t i n u o u s l y from 20 minutes a f t e r the i n i t i a t i o n of f e e d i n g t o 90 minutes a f t e r each e f f e c t i v e f eeding p e r i o d i s over. The i n t e r v a l during which the i n t e s t i n e s are f u l l may be c a l l e d the e f f e c t i v e d i g e s t i o n 156 p e r i o d . I f maximal use was made of t h i s s t r a t e g y the mean e f f e c t i v e d i g e s t i o n p e r i o d with a minimum of two f o r c e d s l e e p i n g periods per day (when rhizomes are not a v a i l a b l e ) would be 16.3 hours. During t h i s time a t o t a l of 212 g (16.3 hr x 13 g f e c e s voided/hr) of f e c e s would be voided r e p r e s e n t i n g an i n t a k e of 2 94 g of rhizomes or 420 k c a l per day. T h i s l e v e l of energy i n t a k e i s 123 k c a l above the p r o j e c t e d l e v e l o f normal energy expenditure. Even during the s h o r t e s t monthly e f f e c t i v e f e e d i n g p e r i o d s of December and January i n t a k e was 72 k c a l per day above the c a l c u l a t e d energy output. The minimum e f f e c t i v e d i g e s t i o n period d u r i n g which the mean d a i l y energy expenditure c o u l d be met was 11.5 hours, or an e f f e c t i v e f e e d i n g p e r i o d of 9.2 hours. I t i s p o s s i b l e that when faced with concurrent days where the e f f e c t i v e f e e d i n g period i s below 9 hours the southward m i g r a t i o n from the F r a s e r D e l t a to S k a g i t F l a t s may be r e l e a s e d . Food i n t a k e i s l i m i t e d by the a b i l i t y of the g i z z a r d to process i t . I f snow geese fed in s i n g l e c o n t i n u o u s bouts each day, as do w h i t e - f r o n t e d (Owen, 1972) and Cape Barren geese ( M a r i o t t , 1970), t h e i r p r o j e c t e d energy expenditure would more c l o s e l y approach t h e i r maximum p o t e n t i a l i n t a k e l e v e l s . T h i s s i t u a t i o n would not a l l o w the b i r d s to s t o r e e x t r a energy for emergencies. Under such c o n d i t i o n s f e e d i n g a c t i v i t y would i n c r e a s e to a mean of 14 hours per day but i n t a k e c o u l d only proceed at a r a t e p r o p o r t i o n a l to passage 157 r a t e . The amount o f rhizomes obtained per u n i t e f f o r t would thus be reduced. Under these c o n d i t i o n s the mean e f f e c t i v e d i g e s t i o n p e r i o d would be 15.2 hours. Intake would then be approximately 238 g of rhizomes or 341 k c a l per day. But energy expenditure would be about 354 k c a l per day (Table 27). T h e r e f o r e , a net i n c r e a s e of approximately 100 k c a l per day would be gained by employing a s t o p - s t a r t over a continuous f e e d i n g s t r a t e g y . The proposed s t r a t e g y would appear to maximize e f f i c i e n t u t i l i z a t i o n of a n u t r i t i o u s but f l u c t u a t i n g food supply. I t a l s o e x p l a i n s the unexpectedly low p r o p o r t i o n of the f l o c k f e e d i n g d u r i n g p e r i o d s of optimal food a v a i l a b i l i t y . Because of the i n t e n s i v e nature of t h e i r f e e d i n g behaviour energy expenditure through e x c e s s i v e p h y s i c a l e x e r t i o n and heat l o s s due to r u f f l e d f e a t h e r s must be very high. A more thorough d i g e s t i o n of the food a l r e a d y consumed combined with a decrease i n f e e d i n g a c t i v i t y , as would occur i n the proposed feeding s t r a t e g y , appears to be of s u r v i v a l advantage and may be an evolved a d a p t a t i o n to the v i g r o u r o u s subterranean f e e d i n g h a b i t s of w i n t e r i n g snow geese. 