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UBC Theses and Dissertations

The bald eagle (Haliaeetus Leucocephalus Alascanus (Townsend)) as an aircraft hazard at Port Hardy Airport Cuthbert, James T. 1979

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THE BALD EAGLE (HALIAEETUS LEUCOCEPHALUS ALASCANUS (TOWNSEND)) AS AN AIRCRAFT HAZARD AT PORT HARDY AIRPORT by JAMES T. CUTHBERT B . S c , UNIVERSITY OF VICTORIA, 1972 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the FACULTY OF GRADUATE STUDIES i n the f a c u l t y o f ZOOLOGY We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o the r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA 1979. (§) James Thomas C u t h b e r t , 197'9 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree a t the U n i v e r s i t y of B r t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and study. I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head of my Depart-ment or by h i s r e p r e s e n t a t i v e . I t i s understood t h a t copy-i n g or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be allowed without my w r i t t e n p e r m i s s i o n . Department of l i v e r s i t y The U n i v e r s i of B r i t i s h Columbia Vancouver 8, Canada Date CLtoJj 30^ /97J ABSTRACT A s i g n i f i c a n t b i r d h a z a r d t o a i r c r a f t o c c u r s a t t i m e s a t P o r t Hardy A i r p o r t t h r o u g h t h e p r e s e n c e o f numbers o f n o r t h -e r n b a l d e a g l e s i n t h e v i c i n i t y o f t h e a i r p o r t and i t s approaches. T h i s s t u d y i n v e s t i g a t e d b a l d e a g l e abundance, d i s t r i b u t i o n , movement p a t t e r n s , p r o d u c t i v i t y and f e e d i n g h a b i t s w i t h i n t h e a i r p o r t v i c i n i t y and s a t e l l i t e r e g i o n . F i n d i n g s were a n a l y z e d i n t h e l i g h t o f comparable e c o l o g i c a l i n f o r m a t i o n a v a i l a b l e on t h e s p e c i e s . The s t u d y extended from October 1972 t o October 1974. The r e s i d e n t summer and w i n t e r p o p u l a t i o n w i t h i n t h e a i r p o r t v i c i n i t y a p proximated 3 e a g l e s . Numbers i n c r e a s e d g r a d u a l l y from l a t e August u n t i l e a r l y November (when salmon were spawning i n t h e Keogh R i v e r ) and when 11 e a g l e s were c o n t i n -u o u s l y p r e s e n t . The maximum number o f e a g l e s a t any one time was 35. Even a r e l a t i v e l y s m a l l spawning ru n o f salmon was adequate t o a t -t r a c t t h e e a g l e s and t h e v e r y l a r g e runs d i d not a t t r a c t e a g l e s i n t h e same r a t i o . E a g l e numbers d e c r e a s e d from e a r l y November u n t i l t h e h e r r i n g spawning season i n March and A p r i l when a t l e a s t 5 e a g l e s were c o n t i n u o u s l y p r e s e n t . The p o t e n t i a l h a z a r d t o a i r c r a f t , e x p r e s s e d as t h e maximum number o f e a g l e s i g h t i n g s and t h e number o f eagles.' • .. .. i v o b s e r v e d per hour, was g r e a t e s t d u r i n g t h e f a l l salmon spawn-i n g season and t h e s p r i n g h e r r i n g spawning season f o r each of the 5 o b s e r v a t i o n a r e a s w i t h i n t h e a i r p o r t v i c i n i t y . The p o p u l a t i o n w i t h i n t h e s t u d y a r e a (200-250 r e s i d e n t e a g l e s ) was s u f f i c i e n t l y l a r g e t o d i s m i s s a k i l l i n g program, even i f t h i s was s o c i a l l y a c c e p t a b l e . Mean n e s t i n g d e n s i t y i n the s t u d y a r e a was a t l e a s t .1 a c t i v e n e s t / l i n e a l km o f c o a s t l i n e w i t h .2 a c t i v e n e s t / l i n e a l km o f c o a s t l i n e i n the a i r p o r t v i c i n i t y . F i f t y seven per c e n t o f t h e n e s t s f a i l e d but t h o s e t h a t produced young averaged 1.4 young/nest. F i v e a c t i v e n e s t s were w i t h i n t h e a r e a o f a i r p o r t a c t i v i t y and t h e y d i d n o t d i f f e r i n s u c c e s s r a t e o r f l e d g e d young per s u c c e s s f u l n e s t from n e s t s more remote. S t a t i s t i c a l a n a l y s i s o f d i s t r i b u t i o n d a t a w i t h i n t h e a i r p o r t v i c i n i t y r e v e a l e d t h a t e a g l e use was s i g n i f i c a n t l y g r e a t e r i n t h e Keogh R i v e r mouth r e g i o n and s i g n i f i c a n t l y l o wer i n t h e i n l a n d r e g i o n t h a n i n t h e r e m a i n i n g o b s e r v a t i o n a r e a s . The a g g r e g a t i o n a r e a a l o n g t h e K e o g h i i R i v e r i n t h e s o u t h e a s t f l i g h t p a t h f o r runway 1028 p r e s e n t e d t h e g r e a t e s t h a z a r d t o a i r c r a f t . D i r e c t e a g l e f l i g h t s a c r o s s t h e f l i g h t p a t h o c c u r r e d a t f r e q u e n t i n t e r v a l s i n September and October and were o f t e n a t t h e same e l e v a t i o n as a p p r o a c h i n g o r d e p a r t i n g j e t a i r c r a f t . S i n c e i t i s not l i k e l y t h a t the b e h a v i o u r o f the e a g l e s can be changed, ways o f a l t e r i n g t h e f l i g h t p a t h s o f t h e a i r c r a f t were c o n s i d e r e d so as t o l e s s e n the f r e q u e n c y V o f i n t e r a c t i o n . T h i s can be done by e x t e n s i o n o f runway 102 8 (by about 610m) t o a l l o w a p p r o a c h i n g o r d e p a r t i n g Boeing 737 j e t s t o pass o v e r , i n s t e a d o f t h r o u g h , t h e haz-ardous zone above th e Keogh R i v e r . v i TABLE OF CONTENTS Page ABSTRACT i i i LIST OF TABLES v i i i LIST OF FIGURES i x ACKNOWLEDGEMENTS x i INTRODUCTION 1 PART I THE STUDY AREA 4 1.1 PORT HARDY AIRPORT CONTROL ZONE . . . 4 1.2 PORT HARDY AIRPORT VICINTY 7 1.3 REGIONAL STUDY AREA 7 1.4 FAUNA 9 PART 2 STUDY METHODS 13 2.1 STUDY PERIOD 13 2.2 CONTROL TOWER OBSERVATIONS 13 2.3 GROUND SURVEYS 15 2.3.1 A i r p o r t V i c i n i t y 15 2.3.2 C o n t r o l Zone 18 2.3.3 R e g i o n a l Study A r e a 19 2.4 BOAT SURVEYS 19 2.5 AERIAL SURVEYS 19 2.6 MARKING AND TELEMETRIC PROJECT . . . . 20 2.7 FOOD RELATIONSHIPS 20 2.8 FLIGHT PATH RECORDING 2 2 v i i Page PART 3 RESULTS 2 4 3.1 ABUNDANCE 2 4 3.1.1 A i r p o r t V i c i n i t y 24 3.1.2 C o n t r o l Zone 30 3.1.3 Regional Findings 30 3.2 DISTRIBUTION AND AIRCRAFT HAZARD . . . . 33 3.2.1 A i r p o r t V i c i n i t y 33 3.2.2 C o n t r o l Zone 41 3.2.3 Regional Findings 41 3.2.4 Comparison Between Areas 45 3.3 ABUNDANCE AND DISTRIBUTION OF NESTS . . . 50 3.3.1 A i r p o r t V i c i n i t y and C o n t r o l Zone. 50 3.3.2 Regional Findings 50 3.4 PRODUCTIVITY 54 3.4.1 A i r p o r t V i c i n i t y and C o n t r o l Zone. 54 3.4.2 Regional Findings 56 3.5 FOOD RELATIONSHIPS 59 3.6: EAGLESFDIGHT PATTERNS... 73 -PART-' 4r-IDISeUSS10N5ATION&: 7:5 BIBLIOGRAPH^Y .. .; 81 v i i i LIST OF TABLES Page 1. S e a s o n a l d i s t r i b u t i o n o f e a g l e s w i t h i n t h e stu d y a r e a as e x p r e s s e d by t h e average number of e a g l e s r e c o r d e d p e r l i n e a l km o f c o a s t l i n e d u r i n g 19 74 boat and a e r i a l s u r v e y s 46 2. Abundance and d i s t r i b u t i o n o f a c t i v e and i n -a c t i v e n e s t s w i t h i n t h e s t u d y a r e a d u r i n g t h e 1974 n e s t i n g season 53 3. S t a t e o f e a g l e n e s t s , n e s t i n g s u c c e s s , and n e s t abandonment w i t h i n t h e s t u d y a r e a d u r i n g t h e 1974 n e s t i n g season 55 4. P r o d u c t i v i t y o f s e l e c t e d e a g l e n e s t s w i t h i n t h e r e g i o n a l s t u d y a r e a d u r i n g t h e 1974 n e s t i n g season . . 57 5. P a r t i c u l a r s o f spawning p i n k , chum, and coho Salmon i n t h e Keogh, Quatse, and T s u l q u a t e R i v e r s d u r i n g the f a l l o f 1972, 1973 and 1974 ( A f t e r Zybut, 1972 and Zybut and Anderson, 1973) 63 6. Food remains found a t 10 e a g l e n e s t s w i t h i n t h e c o n t r o l zone d u r i n g 1974 72 i x LIST OF FIGURES Page 1. The s t u d y a r e a 5 2. A i r p o r t c o n t r o l zone 6 3. A i r p o r t v i c i n i t y 8 4. A i r p o r t v i c i n i t y o b s e r v a t i o n a r e a s and ground s u r v e y r o u t e s 14 5. Average number o f e a g l e s s i g h t e d / d a y from t h e c o n t r o l tower on o r near runways and t h e i r approaches from O c t o b e r , 1971 - O c t o b e r , 1974. 25,26 6. Minimum number of e a g l e s c o n t i n u o u s l y f r e q u e n t i n g the a i r p o r t v i c i n i t y from J u l y , 1972 t o O c t o b e r , 1974 27 7. S i g h t i n g s / h o u r f o r a i r p o r t v i c i n i t y o b s e r v a t i o n a r e a s based on t h e maximum number of e a g l e s i g h t i n g s f o r each a r e a from O c t o b e r , 1972 -O c t o b e r , 1974 28 8. A g e - s p e c i f i c e a g l e abundance w i t h i n t h e a i r p o r t c o n t r o l zone r e c o r d e d d u r i n g 1974 boat s u r v e y s 31 9. A g g r e g a t i o n a r e a s w i t h i n t h e a i r p o r t v i c i n i t y •• o b s e r v a t i o n a r e a s d u r i n g t h e f a l l o f 1972, 1973, and 1974 and from F e b r u a r y t h r o u g h August 1974 36 10. B o e i n g 737 j e t approach p a t t e r n t o runway 1028 from the s o u t h e a s t 38 11. Frequency and a l t i t u d e o f e a g l e f l i g h t s o v e r the Keogh R i v e r d u r i n g t h e f a l l o f 1972, 1973 and 1974 38 X LIST OF FIGURES Page 12. A g g r e g a t i o n a r e a s w i t h i n t h e c o n t r o l zone based on r e s u l t s from ground, b o a t , and a e r i a l s u r v e y s d u r i n g 1972, 1973, and 1974 . . 42 13. A g g r e g a t i o n a r e a s w i t h i n t h e r e g i o n a l s t u d y a r e a based on r e s u l t s from ground, b o a t , and a e r i a l s u r v e y s d u r i n g t h e 1974 n e s t i n g season and d e l i n e a t i o n o f 6 sub-areas c o m p r i s i n g t h e r e g i o n a l s t u d y a r e a 44 14. N e s t s l o c a t e d w i t h i n t h e a i r p o r t c o n t r o l zone and t h e i r s t a t e o f use d u r i n g t h e 19 74 n e s t i n g season 51 15. Minimum number o f e a g l e s c o n t i n u o u s l y f r e q u e n t i n g t h e a i r p o r t v i c i n i t y i n r e l a t i o n t o t h e e s t i m a t e d salmon escapement t o the Keogh R i v e r d u r i n g t h e f a l l o f 1973 61 16. S c a t t e r diagram showing r e g r e s s i o n l i n e s f o r c o r r e l a t i o n between th e abundance of e a g l e s i n t h e a i r p o r t v i c i n i t y d u r i n g t h e f a l l o f 1972, 1973 and 1974 and t h e e s t i n a t e d p i n k salmon escapement t o t h e Keogh R i v e r d u r i n g t h e same p e r i o d . 62 17. J^equetiey^altitC^ f l i g h t s ; -• above.the Keogh River i i i - the;cs6u.the'ase f l i g h t path for runway 1028 during the f a l l of 1972, 1973, and 1974 74 18. Relationship between runway extension distance and ascent pattern of Boeing 737 j e t 79 x i ACKNOWLEDGEMENTS I would l i k e t o e x p r e s s my i n d e b t e d n e s s t o a number o f people whose a s s i s t a n c e p r o v e d v a l u a b l e d u r i n g t h i s s t u d y . To Dr. I a n McTaggart Cowan, P r o j e c t S u p e r v i s o r , f o r a d v i c e and l e a d e r s h i p t h r o u g h o u t t h e s t u d y , and f o r h i s c a r e f u l c r i t i c a l r e v i e w o f the f i n a l r e p o r t ; Dr. John Ward, P r o j e c t A d v i s e r , f o r a s s i s t a n c e i n f i e l d w o r k , r e p o r t w r i t i n g , and h i s many h e l p f u l s u g g e s t i o n s ; and p r o j e c t a d v i s e r s J . S m i t h , N. R. L i l e y , F. B u n n e l l , and T. N o r t h c o t e f o r t h e i r a d v i c e and c r i t i c i s m . I would l i k e t o e x p r e s s my s i n c e r e t h a n k s t o the p e o p l e l i v i n g a t P o r t Hardy A i r p o r t f o r t h e i r s u p p o r t , f r i e n d s h i p , and s e n s i t i v e u n d e r s t a n d i n g . I t i s i m p o s s i b l e t o thank a l l i n -d i v i d u a l s by name, b u t I must e x p r e s s my p a r t i c u l a r i n d e b t -edness t o A i r p o r t Manager, Ed W i l s o n f o r h i s k i n d c o o p e r a t i o n and generous a i d ; A i r p o r t Maintenance Foreman George E l v i s h f o r h i s h e l p f u l s u p p o r t ; MeteoEol:6gifs.ti'Ge'orge£Kearey;.and the a i r p o r t t e c h n i c i a n s f o r t h e i r a s s i s t a n c e i n t h e t e l e -metry program; C o n t r o l Tower C h i e f B i l l R e i d and h i s s t a f f f o r t h e i r f a i t h f u l n e s s i n r e c o r d i n g o b s e r v a t i o n s ; Weather O f f i c e C h i e f Ray Koch and h i s s t a f f f o r p r o v i d i n g c l i m a t o l o g i c a l d a t a ; and Runway P a t r o l C h i e f Gord Smith f o r h i s h e l p i n ob-t a i n i n g f i e l d d a t a . I am i n d e b t e d t o Dr. B i l l Gunn, P r e s i d e n t , L.G.L. L i m i t e d , x i i f o r f i n a n c i a l a s s i s t a n c e and h i s h e l p f u l g u i d a n c e t h r o u g h -out t h e s t u d y ; Dr. B r i s t o l F o s t e r , Chairman, E c o l o g i c a l Reserves Committee, B.C. P r o v i n c i a l Government, f o r h i s v a l u a b l e recommendations; Dr. Dave H a t l e r f o r h i s comments on f i e l d t e c h n i q u e s ; Dr. Tom B e r g e r u d and U n i v e r s i t y o f V i c t o r i a l e c t u r e r s Dr. Hagmeier, Dr. Gregory and A l l a n Brooks f o r g uidance a t t h e b e g i n n i n g o f the s t u d y . I am a l s o i n d e b t e d t o P o r t Hardy F i s h e r i e s O f f i c e r Gordon Zea l a n d and h i s s t a f f f o r t h e i r c o n t i n u o u s h e l p i n s u p p l y i n g d a t a on salmon s t o c k s . C o n s e r v a t i o n O f f i c e r Bud P r a t t p r o v i d e d v a l u a b l e i n f o r m a t i o n and a s s i s t e d i n r e g i o n a l s u r v e y s . My s i n c e r e t h a n k s a r e due t o P a c i f i c Western A i r l i n e s L i m i t e d f o r p r o v i d i n g many f l i g h t p a s ses and f l i g h t - d e c k c l e a r a n c e s between Vancouver and P o r t Hardy d u r i n g 19 74. P a c i f i c West-e r n A i r l i n e s P r e s i d e n t , Mr. Don H a r r i s , and V i c e P r e s i d e n t , C a p t a i n J a c k M i l e s , were p a r t i c u l a r l y h e l p f u l i n t h i s r e g a r d . P a c i f i c Western A i r l i n e s p i l o t s s u p p l i e d v a l u a b l e i n f o r -m a t i o n on b i r d s t r i k e s , c r i t i c a l a r e a s , and s t a t i s t i c a l d a t a on a p p r o a c h i n g and d e p a r t i n g j e t f l i g h t s . A l e r t Bay A i r S e r v i c e s L i m i t e d was e s p e c i a l l y h e l p f u l i n p r o -v i d i n g f l i g h t t i me d u r i n g b o t h c o n t r o l zone and r e g i o n a l s u r v e y s . S p e c i a l t h a n k s i s extended t o A.B.A.S. P r e s i d e n t Don Thompson and the P o r t Hardy O p e r a t i o n s Manager W i l l i e Douglas and h i s crew. I am g r a t e f u l t o Vancouver I s l a n d H e l i c o p t e r s L i m i t e d f o r x i i i donating s e v e r a l hours of f l i g h t time during c o n t r o l zone and r e g i o n a l surveys. V.I.H. Pr e s i d e n t A l S t r i n g e r and Port Hardy p i l o t Don Honeyman were p a r t i c u l a r l y h e l p f u l . I am a l s o indebted to Rudy Bauer, F o r e s t r y Engineer at Mahatta R i v e r , f o r p r o v i d i n g e x c e l l e n t a e r i a l survey cov-erage of the study area, and f o r h i s k i n d h o s p i t a l i t y . I wish to extend my s i n c e r e thanks to the many people at Port Hardy, Port Rupert, P o r t McNeil, S o i n t u l a , A l e r t Bay, Beaver Harbour, Winter Harbour, Telegraph Cove,' Coal Harbour, B u l l Harbour, Holberg, P o r t A l i c e , Rumble Beach, Jeune Landing, Quatsino, and Mahatta R i v e r f o r p r o v i d i n g valuable i n f o r m a t i o n on nest l o c a t i o n s , eagle s i g h t i n g s , and eagle a c t i v i t y p a t t e r n s . I would l i k e t o thank Dr. P i e r r e Dansereau, D i r e c t o r of the Montreal E c o l o g i c a l Research Centre, f o r h i s advice, and Don McLaughlin of the Transport M i n i s t r y ' s Planning D i v i s i o n f o r h i s a s s i s t a n c e i n f o r m u l a t