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Food habits in relation to the ecology and population dynamics of blue grouse. King, Richard Dennis 1968

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POOD HABITS I N RELATION TO THE ECOLOGY AND POPULATION DYNAMICS OF BLUE GROUSE by RICHARD DENNIS KING B.Sc., U n i v e r s i t y o f B r i t i s h Columbia, 1964  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department 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 t h e required standard  THE UNIVERSITY OF BRITISH COLUMBIA F e b r u a r y , 1968  In  presenting  for  thesis  an a d v a n c e d d e g r e e  that  the  Library  Study.  I  thesis  for  Department  or  this  shall  further  freely  of  British  available  permission for  of  for  the  Columbia,  I  reference  and  extensive  copying of  understood that  b y n i:-:.  of  representatives.  this  of  thesis  February  for  permission.  Zoology  26  ,  1968  Columbia  It  is  financial  gain  the  requirements  or  The U n i v e r s i t y o f B r i t i s h V a n c o u v e r 8, C a n a d a Date  University  it  that  fulfilment  by  my w r i t t e n  Department  the  make  agree  partial  s c h o l a r l y p u r p o s e s may be g r a n t e d  publication  without  at  in  Head o f  shall  not  agree  this  my  be  copying  allowed  i ABSTRACT The l a t e s p r i n g and slimmer d i e t o f b l u e grouse on l o w l a n d b r e e d i n g ranges on Vancouver  I s l a n d was d e t e r m i n e d b y e x a m i n a t i o n  o f t h e c o n t e n t s o f 875 c r o p s t a k e n from b i r d s c o l l e c t e d on 3 s t u d y a r e a s i n t h e y e a r s 1950 t h r o u g h 1952 and 1957 through 1966. The s p r i n g and e a r l y summer d i e t o f males was m o s t l y c o n i f e r n e e d l e s , w h i l e a d u l t females a t e m a i n l y l e a f m a t e r i a l and f l o w e r s d u r i n g t h e same p e r i o d .  The f o o d o f c h i c k s was  m a i n l y i n v e r t e b r a t e s u n t i l t h e b i r d s r e a c h e d t h e age o f a p p r o x i m a t e l y t h r e e weeks, a t w h i c h time p l a n t m a t e r i a l the g r e a t e r p o r t i o n o f t h e d i e t .  formed  I n l a t e summer t h e d i e t o f  b o t h a d u l t and j u v e n i l e grouse was p r i m a r i l y f r u i t s and seeds o f t r a i l i n g b l a c k b e r r y , s a l a l , h u c k l e b e r r y , and o t h e r p l a n t s . S e l e c t i o n o f p l a n t f o o d s o c c u r r e d a t t h e time o f o v u l a t i o n and m o u l t .  As a r e s u l t , t h e p r o t e i n and m i n e r a l c o n t e n t o f t h e  d i e t was h i g h e s t d u r i n g p e r i o d s o f g r e a t e s t need. No a p p a r e n t d i f f e r e n c e s i n t h e s p r i n g d i e t o f females were f o u n d w h i c h c o u l d be r e l a t e d t o poor e a r l y s u r v i v a l o f c h i c k s , o r t o a d e l a y e d h a t c h i n 1962. The v a r i o u s f o o d t y p e s were e a t e n i n s i m i l a r r e l a t i v e proportions by adult  and y e a r l i n g grouse, and d i f f e r e n c e s  i n r e p r o d u c t i v e performance  o f these two age c l a s s e s c o u l d  n o t be r e l a t e d t o t h e d i e t o f t h e g r o u s e . The a l t i t u d i n a l m i g r a t i o n o f b l u e grouse i n l a t e summer and autumn does n o t appear t o be r e l a t e d t o t h e a v a i l a b i l i t y o r c o n d i t i o n o f t h e f o o d s u p p l y a t t h e time o f d e p a r t u r e o f t h e b i r d s .  ii TABLE OF CONTENTS' Page ABSTRACT  i  TABLE OF CONTENTS L I S T OF TABLES  i  i  i  i  i  L I S T OF FIGURES  i v  ACKNOWLEDGMENTS  v  INTRODUCTION  1  MATERIALS AND METHODS  4  RESULTS  8  Use  o f food types  s  8  by  a d u l t malos.  8  by  a d u l t females  8  by  chicks  Main foods s  11 13  needles  15  leaves  17  flowers  20  fruits  22  animal  23  grit  25  D i u r n a l rhythm o f feeding DISCUSSION  26 32  A v a i l a b i l i t y and s e l e c t i o n o f foods  35  Nutritional basis of selection  41  I n f l u e n c e o f d i e t upon r e p r o d u c t i o n  47  Autumn m i g r a t i o n  53  SUMMARY  55  LITERATURE CITED  57  iii LIST OF TABLES Table 1 2  Page Number o f c r o p s used i n t h i s s t u d y , by month o f c o l l e c t i o n  5  Main k i n d s o f foods i n t h e summer d i e t o f 3olue g r o u s e , 1957 t h r o u g h 1966  14  Amount o f f r u i t s i n t h e d i e t o f a d u l t and j u v e n i l e g r o u s e , by average o f weekly p e r c e n t a g e s o f w e i g h t and frequency o f occurrence  34  Comparison o f t h e p e r c e n t a g e f r e q u e n c y o f o c c u r r e n c e o f major f o o d p l a n t s on t h e summer range and i n t h e d i e t o f g r o u s e , d u r i n g August  37  Comparison o f t h e p e r c e n t f r e q u e n c y o f o c c u r r e n c e o f major i n v e r t e b r a t e groups on t h e summer range and t h e i r use b y grouse c h i c k s , June and J u l y , 1957 t h r o u g h 1966  39  Comparison o f major f o o d i t e m s i n t h e e a r l y September d i e t o f a d u l t females and j u v e n i l e s  40  7  N u t r i e n t c o n t e n t o f major foods o f Vancouver I s l a n d b l u e grouse  42  8  Food o f a d u l t and y e a r l i n g g r o u s e , A p r i l and May, 1957 t h r o u g h 1966, by p e r c e n t a g e d r y 'height  45  Comparison o f use o f f o o d t y p e s i n t h e e a r l y summer d i e t o f females during year o f poorest c h i c k s u r v i v a l (1962) t o t h e 10 y e a r average v a l u e s f o r t h e d i e t o f f e m a l e s , as a p e r c e n t a g e d r y w e i g h t and f r e q u e n c y o f o c c u r r e n c e  49  3  4  5  6  9  iv L I S T OF FIGURES Figure 1  2  3  4  5  6  7  Page D i e t o f a d u l t males, March A u g u s t , 1957 t h r o u g h 1966  through 9  D i e t of adult females, A p r i l through S e p t e m b e r , 1957 t h r o u g h 1966  10  D i e t o f c h i c k s , June t h r o u g h S e p t e m b e r , 1957 t h r o u g h 1966  12  Amount o f a n i m a l m a t e r i a l i n t h e diet of chicks  13  Needles i n t h e d i e t o f a d u l t males ( a ) , and a d u l t f e m a l e s ( b ) , b y a r e a o f collection  16  Seasonal foods by two week 19, o v e r  t r e n d s i n t h e use o f major a d u l t male b l u e grouse, b y i n t e r v a l s , M a r c h 19 t o A u g u s t a 10 y e a r p e r i o d (1957-1966)  18  Seasonal foods by two week 16, o v e r  t r e n d s i n t h e use o f major a d u l t female b l u e grouse, by i n t e r v a l s , A p r i l 2 t o September a 10 y e a r p e r i o d (1957-1966)  19  8  Seasonal t r e n d s i n t h e use o f major foods b y b l u e g r o u s e c h i c k s , b y two week i n t e r v a l s , J u n e 11 t o S e p t e m b e r 16, o v e r a 10 y e a r p e r i o d (1957-1966) 21  9  Weight o f crop c o n t e n t s o f a d u l t by hour  10  11  males, 23  Weight o f crop concents o f a d u l t f e m a l e s , b y hour  29  Weight o f crop c o n t e n t s o f c h i c k s , by hour  30  V  ACKNOWLEDGMENTS I am g r a t e f u l t o D r . J . F . B e n d e l l provided  f i n a n c i a l support,  data from h i s f i l e s ,  who s u p e r v i s e d  gave f r e e a c c e s s  express  t o unpublished  a n d o f f e r e d many h e l p f u l  during the preparation o f the manuscript.  t h e work,  suggestions  I also wish t o  my s i n c e r e a p p r e c i a t i o n t o D r . F . G . C o o c h , Dean I.McT.  Cowan, D r . H . D . F i s h e r , Dr.W.S.Hoar a n d D r . J . M . T a y l o r f o r t h e i r constructive c r i t i c i s m of the thesis. S p e c i a l t h a n k s a r e e x t e n d e d t o D r . F . C . Z w i c k e l who generously reference advice  provided a d d i t i o n a l data,  permitted use o f h i s  c o l l e c t i o n o f p l a n t m a t e r i a l , and o f f e r e d v a l u a b l e  during the course  o f the study.  I g r a t e f u l l y a c k n o w l e d g e t h e a s s i s t a n c e o f my f e l l o w students  D . G . K i n g a n d A.N.Lance  allowed access theses,  during t h i s study.  Both  t o t h e i r data during the preparation o f t h e i r  e n g a g e d i n numerous h e l p f u l d i s c u s s i o n s , a n d a i d e d  in the identification of plant  foods.  A number o f p e o p l e p r o v i d e d a s s i s t a n c e i n t h e i d e n t i f i c a t i o n of food  items.  I t h a n k a l l who h e l p e d  e s p e c i a l l y Dr.K.Graham, R.T.Kuramoto,  Dr.V.J.Krajina,  J . D . L a m b e r t , W.D.Pearson,  me i n t h i s way, Dr.G.G.E.Scudder, J.E.Simpson and  L.K.Wade. Much h e l p , a d v i c e , a n d e n c o u r a g e m e n t w e r e p r o v i d e d b y K . G . G . B a r r e t t , S . B o r d e n , K.W.Reid, and  I wish  S.G.Sealy, and B.B.Virgo,  t o acknowledge t h e i r a s s i s t a n c e and t h a t o f a l l  o t h e r s who a i d e d i n t h e p r e p a r a t i o n o f t h i s  thesis.  1  INTRODUCTION  The  o b j e c t i v e s o f t h i s s t u d y are t o add  o f the l a t e s p r i n g and Dendraqapus obscurus and  to determine  dynamics o f The 1942  summer f o o d h a b i t s o f b l u e  fuliginosus  grouse,  ( R i d g w a y ) on V a n c o u v e r  t h e i r r e l e v a n c e t o the b i o l o g y and  Island,  population  grouse.  b l u e grouse  through  co-workers  t o w h a t i s known  1944  from  h a s b e e n s t u d i e d on V a n c o u v e r I s l a n d  by Fowle  1950  from  (1960) a n d b y B e n d e l l a n d h i s  through  1953  and  from  1957  to the  present.  D u r i n g t h i s p e r i o d t h e r e have been i m p o r t a n t changes i n the e c o l o g y o f the r e g i o n under s t u d y and marked changes i n the p o p u l a t i o n s of b l u e grouse T h i s s t u d y was grouse  ( Z w i c k e l and  undertaken  Bendell,  to determine  1967).  the food h a b i t s o f  on t h e d i f f e r e n t s t u d y a r e a s , t o r e l a t e t h e s e t o  g e n e r a l ecology of the b i r d s ,  and  the  t o , e x a m i n e them f o r p o s s i b l e  c o r r e l a t i o n w i t h known c h a n g e s i n t h e d e n s i t y a n d r e p r o d u c t i v e success of the p o p u l a t i o n s . examination  Food h a b i t s were s t u d i e d by  of crop contents.  Other  d a t a on t h e b e h a v i o u r  p o p u l a t i o n e c o l o g y of the p o p u l a t i o n s of b l u e grouse  and  used i n  t h i s s t u d y a r e m o s t l y f r o m B e n d e l l (1954, 1955a a n d b ) , Z w i c k e l (1965), B e n d e l l and E l l i o t t (1967).  The  (1966, 1967)  and  Z w i c k e l and  Bendell  data o b t a i n e d from a n a l y s i s of crops p e r m i t t e d a  r e l a t i v e l y i n t e n s i v e s t u d y o f summer f o o d h a b i t s a n d a of food h a b i t s between grouse  from d i f f e r e n t p o p u l a t i o n s .  c r o p s were c o l l e c t e d i n the y e a r s f r o m Lower Quinsam Lake and  comparison  543  1957  through  1966;  from M i d d l e Quinsam  118 Lake.  