9.4 Feeding Pressure on the E s t u a r y The 1974-1975 snow goose popul a t i o n was the s m a l l e s t recorded s i n c e 1947 when the f i r s t counts began (Appendix 158 A). Mot only were few geese present, but they a r r i v e d almost two weeks l a t e r than normal and remained away almost t h r e e weeks longer than usual i n January and February. T h e r e f o r e , a t o t a l use i n t e n s i t y of 744,000 goose days though s t i l l c o n s i d e r a b l e must be considered a minimum. Each goose consumes an average of 0.3 kg of rhizomes per day. No data on wastage are a v a i l a b l e but i n the southern O.S. i t i s estimated t h a t up t o ten times as much v e g e t a t i o n i s r e j e c t e d as consummed (Mcllhenney, 1932). Evidence on the F r a s e r suggests that although some wastage does occur, i t i s not l i k e l y t o approach these p r o p o r t i o n s . C e r t a i n l y , an o v e r a l l removal r a t e of 0.3 kg per goose each day can be c o n s i d e r e d a c o n s e r v a t i v e f i g u r e . T h e r e f o r e , the annual consumption i s approximately 223.2 rat (0.3x744,000). Rhizome consumption being about 75 percent of d i e t t h i s r e p r e s e n t s an annual l o s s of 167 mt or 32 percent of the t o t a l rhizome s t a n d i n g crop. Because p o p u l a t i o n s i z e f l u c t u a t e s widely from one year to the next (Appendix A) h a b i t a t use i n t e n s i t y may run as high as f o u r times the minimum. At these l e v e l s pressure on the marsh would exceed two m i l l i o n goose-days. The e s t u a r y could c o n c e i v a b l y l o s e 100 percent of the rhizome standing crop, r e s u l t i n g i n e x t e n s i v e long-term damage t o marsh i t s e l f . Under such c o n d i t i o n s the present food r e s e r v e s would be inadequate and f i e l d - f e e d i n g would, no doubt, occur. Because of the c h a r a c t e r i s t i c subterranean f e e d i n g 159 h a b i t s of snow geese economic l o s s e s could be dramatic. Complete d e s e r t i o n of the F r a s e r d e l t a c o u l d then be reasonably expected. I t i s proposed that the e x i s t i n g 734 ha of three-square b u l l r u s h a re not of s u f f i c i e n t magnitude t o support a peak snow goose p o p u l a t i o n of more than about 20,000 b i r d s without permantent damage to the marshes. In the absence of estimates of rhizome p r o d u c t i v i t y i t i s d i f f i c u l t to present f u r t h e r c o n c l u s i o n s . 9.5 C r i t i c a l Areas As long as snow geese are a b l e to feed by spreading out along the shore l i n e , t here i s l i t t l e l i k e l i h o o d t h a t they would cause i r r e p a r a b l e damage to t h e i r food supply at pop u l a t i o n s of up to 15,000 to 20,000 b i r d s . However, i n southern L o u i s i a n a and Texas, snow geese that have been concentrated onto small areas w i l l e f f e c t such damage so as to completely d e s t r o y the e c o l o g i c a l i n t r e g r i t y o f the fee d i n g grounds. Op to 20 percent of the t o t a l w i n t e r i n g area may become permanently d e v o i d o f v e g e t a t i o n i n one season (Lynch et a l . , 1947). With the present t r e n d s toward h a b i t a t a l i e n a t i o n on the F r a s e r D e l t a , i t i s necessary to determine those areas o f v i t a l importance to snow geese i n an attempt t o e s t a b l i s h a b a s i s f o r o b t a i n i n g permanent land tenure. 160 A t o t a l of 744,000 snow goose-days were spent on the Fraser River estuary during the winter of 1974-75. Of t h i s t o t a l , 51 percent was c o n c e n t r a t e d on Westham I s l a n d . However, t h i s f i g u r e i s somewhat m i s l e a d i n g i n t h a t i t g i v e s an e r r o n e o u s l y h i g h : e s t i m a t i o n of the value of Westham I s l a n d . The predominant a c t i v i t y at t h i s l o c a t i o n was r e s t i n g . Since r o o s t i n g s i t e s have never been shown to d i c t a t e h a b i t a t s u i t a b i l i t y , i t i s necessary t o