i n g recommendations. The k i n d h o s p i t a l i t y of Sue Baxter and Bruce Manley helped to make my stay at P o r t Hardy a very enjoyable one. F i n a l l y , I must thank my parents and s i s t e r f o r t h e i r con-tinuous encouragement throughout the study. - 1 -INTRODUCTION T h i s i s a s t u d y a r i s i n g from t h e b i r d h a z a r d £o a i r c r a f t i n the a i r s p a c e over an a i r p o r t . To my knowledge i t i s unique i n t h a t the h a z a r d a r i s e s from t h e b a l d e a g l e H a l i a e e t u s l e u c o c e p h a l u s a l a s c a n u s , a b i r d r e g a r d e d as endangered o v e r most o f N o r t h A m e r i c a but abundant i n t h e v i c i n i t y o f t h e s t u d y s i t e - P o r t Hardy a i r p o r t on the n o r t h e r n end o f Vancouver I s l a n d ( l a t i t u d e 50^43'12"N, l o n g i t u d e 127°29'10"W). B i r d s have c o n s t i t u t e d a h a z a r d t o a i r c r a f t a t a i r f i e l d s i n many p a r t s o f t h e w o r l d and t h e r e i s an e x t e n s i v e l i t -e r a t u r e on t h e problem w i t h v a r i o u s s o l u t i o n s sought and t e s t e d . I n g e n e r a l t h e approach t o h a z a r d abatement has been t o reduce t h e number of b i r d s p r e s e n t i n t h e a i r p o r t v i c i n i t y ( P earson, 1967). Many t e c h n i q u e s have been t r i e d i n c l u d i n g s h o o t i n g t h e b i r d s (Solman, 1970); t h e use o f f r i g h t e n i n g d e v i c e s such as d e t o n a t o r s (Murton and W r i g h t , 1968); f l u s h i n g d e v i c e s such as p a t r o l s o f t h e a i r p o r t ; model a i r c r a f t f l o w n over t h e b i r d a g g r e g a t i o n s ; and t h e use o f t r a i n e d f a l c o n s (Solman, 1970). The most f r u i t f u l g e n e r a l approach has been t o a l t e r t h e a t t r a c t i v e n e s s t o b i r d s o f the a i r p o r t and s u r r o u n d i n g a r e a . The most e f f e c t i v e s o l u t i o n t o a b i r d h a z a r d problem a t an a i r p o r t can o n l y be d e t e r m i n e d a f t e r t h e b i o l o g i c a l and p h y s i c a l d i m e n s i o n s o f t h e problem are known. The b e s t - 2 -s t r a t e g y , b i o l o g i c a l l y and e c o n o m i c a l l y , i s s i t u a t i o n s p e c i f i c . Thus, i t i s n e c e s s a r y t o d e t e r m i n e th e s p e c i e s i n v o l v e d ; t h e numbers o f i n d i v i d u a l s i n v o l v e d ; t h e g e n e r a l s i z e o f t h e p o p u l a t i o n and t h e a r e a from w h i c h i t i s drawn; the s e a s o n a l and d i e l d i s t r i b u t i o n o f t h e b i r d a c t i v i t y i n r e l a t i o n t o a i r c r a f t movement; the d e t a i l s o f b i r d movement and agg-r e g a t i o n ; and t h e n a t u r e o f t h e a t t r a c t i o n w h i c h b r i n g s b i r d s t o t h e a r e a and t h u s governs n o t o n l y t h e i r l e n g t h o f s t a y b u t a l s o t h e i r a c t i v i t y w h i c h c r e a t e s t h e h a z a r d . I n t h e p r e s e n t i n s t a n c e i t was a l r e a d y known t h a t t h e major h a z a r d s p e c i e s was the b a l d e a g l e , t h a t i t o c c u r r e d i n t h e v i c i n i t y o f t h e a i r p o r t a l l y e a r round but t h a t numbers changed w i t h t h e b i o l o g i c a l c y c l e t h r o u g h t h e season. I t was a l s o known t h a t a g g r e g a t i o n s o f e a g l e s and t h e i r a c t i v i t y were a s s o c i a t e d w i t h t h e spawning o f salmon i n a r i v e r c l o s e t o t h e end o f t h e main a i r p o r t runway. T h i s o c c u r r e d between the end o f August and t h e end o f O c t o b e r . My s t u d y was d e s i g n e d t o d e t e r m i n e th e d e t a i l s o f t h e problem as o u t l i n e d above and p r o v i d e a s o l u t i o n w h i c h p r e f e r a b l y d i d not i n v o l v e k i l l i n g t h e e a g l e s . B a l d e a g l e s have c o l l i d e d w i t h a i r c r a f t a t P o r t Hardy a t l e a s t t w i c e d u r i n g r e c e n t y e a r s . One o f t h e s e s t r i k e s o c c u r r e d i n t h e l a t e f a l l o f 1975 and i n v o l v e d a s m a l l t w i n e n g ine p l a n e . The a i r c r a f t was l a n d i n g a t t h e time and s t r u c k t h e e a g l e as i t f l e w up from i t s p e r c h a t t h e edge o f t h e runway. The - 3 -a i r c r a f t s u s t a i n e d no damage, b u t t h e e a g l e broke i t s w i n g . A second c o l l i s i o n o c c u r r e d j u s t p r i o r t o t h i s s t u d y and i n v o l v e d a P a c i f i c Western A i r l i n e s t w i n engine C o n v a i r . The s t r i k e o c c u r r e d j u s t above t h e runway, k i l l i n g t h e e a g l e and c a u s i n g c o n s i d e r a b l e damage t o t h e wing o f t h e a i r c r a f t . A l t h o u g h s t r i k e s have been i n f r e q u e n t , t h e y do c o n f i r m t h e p o t e n t i a l h a z a r d t o a i r c r a f t r e s u l t i n g from e a g l e a c t i v i t y near t h e a i r p o r t . - 4 -PART I THE STUDY AREA The s t u d y a r e a was c e n t e r e d upon t h e n o r t h e r n p a r t o f Vancouver I s l a n d . D e t a i l e d o b s e r v a t i o n s were extended over an a r e a o f 4,470 sq.km (1,726 sq.mi.) a d j a c e n t t o P o r t Hardy. The s o u t h e r n boundary was a r b i t r a r i l y s e t a t l a t i t u d e 50^19'N ( F i g . l ) . The r e m a i n i n g b o u n d a r i e s were e s t a b l i s h e d by t h e s e a c o a s t and a d j a c e n t i s l a n d s . I n o r d e r t o p r o v i d e l e v e l s o f d e t a i l r e q u i r e d t o g a i n an u n d e r s t a n d i n g o f t h e e a g l e p o p u l a t i o n , t h e l a r g e r a r e a was s u b d i v i d e d i n t o 3 s m a l l e r ones. These zones were: 1.1 PORT HARDY AIRPORT CONTROL ZONE T h i s zone, based upon c r i t e r i a e s t a b l i s h e d t o govern t h e approach and d e p a r t u r e o f a i r c r a f t , was a c i r c u l a r r e g i o n w i t h an 8 km r a d i u s c e n t e r e d a t t h e a i r p o r t c o n t r o l tower ( F i g . 2 ) . I t i n c l u d e d 20,332 h e c t a r e s e q u a l l y d i v i d e d be-tween l a n d and w a t e r . The zone c o n s i s t e d o f a h e a v i l y f o r -e s t e d c o a s t l i n e a r e a where e a g l e s were numerous because o f the abundance o f f o o d and i d e a l n e s t i n g c o n d i t i o n s . The zone a l s o i n c l u d e d v e r y p r o d u c t i v e s e c t i o n s o f t h e Keogh R i v e r i n terms o f salmon s t o c k s and c o n t a i n e d s e v e r a l b a l d e a g l e b r e e d i n g t e r r i t o r i e s . I n a d d i t i o n t o t h e Keogh R i v e r , t h e Quatse and T s u l q u a t e R i v e r s t r a v e r s e t h e c o n t r o l zone. Each s u p p o r t s a p o p u l a t i o n o f anadromous salmon and t r o u t . S i n c e a l l a i r t r a f f i c w i t h i n t h e zone must r e p o r t and a b i d e Figure 1 The Study Area F i g u r e 2 A i r p o r t C o n t r o l Zone - 7 -by M i n i s t r y o f T r a n s p o r t r e g u l a t i o n s i n approaches t o and d e p a r t u r e s from the a i r p o r t , i t was p o s s i b l e t o o b t a i n d e t a i l s on f l i g h t p a t h s used. 1.2 PORT HARDY AIRPORT VICINITY The a i r p o r t v i c i n i t y was d e f i n e d as a c i r c u l a r r e g i o n w i t h -i n t he c o n t r o l zone w i t h a 3,811m r a d i u s and an a r e a o f 2,2 82 h e c t a r e s (8.8 sq.mi.) c e n t e r e d a t t h e c o n t r o l tower ( F i g . 3 ) . The a i r p o r t v i c i n i t y was t h a t p a r t o f the c o n t r o l zone w i t h -i n w h i c h the f l i g h t p a t h s o f a i r c r a f t and e a g l e s tended t o converge. I t was s m a l l enough t o a l l o w comprehensive cov-erage o f e a g l e a c t i v i t y on a d a i l y b a s i s and i n c l u d e d t h e a i r p o r t runways and a l l f l i g h t p a t h c l e a r i n g s and t h u s t h e ar e a s o f g r e a t e s t b i r d h a z a r d t o a i r c r a f t . I t c o n t a i n e d t h e t i d a l p o r t i o n s o f t h e Keogh R i v e r w i t h i n w h i c h salmon were most c o n c e n t r a t e d and a v a i l a b l e . Almost t h e e n t i r e a i r p o r t v i c i n i t y was v i s i b l e from t h e c o n t r o l tower. 1.3 REGIONAL STUDY AREA In o r d e r t o e s t i m a t e t h e s i z e and p r o d u c t i v i t y o f t h e e a g l e p o p u l a t i o n h a v i n g p o t e n t i a l a c c e s s t o t h e a i r p o r t , s u r v e y s were extended t o a l a r g e r r e g i o n from P o r t A l i c e i n t h e s o u t h t o T e l e g r a p h Cove i n t h e e a s t , t o T r i a n g l e I s l a n d i n t h e west, and i n the northfctooCape S u t i l ( F i g . l ) . These b o u n d a r i e s were a r b r i t r a r y and based upon b e s t judgement o f m y s e l f and o t h e r s f a m i l i a r w i t h movement o f e a g i e s i n t h i s a r e a . De-t a i l e d s u r v e y s were conducted a l o n g t h e c o a s t o f Vancouver F i g u r e 3 A i r p o r t V i c i n i t y - 9 -I s l a n d from Ledge P o i n t near P o r t M c N e i l l i n t h e e a s t , t o Cape S u t i l i n t h e n o r t h , t o Cape S c o t t i n t h e west, and t o the mouth o f C o l o n i a l Creek near P o r t A l i c e i n t h e s o u t h . I s l a n d s a d j a c e n t t o t h e n o r t h e a s t and n o r t h w e s t c o a s t o f Vancouver I s l a n d were a l s o s u r v e y e d i n d e t a i l . The lower r e a c h e s o f a l l major r i v e r s a l o n g t h e n o r t h e a s t and n o r t h w e s t c o a s t o f Vancouver I s l a n d were i n c l u d e d . The l a n d a r e a a d j a c e n t t o roads j o i n i n g W i n t e r Harbour, H o l b e r g , San J o s e p h , P o r t Hardy, C o a l Harbour, Juene L a n d i n g , Rumble Beach, P o r t A l i c e , P o r t M c N e i l l , Beaver Cove, and T e l e g r a p h Cove formed a n o t h e r p a r t o f t h e a r e a s t u d i e d . 1. :4; FAUNA A knowledge o f t h e fauna p r o v i d e s a view o f t h e p o t e n t i a l p r e y a n i m a l s a v a i l a b l e t o b a l d e a g l e s . I had s p e c i a l i n t e r e s t i n any l o c a l c o n c e n t r a t i o n s o f f o o d organisms o r anyi p h y s i c a l c o n d i t i o n s w h i c h might l e a d t o t h e f r e q u e n t o r p e r i o d i c a v a i l a b i l i t y o f f o o d i n amounts l i k e l y t o en-courage t h e a g g r e g a t i o n o f numbers o f e a g l e s . I n thi-s r e v i e w , I have c o n f i n e d m y s e l f t o t h o s e ; j s p e c i e s t h a t o f f e r p o t e n t i a l f o o d s o u r c e s f o r t h e e a g l e . The b a l d e a g l e o f t e n f e e d s l a r g e l y by s c a v e n g i n g . Large mammals a r e used by e a g l e s as c a r r i o n . However, a l t h o u g h b l a c k b e a r , b l a c k - t a i l e d d e e r , h a i r s e a l s , n o r t h e r n sea l i o n , and a v a r i e t y o f s m a l l whales a r e p r e s e n t , they a r e w i d e l y d i s t r i b u t e d , a r e o n l y s p o r a d i c a l l y a v a i l a b l e and a r e - 10 -not a r e g u l a r r e a s o n f o r e a g l e c o n c e n t r a t i o n near the a i r p o r t . M a r i n e b i r d s on t h e o t h e r hand do c o n c e n t r a t e between December and F e b r u a r y i n w a t e r s a d j a c e n t t o t h e a i r p o r t , a r e hunted by e a g l e s and appear t o a t t r a c t e a g l e a c t i v i t y though I was unable t o d e v e l o p a s t a t i s -t i c a l e x p r e s s i o n o f t h i s e f f e c t . S p e c i e s c o n c e n t r a t i n g were s u r f s c o t e r s ( M e l a n i t t a p e r s p i c i l l a t a ) , w h i t e - w i n g e d s c o t e r s ( M e l a n i t t a d e g l a n d i ) , and g r e a t e r s c a l p s (Aythya m a r i l a ) . I t was n o t p o s s i b l e t o e s t i m a t e t h e biomass o f b i r d c a r r i o n a v a i l a b l e t o e a g l e s , o r the d i s t r i b u t i o n o f dead b i r d s w i t h i n t h e a r e a . There was no i n d i c a t i o n o f a c o n c e n t r a t i o n o f c a r r i o n near t h e a i r p o r t t h a t would a t t r a c t e a g l e s . E a g l e s are known t o hunt and k i l l d i v i n g ducks and o t h e r marine b i r d s . The w a t e r s a d j a c e n t t o t h e a i r p o r t v i c i n i t y i n c l u d i n g t h e Keogh, Quatse, and T s u l q u a t e R i v e r s s u p p o r t a v a r i e t y o f f i s h . The abundance o f spawning salmon i n t h e Keogh R i v e r was o f p a r t i c u l a r i m p o r t a n c e t o t h e p r e s e n t s t u d y . P r e -l i m i n a r y r e s e a r c h (L.G.L. L i m i t e d , 1973) i n d i c a t e d t h a t a c l o s e r e l a t i o n s h i p might e x i s t between b a l d e a g l e abundance, d i s t r i b u t i o n , and a c t i v i t y d u r i n g t h e spawning season and the a v a i l a b i l i t y o f salmon as a f o o d s o u r c e i n t h e Keogh R i v e r . The Keogh i s an i m p o r t a n t spawning r i v e r f o r p i n k salmon (Oncorhynchus gorbusha Walbaum). I n even y e a r s - 11 -( i e . 1972, 1974, e t c . ) / the number o f p i n k salmon e n t e r i n g the Keogh t o spawn g e n e r a l l y exceeds 75,000 and can be as h i g h as 150,000 ( Z y b l u t , 1972). These numbers can acc o u n t f o r up t o 10% o f a l l p i n k salmon spawning i n a p p r o x i m a t e l y 60 r i v e r s and streams i n t h e J o h n s t o n e S t r a i t a r e a ( i b i d ) . I n odd y e a r s ( i e . 1973, 1975, e t c . ) , t h e number o f p i n k salmon e n t e r i n g the Keogh i s u s u a l l y l e s s t h a n 10,000, b u t on o c c a s i o n may r i s e as h i g h as 35,000 ( Z y b l u t and Anderson, 19 73). These r e g u l a r f l u c t u a t i o n s between even and odd y e a r s a r e a d i r e c t r e s u l t o f t h e p i n k salmon's 2 y e a r l i f e c y c l e . Up t o 3,000 coho (Oncorhynchus k i s u t c h Walbaum) and 5,000 chum salmon (Oncorhynchus k e t a Walbaum) may spawn a n n u a l l y i n t h e Keogh R i v e r (G. Zealand p e r s . comm.). Chum salmon s e r v e as a f o o d s o u r c e t o e a g l e s . E a g l e s no doubt f e e d on some coho salmon a l t h o u g h I have no e v i d e n c e t o s u p p o r t t h i s . The Quatse and T s u l q u a t e R i v e r s a l s o i n c l u d e i m p o r t a n t spawning grounds f o r p i n k and chum salmon. The d i s t r i b u t i o n and abundance o f spawning salmon and t h e i r a v a i l a b i l i t y as a f o o d s o u r c e t o e a g l e s i s c o n s i d e r e d i n 3.5. O f f s h o r e w a t e r s i n c l u d e d w i t h i n t h e c o n t r o l zone s u p p o r t i m p o r t a n t b u t d i m i n i s h i n g c o n c e n t r a t i o n s o f P a c i f i c h e r r i n g (Clupea p a l l a s i i V a l e n c i e n n e s ) . Coho, p i n k , and s p r i n g (Oncorhynchus t s h a w y t s c h a Walbaum) salmon use t h i s a r e a as - 1 2 -a schooling ground p r i o r to the annual spawning migration. These shallow waters along the coastline contain a large variety of other f i s h , including many kinds of sculpins, some of the f l a t f i s h e s , seaperch, smelt, cod, and rock-f i s h (Sebastodes sp.). The Keogh and Quatse Rivers contain coastal cutthroat (Salmo c l a r k i c l a r k i Richardson), d o l l y varden (Salvelinus malma Walbaum), and rainbow trout (Salmo gairdneri Richardson) and also support an annual steelhead trout (Salmo gairdneri Richardson) run. The variety of coastal habitat within the control zone, along with a marked v a r i a t i o n i n exposure, supports a diverse assemblage of both i n t e r t i d a l and subtidal faunal communities. Univalve and bivalve molluscs, and echinoderms predominate i n the i n t e r - t i d a l zone of the sandstone shelves and rocky coastline, while bivalves and crustaceans are abundant along the gravel and sand beaches. The importance of marine invertebrates as a food source i s discussed i n section 3.5. - 13 -PART 2 STUDY METHODS 2.1 STUDY PERIOD The two-year s t u d y p e r i o d began on 2 8 October 19 72 and t e r m i n a t e d on 31 October 1974. T h i s p e r i o d i n c l u d e d 3 c o n s e c u t i v e salmon spawning seasons. The a u t h o r spent a t o t a l o f 111 days i n the f i e l d c o l l e c t i n g d a t a . T r i p s t o the s t u d y a r e a d u r i n g 1972, 1973, and 1974 c o v e r e d e v e r y month, w i t h c o n c e n t r a t i o n d u r i n g t h e autumn and w i n t e r p e r i o d w h e r e i n e a g l e s were most numerous i n t h e a i r p o r t v i c i n i t y . The m a j o r i t y o f d a t a c o l l e c t i o n o c c u r r e d between F e b r u a r y and October 1974 when 19 t r i p s , c o v e r i n g e v e r y month, were made i n t o the s t u d y a r e a . 