Most  came  2 A d d i t i o n a l s a m p l e s w e r e t h o s e o f 14S b i r d s f r o m L o w e r Q u i n s a m L a k e f r o m 1950 t h r o u g h 1 9 5 2 , a n d 66 f r o m Comox B u r n i n t h e y e a r s 1962  t h r o u g h 1966. The m i g r a t o r y b e h a v i o u r o f b l u e g r o u s e o n V a n c o u v e r  limits of  t h e i r p r e s e n c e o n t h e summer b r e e d i n g r a n g e s  a p p r o x i m a t e l y f o u r months f o r m a l e s ,  and t h r e e t o f o u r months f o r c h i c k s .  Island  to a period  s i x months f o r f e m a l e s ,  During the remainder o f the  year, they i n h a b i t the c o n i f e r f o r e s t s of the surrounding mountains  (Hoffman,  1956; B e n d e l l a n d E l l i o t t ,  1967).  a d e q u a c y o f t h e i r f o o d d u r i n g t h e w i n t e r p e r i o d may the performance season  o f the b i r d s d u r i n g the subsequent  The  influence breeding  ( K o s k i m i e s , 1955; Boag, 1963; J e n k i n s e t a l , ,  1967), b u t  t h i s was o u t s i d e t h e l i m i t s o f t h e p r e s e n t s t u d y . The 1950  p o p u l a t i o n o f b l u e g r o u s e a t Lower Quinsam Lake  t h r o u g h 1952 was e x t r e m e l y d e n s e ,  1954).  a n d was s t a b l e  from  (Bendell,  By 1957, s t r u c t u r a l c h a n g e s i n t h e h a b i t a t h a d o c c u r r e d  and t h e p o p u l a t i o n o f grouse h a d g r e a t l y d e c r e a s e d Bendell and E l l i o t t ,  1967).  ( Z w i c k e l , 1965;  The p o p u l a t i o n s a t M i d d l e  Quinsam  L a k e a n d Comox B u r n w e r e r e l a t i v e l y s t a b l e when s t u d i e d ( Z w i c k e l and B e n d e l l ,  1967), w i t h d e n s i t i e s c o n s i d e r a b l y lower than  f o u n d a t Lower Quinsam Lake i n t h e e a r l y 1950's.  that  T h e r e w e r e no  a p p a r e n t d i f f e r e n c e s i n a n n u a l m o r t a l i t y r a t e s o f a d u l t s among the p o p u l a t i o n s s t u d i e d  (Zwickel and B e n d e l l ,  1967).  No  s i g n i f i c a n t d i f f e r e n c e s i n b r o o d s i z e s were found between a r e a s , b u t such d i f f e r e n c e s d i d o c c u r between years on t h e s t u d y areas (Zwickel and Bendell,  1967; and u n p u b l i s h e d d a t a ) .  3 The Vancouver  s t u d y a r e a s a r e n e a r C a m p b e l l R i v e r on t h e e a s t c o a s t o f I s l a n d , and a r e d e s c r i b e d elsewhere  B e n d e l l and E l l i o t t ,  1967;  (Bendell,  Z w i c k e l and B e n d e l l ,  h a d b e e n c l i m a x f o r e s t w h i c h was  1967).  l o g g e d and b u r n e d .  1954; A l l areas  Middle  Q u i n s a m L a k e a n d Comox B u r n w e r e i n r e l a t i v e l y e a r l y s t a g e s o f plant succession (Zwickel, were c o l l e c t e d , (Bendell,  a s was  1954).  1965)  d u r i n g t h e p e r i o d when g r o u s e  L o w e r Q u i n s a m L a k e f r o m 1950  Artificial  through  1952  r e p l a n t i n g o f c o n i f e r s a t Lower  and  M i d d l e Quinsam Lakes i n c r e a s e d the i m p o r t a n c e o f c o n i f e r s i n the p l a n t cover and h a s t e n e d p l a n t s u c c e s s i o n a l s t a g e s . 1  By 1957,  v e g e t a t i o n a t L o w e r Q u i n s a m L a k e h a d become v e r y d e n s e ,  due  l a r g e l y t o the growth o f c o n i f e r o u s t r e e s .  serai  During the  the  p e r i o d f o l l o w i n g l o g g i n g a n d b u r n i n g , t h e numbers o f b l u e g r o u s e , b l a c k - t a i l e d deer bear  ( O d o c o i l e u s hemionus c o l u m b i a n u s ) , and  (Ursus a m e r i c a n u s ) on an a r e a i n c r e a s e  1967), w h i l e mature grouse  (Bendell,  ( Z w i c k e l and  black Bendell,  f o r e s t i s u n s u i t a b l e b r e e d i n g range f o r b l u e  1954).  4  MATERIALS AND METHODS  Crops were o b t a i n e d from grouse  c o l l e c t e d throughout the  summer i n t h e c o u r s e o f r e s e a r c h o n t h e p o p u l a t i o n d y n a m i c s o f b l u e g r o u s e , a n d from t h o s e s h o t b y h u n t e r s i n autumn.  Usually,  a n e n t i r e v i s c e r a was r e m o v e d , w r a p p e d i n c h e e s e c l o t h , a n d s t o r e d i n 10 p e r c e n t f o r m a l i n u n t i l e x a m i n a t i o n .  C o n t e n t s o f some c r o p s  were a i r - d r i e d and s t o r e d i n i n d i v i d u a l e n v e l o p e s .  A l l grouse  w e r e i d e n t i f i e d a s t o age a n d s e x when t h e c r o p was removed? t h e d a t e , t i m e a n d p l a c e o f c o l l e c t i o n was n o t e d , a s was t h e b e h a v i o u r of t h e grouse a t the time o f c o l l e c t i o n .  A t o t a l o f 976 c r o p s  was c o l l e c t e d f r o m t h e summer r a n g e s a t L o w e r a n d M i d d l e Q u i n s a m L a k e s a n d Comox B u r n  ( T a b l e 1 ) . Of t h e s e , 101 w e r e e m p t y a n d  were d i s c a r d e d . The c o n t e n t s o f e a c h c r o p w e r e s e p a r a t e d i n t o i t e m s a n d identified.  Where p o s s i b l e ,  p l a n t s i n t h e c r o p s v/ere  to s p e c i e s and by p a r t eaten, and animals t o f a m i l y . a r e from Peck  identified P l a n t names  (1941) a n d P r e s t o n ( 1 9 6 1 ) , t h o s e o f i n v e r t e b r a t e s  f r o m B o r r o r a n d DeLong Unidentifiable  (1954) a n d B o r r a d a i l l e ^ t a l . ( 1 9 6 1 ) .  p l a n t m a t e r i a l and g r i t were r e c o r d e d s e p a r a t e l y .  Poods were damp-dried and t h e i r volumes d e t e r m i n e d t o t h e n e a r e s t 0.1 c c b y w a t e r  displacement i n a graduated c y l i n d e r .  l e s s t h a n 0.1 c c w e r e r e c o r d e d a s " T r a c e " .  Volumes  The d r y w e i g h t o f  e a c h f o o d i t e m i n c r o p s c o l l e c t e d f r o m 1957 t h r o u g h 1966 was also taken. dried  To d e t e r m i n e  t h i s weight,  t h e m a t e r i a l s were oven-  (80°C) t o c o n s t a n t w e i g h t , a n d w e i g h e d t o t h e n e a r e s t  milligram.  Dry-weights  a r e much more p r e c i s e t h a n v o l u m e t r i c  T a b l e 1.  Number o f c r o p s o f b l u e g r o u s e  used i n t h i s  study,  May  June  July  b y month o f c o l l e c t i o n . Month 1957  t h r o u g h 1966  Lower and M i d d l e Quinsam Lakes, a n d Comox  females  4  22  80  37  22  4  10  45  33  32  45  50  215  22  91  118  112  343  chicks  Lower Quinsam  Sept  Total  April  Burn  19 50 t h r o u g h 19 52  Lake  males*  Aug  March  169  males*  1  15  9  4  females  1  11  8  14  2  36  17  44  22  83  chicks  29  p  Grand t o t a l * m a l e s a n d f e m a l e s i n c l u d e a l l b i r d s o f a p p r o x i m a t e l y one y e a r o f age  and o l d e r , c h i c k s a r e a l l b i r d s  l e s s t h a n 4 months o l d ( b o t h  sexes)  875  6 measurements  (Watson, 1964).  the f o o d o f c h i c k s , which number o f f o o d i t e m s . of  T h i s i s i m p o r t a n t when c o n s i d e r i n g  o f t e n consume s m a l l q u a n t i t i e s o f a  D r y w e i g h t s were n o t o b t a i n e d f o r c o n t e n t s  c r o p s c o l l e c t e d f r o m 1950 t h r o u g h  c l a s s i f i e d i n t o one o f f i v e  1952.  A l l items were  food types f o r general a n a l y s i s ,  follows; c o n i f e r needles, broad-leaf material, and seeds,  and a n i m a l m a t t e r .  as  flowers, f r u i t s  Broad-leaf material included a l l  leaves except those o f c o n i f e r s . All  d a t a were r e c o r d e d on i n d i v i d u a l c r o p a n a l y s i s  The a g g r e g a t e  percentage  forms.  m e t h o d o f M a r t i n e t a l . (1946) was  in  t a b u l a t i o n o f p e r c e n t volume and p e r c e n t w e i g h t .  of  o c c u r r e n c e was a l s o d e t e r m i n e d ,  used  Frequency  a s i t o f t e n p r e s e n t s a more  a c c u r a t e measure o f what i s e a t e n t h a n v o l u m e t r i c d a t a (Gilfillan  and Bezdek,  1944).  The r e l a t i v e a b u n d a n c e o f f o o d s p e c i e s was m e a s u r e d i n t h e f i e l d t o determine  t h e r e l a t i o n s h i p b e t w e e n w h a t was  a n d w h a t was e a t e n .  available  Data on p l a n t abundance were o b t a i n e d  f r o m L o w e r Q u i n s a m L a k e i n 1952 a n d 1957, a n d f r o m Q u i n s a m L a k e i n 1960 a n d 1 9 6 6 .  Middle  The amount o f g r o u n d  covered  b y p l a n t s p e c i e s a n d t h e i r f r e q u e n c y o f o c c u r r e n c e o n t h e summer range were determined (Bendell,  from l i n e  1954; E l l i o t t ,  i n t e r c e p t s and  quadrats  1966; a n d u n p u b l i s h e d d a t a ) .  The r e l a t i v e a b u n d a n c e o f common i n v e r t e b r a t e s was d e t e r m i n e d b y two s a m p l i n g m e t h o d s .  B e t w e e n May 25 a n d J u l y  1958, i n v e r t e b r a t e s w e r e s a m p l e d a t M i d d l e Q u i n s a m L a k e . i n v e r t e b r a t e s observed w i t h i n a s t r i p o f ground  and on t h e  5,  A l l  7 v e g e t a t i o n t o a h e i g h t o f one f o o t a b o v e t h e g r o u n d w e r e collected  (Stiven,  1961).  D u r i n g 1962, i n v e r t e b r a t e s were  s a m p l e d i n l a t e J u l y a t M i d d l e Q u i n s a m L a k e a n d Comox B u r n w i t h a n i n s e c t sweep n e t a t s i t e s a t w h i c h b r o o d s o f g r o u s e had been observed.  Sweeps w e r e made c l o s e t o t h e s u r f a c e o f  t h e g r o u n d 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 100 f e e t i n e a c h o f the f o u r c a r d i n a l d i r e c t i o n s from t h e approximate c e n t e r o f the brood location  (F.C.Zwickel, personal communication).  The  f r e q u e n c y o f o c c u r r e n c e o f t h e g r o u p s o f i n v e r t e b r a t e s was c a l c u l a t e d a s a p e r c e n t a g e o f t h e t o t a l number o f s a m p l e s t a k e n .  8  RESULTS T y p e s o f f o o d e a t e n o n t h e summer r a n g e C r o p c o n t e n t s o f grouse c o l l e c t e d on a l l t h r o u g h 1966 w e r e c o m b i n e d  areas from  1957  to determine the g e n e r a l food h a b i t s  o f b l u e g r o u s e on t h e i r l o w l a n d b r e e d i n g r a n g e s on  Vancouver  Island. Adult The  males  f o o d o f males  f r o m t h e t i m e o f t h e i r a r r i v a l on  summer r a n g e t o a b o u t t h e m i d d l e o f J u n e was c o n i f e r needles  (Fig. 1).  needles to f r u i t s  T h e r e was  the  predominantly  a rapid shift i n diet  i n t h e month o f J u n e .  The amount o f  material apparently increased i n early A p r i l ,  from  leaf  and t o g e t h e r w i t h  needles formed the b u l k o f the d i e t d u r i n g the b r e e d i n g season. A f t e r June, f r u i t s  r a p i d l y became t h e m a i n f o o d a n d r e m a i n e d  f o r t h e r e s t o f t h e summer.  so  F l o w e r s were e a t e n i n g r e a t e s t  q u a n t i t y d u r i n g June, J u l y and e a r l y A u g u s t .  Animal food  was  t a k e n i n f r e q u e n t l y and i n v e r y s m a l l amounts. Adult  females  A s t r i k i n g d i f f e r e n c e between males  a n d f e m a l e s was  the  p r e f e r e n c e shown b y h e n s f o r e a r l y s p r i n g l e a v e s ( F i g . 2 ) . Leaf m a t e r i a l formed April,  May  55 p e r c e n t o f t h e d i e t o f f e m a l e s  a n d e a r l y J u n e , c o m p a r e d v / i t h 24.5  f o o d o f males  d u r i n g t h e same p e r i o d .  