evaluate each marsh u n i t on i t s a b i l i t y to provide an adequate supply of food. In an attempt to o b t a i n reasonable e s t i m a t e s of the value of each marsh u n i t an index was devised i n c o r p o r a t i n g estimates of the amount of time spent on each segment and the percentage o f that time engaged i n f e e d i n g . To enable comparisons between areas, each was expressed on a per h e c t r e b a s i s . Table (XXI) - The f e e d i n g i n t e n s i t y , use i n t e n s i t y and r e l a t i v e importance of each marsh u n i t f o r w i n t e r i n g snow geese L o c a t i o n Use I n t e n s i t y Mean Feeding Marsh Si z e Index of (1,000 goose- I n t e n s i t y (100 ht) Import-days) {%) ance Brunswick P o i n t 149. 9 0.60 1. 34 67.1 Westham I s l a n d 379.3 0.15 3.50 16.3 Lulu I s l a n d 169.9 0.51 3.54 24.5 Sea I s l a n d 44.9 0.38 1.43 12.0 Brunswick P o i n t i s c l e a r l y the most important s i n g l e 161 marsh per u n i t area and may be assumed c r i t i c a l t o the continued s u r v i v a l of snow geese i n t h i s area. However, the t o t a l rhizome s t a n d i n g crop of Westham I s l a n d p l u s Brunswick Point i s i n s u f f i c i e n t t o s u s t a i n even the minimum number of geese at a maximum ra t e of v e g e t a t i v e regrowth. Th e r e f o r e , p r e s e r v a t i o n of the Lu l u I s l a n d f o r e s h o r e must be i n c l u d e d i n any h a b i t a t c o n s e r v a t i o n p o l i c y designed s p e c i f i c a l l y to maintain the l o c a l snow geese. Sea I s l a n d , though once u t i l i z e d i n t e n s i v e l y by the geese, has been a l t e r e d to such an extent that use i n t e n s i t y has f a l l e n c o n s i d e r a b l y . Notwithstanding i t s s m a l l s i z e , the marsh i n f r o n t of Sea I s l a n d i s s t i l l of higher q u a l i t y f o r f e e d i n g than Westham I s l a n d . I t s d e s i r a b i l i t y f o r p r e s e r v a t i o n as snow goose h a b i t a t i s dampened somewhat by the f a c t t h a t i t i s s i t u a t e d at the western end of the main runway of the Vancouver I n t e r n a t i o n a l a i r p o r t . Because of the i n a r g u a b l e need f o r a r e d u c t i o n i n the p o s s i b l e hazzard to a i r c r a f t , a l l b i r d s should be discouraged from using t h i s area. T h i s need may be hastened by the proposed expansion of the a i r p o r t i n t o the marsh. In the event of complete d e s t r u c t i o n of the Sea I s l a n d marsh, i t w i l l be necessary to e s t a b l i s h a permanent f r e e z e on any and a l l developments which would encroach f u r t h e r on the already minimal snow goose h a b i t a t . 162 As the c o s t of l o s i n g Sea I s l a n d permanent tenure must be granted t o e i t h e r the B.C. F i s h and W i l d l i f e Branch or the Canadian W i l d l i f e S e r v i c e with funds a l o c a t e d to improve the marginal q u a l i t y of other p a r t s of the f o r e s h o r e . I f no such funds are made a v a i l a b l e l o s s of Sea I s l a n d would put e x c e s s i v e pressures on the remainder of the e s t u a r i n e marshes and permanent damage to these areas would ensue. 163 10.0 LITERATURE CITED A l l a n , P.F., 1956. A system f o r e v a l u a t i n g c o a s t a l marshes as duck winter range. J. W i l d l . Manage. 20:247-252. Andrewartha, H.G., 1963. I n t r o d u c t i o n to the study of animal p o p u l a t i o n s . Univ. C h i c a g i o Press. 281p. t and L.C., B i r c h , 1954. The d i s t r i b u t i o n and abundance o f animals. Univ. Chicago Press. P. Andrews, F.M., J.N. Morgan and J.A. Songuist, 1967. M u l t i p l e C l a s s i f i c a t i o n A n a l y s i s - a r e p o r t on a computer program f o r m u l t i p l e r e g r e s s i o n using c a t e g o r i c a l p r e d i c t o r s . Univ.. Mich. P r e s s , Ann Arbor, Mich., 211p. Andrews, F. M., and R.C. Messenger, 1973. M u l t i v a r i a t e Nominal S c a l e A n a l y s i s . I n s t . S o c i a l r e s . , Univ. Mich. Ann arbor 108p. Aschoff, J . , 1966. C i r c a d i a n a c t i v i t y p a t t e r n with two peaks. E c o l . 