2.2 CONTROL TOWER OBSERVATIONS The P o r t Hardy a i r p o r t c o n t r o l tower p r o v i d e d an i d e a l v antage p o i n t from w h i c h t o o b s e r v e e a g l e a c t i v i t y w i t h i n the c o n t r o l zone. A d u l t and immature b i r d s c o u l d n o r m a l l y be d i s t i n g u i s h e d w i t h i n 1.6 km.of the tower. Under f a v o u r -a b l e c o n d i t i o n s , e a g l e s c o u l d be s i g h t e d w i t h i n 4.5 km o f the tower. The f i r s t c a r e f u l d o c u m e n t a t i o n o f e a g l e a c t i v i t y w i t h i n t h e c o n t r o l zone c o v e r e d t h e p e r i o d from October 1971 t o May 1972. E a g l e s i g h t i n g s were r e c o r d e d i n a l o g c o n t i n u o u s l y from October 28, 1972 u n t i l O ctober 31, 1974. Data r e c o r d e d i n -c l u d e d t h e d a t e , t i m e , l o c a t i o n , a c t i v i t y , weather c o n d i t i o n s , - 14 -- ^ - F o o t and V e h i c l e P a t r o l Routes -Observation area\ boundary-F i g u r e 4. A i r p o r t v i c i n i t y o b s e r v a t i o n areas and ground s u r v e y r o u t e s - 15 -number o f e a g l e s and t h e i r age c a t e g o r y . A r a t i n g s c a l e was d e v e l o p e d whereby l i g h t a c t i v i t y was d e f i n e d as 1 t o 2 e a g l e s o b s e r v e d d u r i n g an 8 hour p e r i o d , moderate as 3 t o 5 e a g l e s , heavy as 6 t o 10, and e x t e n s i v e as more than 10. From May t o October 1972, o n l y u n u s u a l s i g h t -i n g s were r e c o r d e d by c o n t r o l tower p e r s o n n e l . 2.3 GROUND SURVEYS S y s t e m a t i c ground s u r v e y s were c a r r i e d out t o de t e r m i n e b a l d e a g l e abundance, d i s t r i b u t i o n , f e e d i n g b e h a v i o u r , and o t h e r a c t i v i t y p a t t e r n s . Other f a c t o r s , such as n e s t s i t e s and t h e salmon spawning sequence, were documented c o n c u r r e n t l y . Ground s u r v e y s were made on f o o t and by v e h i c l e . Three ground s u r v e y a r e a s were d e l i n e a t e d . 2.3.1 A i r p o r t V i c i n i t y The a i r p o r t v i c i n i t y , w h i c h r e c e i v e d t h e most comprehensive s u r v e y s , was d i v i d e d i n t o 5 o b s e r v a t i o n a r e a s of comparable s i z e as shown i n F i g u r e 4. D u r i n g each t r i p t o the stu d y a r e a an attempt was made t o s u r v e y a l l o b s e r -v a t i o n s i t e s u s i n g p r e d e t e r m i n e d r o u t e s . The amount o f time spent i n each a r e a v a r i e d a c c o r d i n g t o a i r c r a f t t r a v e l t h r o u g h t h a t a r e a . Coverage was g r e a t e s t i n t h o s e a r e a s w h i c h were most f r e q u e n t l y used by j e t and o t h e r a i r c r a f t . J e t approaches and d e p a r t u r e s were r e s t r i c t e d t o runway 1028 (area 2 ) ( F i g . 3) and t h e c o r r e s p o n d i n g f l i g h t p a t h s i n ar e a s 1, 3 and 4. A r e a - 16 -5, l o c a t e d i n l a n d and n o t u t i l i z e d by j e t s , r e c e i v e d t h e l e a s t c o v e r a g e . O b s e r v a t i o n p o i n t s and v i e w i n g p r o c e d u r e s were s e l e c t e d f o r each s u r v e y r o u t e . S e v e n t y - f i v e p e r c e n t o f the a i r p o r t v i c i n i t y c o u l d n o t be viewed from the ground because o f t a l l t r e e s . E a g l e s i g h t i n g s were r e c o r d e d e i t h e r i n f i e l d note books or on t a p e . Data i n c l u d e d s t a n d a r d i n f o r m a t i o n p l u s a c t i v i t y , l o c a t i o n , and a t t i m e s e s t i m a t e s o f a l t i t u d e s a l t h o u g h t h e l a t t e r were d i f f i c u l t t o a p p r o x i m a t e a c c u r a t e l y . An e s t i m a t e o f t h e minimum number o f a d u l t and immature e a g l e s c o n t i n u o u s l y f r e q u e n t i n g the a i r p o r t v i c i n i t y was made f o l l o w i n g each ground s u r v e y . T h i s e s t i m a t e was a r r i v e d a t by t a k i n g t h e t o t a l number of s i g h t i n g s and a l l o w i n g f o r r e p e a t s i g h t i n g s o f t h e same b i r d s . T h i s was a c c o m p l i s h e d by c o n s i d e r i n g t h e t o t a l number o f e a g l e s i n any a r e a a t any one t i m e , i n d i v i d u a l c h a r a c t e r i s t i c s (e.g. absence o f c e r t a i n p r i m a r y o r t a i l f e a t h e r s , c o l o r a t i o n p a t t e r n s , e t c . ) and t h e o b s e r v e d movement o f t h e same b i r d s between d i f f e r e n t a r e a s . The p o t e n t i a l h a z a r d t o a i r c r a f t a r i s e s p r i m a r i l y from t h e number o f e a g l e s i n t h e a i r p o r t v i c i n i t y , t h e number o f e a g l e f l i g h t s p e r day a c r o s s runways and t h e i r a p p r o a c h e s , and t h e a l t i t u d e o f t h e s e f l i g h t s . I n an attempt t o a s s e s s t h i s h a z a r d , t h e maximum number of e a g l e s i g h t i n g s i n each o f t h e 5 observation:.are'as.-cjwa-S- :'re*S©rfde%^- Each e a g l e f l i g h t a c r o s s t h e o b s e r v a t i o n a r e a was r e g a r d e d as a s e p a r a t e o b s e r v a t i o n - 17 -whether o r n o t the same b i r d s were i n v o l v e d . Thus t h i s f i g u r e i s a p r o d u c t o f e a g l e numbers and t h e i r f l i g h t f r e q u e n c y . My c o n c e r n was w i t h p o t e n t i a l c o n t a c t s between e a g l e s and a i r c r a f t . I n o r d e r t o p r o v i d e a s t a n d a r d measurement o f e a g l e abundance f o r any o f the 5 o b s e r v a t i o n a r e a s a t any time (and o f c u m u l a t i v e a c t i v i t y i V i m t h e a i r o v e r the a i r p o r t ) , t h e number o f e a g l e s / s i g h t i n g s o b s e r v e d p e r hour o f o b s e r v a t i o n time was c a l c u l a t e d f o r b o t h the minimum number o f e a g l e s and t h e maximum number o f e a g l e s i g h t i n g s . T h i s was a c c o m p l i s h e d by d i v i d i n g the number o f e a g l e s / s i g h t i n g s o b s e r v e d i n an ar e a by t h e number o f hours spent o b s e r v i n g i n t h a t a r e a . T h i s s t a n d a r d measurement was a p p l i e d t o the monthly t o t a l s o f t h e minimum number o f e a g l e s u s i n g t h e a i r p o r t v i c i n i t y as o u t l i n e d below: No. o f e a g l e s o b s e r v e d / h r . / a r e a = A + I + U T where A = no. o f a d u l t s / a r e a / m o n t h I = no. o f immatures/area/month U = no. o f unknown/area/month T = t o t a l o b s e r v a t i o n time/area/month The maximum number o f e a g l e s i g h t i n g s made per hour on a d a i l y b a s i s was d e t e r m i n e d u s i n g t h e f o r m u l a g i v e n above by sub-s t i t u t i n g t o t a l s i g h t i n g s f o r t h e number o f d i f f e r e n t i n d i v i d u a l s . - 18 -In order to i d e n t i f y aggregation areas w i t h i n each observation area, the l o c a t i o n of i n d i v i d u a l eagles when f i r s t observed was p l o t t e d on a d a i l y b a s i s . Areas w i t h s i g h t i n g frequencies (sightings/day) at l e a s t 5 times t h a t o c c u r r i n g i n the r e -mainder of the observation area were d e l i n e a t e d as aggregation areas. Composite maps were prepared f o r the f a l l of 1972 and 1973, the f i r s t 8 months of 1974, and the f a l l of 1974. A s i m i l a r method was used throughout the remainder of the study area to i d e n t i f y important areas of use. B l i n d s were constructed and used f o r observations near the mouth of the Keogh River and i n the southeast f l i g h t path f o r runway 1028. A l l nest t r e e s adjacent to the a i r p o r t were examined i n d e t a i l . Nest t r e e data i n c l u d e d l o c a t i o n , s p e c i e s , t r e e height, height of nest, d i s t a n c e from c o a s t l i n e , and food remains at the base of the t r e e . 2.3.2 C o n t r o l Zone The a i r p o r t c o n t r o l zone (excluding the a i r p o r t v i c i n i t y ) served as the second major ground survey area. Foot p a t r o l s were c a r r i e d out i n the Quatse River area, the Keogh River area, and along the c o a s t l i n e from the a i r p o r t to False Head. A l l roadways w i t h i n the c o n t r o l zone were i n c l u d e d except f o r one short r e s t r i c t e d logging road. An attempt was made to p a t r o l a l l major roadways during each t r i p to the study area. Data were c o l l e c t e d and recorded using the technique o u t l i n e d i n 2.3.1. - 19 -2.3.3 R e g i o n a l Study A r e a The r e g i o n a l s t u d y a r e a ( e x c l u d i n g t h e c o n t r o l zone) comprised t h e r e m a i n i n g ground s u r v e y a r e a (4,267 s q . km). I t was r e g a r d e d as p o t e n t i a l l y i m p o r t a n t as a s o u r c e o f e a g l e s moving i n t o the a i r p o r t a r e a . Data were c o l l e c t e d and r e c o r d e d u s i n g methods o u t l i n e d i n 2.3.1. 2.4 BOAT SURVEYS Boat s u r v e y s were conducted a l o n g c o a s t a l r e g i o n s i n t h e c o n t r o l zone and r e g i o n a l s t u d y a r e a and c o n s i s t e d o f t r a v e l l i n g p a r a l l e l t o t h e s h o r e l i n e a t a d i s t a n c e u s u a l l y v a r y i n g from 100 t o -300 m. T h i s method a l l o w e d a c a r e f u l s u r v e i l l a n c e o f t h e c o a s t a l r e g i o n s f o r b a l d e a g l e n e s t s and e a g l e a c t i v i t y . Boat s u r v e y s extended o v e r 470 km r e p r e s e n t i n g 62% o f t h e t o t a l c o a s t l i n e w i t h i n t h e r e g i o n a l s t u d y a r e a . The r e m a i n i n g 2 8% was t o o exposed f o r s m a l l c r a f t a c c e s s and was s u r v e y e d o n l y by a i r . 2.5 AERIAL SURVEYS A e r i a l s u r v e y s were conducted i n b o t h t h e c o n t r o l zone and r e g i o n a l s t u d y a r e a by f l y i n g p a r a l l e l t o t h e c o a s t l i n e a s h o r t d i s t a n c e o f f s h o r e a t an e l e v a t i o n o f a p p r o x i m a t e l y 100 m above sea l e v e l . T h i s method a l l o w e d a c a r e f u l e x a m i n a t i o n f o r b a l d e a g l e n e s t s and e a g l e a c t i v i t y . A e r i a l s u r v e y s were conducted on a t l e a s t 1 day o f each month i n 1974 from A p r i l t h r o u g h August t o de t e r m i n e n e s t i n g s u c c e s s . The p o s s i b i l i t y o f d e t r i m e n t a l e f f e c t s upon e a g l e p r o d u c t i v i t y r e s u l t i n g from - 20 -disturbance created by near passage of a h e l i c o p t e r was a c o n s i d e r a t i o n which l i m i t e d the c o l l e c t i o n of data on pro-d u c t i v i t y and n e s t i n g success to c e r t a i n areas. 2.6 MARKING AND TELEMETRIC PROJECT An attempt was made to capture, band, mark f o r v i s u a l r e c -o g n i t i o n , and r e l e a s e eagles frequenting the a i r p o r t region i n order to o b t a i n d e t a i l s on d i s t a n c e s the a i r p o r t was drawing i n known b i r d s . The numbers r e q u i r e d to gain u s e f u l r e s u l t s and the d i f f i c u l t i e s i n c a p t u r i n g forced abandomen.t of t h i s approach. For the same reasons, attempts to use radiosondes attached to eagles i n order to improve data on eagle a c t i v i t y p a tterns had to be abandoned. 2.7 FOOD RELATIONSHIPS Seasonal feeding h a b i t s and the a v a i l a b i l i t y of food to b a l d eagles were recorded throughout the study p e r i o d . These s t u d i e s were p a r t of an i n v e s t i g a t i o n to determine the environmental f a c t o r s t h a t a t t r a c t eagles or f a c i l i t a t e t h e i r use of the a i r -p ort c o n t r o l zone. Data on feeding h a b i t s were based upon d i r e c t o bservations, nest contents, and a n a l y s i s of food remains at the base of or ad-jacent to nest t r e e s . Seasonal food h a b i t s could not be determined by stomach analyses because the b i r d s could not be shot. A l l s i g h t i n g s i n v o l v i n g feeding a c t i v i t y were recorded. - 21 -Thorough checks f o r remains o f f o o d i t e m s were c a r r i e d o u t near t h e base o f 10 out o f t h e 17 n e s t t r e e s i n the c o n t r o l zone. Three o f the 17 n e s t t r e e s were c l i m b e d . A l l 17 n e s t s (9 o f w h i c h were a c t i v e i n 1974) w i t h i n t h e c o n t r o l zone were examined c a r e f u l l y by h e l i c o p t e r . Food i t e m s c o n t a i n e d w i t h i n each n e s t were r e c o r d e d . The a v a i l a b i l i t y o f f i s h , b i r d s , and o t h e r f o o d i t e m s was documented s e a s o n a l l y as o u t l i n e d below. Emphasis was p l a c e d on spawning salmon because o f t h e i r i m p o r t a n c e i n t h e d i e t o f b a l d e a g l e s w i t h i n t h e s t u d y a r e a . A n n u a l s t o c k escapements were r e c o r d e d by F e d e r a l F i s h e r i e s p e r s o n n e l f o r p i n k , chum, and coho salmon t o a l l spawning r i v e r s w i t h i n t h e c o n t r o l zone. I n a d d i t i o n , I made r e g u l a r p a t r o l s a l o n g spawning c h a n n e l s t o d e t e r m i n e t h e approximate number o f spawners and p r e -spawners ( u s i n g methods s i m i l a r t o t h o s e proposed by S h e r i d a n , 1962), the s t a g e o f spawning, and t h e c o n d i t i o n o f spawners f o r each s p e c i e s . A number o f p a t r o l s were conducted i n c o n j u n c t i o n w i t h t h e F e d e r a l Department o f F i s h e r i e s . R i v e r l e v e l s were r e c o r d e d r e g u l a r l y d u r i n g t h e salmon spawning season. The c o n c e n t r a t e d s c h o o l i n g o f salmon p r i o r t o upstream m i g r a t i o n was a l s o documented. The presence o f P a c i f i c h e r r i n g (Clupea p a l l a s i i ) was documented i n Beaver Harbour d u r i n g the s p r i n g spawning p e r i o d . I made ho attempt t o a s s e s s t h e a v a i l a b i l i t y o f o t h e r s p e c i e s o f f i s h . O c c u r r e n c e s o f l a r g e numbers o f sea b i r d s w i t h i n the a i r p o r t - 22 -v i c i n i t y were r e c o r d e d as p o t e n t i a l f o o d s o u r c e s . 