during  per cent of the  A gradual t r a n s i t i o n  from n e e d l e s t o o t h e r m a t e r i a l s o c c u r r e d i n the d i e t o f females from A p r i l  t o a b o u t t h e end o f June  (Fig. 2).  The amount o f  f r u i t s and seeds i n the d i e t o f the hens i n c r e a s e d  rapidly  9  FIGURE  D i e t o f a d u l t males, 1957  through  1966.  1  March through  August,  (4)  (10)  (12)  (39)  (33)  (28)  (Sample I  April  I  May  (II)  (14)  (9)  (5)  (4)  size) I  June  I  July  I  10  FIGURE  2  D i e t o f a d u l t females, A p r i l September, 1957 through  1966.  through  (7)  (3)  (20)  (20)  (18)  (13)  (14)  (13)  (Sample l  April  I  May  I  June  (19)  (30)  (3)  (55)  size) I  July  i  August  I  d u r i n g June and J u l y , their  r e p l a c e d l e a v e s , and formed the b u l k o f  food from then u n t i l  S e p t e m b e r when t h e y l e f t t h e summer  range.  Hens a p p e a r e d  t o e a t more f l o w e r s a n d f r u i t s  but l i k e  them, consumed o n l y a s m a l l amount o f a n i m a l  than  males,  material.  Chicks Blue grouse c h i c k s ,  like  the young o f most t e t r a o n i d s ,  l a r g e l y on i n v e r t e b r a t e s d u r i n g t h e i r e a r l y l i f e Zwickel  (Fig. 3).  (1965) g i v e s t h e peak o f h a t c h f o r b l u e g r o u s e  on  V a n c o u v e r I s l a n d a s o c c u r r i n g b e t w e e n June 11 a n d J u l y  1.  In t h e i r f i r s t  two w e e k s a f t e r h a t c h i n g , t h e d i e t o f  c o n t a i n e d o v e r 75 p e r c e n t a n i m a l f o o d f o o d was  t a k e n by c h i c k s i n June,  t h e c h i c k s v/ere a p p r o x i m a t e l y 20 v e g e t a t i o n made up more t h a n h a l f chicks ate v i r t u a l l y  d a y s o f age  chicks  Some p l a n t  ( F i g . 3) o r when (Fig. 4),  their diet.  By l a t e  a l a r g e r amount o f  T h i s agrees w i t h the f i n d i n g s o f Beer  leaf  (1943).  O n l y s m a l l a m o u n t s o f c o n i f e r n e e d l e s w e r e consumed b y and  July,  t h e same k i n d s a n d r e l a t i v e amounts o f  f o o d as t h e a d u l t s , w i t h perhaps material.  (Fig. 4).  and by J u l y  feed  these were e a t e n d u r i n g the l a t e Main f o o d s e a t e n b y a d u l t s and  chicks,  summer. young  The m a i n k i n d s o f f o o d consumed b y g r o u s e o n t h e snmmer range 80  a r e shown i n T a b l e 2.  T h e s e s p e c i e s made up more t h a n  per cent o f the food eaten by a l l  grouse.  The  o f t h e f o o d came f r o m a minimum o f 38 s p e c i e s o f U n i d e n t i f i a b l e m a t e r i a l c o n s t i t u t e d l e s s t h a n 1.5 t h e t o t a l c r o p c o n t e n t s , a n d was  remainder  plants. per cent of  l a r g e l y l e a f fragments.  Thus  FIGURE  Diet of chicks,  3  June t h r o u g h  1957 t h r o u g h 1 9 6 6 .  Septembe  100  80 -  xz CT  60  Q)  5 >»  O 0  S  40 -  20 -  i i r i r (6) (13) (12) (17) (25) (29) (24) (26) (44) (19) (60) (33) (26) T  (3)  (Sample June  i  July  size) I  August  i  FIGURE  4  Amount o f animal m a t e r i a l i n the d i e t of c h i c k s .  100 - i  •  %  frequency  Q  %  dry  of  occurrence  weight  80 ~  0)  o E  60  -  o E  <  40  0*>  20 -  I  T I -3  4-6  7-9  10-12  13-15  16-18  19-21  22-24  25-27  28-30  4 31-33  34-36  16  10  37-39 40-42  J5  1  43-45  46-48  49-51  Age in days 0  5  6  7  II  0  Sample  14  size  10  14  8  17  14  14  grouse,  of foods i n  Main k i n d s  T a b l e 2. 1957  through  1966  *  females (215) it -•- -  %rtt.  of blue  .  males (169)**  Food  t h e summer d i e t  % f . O . " '  %wt.  %f.o.  chicks (343) °/cWt.  %f.o.  -  44.0  55  17.0  23  -  Salix leaves  7.1  23  11.3  29  1.0  7  Pteridium fronds  6.6  19  6.5  28  8.0  27  Gaultheria leaves  1.3  9  2.6  13  -  -  Trifolium leaves  0.5  6  2.6  10  3.0  8  Hvpochaeris flowers  5.3  25  8.5  41  18.5  44  Rubus fruits  11.6  11  10.7  24  15.5  29  Gaultheria fruits  10.0  22  13.3  31  15.5  36  Vaccinium fruits  0.3  8  5.3  17  5.0  24  Animal  0.2  7  0.5  13  22.5  59  Pseudotsuqa needles  matter  * c a l c u l a t e d as the averages ** s a m p l e ***  size  frequency of occurrence  from weekly  values  15 a s m a l l number o f f o o d s p e c i e s c a n b e c o n s i d e r e d t h e s t a p l e o f t h e summer d i e t o f b l u e g r o u s e o n V a n c o u v e r s i m i l a r t o t h e f i n d i n g s o f Korschgen r u f f e d grouse  Island.  This i s  (1966) o n t h e f o o d o f  (Bonasa u m b e l l u s ) .  Conifej: needles Needles o f Douglas  f i r (Pseudotsu^a m e n z i e s i i )  a p p r o x i m a t e l y 80 p e r c e n t e a t e n b y a d u l t males remainder was; S i t k a spruce  (by w e i g h t ) o f t h e c o n i f e r  and f e r a l e s .  needles o f Western hemlock  (Picea s i t c h e n s i s ) , and pine  (Tsuga h e t e r o p h y 1 1 a ) , (Pinus c o n t o r t a and fir  and pine.  a u t h o r s have r e p o r t e d t h e importance o f Douglas f i r  hemlock  material  i n order o f importance, the  _P. m o n t i c o l a ) , a n d a f e w s e e d s o f D o u g l a s  b l u e grouse  comprised  ( B e e r , 1943? S t e w a r t , 1 9 4 4 ) .  Other  as food o f  Needles o f mountain  (Tsuga m e r t e n s i a n a ) were t h e most i m p o r t a n t f o o d o f  grouse on the w i n t e r range on Vancouver preparation).  Island  (King, i n  These b i r d s p r o b a b l y w e r e f r o m t h e summer r a n g e s  a t Lower a n d M i d d l e Quinsam L a k e s , so i n t h e s p r i n g which had descended d i e t from hemlock The  grouse  t o t h e summer r a n g e m u s t h a v e c h a n g e d  needles t o those o f Douglas  fir.  importance o f d i f f e r e n t species o f c o n i f e r s i n the  d i e t o f b l u e g r o u s e -p.r.ies o v e r t h e r a n g e o f t h e g r o u s e 1927;  B e e r , 1 9 4 3 ; S t e w a r t , 1944; H o f f m a n ,  1956; B o a g ,  Blue grouse can a p p a r e n t l y use needles o f Pseudotsuga, Picea,  P i n u s , A b i e s , a n d Lajri_x a s s t a p l e s i n t h e i r  The  their  (Eailey,  1963). Tsuga,  diet.  q u a n t i t y o f needles eaten b y grouse from J u l y t o  S e p t e m b e r was s m a l l  (Fig. 5).  In adults,  the frequency of  FIGURE  Needles and  in  adult  the  diet  females  collection.  5  of  (b),  adult by  males  area  of  100 fs  a)  /  Adult  males  75 H S c  *  T3  50 H  a» a> c  25 H  April  100 -,  Middle Lower Lower  May  June  July  August  Quinsam Lake (by weight) Quinsam L a k e 1957 -1961 (by weight) Quinsam L a k e 1 9 5 0 - 1952 ( b y volume)  b)  Adult  females  75 T3  50  H  a> <D  25 H  /.  April  May  \  June  July  August  17 occurrence of needles t o 35 p e r c e n t  ( f o r two week p e r i o d s ) r a n g e d f r o m  ( F i g s . 6 and  7) f r o m J u l y u n t i l  15  altitudinal  m i g r a t i o n o c c u r r e d , but they c o n s t i t u t e d l e s s than three per cent  (by w e i g h t ) o f t h e t o t a l f o o d d u r i n g t h a t t i m e .  Thus,  n e e d l e s w e r e t a k e n i n f r e q u e n t l y a n d i n s m a l l amounts d u r i n g t h e l a t t e r p a r t o f t h e summer. A r e t u r n t o the w i n t e r d i e t has been r e p o r t e d by v a r i o u s authors to occur a t d i f f e r e n t dates.  No  indication of a  s i g n i f i c a n t i n c r e a s e i n u t i l i z a t i o n o f n e e d l e s was g r o u s e c o l l e c t e d on summer r a n g e  found i n  as l a t e as September  17.  L e s s t h a n t h r e e p e r c e n t o f t h e t o t a l amount o f f o o d e a t e n hens o r c h i c k s d u r i n g the f i r s t h a l f of.September needles. time.  No a d u l t m a l e s r e m a i n e d The  was  by  conifer  on t h e summer r a n g e a t  t r a n s i t i o n t o w i n t e r d i e t , a t l e a s t f o r hens  this and  c h i c k s , m u s t t h e r e f o r e o c c u r some t i m e a f t e r m i d - S e p t e m b e r  on  Vancouver  This  I s l a n d , when t h e b i r d s a r e o n t h e w i n t e r r a n g e .  agrees w i t h the f i n d i n g s o f Beer is  (1943) a n d  Stewart  (1944).  It  l a t e r t h a n t h e t i m e o f c h a n g e f r o m summer t o w i n t e r d i e t  r e p o r t e d b y M a r s h a l l (1946) a n d  Standing  (1960).  Le_af_naj;erj.ajL The  r e l a t i v e use o f e a c h o f t h e k i n d s o f l e a v e s was  similar  i n b o t h s e x e s a l t h o u g h h e n s a t e more l e a v e s t h a n d i d c o c k s .  The  l e a v e s o f w i l l o w ( S a l i x s p p . ) v/ere e a t e n m o s t f r e q u e n t l y a n d i n t h e l a r g e s t amounts b y a d u l t s f r o m A p r i l  t o e a r l y June, and i n  a r e l a t i v e l y c o n s t a n t b u t l e s s e r amount f o r t h e r e m a i n d e r o f summer ( F i g s . 6 a n d  7).  Bracken fronds (Pteridium aquilinum  the  18  FIGURE 6  Seasonal trends i n the use o f major  foods  b y a d u l t m a l e b l u e g r o u s e , b y two week i n t e r v a l s , M a r c h 19 t o A u g u s t 1 9 , o v e r a 10 y e a r p e r i o d  (1957-1966)„  Food item Pseudotsuga  needles  Salix  leaves  Pteridium  fronds  Gaultheria  leaves  J3  «•  Vaccinium  leaves  •fi  —n  Trifolium  leaves  Hypochaeris  flowers  Rubus  fruits  Gaultheria  fruits  Vaccinium  fruits  Animal  material  _1  J1 J l - n  -BO  - n  JH  JBD  Jl Jl  -co.  •n  J l  ED  an  JQ_  •n  -D_  — < — •  BO  Jl  Bl  -O  Eh  Ji  Jl  Jl  Jl  J  ll  JL April  May  % of total weight  June  •  Jl  July  % frequency  August  of  occurrence  19  FIGURE  7  S e a s o n a l t r e n d s i n t h e use o f major  foods  b y a d u l t f e m a l e b l u e g r o u s e , b y two week i n t e r v a l s , A p r i l 2 t o S e p t e m b e r 16, o v e r a 10 y e a r p e r i o d  (1957-1966).  Food  item  Pseudotsuga  needles  Salix  leaves  Pteridium  fronds  Gaultheria  leaves  Vaccinium  leaves  Trifolium  leaves  Hypochaeris  flowers  Rubus  fruits  Gaultheria Vaccinium Animal  -n .-a  B D .  mil  _-a  -Tl  mil.  JD  m  _ J 1 _BD  Jl  -n  _n  _n  -D_  _n  n  _n  -Jl  fruits  -n  Jl Jl  fruits  _-a  material  April  Q  May  % of total weight  •rftl.  June  •  J  —  j i  •a  JD  .a  BO  J X l  1 - 1  —  1 - 1  Jl Jl n JI  sfi J]  j] jfl  tsTl  -H.  July  August  % frequency of  occurrence  20 were eaten  i n g r e a t e s t amounts d u r i n g J u n e when u s e o f w i l l o w  l e a v e s was d e c r e a s i n g , (Figs. 6 and 7 ) .  Small  shallon), huckleberry occurred and  and a g a i n i n September b y hens and c h i c k s amounts o f t h e l e a v e s o f s a l a l ( G a u l t h e r i r .  (Vaccinium  spp.) and c l o v e r  ( T r i f o l i u m sp.)  f r e q u e n t l y i n t h e e a r l y summer d i e t o f a d u l t s  7).  Chicks  or huckleberry  consumed v e r y  (Fig. 8).  little  (Figs.  l r a f m a t e r i a l from  6  salal  The m a i n f o o d o f a d u l t g r o u s e w h i c h  r e m a i n e d o n t h e w i n t e r r a n g e f r o m J u n e t o O c t o b e r was f o l i a g e o f Vaccinium  (King, i n p r e p a r a t i o n ) .  