47:657-661. Barnard, A.E., w i l d l i f e b i o l o g i s t , B.C. F i s h and W i l d l i f e Branch, Burnaby, B.C. Baumgartner, L.L., and A.C. M a r t i n , 1939. P l a n t h i s t o l o g y as an a i d i n s g u i r r e l f o o d - h a b i t s t u d i e s . J . W i l d l . Manage. 3:266- 268. Bernard, J.M., 1974. Seasonal changes i n standing c r o p and primary production i n a sedge wetland and an adjacent dry o l d - f i e l d i n c e n t r a l M i nnisota. E c o l . 55: 350-359. Biondo, G., 1953. Nuova Vet. 29:97. Bossenmaier, E.F. and W.H. M a r s h a l l , 1958. F i e l d f e e d i n g by waterfowl i n south western Manitoba. W i l d l . Monog. 1, 32. Boyd, H., 1955. The r o l e of t r a d i t i o n i n determining the winter d i s t r i b u t i o n o f p i n k f e e t geese i n B r i t a i n . Ann. Rpt. Wildfowl T r u s t 7: 107-122. Boyd, C E . , 1968. Freshwater p l a n t s : a p o t e n t i a l source of p r o t e i n . Econ. Bot. 22:359-368. , and L.W* Hess, 1970. F a c t o r s a f f e c t i n g shoot 164 pro d u c t i o n and mineral n u t r i e n t l e v e l s i n Ixpha l a t i f o l i a . E c o l . , 51:296-300. Bray, J.R., 1963. Root production and the e s t i m a t i o n of net p r o d u c t i v i t y . Can. J . Bot. 41:65-72. Bryant, D.M., and J . Leng, 1976. Feeding d i s t r i b u t i o n and behaviour of shelduck i n r e l a t i o n to food supply. Wildfowl 27:20 -30. Burgess, T.E., 1970. Foods and h a b i t a t of fo u r A n a t i n i d s w i n t e r i n g on the F r a s e r d e l t a t i d a l marshes. Unpub. M.Sc. T h e s i s , H.B,C 124p. Burton, P.J.K., 1960. The brent goose and i t ' s food supply i n Essex. Ann. Rpt... Wildfowl T r u s t 12: 104-112. — — f 1961. The food s u p p l i e s of Essex brent i n the winter o f 1960-61. An. Rpt. Wildfowl T r u s t 13: 117-125. Canadian Hydrographic S e r v i c e , 1973-75. Canadian t i d e and c u r r e n t Tables - V o l . 5., Queen's P r i n t e r , Ottawa. . C a s t l e , E .J., 1956. The passage of food s t u f f s through the alimentary c a n a l of the goat. 1. S t u d i e s on a d u l t animals fed on hay and c o n c e n t r a t e s . B r i t . J . Sutr. 10:15-23. Cooch, F.G., 1958. The breeding b i o l o g y and management of the Blue goose. Unpub. Ph.D. T h e s i s , C o r n e l l Univ., I t h i c a , N. Y. 235p. , Cottam, C., 1935. Blue and Snow geese i n the e a s t e r n United S t a t e s i n the winter of 1934-35, with notes on t h e i r food h a b i t s . Auk 52:432-441. Craighead, J . J . , and D.S. Stockstad, 1956. Measuring hunting pressure on Canada geese i n the Flathead V a l l e y . Trans. N. Am. W i l d l . Conf. 21:210-238. C u l l e n , J.H., 1954. The d i u r n a l rhythm of b i r d s i n the a r c t i c summer. The I b i s 96:31-46. Dahlman, R.C, and C L . Kucera, 1965. Root p r o d u c t i v i t y and turnover i n n a t i v e p r a i r i e . E c o l . 46:84-89. Dean, B.E., 1933., E f f e c t of s o i l type and a e r a t i o n upon root systems o f c e r t a i n a q u a t i c p l a n t s . P l a n t P h y s i o l . 8:202- 222. 165 Dorozunska, N., 1962- Food i n t a k e and d e f e c a t i o n i n the goose, An§§.£ JinsSE- Acta B i o l o g i a e E x p e r i m e n t a l i s 22: 227-240. Dzubin, A., 1965. A study of m i g r a t i n g Ross geese i n western Saskatchewan. The Condor 67:511-535. , H. Boyd, and W.D.S. Stephen, 1973. Blue and Snow goose d i s t r i b u t i o n i n the M i s s i s s i p p i and C e n t r a l f l y w a y s : V o l . 