2.8 FLIGHT PATH RECORDING The approach and d e p a r t u r e f l i g h t p a t h s o f Bo e i n g 7 37 a i r -c r a f t a t P o r t Hardy a i r p o r t were documented d u r i n g 1973 and 1974. R e c o r d i n g s were made b o t h i n - f l i g h t and on t h e ground. T h i s p r o j e c t was u n d e r t a k e n t o p e r m i t d e t e r m i n a t i o n " of t h e a r e a s w h e r e i n a i r c r a f t approach and d e p a r t u r e p a t h s were congruent w i t h e a g l e f l i g h t p a t h s . Three methods were used t o document f l i g h t p a t h r e g i m e s . The f i r s t and most p r e c i s e i n v o l v e d r e c o r d i n g a l t i m e t e r r e a d i n g s d u r i n g approaches and d e p a r t u r e s a t v a r i o u s d i s t a n c e s from t h e a i r p o r t . D i s t a n c e s were d e t e r m i n e d by n o t i n g t h e e x a c t l o c a t i o n d i r e c t l y beneath t h e j e t a t t h e t i m e o f each a l t i m e t e r r e a d i n g . Data from t h i s method were c o l l e c t e d by the a u t h o r when o b s e r v i n g from the c o c k p i t d u r i n g 16 approaches and 4 d e p a r t u r e s . The second i n - f l i g h t method i n v o l v e d r e c o r d i n g a l t i m e t e r r e a d -i n g s a t v a r i o u s d i s t a n c e s from t h e a i r p o r t as shown by a range i n s t r u m e n t i n t h e c o c k p i t . T h i s method was used d u r i n g 3 approaches a t some d i s t a n c e from the a i r p o r t when i t was i m p o s s i b l e t o f i x an e x a c t l o c a t i o n by ground r e f e r e n c e . The t h i r d method c o n s i s t e d o f e s t i m a t i n g a l t i t u d e s from t h e ground as t h e j e t pass e d o v e r p r e d e t e r m i n e d l o c a t i o n s d u r i n g 9 approaches and 5 d e p a r t u r e s . An a p p r o a c h i n g and a d e p a r t i n g - 23 -j e t were photographed as t h e y p a s s e d over t h e s e l o c a t i o n s and the a c t u a l a l t i t u d e s were s u b s e q u e n t l y d e t e r m i n e d from t h e photographs. A s c e n t and d e s c e n t p a t t e r n s v a r i e d due t o f a c t o r s such as f u e l l o a d s , p a s s e n g e r s l o a d s , weather c o n d i t i o n s and i t was n e c e s s a r y t o document t h i s v a r i a b i l i t y i n f l i g h t p a t h s . . A number o f approaches and d e p a r t u r e s were m o n i t o r e d b o t h on the ground and i n f l i g h t w i t h o u t r e c o r d i n g a l t i t u d e s . I n s t e a d , f l i g h t p a t h r o u t e s were r e c o r d e d as w e l l as any e a g l e s o b s e r v e d . a PART 3 RESULTS 3.1 ABUNDANCE Accurate numerical information on numbers, distribution, and behaviour of eagles adjacent to the airport i s essential not only to document the extent of the potential hazard but also to provide the baseline against which the results of possible mitigative actions can be measured. 3.1.1 Airport V i c i n i t y The average number of eagles sighted/day (on a monthly basis) from the control tower on or near runways and their approaches from October, 1971 through October,, 1974 i s graphed i n Figure 5. Figure 6 shows the minimum number of adults and immatures continuously: frequenting the airport v i c i n i t y and their total from July, 1972 to October, 1974, (excepting January through August, 1973 when the author was not i n the field) . The imnimum number of eagles was determined using the method outlined i n 2.3.1. The "resident" summer and winter eagle population within the airport v i c i n i t y approximated 3 individuals (2 adults, 1 immature) during the study period. Thus the major hazard resulted from inmigrant birds. While the number of eagles present i s an important part of the bird hazard problem, the hazard i t s e l f arises from eagle activity across the f l i g h t path areas. The maximum number of eagle sightings/hr. for any given day (as defined i n 2.3.1) for each observation area during the period October 1972 through October 1974 i s given i n Fig. 7. 1 OCT ' NOV 1 DEC j "jAN 1 F E B '.' MAR ' APR 1 MAY 1 JUNE ' JULY ' 1 AUG 1 S E P T ' OCT 1 NOV ' ~DEC | 1971 1972 Figure 5. Average number of eagles sighted/day from the control tower on or near runways and t h e i r approaches from October, 1971 - October, 1974. Single bars show standard deviation on eit h e r side of the mean, double bars show 1.96 standard deviation/ Vsample s i z e . AUG S E P T OCT NOV ' DEC | JAN ' F E B ' MAR ' A P R MAY ' MwT1 JULY AUG ' S E P T ' OCfr 1973 1974 Figure 5, Average number o£ eagles sighted/day from the control tower on or near runways and t h e i r approaches from October^ 1971 - October, 1974. Single bars show standard deviation on eit h e r side of the mean, double bars show 1.96 standard deviation/ Vsample s i z e , 15 1 9 7 2 1 9 7 3 1 9 7 4 Figure 6 . Minimum number of eagles continuously frequenting the a i r p o r t v i c i n i t y from J u l y , 1972 -October, 197*K 0 • o AREA 1 0 0 A R E A 2 &— A AREA 3 B Q AREA 4 A — & AREA 5 These d a t a show th e f r e q u e n c y o f e a g l e o c c u r r e n c e w i t h i n each a r e a and s u g g e s t t h a t use was g e n e r a l l y g r e a t e s t d u r i n g t h e f a l l salmon spawning season and t h e s p r i n g h e r r i n g spawn-i n g season. F a l l v a l u e s peaked a t 14.0/hr. i n November 1972, 18.5/hr. i n September 1973, and 18.0/hr. i n October 1974. S p r i n g v a l u e s peaked a t 21.0/hr. d u r i n g March and A p r i l 1974. S u c c e s s i v e c o u n t s from t h e 1972 salmon spawning season were averaged (September t h r o u g h December; 4.8 s i g h t i n g s / h r ) and compared s t a t i s t i c a l l y w i t h average c o u n t s from the w i n t e r o f 1974 (January t h r o u g h F e b r u a r y ; 2.1 s i g h t i n g s / h r . ) , t h e s p r i n g h e r r i n g spawning season o f 1974 (March t h r o u g h A p r i l ; 5.0 s i g h t i n g s / h r . ) , and t h e summer o f 1974 (May t h r o u g h August; 3.3 s i g h t i n g s / h r . ) t o r e v e a l s i g n i f i c a n t d i f f e r e n c e s between seasons. The n u l l h y p o t h e s i s adopted assumed a normal a b u n r dance f o r a l l 4 seasons (H Q:u^=u 2=u 3=u 4) a t the p= .05 and p= .10 c o n f i d e n c e l e v e l s . S e a s o n a l abundance v a l u e s were compared u s i n g t h e s t u d e n t ' s t d i s t r i b u t i o n f o r m u l a - - t s s:u <z, ~ + t . s x x where u = p o p u l a t i o n mean, s = sample s t a n d a r d d e v i a t i o n , and t = s t u d e n t ' s t v a r i a b l e . Abundance v a l u e s l y i n g o u t s i d e o f t h e range d e t e r m i n e d by t h e above r e l a t i o n s h i p were c o n s i d e r e d t o be s i g n i f i c a n t l y d i f f e r e n t . W i n t e r abundance d u r i n g 1974 was s i g n i f i c a n t l y d i f f e r e n t - -30 -( i e . lower) from a l l o t h e r seasons and abundance v a l u e s from t h e f a l l o f 1 9 7 2 and s p r i n g o f 1 9 7 4 were s i g n i f i c a n t l y d i f f e r e n t ( i e . g r e a t e r ) from summer and w i n t e r v a l u e s a t t h e p = . 1 0 c o n f i d e n c e l e v e l b u t not a t t h e . 0 5 l e v e l . A c c o r d i n g l y , HQ was r e j e c t e d . The number o f e a g l e s , known t o be d i f f e r e n t i n d i v i d u a l s , o b s e r v e d p e r hour f o r each o f t h e 5 o b s e r v a t i o n a r e a s , was a l s o g r e a t e s t d u r i n g t h e f a l l and s p r i n g . Average s i g h t i n g s p e r hour on a monthly b a s i s reached 5.8 f o r a r e a 2 i n November 1 9 7 2 , 4.2 f o r a r e a 4 i n October 1 9 7 3 , and 2 1 . 0 f o r a r e a 3 i n A p r i l 1 9 7 4 . 3 . 1 . 2 C o n t r o l Zone A g e - s p e c i f i c abundance d a t a d e t e r m i n e d d u r i n g 1 9 7 4 boat s u r v e y s a r e p r e s e n t e d i n F i g . 8. C o n t r o l zone abundance appeared t o b e ' h i g h e s t i n s p r i n g and summer. E a g l e numbers peaked i n March when 2 8 i n d i v i d u a l s were o b s e r v e d i n 1 day. 3 . 1 . 3 R e g i o n a l F i n d i n g s O b s e r v a t i o n s r e c o r d e d d u r i n g ground, b o a t , and a e r i a l s u r v e y s i n d i c a t e d t h a t t h e r e s i d e n t b a l d e a g l e p o p u l a t i o n w i t h i n t h e r e g i o n a l s t u d y a r e a numbered between 2 0 0 and 2 5 0 . D u r i n g 1 9 7 4 , 1 9 6 i n d i v i d u a l s were noted d u r i n g a e r i a l s u r v e y s ( 1 6 3 a d u l t s , 2 3 immatures, 1 6 unknowns) and 1 0 9 d u r i n g boat s u r v e y s e x c l u d i n g Q u a t s i n o Narrows ( 7 0 a d u l t s , 2 3 immatures, 1 6 unknowns). The r e s i d e n t p o p u l a t i o n appeared t o be composed p r i m a r i l y o f a d u l t b i r d s as e v i d e n c e d by t h e above o b s e r v a t i o n s ; . - 31 -Figure .-8... A g e - s p e c i f i c eagle abundance w i t h i n the a i r p o r t c o n t r o l zone recorded during 197*+ boat surveys. M A Y J U N E 1 J U L Y ! 9 7 4 A U G S E P T O C T - 32 -83% o f t h e e a g l e s s i g h t e d d u r i n g a e r i a l s u r v e y s and 64% d u r i n g boat s u r v e y s were a d u l t s . However, a e r i a l s u r v e y s were b i a s e d f o r a d u l t s s i n c e t h e y c o n c e n t r a t e d on n e s t s a t t e n d e d by a d u l t s . Boat s u r v e y s were not b i a s e d f o r a d u l t s o r immatures and hence gave t h e most r e l i a b l e age r a t i o s . R e s u l t s from 5 s e p a r a t e boat s u r v e y s o f Q u a t s i n o Narrows from A p r i l 22 - 30, 1974 y i e l d e d an average of 96 e a g l e s w i t h a range from 35 t o 133. The 2 l a r g e s t c o u n t s o f 130 and 133 a r e l i k e l y a r e l i a b l e i n d i c a t i o n o f t h e t o t a l con-c e n t r a t i o n a t t h e t i m e . Immatures were more abundant t h a n a d u l t s i n t h i s g r o u p i n g s „rep.pesenfci-hg. a t " l e a s t t 54% 'jof -• a l l = a g e - s p e c i f i c s i g h t i n g s . ( T h i s was t o be e x p e c t e d s i n c e many a d u l t s were i n c u b a t i n g eggs o r e s t a b l i s h i n g t e r r i t o r i e s d u r i n g t h i s p e r i o d ) . E a g l e s o b s e r v e d a t Q u a t s i n o Narrows r e p r e s e n t e d not o n l y t h e s m a l l r e s i d e n t p o p u l a t i o n b u t more i m p o r t a n t l y , a g a t h e r i n g of e a g l e s from a d j a c e n t r e g i o n s , p a r t i c u l a r l y Q u a t s i n o Sound and t h e a d j o i n i n g i n l e t s . T h i s g a t h e r i n g r e p r e s e n t e d o n l y a p o r t i o n o f t h e p o p u l a t i o n w i t h i n the r e g i o n a l s t u d y a r e a . A t l e a s t 58 a d d i t i o n a l e a g l e s were o b s e r v e d on b o t h t h e e a s t c o a s t ( G o l e t a s Channel) and t h e west c o a s t ( Q u a t s i n o Sound and a d j o i n i n g i n l e t s ) o f Vancouver I s l a n d d u r i n g t h e t i m e o f t h e Q u a t s i n o Narrows s u r v e y s . - 33 -3.2 DISTRIBUTION AND AIRCRAFT HAZARD In o r d e r t o document a r e a s o f s i g n i f i c a n t h a z a r d t o a i r c r a f t , i t was n e c e s s a r y t o d e t e r m i n e t h e s e a s o n a l d i s t r i b u t i o n o f e a g l e s near the a i r p o r t and compare t h i s w i t h t h e f l i g h t p aths used by a p p r o a c h i n g and d e p a r t i n g j e t s . F u r t h e r m o r e , i n o r d e r t o i d e n t i f y t h e s o u r c e o f l o c a l c o n c e n t r a t i o n s i t was n e c e s s a r y t o i n v e s t i g a t e b a l d e a g l e d i s t r i b u t i o n t h r o u g h -out t h e r e g i o n a l s t u d y a r e a . 3.2.1 A i r p o r t V i c i n i t y C o n t r o l tower o b s e r v a t i o n s i n d i c a t e d c o n t i n u a l e a g l e use o f the a i r p o r t v i c i n i t y from October 1971 t h r o u g h October 1974 w i t h 5 a r e a s o f p r e f e r r e d use depending on t h e season: 1. a i r s p a c e d i r e c t l y o v e r and a d j a c e n t t o t h e runways and i n f i e l d ; 2. runways ( e s p e c i a l l y near i n t e r s e c t i o n o f 1028 and 2507); 3. Thomas P t . a r e a ; 4. c o a s t a l r e g i o n from Thomas P t . t o t h e mouth of t h e Keogh R i v e r ; arid 5. mouth and lower r e a c h e s o f t h e Keogh R i v e r . E a g l e use o f the a i r s p a c e over and a d j a c e n t t o t h e runways and i n f i e l d was c o n t i n u a l t h r o u g h o u t t h e y e a r w i t h g r e a t e s t a c t i v i t y o c c u r r i n g d u r i n g s p r i n g and f a l l when more t h a n 6 e a g l e s were o f t e n r e c o r d e d a t a t i m e . E a g l e s were most o f t e n o b s e r v e d p e r c h e d on t h e runways d u r i n g the f a l l . Up t o 6 e a g l e s a t a time were seen d u r i n g t h i s t i me o f t h e y e a r . E a g l e use o f the Thomas P o i n t a r e a , as d e t e r m i n e d by c o n t r o l tower - 34 -observations, was greatest during the spring and summer when at least 3 eagles were often seen soaring i n the area. The coastal region from Thomas Point to the mouth of the Keogh River was used regularly as a t r a v e l route. Its importance to eagles was greatest during !the summer and winter when t h e i r d i e t was composed primarily of marine f i s h , birds, and invertebrates i n the absence of spawning salmon and herring. Eagle use of the mouth and lower reaches of the Keogh River was by far the greatest during the f a l l i n conjunction with the salmon spawning season. Up to 12 eagles were often observed soaring i n the area near the peak of the pink salmon run. It was thought that seasonal d i s t r i b u t i o n would be r e f l e c t e d i n sightings/hr. (Fig. 7) for each of the 5 observation areas. These data were subjected to the s t u d e n t s t test between areas and between seasons to reveal s i g n i f i c a n t differences. Successive counts from each observation area during the 1972, 1973, and 1974 salmon spawning seasons (September through December) were averaged and compared with counts from each of the observation areas during the winter of 1974 (January through February), the spring herring spawn-ing season of 1974 (March through A p r i l ) , and the summer of 1974 (May through August). S i m i l a r l y , counts between ob-servation areas during the same season were also tested. The average abundance values and standard deviations for each - 3 5 -of t h e 5 observation areas d u r i n g a l l 4 seasons were c a l -c u l a t e d t o be 3.4 s i g h t i n g s / h r (s = 1 . 2 ) , 2.5 s i g h t i n g s / h r (s = . 2 ) , 4.4 s i g h t i n g s / h r (s = 2 . 5 ) , 3.3 s i g h t i n g s / h r (s = 1 . 5 ) , and 1.1 s i g h t i n g s / h r (s = .7) f o r o b s e r v a t i o n a r e a 1 , 2, 3, 4 and 5 r e s p e c t i v e l y . The average abundance v a l u e s and s t a n d a r d d e v i a t i o n s f o r a l l 5 o b s e r v a t i o n a r e a s d u r i n g each o f t h e 4 seasons were c a l c u l a t e d t o be 3.3 s i g h t i n g s / h r (s = 1 . 4 ) , 1.8 s i g h t i n g s / h r (s = . 7 ) , 3.7 s i g h t i n g s / h r (s = 2 . 6 ) , and 2.8 s i g h t i n g s / h r (s = 1 . 8 ) f o r t h e f a l l , w i n t e r , s p r i n g , and summer r e s p e c t i v e l y . The n u l l h y p o t h e s i s adopted assumed a normal d i s t r i b u t i o n f o r a l l o b s e r v a t i o n a r e a s and f o r a l l seasons a t t h e p = . 1 0 c o n f i d e n c e l e v e l . Average abundance v a l u e s d u r i n g a l l 4 seasons f o r o b s e r v a t i o n a r e a s 3 and 5 were s i g n i f i c a n t l y d i f f e r e n t ( i e . g r e a t e r and lower r e s p e c t i v e l y ) t h a n t h o s e f o r the r e m a i n i n g 3 o b s e r v a t i o n a r e a s . Average abundance v a l u e s f o r a l l 5 o b s e r v a t i o n s a r e a s d u r i n g t h e w i n t e r and s p r i n g o f 1 9 7 4 d i f f e r e d s i g n i f i c a n t l y ( i e . l o w e r and g r e a t e r r e s p e c t i v e l y ) t h a n t h o s e r e c o r d e d d u r i n g summer and f a l l . A c c o r d i n g l y , HQ was r e j e c t e d . A g g r e g a t i o n a r e a s w i t h i n t h e a i r p o r t v i c i n i t y w h i c h c o i n c i d e d w i t h f l i g h t p a t h s o f a p p r o a c h i n g o r d e p a r t i n g j e t s c r e a t e d a s i g n i f i c a n t h a z a r d . Minimum s i g h t i n g s p l o t t e d on a d a i l y b a s i s f o r t h e f a l l o f 1 9 7 2 , 1 9 7 3 and 1 9 7 4 i n d i c a t e d 2 a g g r e g a t i o n a r e a s ; one i n o b s e r v a t i o n a r e a 3 and t h e o t h e r i n o b s e r v a t i o n a r e a 4 as shown i n F i g . 9 1 The a g g r e g a t i o n a r e a i n o b s e r v a t i o n - 36 -C] F a l l of 1972, 1973, and 1974 | February through August 1974 Figure 9, Aggregation areas w i t h i n the a i r p o r t v i c i n i t y observation areas during the f a l l of 1972, 1973, and 1974 and from February through August 1974. - 37 -a r e a 3 was c e n t e r e d upon t h e mouth o f t h e Keogh R i v e r and the a d j a c e n t c o a s t l i n e . T h i s a r e a o f e a g l e a c t i v i t y was l o c a t e d a p p r o x i m a t e l y 800 m d i r e c t l y o f f t h e e a s t end o f a runway not used by j e t s and t h e r e f o r e d i d n o t p r e s e n t a major h a z a r d . The a g g r e g a t i o n a r e a i n o b s e r v a t i o n a r e a 4 was l o c a t e d w i t h -i n t h e f l i g h t p a t h f o r runway 1028 i n t h e v i c i n i t y o f t h e Keogh R i v e r . The a v a i l a b i l i t y o f salmon a t s h a l l o w r a p i d s and p o o l s , the open n a t u r e o f t h e f l i g h t p a t h , and the e x c e l l e n t v i e w from t a l l t r e e s a l o n g t h e c l e a r i n g l i n e s , a l l c o n t r i b u t e d t o prominent e a g l e use i n t h e a r e a . T h i s aggregation-• p r e s e n t e d t h e g r e a t e s t h a z a r d t o a i r c r a f t o f any s i n c e i t was l o c a t e d i n an a c t i v e f l i g h t p a t h a v e r y s h o r t d i s t a n c e (<700m) from t h e end o f runway 102 8, t h e o n l y runway used by Bo e i n g 7 37 #ets. E a g l e a c t i v i t y i n t h i s a r e a was s t r o n g l y i n f l u e n c e d by t h e a v a i l a b i l i t y o f spawning salmon w h i c h was c o n t r o l l e d by time o f y e a r and r i v e r s t a g e . D i r e c t f l i g h t s a c r o s s t h e f l i g h t p a t h o c c u r r e d c o n t i n u a l l y from September t h r o u g h October and were o f t e n a t t h e same e l e v a t i o n as d e p a r t i n g o r a p p r o a c h i n g j e t a i r c r a f t . R e s u l t s from j e t f l i g h t p a t h r e c o r d i n g e x e r c i s e s o u t l i n e d i n s e c t i o n 2.8 a r e p r e s e n t e d i n F i g s . 