Leaves o f d i f f e r e n t s p e c i e s were e a t e n  i n the order o f t h e i r  appearance i n the s p r i n g , s h o r t l y a f t e r budding. apparent from the c o l o u r , s i z e , the c r o p s .  and t e x t u r e o f the leaves i n  Thus w i l l o w s w e r e a l m o s t f u l l y  was i n t h e " f i d d l e - h e a d " s t a g e  T h i s was  l e a v e d when b r a c k e n  and began t o appear i n c r o p s .  Leaves from t h e f o l l o w i n g p l a n t s were e a t e n i n f r e q u e n t l y and  i n small quantities:  .Rosa sp„, A l n u s  Rubus s p . , M a h o n i a n e r v o s a ,  rubra, Equisetum sp.,  Viccia  Ji J^Lm g r o e n l a n d i c u m , C r e p i s c a p i l l a r i s . e  _L3^oj3odiuni  sp.,  sp., Plantago sp.,  Cerastium  sp.,  L a c t u c a s>->,,  S e l a q i n e l l a s p . , g r a s s , and fronds o f f i v e  species o f ferns. lichens  Ribes sp.,  One a d u l t f e m a l e h a d e a t e n  fragments o f  (C_lajtonia. sp.) „  Flpwe_rs_ The  f l o w e r s o f a number o f p l a n t s c o m p r i s e d a m a j o r  o f t h e summer d i e t .  H y p o c h a e r i s r a d i c a t a f l o w e r s were  f r e q u e n t l y , a n d more f r e q u e n t l y b y a d u l t f e m a l e s frequency  o f occurrence)  than by a d u l t males  part eaten  (45 p e r c e n t  (20 p e r c e n t  f.o.).  FIGURE  8  Seasonal t r e n d s i n t h e use o f major foods b y b l u e grouse week i n t e r v a l s ,  c h i c k s , b y two  J u n e 11 t o S e p t e m b e r  16, o v e r a 10 y e a r p e r i o d  (1957-1966).  Food  item  Salix  leaves  Pteridium  fronds  Trifolium  leaves  Hypochaeris  flowers  Rubus  fruits  Gaultheria  fruits  Vaccinium  fruits  - C l  Efl  Bl «fi  -J->  n  « •  E .  Jl Jl Jl Jl  ril Jl Jl  •n  n  eTI  B  Jl  JI  Jl  Coleoptera  Jl Jl Jl  Hymenoptera Homoptera  and Hemiptera  Other animal groups  i  ^  %  of  total  p  weight  %  —H=-  • July  frequency  ,n  m August  of  -n, -  occurence  22  T h i s f l o w e r made up from t h r e e t o s i x p e r c e n t (dry w e i g h t ) o f the f o o d o f b o t h sexes o v e r t h e summer ( F i g s . 6 and 7 ) . I t o c c u r r e d i n 50 p e r c e n t o f t h e c r o p s o f c h i c k s examined, and c o n s t i t u t e d 16 p e r c e n t (dry w e i g h t ) o f t h e i r summer f o o d (Fig.  8).  S t e w a r t (1944) and Fowle (1960) a l s o f o u n d f l o w e r s  of H y p o c h a e r i s t o be a prominent i t e m i ~ t h e summer d i e t o f blue grouse. S e v e r a l s p e c i e s o f f l o w e r s were e a t e n l e s s f r e q u e n t l y and i n s m a l l amounts.  These i n c l u d e d those o f A c h l y s  triphylla,  Mahonia n e r v o s a . H y p o c h a e r i s g l a b r a , Taraxacum sp., A g o s e r i s s p . , Mimulus sp., V i o l a sp., and Campanula s p .  The f l o w e r s o f  Rubus u r s i n u s and G a u l t h e r i a s h a l l o n v/ere a l s o e a t e n b u t have been i n c l u d e d i n t h e c a t e g o r y o f f r u i t s and seeds because t h e i r f r u i t s h a d begun t o d e v e l o p when t h e y v/ere e a t e n . Fruits The major i t e m s i n t h e l a t e summer d i e t o f a l l grouse were a v a r i e t y o f f r u i t s and s e e d s .  From e a r l y J u l y u n t i l t h e  b i r d s l e f t t h e summer range, a p p r o x i m a t e l y 50 t o 90 p e r c e n t of t h e f o o d e a t e n b y a l l grouse was f r u i t s and seeds 7 and 8 ) .  S i m i l a r f i n d i n g s were r e p o r t e d b y Beer  S t e w a r t (1944), M a r s h a l l (1946) and Fowle  ( F i g s . 6, (1943),  (1960).  The main s p e c i e s o f f r u i t s e a t e n were t r a i l i n g b l a c k b e r r y (Rubus u r s i n u s ) , s a l a l , and h u c k l e b e r r y .  A l l grouse consumed  the f r u i t s o f t h e d i f f e r e n t s p e c i e s i n about t h e same p r o p o r t i o n and a t t h e same t i m e .  B e r r i e s o f t r a i l i n g b l a c k b e r r y v/ere  t a k e n most f r e q u e n t l y and i n t h e g r e a t e s t q u a n t i t i e s d u r i n g  l a t e J u l y a n d e a r l y A u g u s t , w h i l e peak u s e o f h u c k l e b e r r i e s was slightly  later  ( F i g s . 6, 7 a n d 8 ) .  The f r u i t o f s a l a l was e a t e n  i n the l a r g e s t q u a n t i t i e s d u r i n g l a t e August  and September  a l t h o u g h the f l o w e r s and d e v e l o p i n g f r u i t were eaten from e a r l y June u n t i l  the grouse  frequently  l e f t t h e summer r a n g e  (Figs.  6,  7 a n d 8 ) . The peak u s e o f t h e s e f r u i t s o c c u r r e d i n t h e o r d e r i n which  they ripened. Other f r u i t s  and seeds which o c c u r r e d l e s s f r e q u e n t l y were  t h o s e o f M a h o n i a n e r v o s a , F r a g a r i a sp„, P s e u d o t s u g a Pinus sp., Juncus  sp., Carex  menziesii,  sp., Plantago s p . , and A c h l y s  triphylla. Animal  matter  A d u l t grouse on t h e s t u d y areas were almost w h o l l y vegetarian.  A n i m a l f o o d o c c u r r e d i n 5 t o 10 p e r c e n t o f m a l e s  a n d f e m a l e s a n d c o n s t i t u t e d l e s s t h a n 0.4 p e r c e n t of  t h e i r f o o d d u r i n g t h e summer.  (dry weight)  Animal m a t e r i a l reported i n  t h e summer d i e t o f a d u l t b l u e g r o u s e v a r i e s f r o m 26.9 p e r c e n t (Mussehl and F i n l e y , 1943;  Fowle,  1960).  1967) t o 2 t o 3 p e r c e n t Invertebrates, f i r s t  (by volume)  t a k e n i n e a r l y May,  w e r e e a t e n i n s m a l l numbers t h r o u g h o u t t h e summer. e a t e n were Hymenoptera, Hemiptera, L e p i d o p t e r a and O r t h o p t e r a . Arachnida  (spiders),  (Beer,  Insects  Coleoptera, Diptera,  Other i n v e r t e b r a t e s t a k e n were  Isopoda, Diplopoda and Gastropoda.  w e r e e a t e n m o s t f r e q u e n t l y , a n d v/ere f o u n d i n 60 p e r c e n t 30) o f t h o s e a d u l t s w h i c h h a d e a t e n a n i m a l s .  Hemipterans  consumed b y 14 p e r c e n t o f t h e s e b i r d s , a n d no o t h e r  Ants (18 o f were  invertebrate  24 was e a t e n b y more t h a n two (7 p e r c e n t ) o f them. In i n t e r i o r subspecies o f b l u e grouse, grasshoppers and o t h e r i n v e r t e b r a t e s comprise a d u l t s i n t h e l a t e summer 1960).  a large portion of the d i e t of  ( B e e r , 1 9 4 3 ; S t e w a r t , 1944; S t a n d i n g ,  These r e s u l t s a r e i n c o n t r a s t t o t h e f i n d i n g s o f t h i s  study. C h i c k s a t e members o f a l l o r d e r s t a k e n b y a d u l t s a n d s i x a d d i t i o n a l ones;  Homoptera, I s o p t e r a , Odonata,  Psocoptera and Thysanoptera. all  Trichoptera,  With t h e e x c e p t i o n o f homopterans,  these were e a t e n i n f r e q u e n t l y .  consumed i n June were Hymenoptera  The i n s e c t s m o s t f r e q u e n t l y (mainly Formicidae)  which  o c c u r r e d i n 75 p e r c e n t o f t h e c h i c k s e x a m i n e d , H e m i p t e r a a n d Homoptera  (75 p e r c e n t ) a n d C o l e o p t e r a (40 p e r c e n t ) .  most i m p o r t a n t homopterans were C e r c o p i d a e . of these i n v e r t e b r a t e s remained August,  The r e l a t i v e u s e  t h e same t h r o u g h o u t J u l y a n d  and t h e y were t a k e n f r e q u e n t l y  percentage o f the d i e t which  The  ( F i g . 4) a l t h o u g h t h e  they formed  declined.  Chicks  c o n t i n u e d t o f e e d more f r e q u e n t l y o n a n i m a l m a t e r i a l t h a n d i d a d u l t s t h r o u g h t h e l a t t e r p a r t o f t h e summer, a s i s t h e c a s e i n o t h e r s p e c i e s o f grouse  (Helminen and Viramo,  a n d G r i n e r (1933) a n d H e l m i n e n decrease  and Viramo  1962).  Rasmussen  (1962) a t t r i b u t e t h e  i n the frequency o f occurrence o f animal food i nthe  l a t e summer i n t h e d i e t o f j u v e n i l e g r o u s e a v a i l a b i l i t y o f invertebrates a t that time.  t o the decreasing T h i s may be s o  f o r b l u e grouse, f o r where i n v e r t e b r a t e s a r e abundant, as i n dry forest habitats,  t h e h e n s a n d c h i c k s e a t l a r g e amounts o f  25 insects, autumn  p a r t i c u l a r l y g r a s s h o p p e r s , d u r i n g l a t e summer a n d  ( B e e r , 1943? S t e w a r t , 1944? S t a n d i n g ,  1960).  Grit M i n e r a l m a t e r i a l i s t a k e n b y grouse and i s thought t o be of  importance  f o r g r i n d i n g f o o d and as a source o f m i n e r a l s  (Beer and Tidyman, 1942).  S m a l l q u a n t i t i e s o f g r i t were  found  i n 13.4 p e r c e n t  (110 o f 820) o f a l l c r o p s c o l l e c t e d b e t w e e n  1957  The r a n g e  and 1966.  i n weight o f g r i t found i n crops  was f r o m 1.40 grams t a k e n f r o m a c h i c k s h o t o n A u g u s t  31 t o  0.003 grams f r o m a n a d u l t f e m a l e c o l l e c t e d i n m i d - J u n e . was no c o n s i s t e n t p a t t e r n among a d u l t m a l e s , j u v e n i l e s i n the consumption  There  females and  o f g r i t d u r i n g the s p r i n g and  e a r l y summer. The  i n g e s t i o n o f g r i t appears  t o have i n c r e a s e d i n August.  T h i s i s i n c o n t r a s t t o t h e f i n d i n g s o f Beer a n d Tidyman and Powle  (1960) who r e p o r t e d l a r g e amounts o f h a r d  (1942)  seeds  r e p l a c i n g g r i t i n t h e g i z z a r d s o f some b l u e g r o u s e  taken  J u l y u n t i l e a r l y September.  (i960)  Semenov-Tyan-Shansky  from  states that the t o t a l weight of g r i t i n the gizzards of E u r o p e a n t e t r a o n i d s i s g r e a t e s t p r i o r t o t h e o n s e t o f x-zinter. The  a v e r a g e w e i g h t o f g r i t i n c r o p s showed a n i n c r e a s e f r o m  0.073 grams f r o m A p r i l  t o J u l y t o 0,133 grams i n A u g u s t a n d  S e p t e m b e r , b u t was n o t s t a t i s t i c a l l y s i g n i f i c a n t 116 d f ) .  ( t ~ 1.310,  The f r e q u e n c y o f o c c u r r e n c e o f g r i t i n c r o p s  c o l l e c t e d p r i o r t o J u l y 30 was 8.4 p e r c e n t .  I n August and  S e p t e m b e r t h e i n c i d e n c e o f g r i t i n c r e a s e d t o 19.7 p e r c e n t .  This difference i s s t a t i s t i c a l l y s i g n i f i c a n t the 5 per c e n t l e v e l .  Fowle  (Chi  = 4.49)  at  (1960) f o u n d g r i t i n t h e c r o p s o f  11 p e r c e n t o f 38 g r o u s e c o l l e c t e d f r o m J u n e t o O c t o b e r , w h i l e Boag  (1963) f o u n d g r i t  i n t h e c r o p s o f 22.5  per cent of  g r o u s e he e x a m i n e d w h i c h w e r e t a k e n d u r i n g S e p t e m b e r  the  and  October. On V a n c o u v e r to  I s l a n d , b l u e grouse hens and broods  t h e i r w i n t e r range  1967).  