1, Canadian W i l d l . Serv. P r e l i m . Rpt., Ottawa, 81p. E i n a r s e n , A.S., 1955. Food c r i s e s and the i n t e r r e l a t i o n s h i p of waterfowl. The M u r r e l e t 36:39-40. , 1965. The black brant: Sea goose of the P a c i f i c c o a s t . Univ. Wash. Pr e s s . , S e a t t l e , 147p. Environment Canada, 1973-75. Annual m e t e r o r o l o g i c a l summary f o r Vancouver I n t e r n a t i o n a l A i r p o r t . 37p. Evans, K.E., and D.R. D i e t z , 1974. N u t r i t i o n a l e n e r g e t i c s of S h a r p - t a i l e d grouse during winter. J . W i l d l . Manage. 38:622-629. F r e t w e l l , S.D., and H.L. Lucas, J r . , 1970. On t e r r i t o r i a l behaviour and other f a c t o r s i n f l u e n c i n g h a b i t a t d i s t r i b u t i o n i n b i r d s . 1. T h e o r e t i c a l development. Acta B i o t h e o r e t i c a 19:16 -36. F r i n g s , H., M. F r i n g s , B. Cox, and L. P e i s s n e r , 1955. Auditory and v i s u a l mechanisms i n food f i n d i n g behaviour of the H e r r i n g g u l l . Wilson B u l l . 67:155-170. Glazner, B.C., 1946. Food h a b i t s of w i l d geese on the Gulf coast of Texas. J . W i l d l . , Manage. 10:322-329. Hadley, E.B., and L.C. B l i s s , 1966. Energy r e l a t i o n s h i p s of a l p i n e p l a n t s on Mt. Washington, New Hampshire. E c o l - Monogr. 34:331-357. Barker, J.E. , 1958. D i u r n a l rhythms i n the animal kingdom. B i o l . Rev. 33: 1-52. H a r r i s , R.D., W i l d l i f e B i o l o g i s t , Canadian W i l d l i f e S e r v i c e , D e l t a , B.C. Hartman, F.E., 1963. E s t u a r i n e w i n t e r i n g h a b i t a t f o r Black ducks. J . W i l d l . Manage. 27:339-347. 166 Head, G.C., 1971. P l a n t r o o t s . In - Methods o f study i n q u a n t i t a t i v e s o i l ecology: p o p u l a t i o n , p r o d u c t i o n and energy flow. I.B.P. Handbook No. 18, J.P. P h i l l i p s o n ed., B l a c k w e l l , London, pp.14-23. Hoos, L.M., and G.A. Packman, 1974. The F r a s e r r i v e r e s t u a r y - s t a t u s of environmental knowledge t o 1974. Rpt. Of the Estuary Working Group, Dept. E n v i r . , Regional Board, Pac. Region. S p e c i a l Estuary S e r i e s No. 1, 518p. Howard, W.J., 1940. Wintering of the g r e a t e r snow goose Auk 57:523-531. J e f f r e y , R., W i l d l i f e B i o l o g i s t , Washington State Game Dept. , Stanwood, Washington. Keefe, C.W., 1972. Marsh p r o d u c t i o n : a summary of the l i t e r a t u r e . C o n t r i b . In Marine S c i . 16:164-181. Kendeigh, C.S., 1969. Energy responses of b i r d s t o t h e i r thermal environments. Wilson B u l l . 81:441-449-.— r 1970-energy requirements f o r e x i s t e n c e i n r e l a t i o n t o s i z e of b i r d . The Condor 72:60-65. K l o p f e r , P.H., 1958. S o c i a l i n t e r a c t i o n s in d i s c r i m i n a t i o n l e a r n i n g with s p e c i a l r e f e r e n c e to f e e d i n g behaviour i n b i r d s . Behav. 14: 282-299. ' 1 a n (3 j . p . Hailman, 1965. H a b i t a t s e l e c t i o n i n b i r d s . Advances i n the Study of B i r d Behav. 1: 279-303. Kruuk, H., 1972- The Spotted Hyena: a study of p r e d a t i o n and s o c i a l behaviour. Univ. Chicago Press, Chicago, 3 35 p. Lemieux, L., 1959. H i s t o i r e n a t u r e l l e et amenagement de l a grande oie blanche, Chen hyperborea a t l a n t i c a . Canad. 86: 133-192. Leopold, A.S., 1953. I n t e s t i n a l morphology of g a l l i n a c e o u s b i r d s i n r e l a t i o n to food h a b i t s . J . W i l d l . Manage. 17:197-203., Lewin* V., 1963. Reproduction and development of young i n a p o p u l a t i o n of C a l i f o r n i a q u a i l . The Condor 65:249-278. Lynch, J . J . , T. O ' N i e l , and D.W. Lay, 1947. Management s i g n i f i c a n c e o f damage by geese and muskrats to G u l f 167 coas t marshes., J . W i l d l . Manage. 