10 and 17. These f i n d i n g s i n d i c a t e t h a t a p p r o a c h i n g and d e p a r t i n g j e t s were f l y i n g d i r e c t l y - 3 8 -F i g u r e 10. B o e i n g 737 j e t a p p r o a c h p a t t e r n t o runway 1028 from t h e s o u t h e a s t ( B e s t l i n e f i t f o r a l l d a t a p o i n t s ) LU ~> o LU Q < 1000 n 800 600-400 H 200 7.0 T 6.0 5.0 4.0 3.0 2.0 DISTANCE FROM EDGE OF RUNWAY (km) KEOGH RIVER F i g u r e 11, Frequency and a l t i t u d e o f e a g l e f l i g h t s o v e r t h e Keogh R i v e r d u r i n g t h e f a l l o f 1972, 1973, and 1974, (Bes t l i n e f i t f o r a l l d a t a p o i n t s ) See Fig. 17 CO X X FLI PRO 0. LU < _ J CD i < LU cc X tJL o \ CO >- h -o X z o LU _ J o u_ LU ^ . DC Lu I 40 60 80 100 120 140 160 180 200 220 240 260 ALTITUDE OF EAGLE FLIGHTS (m ) - 39 -th r o u g h the hazardous zone above the Keogh R i v e r . T h i s l e d t o a n e a r - s t r i k e i n c i d e n t i n l a t e September 1973 when the p i l o t f l y i n g a j e t d e p a r t i n g towards the s o u t h e a s t had t o t a k e e v a s i v e a c t i o n t o p r e v e n t a c o l l i s i o n w i t h s e v e r a l e a g l e s c i r c l i n g above t h e Keogh R i v e r . The m a j o r i t y o f autumn e a g l e a c t i v i t y ( a p p r o x i m a t e l y 8 0%) i n t h e f l i g h t p a t h c o n s i s t e d o f d i r e c t f l i g h t s above t h e r i v e r . •Average . f l i g h t '-elevation? appeared' 'fco-* vary- i n response^ to water l e v e l and number of" salmon-ipresent. .=; F i g u r e 11 g i v e s a f r e q u e n c y c u r v e o f e a g l e f l i g h t a l t i t u d e s o v er the Keogh R i v e r d u r i n g the f a l l o f 1972, 1973, and 1974. Most f l i g h t s o c c u r r e d between 2 and 6 0 m. F l i g h t s were most f r e q u e n t a t approx-i m a t e l y 40 m above t h e r i v e r w h i c h c o i n c i d e d w i t h t h e approximate a l t i t u d e o f a p p r o a c h i n g j e t s when o v e r the r i v e r ( F i g . 10) . Additional data on f l i g h t patterns are presented i n 3.6. I n c r e a s e d salmon abundance and a v a i l a b i l i t y r e s u l t e d i n a de c r e a s e i n t h e average e l e v a t i o n o f d i r e c t f l i g h t s , extended p e r c h i n g near t o p s o f t a l l t r e e s on b o t h s i d e s o f t h e f l i g h t p a t h , and f r e q u e n t p e r c h i n g a l o n g t h e r i v e r bank e s p e c i a l l y d u r i n g low water c o n d i t i o n s . S o a r i n g o f t e n o c c u r r e d h i g h o v e r t h e r i v e r when c l e a r s k i e s p r e v a i l e d a l o n g w i t h b r i s k s o u t h e a s t winds and c o o l t e m p e r a t u r e s . S o a r i n g was ob s e r v e d up t o 250 m w h i c h marked t h e upward l i m i t o f t h e a g g r e g a t i o n a r e a above and a d j a c e n t t o t h e Keogh R i v e r ( F i g . 1 7 ) . - 40 -An a r e a o f moderate use was r e c o r d e d a l o n g t h e lower r e a c h e s of t h e Keogh R i v e r e x c l u d i n g t h e f l i g h t p a t h c l e a r i n g and r i v e r mouth. T h i s l i n e a r r e g i o n r e c e i v e d r e g u l a r useage d u r i n g t h e f a l l but s u b s t a n t i a l l y l e s s t h a n i n t h e f l i g h t p a t h o r a t the r i v e r mouth. E a g l e a c t i v i t y i n t h i s p a r t o f t h e a i r p o r t v i c i n i t y d i d not c o i n c i d e w i t h j e t f l i g h t p a t h s and t h e r e f o r e d i d not p r e s e n t a h a z a r d . A g g r e g a t i o n a r e a s i d e n t i f i e d by p l o t t i n g minimum s i g h t i n g s on a d a i l y b a s i s from F e b r u a r y t h r o u g h August 19 74 o c c u r r e d i n b o t h o b s e r v a t i o n a r e a s 1 and 3 as shown i n F i g u r e 9. E a g l e c o n c e n t r a t i o n i n o b s e r v a t i o n a r e a 1 was near Thomas P o i n t and d i d not p r e s e n t a major h a z a r d t o a i r c r a f t s i n c e i t was removed from t h e n o r t h w e s t f l i g h t p a t h f o r runway 102 8. The a g g r e g a t i o n .area i n o b s e r v a t i o n a r e a 3 was l o c a t e d j u s t s o u t h e a s t a l o n g t h e c o a s t l i n e from t h e mouth of t h e Keogh R i v e r . E a g l e use a t t h i s l o c a t i o n was c o n c e n t r a t e d around a s u c c e s s f u l n e s t and p r e s e n t e d a minor h a z a r d t o a i r c r a f t s i n c e i t was a d j a c e n t t o the e a s t f l i g h t p a t h f o r runway 1028. An a r e a o f moderate use was r e c o r d e d a l o n g t h e c o a s t l i n e i n o b s e r v a t i o n a r e a 2. T h i s r e g i o n was employed r e g u l a r l y t h r o u g h -out the y e a r as a t r a v e l r o u t e . E a g l e s f l y i n g t o and from the c o a s t l i n e o v e r runway 1028 p r e s e n t e d a h a z a r d t o l a n d i n g and d e p a r t i n g a i r c r a f t . - 41 -3.2.2 C o n t r o l Zone E a g l e d i s t r i b u t i o n i n t h e c o n t r o l zone f a l l s i n t o 2 c a t e g o r i e s on a y e a r - r o u n d b a s i s . D u r i n g the n e s t i n g season, a l l b u t a few a d u l t e a g l e s were a t t h e i r n e s t i n g t e r r i t o r i e s . They spent a l m o s t a l l o f t h e i r t ime a t t h e s e s i t e s and u s u a l l y d i d t h e i r f e e d i n g w i t h i n 3 km o f t h e n e s t . D u r i n g t h i s p e r i o d , immatures were p r e s e n t i n s m a l l numbers and were d i s p e r s e d a p p a r e n t l y a t random a l o n g t h e c o a s t l i n e . D u r i n g t h e n o n - n e s t i n g season ( i e . August t h r o u g h M a r c h ) , e a g l e d i s t r i b u t i o n was p r i m a r i l y r e g u l a t e d by t h e l o c a t i o n o f r e a d i l y a v a i l a b l e f o o d s o u r c e s and c o a s t l i n e l o c a t i o n s o f f e r i n g vantage p o i n t s . A g g r e g a t i o n a r e a s d e t e r m i n e d from ground, b o a t , and a e r i a l s u r v e y s d u r i n g 1972, 1973, and 1974 a r e shown i n F i g u r e 12. Only 1 a r e a p r e s e n t e d a s i g n i f i c a n t h a z a r d t o a i r c r a f t s i n c e t h e e a g l e s g e n e r a l l y moved a t e l e v a t i o n s below a i r c r a f t t r a f f i c . The e x c e p t i o n was t h e c o a s t l i n e from P i l l a r P o i n t t o F a l s e Head a l o n g w h i c h low f l y i n g a i r c r a f t r e g u l a r l y t r a v e l l e d t o and from nearby s e t t l e m e n t s t o t h e s o u t h e a s t . 3.2.3 R e g i o n a l F i n d i n g s S i x sub-areas were d e l i n e a t e d w i t h i n the r e g i o n a l s t u d y a r e a f o r assessment of d i s t r i b u t i o n : Q u a t s i n o Narrows and 5 r e l a t i v e l y homogeneous p h y s i o g r a p h i c r e g i o n s „• ( F i g - 1 3 ) . There was a c o n c e n t r a t i o n o f b a l d e a g l e s a t Q u a t s i n o Narrows - 4 2 -Figure 12. Aggregation areas w i t h i n the c o n t r o l zone based on r e s u l t s from ground, boat, and a e r i a l surveys during 1972, 1973, and 1974. - 43 -d u r i n g t h e l a t t e r p a r t o f A p r i l 1974. A t l e a s t 130 e a g l e s were obser v e d u s i n g t h e Narrows o v e r a 3 day p e r i o d w h i c h r e p r e s e n t e d a p p r o x i m a t e l y one h a l f o f t h e t o t a l e s t i m a t e d p o p u l a t i o n i n h a b i t i n g t h e r e g i o n a l s t u d y a r e a . The d i s t r i b u t i o n o f e a g l e s t h r o u g h o u t t h e remainder o f t h e r e g i o n a l s t u d y a r e a was e x p r e s s e d i n t h e form o f composite maps combining t h e l o c a t i o n s o f i n d i v i d u a l e a g l e s when f i r s t o b s e r v e d d u r i n g gcound, b o a t , and a e r i a l s u r v e y s . A l l r e g i o n s were s u r v e y e d d u r i n g t h e n e s t i n g season from A p r i l t o August e x c e p t f o r the S c o t t I s l a n d s and t h e n o r t h w e s t e r n t i p o f Vancouver I s l a n d w h i c h were s u r v e y e d d u r i n g O c t o b e r . R e s u l t s from such s u r v e y s showed t h a t e a g l e s were n o r m a l l y l o c a t e d w i t h i n n e s t i n g t e r r i t o r i e s o r c o n c e n t r a t e d a t f e e d i n g l o c a t i o n s . Three a g g r e g a t i o n a r e a s were r e c o r d e d d u r i n g t h e e a r l y p a r t o f t h e 1974 n e s t i n g season. The f i r s t was c e n t e r e d on t h e n o r t h w e s t c o r n e r o f H u r s t I s l a n d w h i l e t h e second was l o c a t e d on t h e e a s t s i d e o f N i g e i as shown i n F i g u r e 13. The t h i r d a g g r e g a t i o n a r e a , w h i c h a t t r a c t e d by f a r t h e , g r e a t e s t number o f e a g l e s , was l o c a t e d a t Q u a t s i n o Narrows as d e s c r i b e d above. ***** Figure 13. Aggregation areas w i t h i n the r e g i o n a l study area based on r e s u l t s from ground, boat, and a e r i a l surveys during the 1974 n e s t i n g season and d e l i n e a t i o n of 6 sub-areas comprising the r e g i o n a l study area. - 45 -3.2.4 Comparison Between Ar e a s I n o r d e r t o compare s e a s o n a l d i s t r i b u t i o n between d i f f e r e n t p a r t s o f t h e s t u d y a r e a , d i s t r i b u t i o n as e x p r e s s e d by t h e number o f e a g l e s r e c o r d e d p e r l i n e a l km o f c o a s t l i n e was d e t e r m i n e d monthly where p o s s i b l e f o r the c o n t r o l zone, Q u a t s i n o Narrows, and t h e 5 a r e a s c o m p r i s i n g t h e r e m a i n i n g p a r t o f t h e r e g i o n a l s t u d y a r e a . Each of t h e s e 5 a r e a s was c h a r a c t e r i z e d by a r e l a t i v e l y homogeneous c o a s t l i n e , t o pography, and degree o f exposure ( F i g . 1 3 ) . They were d e s i g n a t e d a s : a r e a A, t h e n o r t h e a s t c o a s t l i n e from Ledge P o i n t , near P o r t M c N e i l l t o Cape S u t i l (most n o r t h e r l y p o i n t on Vancouver I s l a n d ) e x l u d i n g t h e a i r p o r t c o n t r o l zone but i n c l u d i n g t h e l a r g e s t o f t h e P e a r s e I s l a n d s , Cormorant I s l a n d , and p a r t o f M a l c o l m I s l a n d ; a r e a B, the i s l a n d s f o r m i n g t h e n o r t h s i d e o f GoiLetas C h a n n e l ; a r e a C, the n o r t h w e s t e r n t i p o f Vancouver I s l a n d from Cape S u t i l t o Cape S c o t t t o Cape P a r k i n g ; a r e a D, the S c o t t I s l a n d s i n c l u d i n g T r i a n g l e I s l a n d ; and a r e a E, Q u a t s i n o Sound and t h e a d j o i n i n g i n l e t s . S e a s o n a l d i s t r i b u t i o n r e s u l t s (as e x p r e s s e d by t h e number o f e a g l e s r e c o r d e d per km o f c o a s t l i n e ) f o r the c o n t r o l zone, Q u a t s i n o Narrows, and t h e r e m a i n i n g 5 a r e a s w i t h i n t h e r e g i o n a l s t u d y a r e a d u r i n g 1974, are g i v e n i n T a b l e 1. A l l r e g i o n s , e x c e p t a r e a s C and D, were c o v e r e d by b o t h boat and a e r i a l s u r v e y s . E a g l e d e n s i t y was g r e a t e s t i n Q u a t s i n o Narrows d u r i n g - 46 -Table 1. Seasonal d i s t r i b u t i o n of eagles within the study area as expressed by the average number of eagles recorded per l i n e a l km of co a s t l i n e during 1974 boat and a e r i a l surveys, LOCATION FEBRUARY A I U T A MARCH I U T A APRIL I U T Control Zone .11 .22 . 3 9 * • 95 .65 M * 2 . 0 7 .15 .06* .02 .23 Quatsino Narrows (k. 6*2)(U. 3*8) 2 . 6 9 (11.69*) Vancouver Island: a. b. c. d. e. .21 .57* 0 .35 0 .12 * . 2 1 1.01+ * . 2 1 .ch .08 * . 3 3 " LOCATION A MAY I U T A JUNE I U T A JULY I U T Control Zone * (.07) 8 0 .07 • 30 * . 0 6 0 • 36 M * (.07) .07 .57 Quatsino' Narrows * .18 * 0 0 .18 .15 (.15) 0 . 3 0 Vancouver Island: a. b. c. * (.37) (. 12) . 0 2 .51 .27 (.65) . 0 8 (0) 00 . 0 1 • 35 (.66) d.oUf .15 (.39) • 30 •13 .61 ( 1 . 5 $ d. • e. * . .21 -03 0 ' .2k • (.08) . 0 8 0 (;16) LOCATION AUGUST SEPTEMBER OCTOBER A I U T A I U T A . I u T Control Zone .21 .12 .08 M * .03 * .03 0 . 0 6 (.17) 0* 0 (.17) Quatsino Narrows (.in) U l ) 0 (.82) Vancouver Island: a. .01+ .07 6 * .11 b. c. d. . 0 9 . 0 6 0 (.03) G 0 . 0 9 •09 • e. . 0 8 .Ik 0 .22 (.01* 0 0 (.Of) NOTE: A l l values are based on the greatest d a i l y t o t a l of the minimum number of eagles (as defined i n 2.3.1) for any given segment of coastline. KEY: A -I -U -T -adults immatures unknowns t o t a l Vancouver Island: a. N.E. Coast b. N.E. Islands c. N.W. Coast d. Scott Islands e. Quatsino Sound 05 s i g n i f i c a n c e l e v e l f o r a * , . . s i g n i f i c a n t l y d i f f e r e n t between months at given age class or t h e i r t o t a l . . , . ^ n r. , , ( I n s i g n i f i c a n t l y d i f f e r e n t between locations within same month at ,05 l e v e l for a given age class or t h e i r t o t a l , . •••• - 4 7 -A p r i l , when an average o f o v e r 1 1 e a g l e s p e r km o f c o a s t l i n e was r e c o r d e d . The nex t h i g h e s t d e n s i t y was r e g i s t e r e d i n the c o n t r o l zone w i t h an average o f o v e r 2 e a g l e s p e r km o f c o a s t l i n e . E a g l e d e n s i t y was a l s o h i g h i n a r e a B d u r i n g A p r i l and J u l y , when averages o f o v e r 1 and 1.5 e a g l e s p e r km o f c o a s t l i n e r e s p e c t i v e l y were r e c o r d e d . The l o w e s t e a g l e d e n s i t y was documented d u r i n g October i n p a r t o f a r e a E w i t h an average o f o n l y . 0 1 e a g l e p e r km o f c o a s t l i n e . D i s t r i b u t i o n d a t a from T a b l e 1 were t e s t e d s t a t i s t i c a l l y t h r o u g h b o t h a 1 - f a c t o r and a 2 - f a c t o r a n a l y s i s o f v a r i a n c e t o r e v e a l s i g n i f i c a n t l o c a t i o n and monthly d i f f e r e n c e s . The d i s t r i b u t i o n d a t a o f unaged b i r d s as a c a t e g o r y was n o t compared between months o r l o c a t i o n s but t h e s e d a t a were i n -c o r p o r a t e d i n t o t h e t o t a l monthly v a l u e s f o r each l o c a t i o n . The n u l l h y p o t h e s i s adopted f o r b o t h a n a l y s e s assumed a normal d i s t r i b u t i o n o f e a g l e s a l o n g t h e c o a s t l i n e a t a l l l o c a t i o n s and a t a l l t i m e s a t t h e . 0 5 s i g n i f i c a n c e l e v e l (HQ: u^ = u^ = U 3 = U 4 = ^ 5 = \ = V -The 1 - f a c t o r a n a l y s i s o f v a r i a n c e i n v o l v e d c a l c u l a t i o n o f monthly d i s t r i b u t i o n means and.'sample s t a n d a r d d e v i a t i o n s (s) f o r a d u l t s , immatures, and t h e i r t o t a l a t each o f t h e 7 l o c a t i o n s . D i s t r i b u t i o n v a l u e s l y i n g o u t s i d e o f t h e range d e t e r m i n e d ' by t h e r e l a t i o n s h i p .X' ± 1 . 