The  i n e a r l y September  r e l a t e t o a need f o r a w i n t e r s u p p l y o f  (Semenov-Tyan-Shansky, 1960), f o o d s s u c h as h a r d s e e d s  t o a need f o r c o p i n g w i t h  (Kbrschgen,  1966),  of r e t e n t i o n of g r i t i n the g i z z a r d  1942), o r t o a c o m b i n a t i o n o f t h e s e . of  Elliott,  i n c r e a s e i n the frequency of occurrence of g r i t i n  t h e i r c r o p s may  degree  ( B e n d e l l and  migrate  grit rougher  t o a change i n the (Beer and  Changes i n t h e  Tidyman, texture  the foods eaten are a s s o c i a t e d w i t h d i f f e r e n c e s i n the  retention of g r i t  i n the g i z z a r d  (Semenov-Tyan-Shansky,  1960),  and b y m i d - J u l y the d i e t s o f a d u l t males and females c o n t a i n e d t h e g r e a t e s t amounts o f f r u i t s  (and t h u s o f h a r d s e e d s ) ,  were a l s o h e a v i l y u t i l i z e d b y c h i c k s a t t h a t time and  which  ( F i g s . 1,  2  3). D i u r n a l rhythm The  of feeding  d i u r n a l rhythm  o f f e e d i n g was  determined  by  examination of the weight of c r o p contents of b i r d s k i l l e d a t d i f f e r e n t t i m e s o f day. was to  The w e i g h t o f c r o p c o n t e n t s o f  chicks  e x p r e s s e d as a p e r c e n t a g e o f t h e body w e i g h t o f t h e b i r d s compensate f o r t h e e f f e c t o f t h e s i z e o f t h e c h i c k on  the  27 amount o f f o o d c o n s u m e d . Considerable v a r i a t i o n i n weights of crop contents o c c u r r e d w i t h i n each h o u r l y i n t e r v a l .  T h i s v a r i a t i o n may  l e a s t p a r t i a l l y be a r e s u l t o f t h e i n f l u e n c e o f w e a t h e r on the f e e d i n g a c t i v i t y o f t h e b i r d s 1958).  ( K r a f f t , 1954;  at  conditions  Peters,  C r o p s w h i c h c o n t a i n e d o n l y t r a c i amounts o f f o o d o r  w h i c h were empty were c o l l e c t e d a t a l l t i m e s o f All  c r o p s c o l l e c t e d f r o m 6:00  relatively  little  food.  An  a.m.  t o 10:00  day. a.m.  contained  i n c r e a s e i n the average weight  crop contents occurred throughout  the day.  Feeding  of  was  i n t e n s i f i e d i n the l a t e a f t e r n o o n and e v e n i n g w i t h g r e a t e s t w e i g h t s o f c r o p c o n t e n t s r e a c h e d a f t e r 7s00 p.m. and  11).  Peters  ( F i g s . 9,  These r e s u l t s a r e s i m i l a r t o those o f K r a f f t  (1958), and S e i s k a r i  Bendell  10  (1954),  (1962).  (1954) f o u n d d a i l y p e a k s o f a c t i v i t y i n b l u e  a t a p p r o x i m a t e l y 0300 t o 0500 a n d  1900  t o 2200, a n d  attributed  the g r e a t e s t p a r t of t h i s a c t i v i t y t o the f o r a g i n g of on o r n e a r the t e r r i t o r i e s o f m a l e s .  grouse  No c r o p s w e r e  females available  f r o m grouse c o l l e c t e d e a r l i e r t h a n 0600, and the t i m e  required  f o r passage  not been  determined. 1954)  may  o f f o o d from the c r o p s o f b l u e grouse has F o o d e a t e n b e f o r e 0600  ( C a s w e l l , 1953;  Bendell,  m o s t l y have passed from the c r o p t o the g i z z a r d  the time the grouse were c o l l e c t e d .  No e v i d e n c e o f t h e peak  of morning  f e e d i n g a t a p p r o x i m a t e l y 0700 a s s u g g e s t e d b y  (1943) a n d  Stewart  (1967) was  found.  by  Beer  FIGURE 9  Weight of crop contents of a d u l t males, by hour.  Dry  •  weight  of  crop  contents in  OJ  Ol  o  o  o  _L_  _1_  grams  o  ••• •  (0  ro  29  FIGURE  10  Weight of crop contents of females, by  adult  hour.  V  Dry  o  crop OJ  o  o  I  0)  weight of  _  I  contents  in cn o  L_  grams o  _J  o o o  03  o o o o o  ro o o  3  -  o  o o  Q. Q «<  I  -  o c  00  o o  §  J  o N  ro o o  ro -i o o  oo  FIGURE  11  Weight of crop contents of by  hour.  chicks,  Dry  weight  o o o o  of  crop  o o ro O  o o o _l_  • •• •  contents  , as  o o  %  of  body  o o o  04  o  weight  o o cn o  o o o  •  f»f • • • • •  I ft* •• •••• •  t  l»"SSt*St ••%•% •  •••  • • •• •• •  •  h  •  t o  U  00  •  • •  o  The  highest weights of crop contents  d u r i n g o r a f t e r the evening (1954). food  The  were from b i r d s  peak o f a c t i v i t y r e p o r t e d b y  Bendell  l a r g e number o f a d u l t m a l e s w i t h s m a l l amounts o f  i n t h e i r crops  d u r i n g t h i s p e r i o d c a n be  at least  e x p l a i n e d by males f e e d i n g a t n i g h t a f t e r c e s s a t i o n of (Stewart,  taken  partly hooting  1967).  C r o p c o n t e n t w e i g h t s o f c h i c k s t e n d e d t o r e m a i n more constant  t h r o u g h o u t t h e day  than d i d those  of a d u l t s .  This  s u g g e s t s t h a t c h i c k s f e d more c o n s t a n t l y t h a n d i d a d u l t s , w h i c h w o u l d be  i n keeping  w i t h t h e i r greater food requirements f o r  g r o w t h as w e l l a s m a i n t e n a n c e . of Beer  (1943),  Bendell  (1954),  I t supports Fowle  field  (1960) a n d  observations  Zwickel  (1967).  32 DISCUSSION A number o f p o i n t s m u s t be c o n s i d e r e d i n s a m p l i n g c r o p s f o r analysis of food habits. of major  S e a s o n a l changes i n the  foods a f f e c t s t h e i r u t i l i z a t i o n .  c o l l e c t i o n can g r e a t l y i n f l u e n c e  Gaultheria  F o r example, f r u i t s r i p e n from  Thus, d a t e  of  the apparent importance  d i f f e r e n t f o o d s a n d r e s u l t s s h o u l d be collection.  availability  r e l a t e d to time  of  o f Rubus, V a c c i n i u m ,  l a t e June u n t i l A u g u s t .  The  of  and  peaks o f  u t i l i z a t i o n o f these f r u i t s o c c u r r e d i n the o r d e r o f t h e i r ripening.  Samples t a k e n i n June w i l l  show Rubus a s  i m p o r t a n t f o o d and those t a k e n i n August w i l l  an  contain  mainly  Gaultheria. There  i s danger i n comparing  samples o f s p e c i e s o f p l a n t s . plants  foods eaten w i t h  The  degree  quadrat  of u t i l i z a t i o n  of  i s p r o b a b l y more d e p e n d e n t u p o n t h e t i m e , a n d amount o f  production of acceptable parts, occurrence o r ground Age Dietary  t h a n upon the n u m e r i c a l  cover of i n d i v i d u a l plants  (Hungerford,  1962).  a n d s e x o f t h e b i r d s c o l l e c t e d m u s t be c o n s i d e r e d . d i f f e r e n c e s between a d u l t s and  shown f o r many s p e c i e s o f b i r d s S t e w a r t , 1944;  Perret,  1962;  j u v e n i l e s have been  (Rasmussen, 1938;  Boag, 1963;  Beer,  and o t h e r s ) .  o f d i f f e r e n t foods, o r the d i f f e r e n t degree  1943; The  use  o f u s e o f t h e same  f o o d s , b y a d u l t m a l e s a n d f e m a l e s h a s a l s o b e e n shown b y Seiskari others, adults  (1962), P e r r e t  (1962), Korschgen  as w e l l as i n t h i s s t u d y . and  (1964,  1966)  and  P o o l i n g o f the foods eaten  j u v e n i l e s , o r o f m a l e s a n d f e m a l e s may  thus  obscure  by  33 d i f f e r e n c e s i n t h e f e e d i n g o f age Fowle grouse  o r sex  classes.  (1960) d i d n o t f i n d t h e same s e l e c t i v e f e e d i n g o f  a s f o u n d h e r e b e c a u s e he  d i d n o t c o n s i d e r the s e a s o n a l  n a t u r e o f f o o d h a b i t s and g e n e r a l i z e d from a sample t a k e n i n l a t e summer.  F u r t h e r , he  reported that chicks ate  fewer  b e r r i e s o f Rubus a n d more o f G a u l t h e r i a t h a n d i d a d u l t s , a n d  he  a t t r i b u t e d t h i s t o t h e c h i c k s b e i n g o n a n a n i m a l d i e t when b l a c k b e r r i e s were r i p e , and  later selecting Gaultheria  fruits.  However, t h i s a p p a r e n t g r e a t e r s e l e c t i o n o f G a u l t h e r i a b y  chicks  t h a n b y a d u l t s c a n a l s o be e x p l a i n e d b y t h e amount o f f o o d e a t e n at  d i f f e r e n t ages,  and b y what i s s e a s o n a l l y a v a i l a b l e .  c h i c k s grow, t h e y e a t m o r e . are  Thus, i t e m s t a k e n i n l a t e  As summer  e a t e n i n g r e a t e r q u a n t i t y t h a n t h o s e e a t e n i n June and  J u l y , and t h e y w i l l appear  early  t o form a g r e a t e r p o r t i o n o f the  diet  than i s a c t u a l l y the case, i f the data from young and o l d c h i c k s are  p o o l e d a s was  done b y F o w l e .  Averaging the  percentages which each food comprises reduces t h i s i s done, t h e r e l a t i v e u s e o f f r u i t s i n a d u l t s and c h i c k s The  this error.  i s seen t o be  similar  (Table 3 ) .  ( T a b l e 3) c a n be  e x p l a i n e d by the e a r l i e r  departure  m a l e s f r o m t h e summer r a n g e a n d t h e l a t e r i p e n i n g o f  fruit.  If  l e s s e r use o f V a c c i n i u m f r u i t s by males t h a n by hens  and c h i c k s of  weekly  A l t h o u g h f l o w e r s and d e v e l o p i n g f r u i t o f  this  Gaultheria  were e a t e n f r e q u e n t l y from e a r l y June u n t i l a l l b i r d s l e f t summer r a n g e , diet until  they d i d not c o n s t i t u t e a l a r g e percentage of  t h e y r i p e n e d i n l a t e J u l y and  August.  the the  34  T a b l e 3.  Amount o f f r u i t s  grouse, by average o f weekly  i n the d i e t o f a d u l t and j u v e n i l e percentages o f w e i g h t and  frequency of occurrence.  . F  r  u  i  t  a d u l t males %wt. % f . o .  a d u l t females °/Mt. %f.o.  juveniles °Ait. % f . o .  Rubus  23  21  IS  41  16  26  Gaultheria  20  48  24  52  15  37  1  20  9  28  5  24  Vaccinium  35 A v a i l a b i l i t y and D i e t may  s e l e c t i o n of  r e f l e c t the  foods  r e l a t i v e a v a i l a b i l i t y of  foods  ( T r a u t m a n , 1952;  Peters,  1958;  Robel,  others)  o r a combination of what i s a v a i l a b l e  and  1964;  the  and  preferences  B o a g , 1963;  of the  Fowle, I960; P e r r e t ,  species  Korschgen, 1966).  s e l e c t i o n of foods by blue  (Yocom a n d  Keller,  There i s o b v i o u s l y  grouse f o r the  1962;  1961;  some  f o l l o w i n g reasons.  I n s p r i n g , f e m a l e s a t e c o n s i d e r a b l y more d e c i d i o u s m a t e r i a l than d i d males. i n s p r i n g f r o m 1957 c o n i f e r needles,  Since  leaf  the most abundant f o o d a v a i l a b l e  on a t Lower and  Middle  h e n s c l e a r l y s e l e c t e d new  Quinsam Lakes  was  leafy vegetation.  I n e x p e r i m e n t s on c a p t i v e g r o u s e , S i i v o n e n  (1957) f o u n d  hens s u p p l i e d w i t h e a r l y green f o l i a g e ate  i t "immediately  ravenously", food.  The  1 and  2)  w h i l e males were r a t h e r i n d i f f e r e n t towards marked s e a s o n a l  show t h a t t h e  p l a n t s as  changes i n the  grouse were s e l e c t i n g p a r t s o f  (Figs.  various  t h e y became a v a i l a b l e .  w e r e n o t u s e d as f o o d . margaritacea),  Canadian t h i s t l e (Thuja  and  this  d i e t of a d u l t s  A number o f p l a n t s w h i c h w e r e a b u n d a n t o n  (Anaphalis  that  a g a i n s t as f o o d  summer r a n g e  These i n c l u d e d p e a r l y e v e r l a s t i n g fireweed  (Epilobium  (Cirsium canadensis),  plicata).  the  These and  other  angustifolium.  and w e s t e r n r e d  p l a n t s were thus  cedar  selected  items.  Hens w i t h b r o o d s a r e m o s t f r e q u e n t l y f o u n d i n m o i s t a r e a s on  the  summer r a n g e  (Elliott,  p r o t e c t e d by c a t t l e e x c l o s u r e s  1966;  Lance, 1967).  