11:50-76. MacFadyen, ft., 1963. The ecology of i n d i v i d u a l s . In -Animal Ecology: aims and methods. S i r Iasaac Pitman and sons L t d . , London, pp.1-84. MacNaughton, J.S., 1966. Ecotype f u n c t i o n i n the Tv.pha community-type. E c o l . Monogr. 36:297-325. Malone, C., 1965. D i s p e r s a l o f plankton: r a t e of food passage i n mallard ducks. J. W i l d l . Manage. 29:529-533. Markgren, G., 1963. M i g r a t i n g and s i n t e r i n g geese i n southern Sweden. Acta V e r t e b r a t i c a 2:297-418. Markgren, M., 1960. F u g i t i v e r e a c t i o n s i n avian behaviour. Acta V e r t e b r a t i c a 2:1-160. M a r r i o t , R.W., 1970. The food and water requirements of Cape Barren geese. Ph.p., T h e s i s , Monash Univ., , and D.K. Forbes, 1970. The d i g e s t i o n of lucerne c h a f f by Cape Barren geese. Austr. J . Zo o l . 18:257-263. Mattocks, G., 1972. Goose f e e d i n g and c e l l u l o s e d i g e s t i o n . Wildfowl 22: 107-113., McAtee, G.E., 1910. Notes on Chen c a e r u l e s c e n s , c*_ Rossi and other waterfowl. Auk 27:337-339. Mcllhenny, E.A., 1932. The Blue goose i n i t s winter h a b i t a t . Auk 49:279-306. McKinney, F., 1965. The comfort movements of anatid a e . Behav. 25: 120-220. M c N i c h o l l , M.K. , 1975. L a r i d s i t e t e n a c i t y and group adherence i n r e l a t i o n to h a b i t a t . Auk 92:98-104. M i l l e r , M.R. , 1975. Gut morphology of M a l l a r d s i n r e l a t i o n n t o d i e t q u a l i t y . J . W i l d l . Manage. 39:168-173., Moss, R., 1974. Winter d i e t s , gut l e n g t h s and i n t e r s p e c i f i c c ompetition i n Alaskan ptarmigan. Auk 91:737-746. Na t i o n a l Academy of Scienc e s , 1971. N u t r i t i o n a l requirements o f p o u l t r y . 6th ed. Washington D.C, 54p. 168 , 1972. Ha b i t a t s e l e c t i o n , f o o d c h o i c e and fe e d i n g h a b i t s of d i v i n g ducks i n c o a s t a l waters of south Sweden during the non-breeding season* O r n i s . Scand. 3:55-78. Ovington, J.D., J . Heitkamp, and D.B. Lawrence, 1963. Pl a n t biomass and p r o d u c t i v i t y of p r a i r i e , savanah, oakwood, and maize f i e l d ecosystems i n c e n t r a l M i n nisota. E c o l . 44:52- 63. Owen, M. , 1971. The s e l e c t i o n of feed i n g s i t e by White-f r o n t e d geese i n winter. J . A p p l i e d E c o l . 8:89 3-905-, 1972., Some f a c t o r s a f f e c t i n g food i n t a k e and s e l e c t i o n i n White-fronted geese. J . Animal E c o l . 41:79-9 2. Palmgren, P., 1949. On the d i u r n a l rhythm of a c t i v i t y and r e s t i n b i r d s . The I b i s 91:561-575. P e a r s a l l , W.H., and E. Gorham, 1956. Pr o d u c t i o n ecology I. Standing crops of n a t u r a l v e g e t a t i o n . Oikos 7:193-201. Pendergast, B.A., and D.A. Boag, 1973. Seasonal changes i n the i n t e r n a l anatomy of Spruce grouse i n A l b e r t a . Auk 90:307 - 317., Penney, J.G., and E. D. B a i l e y , 1970. Comparison o f the energy requirements of f l e d g l i n g Black ducks and American c o o t s . J . W i l d l . Manage. 34:105-114. Racey, K., 1924. Snow goose near Vancouver, B.C. The Murrel e t 5: 10- 11-Ranwell, D.S., and B.M. Downing, 1959. Brent goose winter f e e d i n g p a t t e r n and Z o s t e r a r e s o u r c e s at S c o l t Head i s l a n d , N o r f o l k . Animal Behav. 7:42-56. , Rave l i n g , D.G., 1969. Roost s i t e s and f l i g h t p a t t e r n s of Canada geese i n winter. J . W i l d l . Manage. 33:319-330. Remezov, N.P., L.E. Rodin, and N.I. B a z i l e v i c h , 1963. I n s t r u c t i o n s on methods of s t u d y i n g the b i o l o g i c a l c y c l e o f ash elements and n i t r o g e n i n the above ground p a r t s of p l a n t s i n the main n a t u r a l zones o f the temperate b e l t . {Russian-with E n g l i s h summary). Bot. Zhur. 48: 869-877. R y b i c k i , M., 1965. X-ray o b s e r v a t i o n s on the passage of food i n Anser anser L A Z o o l o g i c a P o l o n i a e 15:111-115. 