9 6 s/ y~n were d e t e r m i n e d t o be s i g n i f i c a n t l y d i f f e r e n t between months (Table 1.) . L i k e -w i s e , t h e d i s t r i b u t i o n means and s t a n d a r d d e v i a t i o n s f o r a d u l t s , - 48 -immatures, and t h e i r t o t a l were c a l c u l a t e d f o r each month (where p o s s i b l e ) and i n s e r t e d i n t o t h e above r e l a t i o n s h i p t o r e v e a l s i g n i f i c a n t d i f f e r e n c e s between l o c a t i o n s w i t h i n t h e same month (Table 1 ) . T h i r t y f i v e p e r c e n t o f the d i s t r i b u t i o n s compared between months were s i g n i f i c a n t l y d i f f e r e n t c a u s i n g r e j e c t i o n o f the n u l l h y p o t h e s i s and c o n f i r m a t i o n o f s i g n i f i c a n t s e a s o n a l d i f f e r e n c e s w i t h i n a l l l o c a t i o n s e x c e p t a r e a s C and D whi c h were s u r v e y e d o n l y once. T h i r t y one p e r c e n t o f t h e d i s t r i b u t i o n s compared between l o c a t i o n s w i t h i n t h e same month were s i g n i f i c a n t l y d i f f e r e n t c a u s i n g r e j e c t i o n o f t h e n u l l h y p o t h e s i s and c o n f i r m a t i o n o f s i g n i f i c a n t d i s t r i b u t i o n a l d i f f e r e n c e s between l o c a t i o n s . The 2 f a c t o r t e s t was conducted i n o r d e r t o s i m u l t a n e o u s l y make i n f e r e n c e s about t h e u n e x p l a i n e d v a r i a t i o n i n b o t h monthly d i s t r i b u t i o n s f o r t h e same l o c a t i o n and l o c a t i o n d i s t r i b u t i o n s f o r t h e same month. The a n a l y s i s was l i m i t e d t o a comparison o f t o t a l d i s t r i b u t i o n s between A p r i l and June s i n c e t h e s e were t h e o n l y months i n w h i c h d a t a were c o l l e c t e d from a l l l o c a t i o n s w i t h t h e e x c e p t i o n o f a r e a s C and D w h i c h were s u r v e y e d o n l y once. A 2 - f a c t o r anova t a b l e was con-s t r u c t e d t o d e t e r m i n e t h e sample mean (x) f o r each f a c t o r ( i e . month and l o c a t i o n ) , t h e grand mean (••%) , t h e sum o f = 2 squares f o r each f a c t o r (f S ( x ^ - x) ) and t h e i r t o t a l , t h e e r r o r sum o f s q u a r e s , and t h e mean and e r r o r mean s q u a r e s . - 49 -Two v a l u e s o f the F s t a t i s t i c were c a l c u l a t e d , 1 f o r t h e month f a c t o r (F=.65) and 1 f o r t h e l o c a t i o n f a c t o r (F=.91), by d i v i d i n g t h e a p p r o p r i a t e mean square by t h e r e s p e c t i v e e r r o r mean square. To dete r m i n e s i g n i f i c a n t d i f f e r e n c e i n t h e d i s t r i b u t i o n r e s u l t s , t h e c r i t i c a l v a l u e f o r 1 numerator and 4 denominator degrees o f freedom was t a k e n from a s t a n d a r d F d i s t r i b u t i o n t a b l e and compared w i t h t h e c a l c u l a t e d v a l u e s o f F. Both c a l c u l a t e d v a l u e s o f F (.65, .91) were g r e a t e r t h a n t h e F rt_ v a l u e from the t a b l e (7.71) r e s u l t i n g i n a f a i l u r e . (J b t o r e j e c t t h e n u l l h y p o t h e s i s . The t e s t f a i l e d t o y i e l d a c o n c l u s i o n e x c e p t t h a t a d d i t i o n a l d a t a a r e needed t o a r r i v e a t a d e c i s i o n r e g a r d i n g t h e n u l l h y p o t h e s i s . - 50 -t 3.3 ABUNDANCE AND DISTRIBUTION OF NESTS S i n c e t h e number o f e a g l e s u s i n g the P o r t Hardy a r e a depended i n p a r t on t h e number o f n e s t i n g p a i r s a l o n g t h e a d j a c e n t c o a s t l i n e , i t was n e c e s s a r y t o examine t h i s and t o s e a r c h f o r any p a t t e r n s o f n e s t d i s t r i b u t i o n w h i c h might i n d i c a t e po-t e n t i a l d e n s i t i e s . 3.3.1 A i r p o r t V i c i n i t y and C o n t r o l Zone E i g h t e e n n e s t s were found a l o n g t h e 40 km o f c o a s t l i n e w i t h an average o f .5 nest/km o f c o a s t l i n e . The l o c a t i o n s o f n e s t s and t h e i r s t a t e o f use d u r i n g t h e 1974 n e s t i n g season a r e shown i n F i g u r e 14. T a b l e 2 o u t l i n e s t h e d i s t r i b u t i o n o f bo t h a c t i v e and i n a c t i v e n e s t s w i t h i n t h e a i r p o r t v i c i n i t y , c o n t r o l zone, and r e g i o n a l s t u d y a r e a . The a i r p o r t v i c i n i t y and c o n t r o l zone s u p p o r t e d .2 a c t i v e nest/km o f c o a s t l i n e w i t h an average i n t e r - a c t i v e n e s t d i s t a n c e o f 2.2 km. D u r i n g the 1974 n e s t i n g season, t h e average d i r e c t d i s t a n c e between any a c t i v e n e s t and t h e c l o s e s t a c t i v e n e s t was 1.9 km w i t h a range from 1.2 km t o 2.5 km. A l l n e s t t r e e s were l o c a t e d w i t h i n a s h o r t d i s t a n c e o f t h e c o a s t l i n e . The 5 n e s t t r e e s on the i s l a n d s o f Beaver Harbour tended t o be c l o s e r t h a n t h e r e m a i n i n g 12 n e s t t r e e s on t h e c o a s t o f Vancouver I s l a n d . The average d i s t a n c e o f a l l n e s t s from t h e c o a s t l i n e was 102 m w i t h a range from 3 t o 309 m. 3.3.2 R e g i o n a l F i n d i n g s N i n e t y n i n e b a l d e a g l e n e s t s were l o c a t e d i n t h e r e g i o n a l - 51 -F i g u r e 1 4 - West l o c a t e d w i t h i n the a i r p o r t c o n t r o l zone and t h e i r s t a t e of use d u r i n g the 197*+ n e s t i n g season. - 52 -stu d y a r e a o f w h i c h a t l e a s t 34 were a c t i v e . T a b l e 2 o u t l i n e s t h e abundance and d i s t r i b u t i o n o f b o t h a c t i v e and i n a c t i v e n e s t s d u r i n g the 1974 n e s t i n g season. The n o r t h -west c o a s t l i n e (area C) and the S c o t t I s l a n d s (area D) were surv e y e d i n October f o l l o w i n g t h e 1974 n e s t i n g season and t h e r e f o r e t h e number o f a c t i v e n e s t s was n o t d e t e r m i n e d . Nest d i s t r i b u t i o n was f a i r l y even t h r o u g h o u t a r e a C e x c e p t i n t h e San J o s e f Bay r e g i o n where t h e r e was a n o t a b l e absence o f n e s t s d e s p i t e many k i l o m e t e r s o f c o a s t l i n e . W i t h i n a r e a D, n e s t s were e v e n l y d i s t r i b u t e d on Lanz I s l a n d b u t were c o n c e n t r a t e d a l o n g t h e west and s o u t h s h o r e l i n e o f Cox I s l a n d . Nest d i s t r i b u t i o n was f a i r l y even t h r o u g h o u t a r e a E e x c e p t f o r H o l b e r g I n l e t where o n l y 1 n e s t was l o c a t e d a l o n g 81.3 km o f c o a s t l i n e and Q u a t s i n o Narrows where 4 n e s t s were s i t u a t e d a l o n g o n l y 13.0 km o f c o a s t l i n e . I n t o t a l , 116 n e s t s were l o c a t e d a l o n g the 736 km o f c o a s t l i n e w i t h i n t h e e n t i r e s t u d y a r e a . The average i n t e r - n e s t i l i n e a r d i s t a n c e was 2.6 km. I t was n o t p o s s i b l e t o a c c u r a t e l y d e l i n e a t e t h e a c t u a l s i z e o r shape o f any e s t a b l i s h e d t e r r i t o r y d u r i n g t h e p r e s e n t s t u d y . Table 2. Abundance and d i s t r i b u t i o n o f a c t i v e and i n a c t i v e n e s t s w i t h i n t h e s t u d y a r e a d u r i n g t h e 1974 n e s t i n g season. Area Length of Coastline (km) No. of Nests Nests A m No. of Active Nests Active Nests /km Average Distance Between Active Nests Control Zone 40.0 18 .5 9 .2 2.2 Mouth of Keogh S.E. Boundary 7.4 6 .8 2 .3 1.3 Vancouver Island Coastline 28.2 12 .4 7 .2 2.3 Vancouver Island Conponent 736.0 116 .2 - - -Area A N.E.Coastline 98.4 25 .3 7 .1 4.0 Area B N.E.Islands 117.3 18 .2 8 .1 4.8 Area C N.W. Coast l i n e 113.8 15 .1 — Area D Scott Islands 36.4 9 .2 — — — Area E 336.0 31 .1 10 .03 7.9 Quatsino Sound & Adjoining In l e t s - 54 -3.4 PRODUCTIVITY The a n n u a l r e c r u i t m e n t t o the b a l d e a g l e p o p u l a t i o n was e s t -imated w i t h i n t h e c o n t r o l zone and r e g i o n a l s t u d y a r e a . T h i s i n f o r m a t i o n was o f p a r t i c u l a r i m p o r t a n c e f o r the a i r p o r t v i c i n i t y and c o n t r o l zone, where t h e o c c u r r e n c e o f a d d i t i o n a l e a g l e s i n c r e a s e d t h e p o t e n t i a l h a z a r d t o a i r c r a f t . 3.4.1 A i r p o r t V i c i n i t y and C o n t r o l Zone Ta b l e 3 shows the s t a t e o f t h e n e s t s , whether a c t i v e , i n a c t i v e , s u c c e s s f u l , o r unknown d u r i n g t h e 1974 n e s t i n g season. The term " a c t i v e " was used t o d e s c r i b e t h o s e n e s t s c o n t a i n i n g a d u l t s i n i n c u b a t i n g p o s t u r e d u r i n g A p r i l . " I n a c t i v e " d e s c r i b e d t h o s e n e s t s w h i c h d i d not c o n t a i n i n -c u b a t i n g a d u l t s and tho s e w h i c h were e v i d e n t l y i n a s t a t e o f o b s o l e s c e n c e . " S u c c e s s f u l " r e f e r r e d t o t h o s e n e s t s w h i c h produced young. Nest abandonment was c a l c u l a t e d u s i n g the e q u a t i o n , Nest abandonment = (Ta - Ts) x 100% T.a where Ta i s t h e t o t a l number o f a c t i v e n e s t s and Ts i s t h e t o t a l number o f s u c c e s s f u l n e s t s . N e s t i n g s u c c e s s , d e f i n e d as t h e average number o f b i r d s r a i s e d p e r s u c c e s s f u l n e s t , and n e s t abandonment a r e g i v e n i n T a b l e 3. N e s t i n g s u c c e s s and n e s t abandonment w i t h i n t h e a i r p o r t v i c i n i t y and c o n t r o l zone d i d not d i f f e r s i g n i f i c a n t l y from t h e r e g i o n a l s t u d y a r e a . - 55 -T a b l e 3. S t a t e o f e a g l e n e s t s , n e s t i n g s u c c e s s , and n e s t abandonment w i t h i n the s t u d y a r e a d u r i n g t h e 19 74 n e s t i n g season. No.of No.Active No.Inactive Nests Nests Nests No.Unknown No.Nesting No.ofSuccessful, No. of Nests Pairs Nests Young Fledged A. Airport V i c i n i t y and Control Zone 17 9 8 0 9 4 6 B. Regional Study Area 99 24 41 34 24 10 12 Average Nesting Success Average Nest Abandonment 1.35 young/nest 56.9% Nine o f the 17 n e s t s l o c a t e d w i t h i n t h e a i r p o r t v i c i n i t y and c o n t r o l zone d u r i n g 1974 were a c t i v e . Of t h e 9 a c t i v e n e s t s , 4 were s u c c e s s f u l , namely n e s t s 1, 2, 10 and 12 w h i c h produced 2, 2, 1, and 1 young r e s p e c t i v e l y ( F i g . 1 4 ) . I t w i l l t a k e a more extended s t u d y than the p r e s e n t one t o de t e r m i n e t h e s i g n i f i c a n c e o f t h i s l e v e l o f f l e d g l i n g young on the p o t e n t i a l h a z a r d t o a i r c r a f t a t t h e a i r p o r t . Nest 12 was s i t u a t e d between 2 f l i g h t p a t h s and l e s s t h a n 1 km from t h e a i r p o r t runways. I t can be c o n c l u d e d t h a t e s t a b l i s h e d n e s t s were s u c c e s s f u l l y p r o d u c i n g young and t h a t p r o x i m i t y t o t h e a c t i v i t i e s o f t h e a i r p o r t was not i n h i b i t i n g s u c c e s s . These young were thought t o remain i n t h e a r e a u n t i l l a t e f a l l . - 56 -S i n c e o n l y 1 f l e d g l i n g i n t h e c o n t r o l zone was marked and o n l y 1 r a d i o - t r a c k e d , i t was n o t p o s s i b l e t o a c c u r a t e l y d e t e r m i n e t h e c o n t r i b u t i o n o f l o c a l l y r a i s e d b i r d s t o t h e a n n u a l f a l l assemblage o f e a g l e s around t h e a i r p o r t . However, t h i s con-c e n t r a t i o n was composed p r i m a r i l y o f immatures and most l i k e l y i n c l u d e d c o n t r o l zone o f f s p r i n g . Immatures c o m p r i s e d an average o f 62% o f t h e e a g l e s c o n c e n t r a t e d a t t h e Keogh R i v e r d u r i n g t h e f a l l o f 1972, 1973, and 1974 and were abundant a t o t h e r salmon r i v e r s a l o n g the n o r t h c o a s t o f Vancouver I s l a n d a t the same t i m e . T h i s compares w i t h a p r o p o r t i o n o f immature t o a d u l t e a g l e s o f 33% f o r the t o t a l p o p u l a t i o n o f t h e s t u d y a r e a . 3.4.2 R e g i o n a l F i n d i n g s T a b l e 3 shows the s t a t e o f the n e s t s as w e l l as n e s t i n g s u c c e s s and n e s t abandonment w i t h i n t h e r e g i o n a l s t u d y a r e a d u r i n g t h e 1974 n e s t i n g season. The a n n u a l r e c r u i t m e n t t o t h e e a g l e p o p u l a t i o n t h r o u g h o u t t h e r e g i o n a l s t u d y a r e a was e s t i m a t e d t o be a p p r o x i m a t e l y 18 young. T h i s c a l c u l a t i o n was made by expanding t h e i n a c t i v e / a c t i v e / s u c c e s s f u l n e s t r a t i o t o i n c l u d e unknown n e s t s . Some of t h e s e young b i r d s l i k e l y move t o t h e P o r t Hardy a i r p o r t d u r i n g s p r i n g and f a l l and t h u s i n c r e a s e the p o t e n t i a l h a z a r d t o a i r c r a f t . However, the c o n t r i b u t i o n o f b i r d s r a i s e d i n t h e r e g i o n a l s t u d y a r e a t o the a n n u a l s p r i n g and f a l l c o n c e n t r a t i o n o f e a g l e s around th e a i r p o r t c o u l d n o t be d e t e r m i n e d . C l u t c h s i z e was d e t e r m i n e d f o r a number of n e s t s i n i s o l a t e d - 57 -a r e a s where d i s t u r b a n c e o t h e r t h a n t h a t c r e a t e d by c o u n t i n g eggs was m i n i m a l o r n o n - e x i s t e n t . P r o d u c t i v i t y i n terms o f the number of young f l e d g e d compared t o t h e number o f eggs l a i d i s g i v e n i n T a b l e 4. T a b l e 4. P r o d u c t i v i t y o f s e l e c t e d e a g l e n e s t s w i t h i n t h e r e g i o n a l s t u d y a r e a d u r i n g t h e 1974 n e s t i n g season. N est No. No. Eggs L a i d No. Young F l e d g e d 26 2 1 30 2 1 36 2 2 44 2 0 46 2 1 52 2 1 234 12 • 6 P r o d u c t i v i t y : T o t a l No. o f Young F l e d g e d X 100% - 6 X 100% = 50% ...12 T o t a l No. o f Eggs L a i d C o n s i d e r i n g a l l 14 s u c c e s s f u l n e s t s i n t h e s t u d y a r e a (Table 3 ) , 4(29%) a p p a r e n t l y produced 2 young each, w h i l e 10 (71%) a p p a r e n t l y produced 1 young each. I t i s p o s s i b l e t h a t t h e r e were more th a n 4 n e s t s c o n t a i n i n g 2 young s i n c e 1 o f t h e 2 young may have f l e d g e d b e f o r e t h e surveys^. The mean c l u t c h s i z e r e c o r d e d e l s e -where i n t h e b a l d e a g l e ' s range i s a l m o s t i n v a r i a b l y 2 eggs (Beebe, 1974). N e s t s c o n t a i n i n g 2 o r 1 young g e n e r a l l y o c c u r - 58 -about e q u a l l y on t h e P a c i f i c C o a s t , n e s t s c o n t a i n i n g 3 young ar e r a r e ( i b i d . ) . The 14 s u c c e s s f u l n e s t s i n t o t a l produced 18 young r e s u l t i n g i n an average o f 1.3 young/nest. The e g g - l a y i n g p e r i o d i n t h e s t u d y a r e a extended from l a t e March u n t i l e a r l y May. - 59 -3 . 5 FOOD RELATIONSHIPS The r e l a t i o n s h i p between th e p r e s e n c e , abundance and a v a i l -a b i l i t y o f f o o d and t h e o c c u r r e n c e , p r o f u s i o n and b e h a v i o u r of e a g l e s was examined i n o r d e r t o d e t e r m i n e t h e i m p o r t a n c e o f f o o d s o u r c e s w i t h i n t h e a i r p o r t v i c i n i t y and c o n t r o l zone as an a t t r a c t a n t t o e a g l e s t h r o u g h o u t t h e s t u d y a r e a . Where a ready and abundant foo d s o u r c e was p r e s e n t and accompanied by l a r g e r numbers o f e a g l e s t h a n were p r e s e n t where no such f o o d s o u r c e s o c c u r r e d , i t was assumed t h a t a c a u s e - e f f e c t r e l a t i o n -s h i p e x i s t e d . D i r e c t o b s e r v a t i o n s t h r o u g h o u t t h e s t u d y p e r i o d i n d i c a t e d t h a t t h e s u b s i s t e n c e d i e t o f e a g l e s , f e e d i n g w i t h i n t h e a i r p o r t v i c i n i t y and c o n t r o l zone, was a l m o s t e n t i r e l y composed o f f i s h , b i r d s , and marine i n v e r t e b r a t e s . The a v a i l a b i l i t y o f f i s h , b i r d s , and o t h e r substenance i t e m s w i t h i n the a i r p o r t v i c i n i t y and c o n t r o l zone i s d i s c u s s e d i n s e c t i o n 1.4. E a g l e s s u s b s i s t p r i m a r i l y on p r e - s p a w n i n g , spawning, and spent salmon from e a r l y September u n t i l l a t e November. A l t h o u g h c o n c e n t r a t e d s c h o o l i n g o f p i n k and chum salmon o c c u r r e d near t h e s u r f a c e o f the water i n t h e mouth of the Keogh R i v e r , t h e r e i s l i t t l e i n d i c a t i o n t h a t t h e s e salmon a r e f r e q u e n t l y c a p t u r e d by e a g l e s . T i g h t s c h o o l s o f p i n k salmon were o b s e r v e d d u r i n g t h e e a r l y p a r t o f September w h i l e chum s c h o o l i n g was n o t o b s e r v e d u n t i l t h e end o f September. Coho salmon d i d n o t appear t o s c h o o l - 60 -i n t i g h t groups. I n o r d e r t o det e r m i n e i f a r e l a t i o n s h i p e x i s t e d between t h e abundance o f salmon i n t h e Keogh R i v e r ( s e r v i n g as a f o o d s o u r c e t o e a g l e s ) and t h e numbers of e a g l e s w i t h i n t h e a i r p o r t v i c i n i t y , t h e minimum number of e a g l e s r e c o r d e d was compared t o t h e e s -t i m a t e d salmon escapement as shown i n F i g u r e 15. S i m i l a r f i g u r e s were p r e p a r e d f o r the f a l l o f 1972 and the f a l l o f 1974. E a g l e abundance v a l u e s from t h e s e f i g u r e s were p l o t t e d a g a i n s t t h e c o r r e s p o n d i n g p i n k salmon escapement l e v e l s ( i e . t h e number of t h i s s p e c i e s o f salmon e n t e r i n g t h e r i v e r ) t o produce a s c a t t e r d iagram ( F i g . 