Vegetation  a t water sources received  constant  use a s f o o d f o r r u f f e d grouse  (Hungerford,  19 5 7 ) .  Broods o f  b l u e g r o u s e may a l s o f r e q u e n t m o i s t a r e a s f o r t h i s Finally,  the percentage  p l a n t s o n t h e summer r a n g e  o f ground  covered b y main f o o d  c o u l d n o t be r e l a t e d t o t h e i r  frequency o f occurrence o r percentage (Table 4 ) .  reason.  by weight as foods  Newton (1967) f o u n d s i m i l a r r e s u l t s w i t h b u l l f i n c h e s  (Pvrrhula pyrrhula),  i n t h a t t h e c o m p o s i t i o n o f t h e i r d i e t was  not d i r e c t l y r e l a t e d t o the a v a i l a b i l i t y o f the v a r i o u s seed species which  t h e y f e d upon.  F o r t h e s e r e a s o n s , t h e c o n c l u s i o n was r e a c h e d grouse Fowle  s e l e c t p l a n t f o o d s o n t h e summer r a n g e . ( I 9 6 0 ) , who f o u n d a r o u g h  that blue  This  contradicts  p a r a l l e l between p e r c e n t  frequency o f occurrence o f p l a n t s on h i s study area and t h e i r volume i n t h e d i e t o f t h e g r o u s e . S e l e c t i o n o f food appears  t o be d i r e c t e d towards  such as l e a v e s , f l o w e r s , and f r u i t s , species.  W i t h i n each  food types,  r a t h e r than to p a r t i c u l a r  f o o d type, the degree o f use o f s u i t a b l e  f o o d s p e c i e s seems r e l a t e d t o t h e i r a v a i l a b i l i t y a n d c o n d i t i o n . L e a f m a t e r i a l was t a k e n i n g r e a t e s t amounts s h o r t l y a f t e r and peak use o f f r u i t s ripening  budding,  seems t o c o i n c i d e w i t h t h e i r p e a k o f  ( F i g s . 6, 7 a n d 8 ) .  The f r u i t s w h i c h w e r e e a t e n m o s t  f r e q u e n t l y and i n g r e a t e s t q u a n t i t i e s  (Rubus u r s i n u s a n d  G a u l t h e r i a s h a l l o n ) v/ere t h o s e w h i c h w e r e m o s t common o n t h e summer r a n g e spp.,  (Tables 3 and 4 ) .  L e s s common f r u i t s  (Vaccinium  Mahonia n e r v o s a , a n d F r a g a r i a spp.) were e a t e n i n amounts  c o r r e s p o n d i n g t o t h e i r r e l a t i v e abundance on t h e a r e a s .  Similar  37  T a b l e 4. of major  Comparison  o f the percentage  frequency of occurrence  f o o d p l a n t s o n t h e summer r a n g e a n d i n t h e d i e t o f  grouse, during  August.  Species of food plant  Rubus u r s i n u s Pteridium  aquilinum  Hypochaeris r a d i c a t a Gaultheria  shallon  S a l i x spp. Pseudotsuga  menziesii  Vaccinium spp.  On summer r a n g e % ground cover  adult adult males females % f.o. % f.o.  chicks % f.o.  3.2  25  33  27  15.4  50  42  58  1.9  50  58  50  12.8  50  63  57  6.2  25  18  11  9.3  25  12  6  1.7  50  44  35  f i n d i n g s were r e p o r t e d b y Beer eaten on t h e w i n t e r  (1943)  Hemlock n e e d l e s were  r a n g e i n t h e same r e l a t i v e  these trees occurred  i n r e l a t i o n to other  proportion as  conifers  (King, i n  preparation). The f r e q u e n c y o f o c c u r r e n c e o f i n v e r t e b r a t e s o n t h e summer r a n g e was m e a s u r e d i n o r d e r degree o f u t i l i z a t i o n  t o r e l a t e t h e i r abundance t o t h e  i n the d i e t o f grouse.  The r e l a t i v e  a b u n d a n c e o f i n v e r t e b r a t e s was d e t e r m i n e d b y d i f f e r e n t m e t h o d s d u r i n g May, J u n e a n d J u l y o f 1958 b y S t i v e n F.C. Z w i c k e l  i n J u l y o n 1962, a t M i d d l e Q u i n s a m L a k e .  invertebrates and  (1961), and b y The  found i n the crops of chicks c o l l e c t e d during  J u l y were compared w i t h  t h e r e s u l t s o f t h e s e samples (Table 5).  Invertebrates  were e a t e n i n t h e i r order  field.  suggests t h a t young c h i c k s f e e d on a n i m a l  as the  This  i t i s available.  o f abundance i n t h e  Rasmussen a n d G r i n e r  material  (1938) showed  that  i n s e c t s most f r e q u e n t l y e a t e n b y young sage grouse  (Centrocercus area.  u r o p h a s i a n u s ) were those most a v a i l a b l e i n t h e  By l a t e J u l y t h e d i e t o f j u v e n i l e s c l o s e l y r e s e m b l e s  t h a t o f a d u l t females i n type and k i n d o f food eaten and  June  (Figs. 2  3, T a b l e 6 ) . I n 1958 S t i v e n s a m p l e d i n v e r t e b r a t e s  vegetation  and the ground surface w i t h an a s p i r a t o r , w h i l e i n  1962 Z w i c k e l The g r e a t e r  from both the  u s e d a sweep n e t a n d t o o k o n l y t h o s e o n p l a n t s . s i m i l a r i t y between the d i e t o f c h i c k s and the  i n v e r t e b r a t e s t a k e n b y sweep n e t s u g g e s t s t h a t t h e i n v e r t e b r a t e s e a t e n were o b t a i n e d  l a r g e l y from the v e g e t a t i o n  and n o t from the  39  Table  5.  Comparison o f t h e per cent frequency o f occurrence  o f m a j o r i n v e r t e b r a t e g r o u p s o n t h e summer r a n g e by grouse  and t h e i r use  c h i c k s , J u n e a n d J u l y , 1957 t h r o u g h 1 9 6 6 .  invertebrates  o n summer r a n g e . ^ sv/eep n e c s a s p i r a t o r (1962) (Stiven,1961)  i n crop contents ( crops) June - J u l y (1957-1966) 1 0 5  Hymenoptera  93  94  78  Hemiptera & Homoptera  42  100  58  Coleoptera  48  31  35  Diptera  29  69  14  Arachnida  10  100  17  Isopoda  0  38  13  Myriapoda  0  13  6  Lepidoptera  0  31  8  Orthoptera  5  * Stiven he  *  5  e x c l u d e d members o f t h e o r d e r O r t h o p t e r a , a l t h o u g h  c o l l e c t e d them.  40  T a b l e 6.  Comparison o f major f o o d items i n the early-  September d i e t o f a d u l t f e m a l e s and  a d u l t females (41)* %Jt . %f. o.  Food  juveniles.  j u v e n i l e males (45) °/&7t .  % f .O .  j u v e n i l e females (36) %at.  %f.o.  7  0.7  6  A  12  2.9  32  40  9.1  40  16.1  50  8.2  16  8.9  17  18.5  22  miscellaneous leaves  0.7  14  0.6  17  1.0  22  Hypochaeris flowers  9.4  60  12.9  57  16.0  55  Rubus . fruit  12.4  10  0.5  2  0.1  3  Gaultheria fruit  41.0  70  41.1  51  30.7  61  Vacciinium fruit  6.2  23  4.1  22  8.1  35  animal material  0.1  8  1.1  20  0.3  33  Pseudotsuqa needles  1.6  12  0.8  Salix leaves  1.5  20  A  Pteridium fronds  13.6  Trifolium leaves  * Sample  size  — o  —  41 ground,  Zwickel  vegetation and  (1967) o b s e r v e d t h a t c h i c k s p e c k e d a t t h e  f o r i n s e c t s , b u t seldom a t the ground.  myriopods, which a r e found almost e x c l u s i v e l y on t h e ground,  were t a k e n b y c h i c k s . feeding  There must t h e r e f o r e  upon i n v e r t e b r a t e s  from the ground  N u t r i t i o n a l basis o f food The  winter  h a v e b e e n some surface.  selection  d i e t a r y d i f f e r e n c e s o f a d u l t males and f e m a l e s have  been mentioned p r e v i o u s l y  and  Isopods  ( F i g s . 1 and 2 ) .  t o summer f o o d s o c c u r s e a r l i e r  The t r a n s i t i o n  from  i n hens than i n cocks,  r e s u l t s i n differences i n the n u t r i e n t composition of t h e i r  diets.  These d i f f e r e n c e s a p p e a r t o be r e l a t e d t o d i f f e r e n c e s  i n the b i o l o g y of the sexes. Requirements f o r p r o t e i n and m i n e r a l s necessary f o r maintenance l e v e l s during moult and growth o f b i r d s 1964  a n d 1966; a n d o t h e r s ) .  (Gelting, and  (Hill,  increase  periods  those  of ovulation,  1944; S i i v o n e n ,  1957; K o r s c h g e n ,  Evidence has been presented  1937; McCann, 1 9 3 9 ; S a d l e r ,  1 9 6 1 ; K o r s c h g e n , 1964  1966) t o show t h a t g a l l i n a c e o u s b i r d s a d j u s t  meet t h e i r c u r r e n t  over  their diets to  requirements.  Values f o r the n u t r i e n t composition o f the major food i n t h e s p r i n g a n d summer d i e t o f V a n c o u v e r I s l a n d b l u e were o b t a i n e d  from the l i t e r a t u r e  to determine the trends adult blue of  (Table  7).  the main foods.  Data from S t i v e n  grouse  These w e r e u s e d  i n the n u t r i t i o n a l value  grouse, r e s u l t i n g from seasonal  items  of the d i e t of  v a r i a t i o n i n the use  (1961) w e r e o b t a i n e d  p l a n t s a n d a n i m a l s w h i c h w e r e c o l l e c t e d i n J u n e o f 1958 a t  from  42  Table blue  7.  N u t r i e n t content of major foods of Vancouver  grouse*.  Pood i t e m  Protein  Pseudotsuqa Salix  needles  leaves  Pteridium  fronds  Hypochaeris Rubus  island  flowers  fruits  Gaultheria  fruits  Formicidae  Ether extract  N-free extract  Crude fiber  Ash  6,.5  7. 8  62,.7  19. 9  3 .2  8,.8  2. 6  60. .2  21. 0  7 .4  12..9  2. 4  49. .2  27. 0  8 .5  14. » d*  5. 4  53..5  14. 0  12 .7  13.,4  1. 4  64. .3  15. 0  5 .9  9. .2  2. 0  63..8  20. 0  5 .0  66. ,8  2. 9  23,.7  4. 0  2 .6  * v a l u e s f o r P s e u d o t s u q a f r o m Cowan e t a l . ( 1 9 5 0 ) , a l l o t h e r s from S t i v e n  (1961).  43  M i d d l e Quinsam Lake. the  The m a t e r i a l was t h e r e f o r e  taken  during  t i m e a t w h i c h i t was u t i l i z e d b y g r o u s e a n d f r o m t h e same  a r e a on w h i c h t h e b i r d s were c o l l e c t e d .  The d i f f e r e n c e s i n  n u t r i e n t c o n t e n t o f p l a n t s w h i c h h a v e b e e n shown t o e x i s t between p l a n t p a r t s , between areas, d i f f e r e n t aged stands, Golley, these  between v e g e t a t i o n  a n d b e t w e e n months  from  (Cowan e t aJL., 1950;  1 9 6 1 ; W e s t a n d Meng, 1966) s h o u l d  t h u s be m i n i m a l f o r  values. The p r o t e i n a n d m i n e r a l  content of c o n i f e r needles  e t a l , , 1950; H o f f m a n , 1 9 6 1 ; S t i r l i n g ,  1965; E l l i s o n ,  lower than t h a t o f a l l other main foods  (Table  (Cowan  1966) i s  7 ) , and the  p r e s e n c e o f l a r g e amounts o f n e e d l e s i n t h e s p r i n g a n d summer d i e t o f grouse w i l l  therefore  decrease the r e l a t i v e  amounts  o f t h e s e components i n the d i e t . The s e l e c t i o n o f b r o a d - l e a f e d f i r s t became a v a i l a b l e increased  m a t e r i a l b e g a n when  ( F i g s . 1 and 2 ) .  T h e i r use b y hens  t h r o u g h o u t A p r i l a n d was h i g h e s t  w h i c h i s t h e peak p e r i o d f o r t h e b e g i n n i n g 1 9 6 5 ) , a n d u s e o f l e a v e s was during  this period  t h a t t i m e was  i n mid-May of laying  ( F i g . 7) (Zwickel,  g r e a t e r by hens t h a n b y c o c k s  ( F i g s . 1 and 2 ) .  still  leaves  The f o o d  l a r g e l y c o n i f e r needles.  a n i m a l m a t e r i a l b y f e m a l e s was g r e a t e r  o f males a t The u s e o f  than t h a t by males  ( F i g s . 6 and 7 ) , a l t h o u g h i n v e r t e b r a t e s were n o t a m a j o r c o n s t i t u e n t b y e i t h e r w e i g h t o r volume i n the c r o p o f any a d u l t female. d i e t o f f e m a l e s was  The p r o t e i n a n d m i n e r a l thus c o n s i d e r a b l y  higher  contents  content of the  than t h a t of males  44 d u r i n g the r e p r o d u c t i v e season.  