169 Savoury, C.J., and M.J. Gentle, 1976. E f f e c t s o f d i e t a r y d i l u t i o n with f i b r e on the food i n t a k e and gut dimensions of Japonese q u a i l . Br. Po u l t . S c i . 17: 561-570. S c o t t , M.L., M.C. Nesheim, and R.J. Young, 1969. N u t r i t i o n o f the Chicken. M.L. S c o t t and a s s o c i a t e s , I t h i c a , N. Y., 511p. S c o t t , E. S. , and D.P. Olson, 1973. Food-habitat r e l a t i o n s h i p o f sea ducks on the New Hampshire c o a s t l i n e . , E c o l . 54:996- 1007. S e i b e r t , H.C., 1951. L i g h t i n t e n s i t y and the r o o s t i n g f l i g h t of herons i n New J e r s e y . Auk 68:63-74. S i e g f r i e d , W.R., 1974. Time budget of behaviour among Lesser scaups on D e l t a marsh. J . ¥ildl. Manage. 38:708-713. Sladen, W.S.L., American r e p r e s e n t a t i v e , U.S.A--0.S.S.R c o o p e r a t i v e waterfowl banding p r o j e c t , Johns Hopkins Oniv., Baltimore, Maryland. Soper, J.D., 1942. The l i f e h i s t o r y of the Blue goose. Proc. Boston Soc. N a t u r a l H i s t . 42: 121-225. Sprout, P.N., and W.D. Holland, 1959. S o i l survey of De l t a m u n i c i p a l i t y . B.C. Dept. A g r i . , S o i l Surv. P r e l i m . Rept. (2), and s o i l map t r a c i n g (79), 80p. S t u r k i e , P.D., 1965. Avian P h y s i o l o g y . C o r n e l l Oniv. Press , I t h i c a , N.Y., 766p. Swanson, G.A., and J.C. Bartonek, 1970. B i a s a s s o c i a t e d with food a n a l y s i s i n g i z z a r d s of Blue-winged t e a l . J . W i l d l . Manage.. 34:739-746. -r and A. B. Sargeant, 1972. Observations of n i g h t - time f e e d i n g behaviour of ducks. J . W i l d l . Manage. 36:959- 961. Sugden, L.S., 1971. M e t a b o l i z a b l e energy of s m a l l g r a i n s f o r M a l l a r d s . J . W i l d l . Manage. 35:781-785. 8 Telpov, V.P., and T.P. Shevareva, 1965. On seasonal movements and the bag of Snow geese. In - The M i g r a t i o n s of B i r d s and Mammals., pp. 23-38. Publishinghouse Nauka, Moscow., tr a n s from Russian. Tinbergen, N., 1953. The Herring G u l l ' s l o r l d . 255p., 170 London. , 1957. The f u c n t i o n s o f t e r r i t o r y . B i r d Study 4:14-27. Thorpe, W.H., 1951. The l e a r n i n g a b i l i t i e s of b i r d s . The I b i s 93: 1-52. Tuckey, R., B.E. March, and J . B i e l y , 1958. D i e t and the r a t e of food passage i n the growing c h i c k . P o u l t . •, S c i . 37:786-792. Uspenski, S.M., 1963. The white goose, Chen c. cagru1escens. P r i r o d a 9:58-62 t r a n s from Russian by Canada Dept. Of State f o r Canadian W i l d l . Serv. Ottawa. D t t e r , J.M., and E.A. LeFebvre, 1970w Energy expenditure f o r f r e e f l i g h t by the Purple M a r t i n . Comp. Biochem. P h y s i o l . 35:713-719. Weaver, J.E. and W.J. Himmel, 1930. R e l a t i o n of i n c r e a s e d water content and decreased a e r a t i o n to root development i n hydrophytes. P l a n t P h y s i o l . 5:69-92. Westlake, D.F., 1963. Comparisons of p l a n t p r o d u c t i v i t y . B i o l . Rev. (Cambridge) 38:385-425. Winner, R.W., 1959. F i e l d - f e e d i n g p e r i o d i c i t y of Black and M a l l a r d ducks. J . W i l d l . Manage. 23:197-202. White, E.F.G., and H.F. Lewis, 1937. The Greater Snow goose i n Canada. Auk 54:440-444. Yamanaka, K., 1975. Primary p r o d u c t i v i t y of the F r a s e r r i v e r d e l t a f o r e s h o r e , y i e l d e s t i m a t e s of emergent v e g e t a t i o n . Unpub. M.Sc. T h e s i s , U.B.C., 134p. Yocum. C.F., and M. K e l l e r , 1961. C o r r e l a t i o n of food h a b i t s and abundance of waterfowl, Hurabolt Bay, C a l i f o r n i a . , C a l i f . F i s h and Game 47:41-53. Zar, J.H., 1974. M u l t i p l e comparisons. In - B i o s t a t i s t i c a l A n a l y s i s . P r e n t i c e - H a l l , N.J., pp. 151-162. 