1 6 ) . R e g r e s s i o n l i n e s i n d i c a t e a p o s i t i v e c o r -r e l a t i o n between e a g l e abundance and e s t i m a t e d p i n k salmon escapement. Summary r e s u l t s o f escapement l e v e l s i n 3 o f t h e 4 spawning r i v e r s w i t h i n t h e c o n t r o l , zone, d u r i n g 3 s u c c e s s i v e salmon spawning seasons, are g i v e n i n T a b l e 5. (Eagle abundance was compared w i t h escapement l e v e l s f o r p i n k salmon o n l y s i n c e e a g l e use o f chum and coho spawners was l i m i t e d ) . When computing the c o r r e l a t i o n between e a g l e abundance and salmon escapement d u r i n g 1972 and 1973, escapement l e v e l s were l a g g e d by 1 month t o t a k e i n t o account t h e i m p o r t a n c e o f spent p i n k salmon i n t h e d i e t o f e a g l e s , e s p e c i a l l y as t h e r i v e r l e v e l p r o g r e s s i v e -l y i n c r e a s e s d u r i n g O c t o b e r . (The e f f e c t o f r i v e r s t a g e on t h e a v a i l a b i l i t y o f salmon i s d i s c u s s e d l a t e r i n t h i s s e c t i o n ) . E a g l e abundance c l i m a x e d near t h e end o f t h e p i n k r u n d u r i n g 19 72 and 1973, a p p r o x i m a t e l y 1 month a f t e r the peak i n t h o s e r u n s . - 61 -Figure 15. Minimum number of eagles c o n t i n u o u s l y f r e q -u e nting the a i r p o r t v i c i n i t y i n r e l a t i o n t o the estimated salmon escapement t o the Keogh R i v e r d u r i n g the f a l l of 1973 • r 8 12 II io H 9 cn „ LU 8 _j u> < 7 LU 51 or. LU CD 4 *>; * 3 AUG O o 7 0_ 6 I -LU LU CU < t o LU -5 O 111 < CO LU t2 \ \ S E P T O C T !973 NOV D E C - 62 -Figure 16. Scatter diagram showing regression l i n e s f o r c o r r e l a t i o n between the abundance of eagles i n the a i r p o r t v i c i n i t y 2 3 4 5 6 7 8 estimated escapement (x 10,000) A. 1972 + 1974 - 63 -Table ,5. Particulars of spawning pink, chum, and coho salmon in the Keogh, Quatse, and Tsulquate Rivers during the f a l l of 1972, 1973 and 197*4. '• • ; A) 1972 ARRIVAL I N DURATION TOTAL SPECIES STREAM START PEAK END ESCAPEMENT Keogh River Pink Chum Coho 25/8/72 3/10/72 27/9/72 20/9/72 10/72 10/72 3/10/72 19/10/72 6/11/72 3/10/72 3/10/72 31/12/72 75,000 5,000 2,000 Quatse River Pink Chum 9/72 10/72 9/72 10/72 10/72 11/72 11/72 11/72 16,000 2,500 Tsulquate River Pink Chum 8/72 10/72 8/72 10/72 9/72 10/72 11/72 ..11/72 U ,500 550 B ) 1973 ARRIVAL I N DURATION TOTAL SPECIES STREAM START PEAK END ESCAPEMENT Keogh River Pink Chum Coho 25/8/73 2/10/73 28/9/73 20/9/73 10/73 10/73 2/10/73 20/10/73 25/10/73 18/10/73 31/10/73 31/12/73 7,000' 700 2,200 Quatse River Pink Chum 8/9/73 10/10/73 15/9/73 5/10/73 15/10/73 31/10/73 11/73 11/73 1,000 600 Tsulquate River Pink Chum 3/9/73 tyl0/73 3/9/73 Vl°/73 28/9/73 25/10/73. 20/10/73 11/73 7 ,000 U25 C) 197*4 ARRIVAL I N DURATICiT TOTAL SPECIES STREAM START P3iS EiiD . ESCAPE:-SNT Keogh River Pink Chum Coho 1st large escapement 7,8/9/7*4 2*4/8/7*4 30/9/7** 19/9/7*4 17/9/7!+ ll/lO/7*4 23/10/7*4 55,500 10/714- - 2C/lO/714- 3l/lO/7*4 400 10/7*4 near end 3l/l2/7*4 200 o f Oct. Quatse River Pink Chum 7/9/7*4 15/9/7*4 h/xc/lh 15/11/7*4 66 ,000 8/10/7*4 10/10/7*4 20/10/7*+ 1/11/7*4 *400 Tsulquate River Pink Chum 7/9/7*4 15/9/7*4 30/9/7*4 11/7*4 11,000 2/10/7*4 5/10/7*4 15/10/7*4 30/10/7*4 500 The peak i n t h e p i n k r u n was c o i n c i d e n t w i t h t h e peak i n e a g l e abundance d u r i n g 1974 when t h e r i v e r l e v e l remained v e r y low i n t o O c t o b e r . A c c o r d i n g l y , escapement l e v e l s were n o t l a g g e d . The c o e f f i c i e n t o f l i n e a r c o r r e l a t i o n (r) was computed from e a g l e abundance and salmon escapement d a t a f o r two i n t e r v a l s d u r i n g each salmon spawning season, t h e p e r i o d when th e number of p i n k spawners i n the Keogh R i v e r was i n c r e a s i n g and t h e p e r i o d when the number o f p i n k spawners was d e c r e a s i n g . C a l c u l a t e d c o r r e l a t i o n c o e f f i c i e n t v a l u e s were a l l s l i g h t l y l e s s t h a n 1.0 as shown i n F i g u r e 16 i n d i c a t i n g a v e r y s t r o n g c o r r e l a t i o n between b o t h t h e r a t e o f i n c r e a s e i n e a g l e abundance and t h e r a t e o f i n c r e a s e i n p i n k spawners as w e l l as between t h e r a t e o f d e c r e a s e i n e a g l e abundance and the r a t e o f d e c r e a s e i n p i n k spawners. The i n c r e a s e and d e c r e a s e i n e a g l e abundance each f a l l was n o t d i r e c t l y c o r r e l a t e d w i t h t h e a c t u a l number of p i n k salmon i n t h e Keogh R i v e r . F a l l e a g l e abundance v a r i e d l i t t l e compared t o the g r e a t v a r i a t i o n i n salmon escapement l e v e l s between even and odd y e a r s . T h i s i n d i c a t e s t h a t t h e r e was a p l e n t i f u l f o o d s u p p l y even i n odd y e a r s when the t o t a l number o f spawning salmon was much s m a l l e r . I t a l s o s u g g e s t s t h a t e a g l e s were a t t r a c t e d from a l i m i t e d a r e a s i n c e the abundance o f salmon i n t h e Keogh R i v e r c o u l d have s u p p o r t e d a much g r e a t e r number o f e a g l e s . I t was obse r v e d t h a t o f the 3 s p e c i e s o f salmon i n t h e Keogh R i v e r , p i n k spawners were most a c c e s s i b l e t o e a g l e s due t o - 65 -t h e i r s m a l l s i z e (average w e i g h t 1.4-1.8 k i l o g r a m s ) , l a r g e numbers, and t i g h t s c h o o l i n g c h a r a c t e r i s t i c s . P i n k salmon were most v u l n e r a b l e t o p r e d a t i o n towards th e end o f t h e spawning season when many became so weak t h a t t h e y were swept downstream, o f t e n near the s u r f a c e o f t h e w a t e r . From t h e i r s t r a t e g i c p e r ches a l o n g t h e r i v e r bank, e a g l e s e a s i l y l o c a t e d and sub-s e q u e n t l y p r e y e d on d y i n g f i s h . As mentioned e a r l i e r , e a g l e abundance was g e n e r a l l y g r e a t e s t near the end o f t h e p i n k salmon spawning ru n i n d i c a t i n g t h e i m p o r t a n c e o f dead and d y i n g p i n k s as a f o o d s o u r c e . The p r e f e r r e d spawning grounds f o r p i n k spawners were i n t h e lower r e a c h e s o f the Keogh, b e g i n n i n g a t t h e mouth. I n even y e a r s , p i n k spawners may on o c c a s i o n e x t e n d a l l t h e way up t o Keogh Lake, but i n odd y e a r s t h e y o c c u r o n l y i n t h e f i r s t few m i l e s o f r i v e r . The s m a l l number o f coho spawners i n the Keogh were g e n e r a l l y i n good c o n d i t i o n and r a r e l y seen d u r i n g p a t r o l s a l o n g t h e r i v e r . I t i s thought t h a t v e r y l i m i t e d a c t i v e e a g l e p r e d a t i o n o c c u r s on t h i s s p e c i e s because o f i t s s u p e r i o r s t r e n g t h , l a r g e s i z e , p r o t e c t i v e c a mouflage, l i m i t e d numbers, and p r e f e r e n c e f o r deep wa t e r . Only f u l l y mature coho were o b s e r v e d , r a n g i n g i n s i z e from a p p r o x i m a t e l y 2.5 kg. t o 6.5 kg. Coho p r e f e r r e d spawning grounds a c o n s i d e r a b l e d i s t a n c e upstream from t h e mouth. E a g l e s no doubt f e d on some dead and/or d y i n g spawners and p o s s i b l y on some inc o m i n g coho a t t h e r i v e r mouth under low r i v e r and low t i d e c o n d i t i o n s . - 66 -Chum salmon appeared t o be more v u l n e r a b l e t o e a g l e p r e d a -t i o n t h a n cohos because of t h e i r s l o w e r speed. However, e a g l e p r e d a t i o n on chum was l i m i t e d due t o t h e i r l a r g e s i z e and s u f f i c i e n t l y h i g h r i v e r l e v e l s d u r i n g t h e chum r u n . I n l a t e O c t o b e r , e a g l e s were o b s e r v e d f e e d i n g r e g u l a r -l y on dead chums. S i m i l a r t o p i n k salmon, chum-also p r e f e r r e d the lower r e a c h e s o f t h e r i v e r f o r spawning. Surveys a t s e v e r a l l o c a t i o n s a l o n g t h e e n t i r e 32 km l e n g t h o f t h e Keogh R i v e r i n d i c a t e d t h a t o n l y l i m i t e d spawning ( l i k e l y coho) o c c u r r e d i n t h e upper 18 km o f r i v e r . A l m o s t a l l o f t h e p i n k , chum,and coho spawned w i t h i n t h e lower 14 km. The l e v e l o f t h e Keogh R i v e r g r e a t l y i n f l u e n c e d t h e upstream m i g r a t i o n and a v a i l a b i l i t y o f spawning salmon t o e a g l e s . R i v e r l e v e l s were g e n e r a l l y v e r y low d u r i n g September when most p i n k spawners e n t e r e d t h e Keogh. R i v e r s t a g e was p a r t i c u l a r l y i m p o r t a n t a t the r i v e r mouth and j u s t upstream. The a n n u a l c o n c e n t r a t i o n o f e a g l e s i n t h i s a r e a ( F i g . 9) d u r i n g t h e spawn-i n g season was i n l a r g e p a r t due t o t h e easy a c c e s s i b i l i t y o f i n c o m i n g salmon, e s p e c i a l l y d u r i n g low t i d e c o n d i t i o n s and low r i v e r l e v e l s . Under t h e s e c o n d i t i o n s , much o f t h e e x t e n s i v e sandstone s h e l f a t t h e mouth was exposed, f o r c i n g i n c o m i n g salmon i n t o narrow, s h a l l o w c h a n n e l s where t h e y were h i g h l y v u l n e r a b l e t o e a g l e s p e r c h e d nearby. I n September i t was o f t e n n e c e s s a r y f o r salmon t o e n t e r t h e r i v e r a t the time of h i g h t i d e s , s i n c e low t i d e c o n d i t i o n s (low r i v e r l e v e l s p l u s i m p a s s a b l e w a t e r f a l l s a t t h e edge o f the s h e l f ) were p r o h i b i t i v e t o upstream m i g r a t i o n . As t h e r i v e r l e v e l dropped w i t h t h e t i d e r e c e d i n g , s c h o o l s o f p i n k salmon were t r a p p e d i n s h a l l o w p o o l s a l o n g t h e lower .5 km o f r i v e r . Under t h e s e c o n d i t i o n s , e a g l e s were a b l e t o t a k e salmon from t h e s e s c h o o l s but t h i s t y p e o f p r e d a t i o n was l i m i t e d by the dark c o l o u r a t i o n o f r i v e r w a t e r and t h e t h i c k canopy p a r t i a l l y c o v e r i n g t h e r i v e r j u s t upstream from t h e mouth. When r a i n f a l l i n c r e a s e d r i v e r l e v e l s d u r i n g September and O c t o b e r , salmon m i g r a t e d upstream i n l a r g e numbers even though r i v e r l e v e l s remained r e l a t i v e l y low. These c o n d i t i o n s l e d t o a change i n t h e f e e d i n g b e h a v i o u r o f e a g l e s . I n s t e a d o f f e e d -i n g m o s t l y on in c o m i n g p i n k s near t h e r i v e r mouth, e a g l e s began f e e d i n g a t v a r i o u s l o c a t i o n s upstream, where s t i l l r e l a t i v e l y low water c o n d i t i o n s and the g r e a t number of salmon r e s u l t e d i n an e a s i l y a c c e s s i b l e f o o d s o u r c e . T h i s was p a r t i c u l a r l y n o t i c e a b l e i n t h e west h a l f o f the f l i g h t p a t h c l e a r i n g where t h e r e were s e v e r a l s h a l l o w p o o l s and a d j o i n i n g r a p i d s ( F i g . 1 0 ) . Salmon were o f t e n p a r t i a l l y exposed when swimming upstream between p o o l s . S e v e r a l s t r a t e g i c l o c a t i o n s were found a l o n g the lower s t r e t c h e s o f t h e Keogh where e a g l e s had spent con-s i d e r a b l e time w a t c h i n g salmon. The change i n f e e d i n g be-h a v i o u r appeared t o be accompanied by an i n c r e a s e d f r e q u e n c y o f - 68 -e a g l e f l i g h t s a c r o s s t h e a i r f i e l d . A marked i n c r e a s e i n the l e v e l o f the Keogh R i v e r o c c u r r e d d u r i n g e a r l y f a l l each y e a r a t a p p r o x i m a t e l y t h e same ti m e and t h i s was thought t o t r i g g e r upstream m i g r a t i o n o f coho and chum salmon. A l t h o u g h t h e i n c r e a s e d l e v e l r e s u l t e d i n more salmon i n t h e r i v e r , i t made i t d i f f i c u l t f o r e a g l e s t o p r e y on i n c o m i n g and spawning salmon due t o t h e depth and speed o f t h e r i v e r w a t e r . The i n c r e a s e d r i v e r l e v e l a l s o q u i c k l y swept away t h e remains of spent salmon from a l o n g t h e r i v e r bank. As a r e s u l t , t h e f e e d i n g b e h a v i o u r o f e a g l e s changed once a g a i n . I n s t e a d o f f e e d i n g on p i n k spawners a t v a r i o u s p o i n t s upstream, e a g l e s began f e e d i n g p r i m a r i l y on dead and d y i n g p i n k s a t the r i v e r mouth. By e a r l y November, r i v e r l e v e l s had d e c r e a s e d a g a i n ; few, i f any p i n k spawners remained and e a g l e s appeared t o be f e e d i n g e x c l u s i v e l y on dead and d y i n g chum salmon. Thus f o r 2 months (September and October) t h e p i n k salmon i n t h e Keogh R i v e r produced a s u r p l u s of f o o d f o r t h e e a g l e s c o n c e n t r a t e d a t t h e a i r p o r t . F e e d i n g on spent salmon c o n t i n u e d w e l l i n t o November a t the mouth and a l o n g t h e lower r e a c h e s o f the r i v e r . Coho spawners peaked d u r i n g l a t e October o r e a r l y November and remained i n the Keogh R i v e r f o r some t i m e . There was no e v i d e n c e found o f e a g l e s f e e d i n g on e i t h e r l i v e o r dead coho salmon. The t o t a l number o f coho i n t h e r i v e r g r a d u a l l y de-c r e a s e d t h r o u g h November and December. - 69 -E a g l e s d i d n o t f e e d on salmon from t h e Keogh R i v e r t o any s i g n i f i c a n t e x t e n t a f t e r t h e l a s t o f t h e chum had been con-sumed by mid-November. I t i s p o s s i b l e t h a t remains o f spawn-i n g salmon l e f t by b l a c k b e a r a l o n g t h e r i v e r bank may have been s e a r c h e d out and e a t e n p r i o r t o and f o l l o w i n g t h i s d a t e . Salmon spawning i n t h e Quatse and T s u l q u a t e R i v e r a l s o a t t r a c t -ed eagles, but a p p a r e n t l y t o a l e s s e r degree t h a n salmon i n t h e Keogh R i v e r . I t was n o t p o s s i b l e t o d e t e r m i n e t h e number o f e a g l e s a t t r a c t e d t o t h e former 2 r i v e r s , but each y i e l d e d fewer s i g h t i n g s / h o u r t h a n the Keogh. A v a r i e t y o f sea b i r d s was p r e s e n t i n t h e c o n t r o l zone t h r o u g h -out t h e y e a r and t h u s p r o v i d e d a c o n t i n u a l p o t e n t i a l s o u r c e o f food.. L i k e w i s e , the many d i f f e r e n t t y p e s o f i n t e r t i d a l i n v e r t e b r a t e s were a v a i l a b l e as p o t e n t i a l f o o d i t e m s and were