A similar situation  was  r e p o r t e d by Korschgen  found a d i f f e r e n c e ,  which  was  ( 1 9 6 4 ) , who  g r e a t e s t d u r i n g the r e p r o d u c t i v e season, between the  t a k e n by male and female colchicus).  ring-necked pheasants  (Phasianus  Marked changes i n the n u t r i t i o n a l v a l u e o f  d i e t o f t h e h e n s o c c u r r e d d u r i n g t h a t p e r i o d , b u t no c h a n g e was  foods  observed i n the d i e t o f r o o s t e r s .  and m i n e r a l i n t a k e o f r u f f e d grouse  (Bonasa  The  the  such  protein  umbellus) i n c r e a s e d  when p r o t e i n r e q u i r e m e n t s o f f e m a l e s i n c r e a s e d d u r i n g o v u l a t i o n (Korschgen,  1966) .  A comparison  o f the d i e t s o f a d u l t and s u b a d u l t males  d u r i n g s p r i n g a n d e a r l y summer showed t h a t t h e y a t e t h e same p e r c e n t a g e s o f t h e d i f f e r e n t f o o d t y p e s Few  y e a r l i n g males e s t a b l i s h t e r r i t o r i e s  1967).  M o s t move o v e r w h a t a p p e a r s  home r a n g e ,  s h o w i n g movements s i m i l a r  ( B e n d e l l and E l l i o t t ,  1967;  Lance,  (Table 8 ) .  ( B e n d e l l and  t o be  Elliott,  a relatively  to those of  1967).  essentially  The  large  females  similarity  the d i e t s o f a d u l t s and y e a r l i n g s f u r t h e r s u p p o r t s t h e  concept  t h a t b r e e d i n g and t e r r i t o r i a l b e h a v i o u r d i d n o t impose a s t r a i n upon The  o c c u r r e n c e o f f l o w e r s and f r u i t s  i n the d i e t of  adults,  (Figs.  By e a r l y J u l y t h e amount o f c o n i f e r n e e d l e s e a t e n  b o t h sexes decreased t o l e s s than three per c e n t of  dietary  males.  b o t h m a l e s a n d f e m a l e s , i n c r e a s e d g r e a t l y d u r i n g June and 2 ) .  of  the foods eaten.  The  1  by  (dry weight)  nutrient composition of f r u i t s  f l o w e r s i s h i g h i n p r o t e i n and m i n e r a l s (Table 7 ) .  The  and quality  45  T a b l e 8.  Food o f a d u l t and y e a r l i n g grouse, A p r i l and  1957 t h r o u g h 1966, b y p e r c e n t a g e  Food type  May,  dry weight.  males adults yearlings  females adults yearlings  73  IS  37  18  64.2  65.7  55.2  49.7  31.6  23.7  41.4  48.3  flowers  0.6  1.2  0.3  0  fruits  3.0  9.3  3.0  1.9  0.6  0.1  0.1  0.1  sample conifer leaf  size needles  material  animal  material  46 o f t h e d i e t o f the hens remained h i g h , reproductive similar  season, w h i l e  resembling  t h a t o f the males i n c r e a s e d  the replacement o f the f i r s t  of primaries end  to a  level.  D u r i n g l a t e May, a d u l t m a l e s b e g i n with  that of the  t h e i r annual moult  primary feather.  Growth  2, 3, a n d 4 i s c o m p l e t e d o r i n p r o g r e s s  a t the  o f June, a t w h i c h time moult o f t h e c o n t o u r f e a t h e r s  (Bendell,  1955b).  T h e r e i s some q u e s t i o n  of a d u l t females begins. apparently  begins  a s t o when t h e m o u l t  The o n s e t o f f e a t h e r r e p l a c e m e n t i s  r e l a t e d to the reproductive  H6hn (1961) s t a t e s t h a t c y c l i c  status o f the b i r d s .  f l u c t u a t i o n s i n production of  g o n a d a l hormones, t o g e t h e r w i t h changes i n t h e l e v e l o f t h y r o i d hormone, c o n t r o l t h e p o s t n u p t i a l m o u l t o f b i r d s . (1955b) r e p o r t e d  t h a t a d u l t f e m a l e s commenced t h e m o u l t  c o n c u r r e n t l y w i t h a d u l t males, w h i l e breeding  hens began m o u l t i n g  approximately females. for  Bendell  Boag  (1965) f o u n d  after termination of incubation,  f o u r weeks l a t e r t h a n males and n o n - b r e e d i n g  Nevertheless,  b y l a t e June m o u l t i n g  i s i n progress  b o t h males and females, and t h e process c o n t i n u e s  A u g u s t and September.  An adequate supply  Korschgen, 1966).  ( H i l l , 1944;  The n e e d t o meet t h i s demand may e x p l a i n  the abrupt t r a n s i t i o n i n the d i e t o f males, from needles t o f r u i t s and f l o w e r s which have h i g h d i e t o f c h i c k s from mid-July  summer r a n g e  through  of protein i n the  d i e t seems n e c e s s a r y f o r g o o d f e a t h e r d e v e l o p m e n t  The  that  predominantly  protein  contents.  u n t i l they leave the  ( F i g . 3) i s s i m i l a r t o t h a t o f a d u l t s , w i t h  a  47 g r e a t e r use o f animal  foods.  A s u i t a b l e d i e t f o r meeting the  requirements o f growth and moult, as w e l l as f o r maintenace, i s necessary  f o rchicks.  r e l a t i v e l y high  The l a t e summer d i e t o f c h i c k s was  i n p r o t e i n and m i n e r a l content.  m a t e r i a l h a s a much h i g h e r foods eaten to  capture  (Table  p r o t e i n content  necessary  s u f f i c i e n t i n v e r t e b r a t e s t o meet t h e n u t r i t i o n a l  I n f l u e n c e o f d i e t upon  prohibitive.  reproduction  The e x i s t e n c e o f a m a t e r n a l  in  than the plant  7 ) , b u t the energy expenditure  r e q u i r e m e n t s o f t h e g r o w i n g b i r d s may b e  and  Animal  i n f l u e n c e on the v i a b i l i t y  s u r v i v a l o f g a l l i f o r m c h i c k s was s u g g e s t e d b y Y o u n g Z w i c k e l , 1965) a n d h a s b e e n s u p p o r t e d  Nestler  (1946),  Bump e t a l . ( 1 9 4 7 ) ,  e t a l . (1967) a n d Z w i c k e l  (1965).  (1868,  by the f i n d i n g s o f  Siivonen  (1957),  Jenkins  Yearly v a r i a t i o n i n the  q u a l i t y of the staple winter food  i s b e l i e v e d b y some w o r k e r s  to be r e s p o n s i b l e f o r d e t e r m i n i n g  the c o n d i t i o n o f the hen,  and  through her, the v i a b i l i t y  Lauckhart,  o f the chicks  1 9 5 7 ; Boag, 1 9 6 3 ; J e n k i n s ,  bobwhite q u a i l  1963).  ( K o s k i m i e s , 1955; However,  ( C o l i n u s v i r g i n i a n u s ) were found b y N e s t l e r  (1944) t o show no s t a t i s t i c a l l y  significant differences i n  f e r t i l i t y and h a t c h a b i l i t y c f t h e eggs o f b i r d s m a i n t a i n e d winter diets of different protein levels.  Dale and DeWitt  (1958) s t a t e t h a t p h e a s a n t s k e p t o n a l o w - p r o t e i n w i n t e r were a b l e  on  diet  t o r e p r o d u c e s u c c e s s f u l l y d u r i n g t h e f o l l o w i n g summer  p r o v i d i n g the reproductive  d i e t was  satisfactory.  48 Siivonen  (1957) s u g g e s t e d  t h a t t h e change i n o v e r a l l  q u a l i t y o f t h e d i e t o f t h e h e n s i n s p r i n g may b e a f a c t o r in  determining the r e p r o d u c t i v e success o f t e t r a o n i d s , and  t h a t t h e t i m e o f g r e a t e - s t i m p o r t a n c e was t h e t h r e e week p e r i o d immediately preceding l a y i n g . (Lagopus l a g o p u s )  The s u r v i v a l o f r e d g r o u s e  c h i c k s h a s been f o u n d t o be r e l a t e d t o t h e  amount o f g r e e n h e a t h e r a v a i l a b l e a s f o o d f o r b r e e d i n g b i r d s .... i n t h e s p r i n g  ( J e n k i n s e t a_l.,. ^.967) .  No d i f f e r e n c e was f o u n d i n r e p r o d u c t i v e s u c c e s s o f g r o u s e f r o m t h e d i f f e r e n t s t u d y a r e a s d u r i n g t h e same y e a r , b u t mean brood  s i z e b e t w e e n y e a r s was s i g n i f i c a n t l y d i f f e r e n t  and B e n d e l l , 1967). study  (Zwickel  The y e a r o f l o w e s t c h i c k s u r v i v a l o n t h e  r e a s was 1962, when n e s t i n g was a l s o d e l a y e d ( Z w i c k e l  and B e n d e l l , 1967).  The f o o d s o f h e n s c o l l e c t e d d u r i n g A p r i l  a n d May o f t h e y e a r s 1960 t h r o u g h  1963 w e r e c o m p a r e d b e t w e e n  years t o determine whether d i e t a r y d i f f e r e n c e s o c c u r r e d which c o u l d be r e l a t e d t o d e l a y e d n e s t i n g o r t o t h e p o o r s u r v i v a l o f c h i c k s i n 1962.  A h i g h e r percentage  early of conifer  n e e d l e s i n t h e p r e - n e s t i n g d i e t o f hens w o u l d be e x p e c t e d i n a year o f l a t e n e s t i n g and low c h i c k s u r v i v a l ,  i f the a v a i l -  a b i l i t y o f f o o d t o h e n s was a f f e c t i n g t h e i r t i m e o f n e s t i n g o r the v i a b i l i t y o f t h e i r c h i c k s .  No s u c h d i f f e r e n c e i n t h e u s e  of  n e e d l e s b y h e n s was f o u n d b e t w e e n 1962 a n d a n y o t h e r y e a r ,  or  b e t w e e n 1962 a n d t h e p o o l e d v a l u e s f o r a l l o t h e r y e a r s  (t-test,  5% l e v e l ) .  The u s e o f a l l f o o d t y p e s b y h e n s was  s i m i l a r i n 1962 t o t h a t i n o t h e r y e a r s  (Table 9 ) .  The d i e t  49  T a b l e 9. * summer  C o m p a r i s o n o f use o f f o o d t y p e s i n t h e d i e t of females  survival  during year of poorest  chick  (1962) t o t h e 10 y e a r a v e r a g e v a l u e s f o r t h e  d i e t o f f e m a l e s , as a p e r c e n t a g e of  early  dry weight,  and  frequency  occurrence.  Food  1962  type  (Sample  size)  10 y e a r  average  (55)  (18)  .o.  wt.  f .o.  wt.  31.2  74  36.8  64  66.6  93  58.1  93  flowers  0.6  40  1.7  48  fruits  1.5  33  2.3  25  0.1  13  0.4  10  conifer leaf  needles  material  animal  material  * d u r i n g May  and  June  J-  50 o f hens as d e t e r m i n e d b y t h i s measure c a n n o t  t h e r e f o r e be  related  t o the l a t e h a t c h o r t o the poor e a r l y s u r v i v a l o f c h i c k s i n 1962.  No  data f o r n u t r i e n t c o n t e n t of p l a n t s from the  areas are a v a i l a b l e from d i f f e r e n t years to determine  study  yearly  v a r i a t i o n i n the n u t r i e n t c o m p o s i t i o n o f the main f o o d s p e c i e s o c c u r r e d , a s h a s b e e n r e p o r t e d b y S i i v o n e n (1957) a n d  Lauckhart  (1957). A l t h o u g h a l l s t u d y a r e a s were w i t h i n 2 5 m i l e s o f a n o t h e r , and a l l had been l o g g e d and burned,  one  t h e r e were  d i f f e r e n c e s i n t h e i r p l a n t c o v e r a t t h e t i m e when g r o u s e collected.  The  c o v e r a g e b y c o n i f e r s on t h e a r e a s  b e i n g l o w e s t a t Comox B u r n d u r i n g t h e p e r i o d 1957 (Zwickel,  1965).  Artificial  differed, through  r e p l a n t i n g of Douglas  fir  t h e n a t u r a l p a t t e r n o f p l a n t s u c c e s s i o n on t h e a r e a s 1954;  Z w i c k e l , 1965).  were  1966  altered  (Bendell,  The v e g e t a t i o n a t Lower Q u i n s a m L a k e  c h a n g e d m a r k e d l y b e t w e e n 1953  and  1957,  ( Z w i c k e l and  Bendell,  1 9 6 7 ) , w i t h a n i n c r e a s e i n t h e amount o f d e n s e c o v e r . In order to determine  the e x t e n t to which  plant  cover  i n f l u e n c e d t h e d i e t o f g r o u s e , d a t a on f o o d s e a t e n b y t h e b i r d s c o l l e c t e d from the d i f f e r e n t a r e a s were examined The  percentage o f c o n i f e r n e e d l e s e a t e n by hens c o l l e c t e d  L o w e r Q u i n s a m L a k e f r o m 19 50 t h r o u g h 1952 1961  a n d f r o m 1957  showed no s i g n i f i c a n t d i f f e r e n c e s a t t h e 5% l e v e l  f o r any was  separately.  