171 APPENDIX A GENERAL POPULATION CHARACTERISTICS January censuses of the S k a g i t snow goose f l o c k began i n 1947 and i n c l u d e at l e a s t one count, o f t e n a photograph, f o r each year up to and i n c l u d i n g 1975. These counts are much more complete than those taken on the F r a s e r D e l t a . Because these two f l o c k s c o n s t i t u t e a s i n g l e , presumably homogeneous p o p u l a t i o n the c h a r a c t e r i s t i c s o f e i t h e r one should be r e p r e s e n t a t i v e o f the t o t a l . The average January snow goose p o p u l a t i o n on the Skagit f l a t s f o r the past 29 years (January 1947 to January 1975) has been approximately 20,500. The counts f o r each year v a r i e d from a high of 39,000 i n 1947 to a r e c o r d low of 10,450 i n 1974. The f l u c t u a t i o n s from one year t o the next are very l a r g e , and d i r e c t u t i l i z a t i o n o f these t o t a l s i s fraught with e r r o r . About 50 percent of the counts were made by d i r e c t o b s e r v a t i o n , without a v e r i f y i n g photo count, which lends i t s e l f t o v a r i o u s e r r o r f a c t o r s such as b i r d movement, spacing of the b i r d s , experience of the counters, movement of the plane, e t c . In a d d i t i o n there i s not n e c e s s a r i l y any s i g n i f i c a n c e t o t h e f a c t t h a t a l l counts were made i n January., There i s no assurance or the same core of a d u l t geese r e c u r r i n g on the S k a g i t and maintaining 172 i t s i n t e g r i t y at the same time each year. As mentioned e a r l i e r , snow geese o f t e n change t h e i r w i n t e r i n g grounds from one year to the next. Probably a more r e p r e s e n t a t i v e measure of the v a r i a b i l i t y of the p o p u l a t i o n changes from one year to the next i s number of immature b i r d s present i n the p o p u l a t i o n expressed as a percent of the t o t a l p o p u l a t i o n . Even t h i s measurement cannot be p r e c i s e . I f the count i s taken too e a r l y i n the season, not a l l of the f a m i l y groups, who migrate l a t e r than non-breeders, w i l l have a r r i v e d . I f taken too l a t e , the d i s p r o p o r t i o n a t e s u s c e p t a b i l i t y of immatures t o hunting m o r t a l i t y w i l l a l t e r the r a t i o . However, acknowledging these problems, the change i n percent immatures i s a more u s e f u l measure of annual f l u c t u a t i o n s than d i r e c t counts. These p o p u l a t i o n changes are d i r e c t m a n i f e s t a t i o n s of j u v e n i l e s u r v i v a l as caused by the v i o l e n t and unpredicTable nature o f the weather condtions over t h e i r breeding grounds. From 1972 t o 1975 the recruitment has been below 1 percent. In f a c t d u r i n g more than 300 hours of i n t e n s i v e o b s e r v a t i o n i n the winter of 1974-1975, not a s i n g l e immature b i r d was recorded. A snow storm i n the middle of J u l y on Wrangel I s l a n d was blamed f o r the t e r r i b l e p r oduction. The year that t h i s study was conducted followed two years of r e l a t i v e l y poor j u v e n i l e s u r v i v a l . Thus, the estimate of 744,000 goose days must be c o n s i d e r e d a minimum l e v e l of snow goose pressure on the F r a s e r D e l t a marshes. 173 F igure 4 '• Est imated Population Size of the January Snow G o o s e Flock at Skag i t Flats from 1947 to 1975 1975 1974 1973 1972 1971 1970 1969 1968 1967 1966 1965 1964 1963 1962 196 1 CD I9 60 Q 1959 19 58 19 57 1956 19 55 19 54 1953 1952 1951 • 1950 • 1949 1948 1947 40 35 30 25 20 15 IO Est imated Population Size ( l , o o o g e e s e ) 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0093981/manifest

Comment

Related Items