r e g u l a r l y used d u r i n g the p e r i o d s o f t h e y e a r when t i d e s low enough t o expose them o c c u r r e d d u r i n g d a y l i g h t h o u r s . D u r i n g t h e p e r i o d between t h e salmon spawning season and t h e h e r r i n g spawning season (December t h r o u g h F e b r u a r y ) , e a g l e s w i t h i n t h e c o n t r o l zone f e d p r i m a r i l y on w i n t e r i n g sea b i r d s and marine f i s h e s . W i t h t h e b e g i n n i n g o f t h e h e r r i n g spawning season i n l a t e March, e a g l e s once a g a i n had a c c e s s t o a c o n c e n t r a t e d f o o d s o u r c e . W h i l e e x t e n s i v e spawning grounds were a t one t i m e l o c a t e d around the p e r i m e t e r o f most i s l a n d s i n Beaver Harbour, t h e y are now r e s t r i c t e d to regions north of Deer I s l a n d and south of the C a t t l e I s l a n d s . Eagles were observed c a p t u r i n g h e r r i n g from t i g h t schools near the C a t t l e Islands and a number of f i s h were found beneath t r e e s on the I s l a n d s . Herring appear to be the s t a p l e d i e t of eagles during the l a t t e r p a r t of March and the e a r l y p a r t of A p r i l . Herring-spawn attached to Macrocystis beds was taken e x t e n s i v e l y by g u l l s , however, eagles were not observed feeding on the spawn. Eagle numbers i n the v i c i n i t y of the a i r p o r t again increased at t h i s time. Deta-ils were discussed e a r l i e r . From the end of the h e r r i n g spawn i n l a t e A p r i l u n t i l the beginning of the salmon spawning season i n l a t e August, the main components of the eagles' d i e t appeared to be sea b i r d s , marine f i s h e s , and i n t e r t i d a l i n v e r t e b r a t e s . During t h i s p e r i o d eagles were dispersed along the c o a s t l i n e . Feeding h a b i t i n f o r m a t i o n based on the a n a l y s i s of food remains at the base of nest t r e e s and nest contents i s given i n Table 6. This evinces the food a v a i l a b l e and brought to the nest during the p e r i o d of nest occupancy by the e a g l e t s (May -August). Marine f i s h e s accounted f o r 23% of the food remains at 10 nests w i t h i n the c o n t r o l zone during 197 4. These f i s h i n c l u d e d h e r r i n g , cod, r o c k f i s h , salmon, and d o g f i s h . B i r d s accounted f o r 34% of the food remains and i n c l u d e d s c o t e r s , - 71 -g u l l s , a r h i n o c e r o s a u k l e t , and a g r e a t b l u e h e r o n . M a r i n e i n v e r t e b r a t e s a ccounted f o r t h e l a r g e s t p e r c e n t a g e (42%) of t h e f o o d i t e m s and i n c l u d e d a b a l o n e , o t h e r u n i v a l v e s , b i v a l v e s , b a r n a c l e s , c r a b s , and sea urchins.. One un-i d e n t i f i e d mammal was found a c c o u n t i n g f o r 1% o f t h e f o o d remains. A l l t h e s e f i g u r e s a r e p e r c e n t a g e by o c c u r r e n c e . A l t h o u g h many marine i n v e r t e b r a t e f o o d i t e m s were found, t h e y were g e n e r a l l y v e r y s m a l l and i n volume p r o b a b l y ranked t h i r d i n imp o r t a n c e a f t e r b i r d s and marine f i s h e s . Some food i t e m s such as c a r r i o n t a k e n from s e a l s can be c o m p l e t e l y d i g e s t e d and t h e r e f o r e would n ot be d e t e c t e d by the method used. E a g l e s supplement t h e i r d i e t t h r o u g h o u t the y e a r by f e e d i n g on c a r r i o n , p a r t i c u l a r l y a l o n g t h e c o a s t -l i n e . - 72 -Table 6. Food remains found at ten b a l d eagle nests w i t h i n the c o n t r o l zone d u r i n g 1974. OCCURRENCE F i s h e s : h e r r i n g (Clupeidae) 5 5.8 p a c i f i c cod (Gadus macrocephalus) 6 7.0 r o c k f i s h (Sebastodes sp.) 4 4.7 salmon (Oncorhynchus sp.) 1 1.2 d o g f i s h 2 2.3 u n i d e n t i f i e d f i s h 2 2.3 T o t a l 2 0 2 3.3 B i r d s : r h i n o c e r o s a u k l e t 1 1.2 s c o t e r ( M e l a n i t t a sp.) 2 2.3 grea t blue heron (Ardea herodias) 1 1.2 g u l l (Larus sp.) 2 2.3 u n i d e n t i f i e d b i r d 23 26.7 T o t a l 29 33.7 I n v e r t e b r a t e s : abalone ( H a l i a t u s ) 5 5.8 b i v a l v e s 10 11.6 uuni'val'ves (Gastropoda) (3 limpets) 10 11.6 ba r n a c l e s 5 5.8 crabs 3 3.5 sea u r c h i n s _3 3.5 T o t a l 36 41.8 Mammals: u n i d e n t i f i e d mammal 1 1 • 2 T o t a l 1 1.2 GRAND TOTAL 86 100.0 - 73 -3.6 EAGLE FLIGHT PATTERNS The autumn aggregation of eagles i n the f l i g h t path for runway 1028 i n the v i c i n i t y of the Keogh River presented the greatest hazard to aircraft. This hazard arose since the aggregation was located i n an active f l i g h t path less than 700m from the end of runway 1028, the only runway used by Boeing 737 jets. My findings indicated that approac±iing and departing jets were flying directly through the airspace used by eagles when flyin g above the river. Approximately 80% of autumn eagle a c t i v i t y i n the f l i g h t path consisted of direct flights above the river. The remaining 20% consisted of soaring high over the river when clear skies prevailed along with brisk southeast winds and cool temperatures. Soaring was observed up to 250m which marked the upward limit of the aggregation area above and adjacent to the Keogh River. Figure 17 gives a frequency-altitude p r o f i l e of direct eagle flights above the Keogh River i n the f l i g h t path during the f a l l of 1972, 1973, and 1974. As stated i n 2.3.1, my altitude data are based on estimates due to the d i f f i c u l t y of accurately approximating the elevation of swiftly fl y i n g birds. However, i t was usually possible to compare the altitude of eagle flights with the altitude of known reference points (e.g. river bank,tree height,jet altitude) i n order to obtain a reliable estimate. Essentially a l l direct eagle flights above the river occurred between 2 and 60m. Flights were most frequent i n the 35-40m and 40-45m range which coincided with the approach altitudes of jets when over the river (30-60m). This potential for mid-air strikes had to be substantially reduced i n order to provide a significant and long term solution to the airport's bird hazard problem. Figure 17. Frequency-altitude histogram of d i r e c t eagle f l i g h t s above the Keogh River i n the southeast f l i g h t path f o r runway 1028 during the f a l l of 1972, 1973, and 1974. PART 4 DISCUSSION T h i s s t u d y has r e v e a l e d t h a t t h e P o r t Hardy a i r p o r t i s s i t u a t e d i n an a r e a o f h i g h e a g l e d e n s i t y ^ ' y e a r - r o u n d . N e s t i n g d e n s i t y i n t h e e n t i r e s t u d y a r e a was a t l e a s t .1 a c t i v e n e s t / l i n e a l km o f c o a s t l i n e w i t h a h i g h e r d e n s i t y i n t h e immediate v i c i n i t y o f t h e a i r p o r t (.2 a c t i v e n e s t / l i n e a l km o f c o a s t l i n e ) . D e n s i t i e s r e p o r t e d a t B a r k l e y Sound (Hancock 1970, R e t f a l v i 1977) and K a r l u k LaKe (Anonymous 1958, H e n s e l and T r o y e r 1964/1965, Robards and K i n g 196 6) exceed t h o s e near P o r t Hardy a i r p o r t . These 2 2 were .53 eagles/km and .78 eagles/km r e s p e c t i v e l y . D e s p i t e the d i f f e r e n c e i n d e n s i t y , n e s t i n g s u c c e s s was s i m i l a r t o t h a t r e c o r d e d f o r s t a b l e p o p u l a t i o n s i n F l o r i d a and a t K a r l u k Lake. I n my s t u d y a r e a 57% o f t h e n e s t s f a i l e d b u t t h o s e t h a t produced young averaged 1.4 young/nest. Comparable f i g u r e s have been r e c o r d e d a t K a r l u k Lake where 42% o f t h e n e s t s f a i l e d i n 1962 and t h e mean young p e r s u c c e s s f u l n e s t d u r i n g 1959, 1961, and 1962 was .9, .6 and 1.4 r e s p e c t i v e l y (Hensel and T r o y e r , 1964). B r o l e y (1947) showed t h a t 56 n e s t s i n 1946 produced an average o f 1.8 b i r d s per. n e s t . Robbins (1960) r e c o r d e d what he termedea good r e p r o d u c t i o n s u c c e s s i n 1959 a t E v e r g l a d e s N a t i o n a l Park when 18 young were r a i s e d i n 11 n e s t s (1.6 p e r n e s t ) . There were 5 a c t i v e n e s t s w i t h i n t h e o r b i t o f P o r t Hardy a i r p o r t a c t i v i t y and they d i d not d i f f e r i n s u c c e s s r a t e o r f l e d g e d young per s u c c e s s f u l n e s t from n e s t s more remote. I t can be c o n c l u d e d t h a t a i r p o r t a c t i v i t y does not i t s e l f reduce t h e r e a r i n g s u c c e s s o f the b a l d e a g l e s . S t u d i e s o f the r e l a t i o n s h i p between the number of e a g l e s u s i n g t h e a i r p o r t v i c i n i t y d u r i n g t h e autumn p e r i o d when t h e salmon were e n t e r i n g the Keogh R i v e r demonstrated a p o s i t i v e c o r r e l a t i o n . F i n d i n g s r e v e a l e d t h a t even a r e l a t i v e l y s m a l l spawning run o f salmon was adequate t o a t t r a c t the e a g l e s and t h a t t h e v e r y l a r g e runs d i d not a t t r a c t a d d i t i o n a l e a g l e s i n t h e same r a t i o . The c o n c e n t r a t i o n o f e a g l e s a t t h e a i r p o r t c o n t a i n e d a d i s -p r o p o r t i o n a t e number of immatures, s u g g e s t i n g t h a t t h e a d u l t s were l e s s a t t r a c t e d t o t h e f o o d c o n c e n t r a t i o n . I t i s i m p o r t a n t t o r e c o g n i z e t h a t t h e l a r g e s t number o f e a g l e s i n t h e v i c i n i t y o f the a i r p o r t (35) c o u l d have been drawn from a r e l a t i v e l y s m a l l a r e a a d j a c e n t . These f i n d i n g s s u g g e s t t h a t e l i m i n a t i o n o r s u b s t a n t i a l r e d u c t i o n o f the number of e a g l e n e s t s w i t h i n 8 km o f t h e a i r p o r t ( c o n t r o l zone r a d i u s ) would p r o b a b l y s i g n i f i c a n t l y reduce t h e number o f e a g l e s , p r e s e n t t h e r e . T h i s might be a p r a c t i c a l approach t o m i t i g a t -i n g t h e problem w i t h o u t r e d u c i n g t h e p o p u l a t i o n o f t h e e n t i r e s t u d y a r e a by more t h a n a p p r o x i m a t e l y one t e n t h . Removal would p r o b a b l y have t o be done a n n u a l l y . - 77- -There i s no e v i d e n c e as t o t h e d i s t a n c e from w h i c h th e e a g l e s a r e drawn t o t h e h e r r i n g spawn i n F e b r u a r y and March. T h i s c o n c e n t r a t i o n , however, has d i f f e r e n t f l i g h t p a t t e r n s and does not c r o s s t h e a i r c r a f t f l i g h t p a t h as f r e q u e n t l y as does the autumn c o n c e n t r a t i o n and t h e r e f o r e i s l e s s h azardous. The terms o f r e f e r e n c e o f t h i s s t u d y were t o seek a s o l u t i o n w h ich d i d not n e c e s s i t a t e k i l l i n g e a g l e s . The s t u d i e s o f f l i g h t f r e q u e n c i e s , a l t i t u d e s , and d i r e c t i o n s s uggest such a s o l u t i o n . The c u r v e o f a l t i t u d e o f a i r c r a f t l a n d i n g and t a k e - o f f p a t h s r e v e a l s a c o n c e n t r a t i o n between 30 and 210m above t h e Keogh R i v e r . S i m i l a r l y , t h e c u r v e o f e a g l e f l i g h t a l t i t u d e s above the r i v e r d emonstrated h i g h e s t f r e q u e n c i e s between 2 and 60m. E a g l e f l i g h t s were most f r e q u e n t a t a p p r o x i m a t e l y 40m above the r i v e r w h i c h c o i n c i d e d w i t h t h e approximate a l t i t u d e o f a p p r o a c h i n g j e t s when o v e r t h e r i v e r . S i n c e i t i s not l i k e l y t h a t t h e b e h a v i o u r o f t h e e a g l e s can be changed i t i s u s e f u l t o c o n s i d e r ways o f a l t e r i n g t h e f l i g h t p a t h s o f . t h e . a i r c r a f t so as t o g r e a t l y l e s s e n t h e f r e q u e n c y . o f i n t e r a c t i o n . T h i s can be a c h i e v e d by e x t e n s i o n o f runway 102 8 i n t h e n o r t h -west d i r e c t i o n f o r a d i s t a n c e o f a p p r o x i m a t e l y 610m. The runway e x t e n s i o n would a l l o w B o e i n g 737 j e t s t a k i n g o f f t o t h e s o u t h e a s t t o pass o v e r , i n s t e a d o f t h r o u g h , t h e hazardous zone above t h e Keogh R i v e r . They would thus have a g r e a t e r chance o f b e i n g above any e a g l e s s o a r i n g o r f l y i n g up and down t h e r i v e r . The g r e a t e s t e a g l e h a z a r d t o g e t a i r c r a f t o c c u r r e d d u r i n g t h e t a k e - o f f and c l i m b - o u t regime when f u l l power was used t o g a i n a l t i t u d e q u i c k l y . An e a g l e s t r i k e a t t h i s t i m e would l i k e l y r e s u l t i n a c r a s h . A s t r i k e d u r i n g t h e approach and l a n d i n g regime would be l e s s dangerous due t o t h e d e c r e a s e d power r e q u i r e m e n t and p r o x i m i t y o f t h e runway. F o r t h e s e r e a s o n s , major emphasis was p l a c e d on the e a g l e h a z a r d t o a i r c r a f t d u r i n g t a k e - o f f and c l i m b o u t . The r a t i o n a l e b e h i n d t h e runway e x t e n s i o n i s p r e s e n t e d i n F i g u r e Iff. D u r i n g t h e s t u d y , the t a k e - o f f a l t i t u d e o v e r t h e Keogh ranged between 120 and 210m (as checked from t h e c o c k p i t ) . A 610m runway e x t e n s i o n would a l l o w t h i s a l t i t u d e t o b e ' i n c r e a s e d t o between 300 and 450m. The g a i n i n e l e v a t i o n o v e r t h e Keogh R i v e r a c h i e v e d by l i f t i n g o f f from a p o i n t 600m f u r t h e r from the r i v e r would m i n i m i z e t h e p o t e n t i a l h a z a r d d u r i n g d e p a r t u r e s . S i m i l a r l y , i f a i r c r a f t l a n d i n g from t h e s o u t h e a s t c o u l d l a n d 600m f a r t h e r down t h e runway, i t would t h e n be p o s s i b l e f o r them t o approach a t a h i g h e r a l t i t u d e o v e r the Keogh R i v e r . D u r i n g t h e s t u d y , t h e approach a l t i t u d e o v e r the Keogh was a p p r o x i m a t l e y 30 - 6 0m. An a d d i t i o n a l 610m o f runway would a l l o w j e t t r a f f i c t o a p p r o x i m a t e l y d o u b l e i t s h e i g h t over t h e Keogh. A l t h o u g h t h i s would n ot remove a p p r o a c h i n g a i r c r a f t F i g u r e '18. R e l a t i o n s h i p between runway e x t e n s i o n d i s t a n c e and ascent p a t t e r n of Boeing 737 j e t . T H O M A S PT. R I D G E P R E S E N T N.W. E N D O F R U N W A Y P R E S E N T S . E . E N D O F R U N W A Y S . E . E N D O F F L I G H T P A T H 1,000 m-B E A V E R H A R B O U R 0-305 m. EXTENSION"" P R E S E N T P O I N T O F J E T D E P A R T . / P O T E N T I A L L Y H A Z A R D O U S Z O N E / />'/ / / ' / I / - | — M I N . D E P A R T . E L . ('73) M A X . D E P A R T . E L E V . " W I T H 610 m. E X T . M A X . D E P A R T . E L E V . ' W I T H 305m. E X T . - M A X . D E P A R T . E L . ('73) - A V E R . D E P A R T . EL.('73) N.B. A N G L E <S> L E S S T H A N 3° 0 500 1000 ( METERS) K E O G H R I V E R e n t i r e l y from the zone of eagle s o a r i n g , i t would put the a i r c r a f t above most of the f l i g h t s up and down the Keogh Ri v e r . A runway extension of 610m would s t i l l a llow f o r the minimum g l i d e path slope of 3 degrees f o r a i r c r a f t approaching from the northwest. However, low h i l l s l o c a t e d to the northwest would i n t e r f e r e w i t h any l a r g e extensions beyond the 610m d i s t a n c e . Approaches and departures at the northwest end of runway 102 8 are l a r g e l y f r e e of the eagle problems because of the eagles' c l o s e a s s o c i a t i o n w i t h the Keogh R i v e r . My s t u d i e s have a l s o revealed t h a t there i s a strong season-a l i t y to the hazard w i t h c o n c e n t r a t i o n during the September through November p e r i o d when eagles are c r o s s i n g the south-east approach to runway 102 8 i n t h e i r movements along the Keogh R i v e r . 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