two week i n t e r v a l  at  through (t-test)  d u r i n g t h e s p r i n g o r summer.  a l s o no d i f f e r e n c e b e t w e e n t h e n e e d l e c o n t e n t o f t h e  There diets  o f f e m a l e s f r o m L o w e r a n d M i d d l e Q u i n s a m L a k e s b e t w e e n 1957  and  51 1966, from  o r b e t w e e n t h e s e b i r d s a n d t h o s e c o l l e c t e d a t Comox 1962 t h r o u g h 1 9 6 6 . The  d i e t s o f m a l e s c o l l e c t e d a t Lower Q u i n s a m L a k e d u r i n g  t h e two s a m p l i n g p e r i o d s d i d show a d i f f e r e n c e of  Burn  c o n i f e r needles which  they contained.  i n the percentage  D u r i n g e a r l y May,  a d u l t m a l e s t a k e n f r o m 1950 t h r o u g h 19 52 h a d e a t e n s m a l l e r amounts o f c o n i f e r n e e d l e s t h a n h a d t h o s e c o l l e c t e d b e t w e e n 1957 level  a n d 1 9 6 1 , a n d t h i s d i f f e r e n c e was s i g n i f i c a n t a t t h e 1 0 % (t=2.042,  11 d f ) .  I n l a t e May a n d J u n e ,  the difference  b e t w e e n t h e d i e t s o f m a l e s f r o m t h e two c o l l e c t i o n p e r i o d s i n c r e a s e d , a n d was s i g n i f i c a n t a t t h e 1 % l e v e l During July, no d i f f e r e n c e  f o l l o w i n g the decrease  (t=4.589,  37 d f ) .  i n ' n e e d l e s use ( F i g . 1 ) ,  i n t h e percentage o f needles eaten b y males  t h e two p e r i o d s o f c o l l e c t i n g e x i s t e d .  T h e r e w e r e no  s i g n i f i c a n t d i f f e r e n c e s i n needle consumption Lower a n d M i d d l e Quinsam Lakes  from  f r o m 1957 o n .  b y males  from  Insufficient  a d u l t m a l e s w e r e c o l l e c t e d a t Comox B u r n t o t e s t  statistically  the percentage o f needles i n t h e i r d i e t a g a i n s t t h a t o f b i r d s from the o t h e r a r e a s .  The l i m i t e d d a t a a v a i l a b l e  suggest  t h a t m a l e s a t Comox B u r n a t e a p p r o x i m a t e l y t h e same amount o f n e e d l e s a s d i d t h o s e f r o m Lower Q u i n s a m L a k e b e t w e e n 1950 a n d 1952,  a n d l e s s t h a n t h o s e males c o l l e c t e d a t Lower a n d M i d d l e  Quinsam Lakes a f t e r 1957. These f i n d i n g s s u p p o r t t h e c o n c l u s i o n t h a t f e m a l e s  select  foods o t h e r than needles d u r i n g the r e p r o d u c t i v e season. Zwickel  (1965) f o u n d no e v i d e n c e o f a r e l a t i o n s h i p b e t w e e n mean  52 b r o o d s i z e and h a b i t a t type on t h e s e s t u d y a r e a s .  The  s e l e c t i o n o f f o o d b y hens r e s u l t e d i n a s i m i l a r i t y o f d i e t s d e s p i t e the h a b i t a t d i f f e r e n c e s between a r e a s , and any i n f l u e n c e o n r e p r o d u c t i v e s u c c e s s due t o d i f f e r e n t o f foods w o u l d t h e r e f o r e have been  dietary  availability  nullified.  M a l e s showed a l e s s e r d e g r e e o f s e l e c t i o n o f f o o d t h a n d i d hens d u r i n g the b r e e d i n g season.  When t h e m a l e s c h a n g e d  f r o m a p r e d o m i n a n t l y n e e d l e d i e t t o one c o n s i s t i n g m a i n l y o f f r u i t s and s e e d s , a r e a l d i f f e r e n c e s d i m i n i s h e d and t h e use o f m a i n t y p e s o f f o o d s became v e r y s i m i l a r .  I t t h e r e f o r e appears  t h a t when t h e n u t r i t i o n a l r e q u i r e m e n t s o f g r o u s e  result i n a  s e l e c t i o n o f f o o d s , t h e e f f e c t o f t h e h a b i t a t on t h e d i e t i s diminished.  At other times, r e l a t i v e a v a i l a b i l i t y of acceptable  f o o d i t e m s seems t o e x e r t a s t r o n g e r i n f l u e n c e o n t h e i r u s e . I n b l u e g r o u s e , a d u l t h e n s a p p e a r t o p r o d u c e more y o u n g t h a n do y e a r l i n g s  (Zwickel,  and t h e p o s s i b i l i t y investigated.  1965; B e n d e l l a n d E l l i o t t ,  1967)  t h a t t h i s may h a v e a d i e t a r y b a s i s  was  The m a i n t y p e s o f f o o d e a t e n b y a d u l t a n d  y e a r l i n g g r o u s e o f b o t h s e x e s , d u r i n g A p r i l a n d May o f t h e y e a r s 1957 t h r o u g h 1966 w e r e e x a m i n e d ( T a b l e 8 ) .  April  and  May w e r e c h o s e n b e c a u s e t h i s i s t h e t i m e o f peak b r e e d i n g activity,  and the t r a n s i t i o n i n t h e d i e t o f hens o c c u r r e d  d u r i n g t h e s e months.  The amounts o f t h e f i v e  types of food  e a t e n b y a d u l t a n d y e a r l i n g h e n s w e r e v i r t u a l l y t h e same. T h e r e f o r e , where b o t h a d u l t and y e a r l i n g f e m a l e s were  likely  e a t i n g t h e same f o o d s i n e v e r y y e a r , d i f f e r e n c e s i n r e p r o d u c t i v e  53 performance between a d u l t and y e a r l i n g hens were  probably  r e l a t e d to innate  differences  i n their physiological  for reproduction,  and n o t t o the f o o d w h i c h they a t e .  capacity  Autumn m i c f r a t i o n D u r i n g l a t e summer a n d autumn, b l u e g r o u s e l e a v e t h e lowland b r e e d i n g ranges and r e t u r n t o t h e i r w i n t e r the mountains.  Beer  (1943) a n d M a r s h a l l  this a l t i t u d i n a l migration and  range i n  (1946) s u g g e s t  that  may b e r e l a t e d t o t h e c o n d i t i o n  a b u n d a n c e o f f r u i t s o n t h e summer r a n g e a n d t h e i r r i p e n i n g  l a t e r a t higher  altitudes.  males b e g i n t h e i r m i g r a t i o n  However, o n t h e s t u d y a r e a s ,  i n e a r l y summer a n d v i r t u a l l y a l l  have l e f t t h e lowlands b y e a r l y August. males occurs p r i o r t o and d u r i n g  The d e p a r t u r e o f t h e  the period o f  a b u n d a n c e o f t h e f r u i t s o f Rubus a n d G a u l t h e r i a . greatest  adult  use b y hens and c h i c k s .  greatest and t h e i r  The t i m e o f d e p a t u r e o f  a d u l t m a l e s f r o m t h e summer r a n g e i s r e l a t e d t o t h e s e a s o n a l decrease i n t e s t i c u l a r volume This  s t r o n g l y suggests that  (Bendell,  1955a; Simard,  1964).  t h e a l t i t u d i n a l movement o f m a l e s  i s caused by the p h y s i o l o g i c a l c o n d i t i o n o f the b i r d s and i s not  r e l a t e d to the supply of food. Most o f t h e m i g r a t i o n  i n e a r l y September  (Bendell  o f hens and c h i c k s a p p a r e n t l y and E l l i o t t ,  amounts o f Rubus a n d G a u l t h e r i a A u g u s t and September  The  greatest  f r u i t s w e r e e a t e n b y them i n  ( F i g s . 7 and 8 ) .  d e c r e a s e i n t h e amount o f f r u i t s  1967).  occurs  T h e r e was no a p p a r e n t  i n t h e d i e t o f hens o r c h i c k s  w h i c h seemed r e l a t e d t o t h e m i g r a t i o n  o f hens w i t h  chicks.  54  A l s o , i t appears t h a t hens w i t h b r o o d m i g r a t e a t about t h e same time each y e a r ( B e n d e l l and E l l i o t t ,  1967) and m i g r a t i o n  i s f a i r l y r a p i d once i t has begun (Lance, 1967).  The  e v i d e n c e s u g g e s t s t h a t i n hens and young, as i n the c o c k s , p h y s i o l o g i c a l e v e n t s a r e more i m p o r t a n t i n m i g r a t i o n t h a n i s the food supply.  55 SUMMARY  1.  The c r o p c o n t e n t s  c f 875 b l u e  grouse c o l l e c t e d a t three  a r e a s o n V a n c o u v e r I s l a n d v/ere a n a l y z e d  t o determine the  l a t e s p r i n g a n d summer f o o d h a b i t s o f t h e b i r d s . 2.  The t r a n s i t i o n f r o m t h e w i n t e r summer f o o d s o c c u r r e d  3.  d i e t t o more  succulent  l a t e r i n males than i n females.  The s p r i n g a n d e a r l y summer d i e t o f a d u l t f e m a l e s was m a i n l y l e a f m a t e r i a l and f l o w e r s .  4.  Adults the  5.  c o n s u m e d s m a l l amounts o f i n v e r t e b r a t e s  throughout  summer.  The d i e t o f c h i c k s c o n s i s t e d m a i n l y o f i n v e r t e b r a t e s t h e b i r d s v/ere a p p r o x i m a t e l y t h r e e w e e k s o f a g e .  until  After  t h a t time p l a n t foods predominated i n the d i e t and by l a t e summer t h e f o o d s o f c h i c k s v/ere v e r y  similar to  those eaten by a d u l t s . 6.  O v e r 80 p e r c e n t  (by w e i g h t ) o f t h e d i e t o f t h e b i r d s  e x a m i n e d was made u p b y t h e f o l l o w i n g f o o d Pseudotsuqa m e n z i e s i i needles, Pteridium  acruilinum fronds,  T r i f o l i u m spp. leaves, Rubus u r s i n u s  fruits,  Vaccinium spp. f r u i t s , 7.  itemst  S a l i x spp. leaves,  Gaultheria shallon  Hypochaeris r a d i c a t a Gaultheria  shallon  flowers,  fruits',  and animal matter.  The f r e q u e n c y o f o c c u r r e n c e o f g r a v e l i n c r o p s i n the late  summer.  leaves,  increased  56 8.  The w e i g h t o f c r o p c o n t e n t s i n c r e a s e d t h r o u g h o u t t h e and  9.  day,  the h i g h e s t w e i g h t s were from b i r d s c o l l e c t e d a t dusk.  B l u e grouse were found t o s e l e c t p a r t s o f p l a n t s w h i l e o n t h e summer r a n g e .  10.  The  degree  o f use o f f o o d i t e m s w i t h i n a f o o d t y p e  i n f l u e n c e d by t h e i r a v a i l a b i l i t y and 11.  was  condition.  C h i c k s a t e a n i m a l f o o d i n the o r d e r o f abundance o f i n v e r t e b r a t e s i n the  the  field.  12.  I n v e r t e b r a t e s were t a k e n m a i n l y from the v e g e t a t i o n .  13.  The  p r o t e i n and m i n e r a l c o n t e n t o f the d i e t o f  i n c r e a s e d d u r i n g t h e r e p r o d u c t i v e s e a s o n due of  foods.  at which mineral 14.  selection moult,  time the d i e t of males i n c r e a s e d i n p r o t e i n  and  level.  T h e r e w e r e no a p p a r e n t d i f f e r e n c e s ,  ( y e a r l i n g ) b i r d s w h i c h c o u l d be i n r e p r o d u c t i v e performance The  to  They r e m a i n e d h i g h d u r i n g t h e p e r i o d o f  i n e i t h e r males o r  f e m a l e s , between the d i e t s o f a d u l t and  15.  females  sub-adult  r e l a t e d to  o f t h e two age  differences classes.  s p r i n g d i e t o f hens c o u l d n o t be r e l a t e d t o t h e  e a r l y s u r v i v a l o f c h i c k s i n 1962,  or to the l a t e  poor  hatch  that year. 16.  S e l e c t i o n of foods r e s u l t e d i n s i m i l a r d i e t s f o r grouse from a r e a s w h i c h were d i f f e r e n t i n terms o f type amount o f v e g e t a t i o n a l  17.  The  altitudinal  and  cover.  m i g r a t i o n o f b l u e grouse  i n autumn  t o be c a u s e d b y f a c t o r s o t h e r t h a n t h e f o o d s u p p l y .  appears  57 LITERATURE CITED  B a i l e y , A.M.  192 7. 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