Open Collections

UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Comparative habitats of, and competition between, the long-billed marsh wren and the red-winged blackbird… Runyan, Craig Steven 1979

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

Notice for Google Chrome users:
If you are having trouble viewing or searching the PDF with Google Chrome, please download it here instead.

Item Metadata

Download

Media
831-UBC_1979_A6_7 R85.pdf [ 5.87MB ]
Metadata
JSON: 831-1.0094587.json
JSON-LD: 831-1.0094587-ld.json
RDF/XML (Pretty): 831-1.0094587-rdf.xml
RDF/JSON: 831-1.0094587-rdf.json
Turtle: 831-1.0094587-turtle.txt
N-Triples: 831-1.0094587-rdf-ntriples.txt
Original Record: 831-1.0094587-source.json
Full Text
831-1.0094587-fulltext.txt
Citation
831-1.0094587.ris

Full Text

C O M P A R A T I V E H A B I T A T S O F , AMD C O M P E T I T I O N B E T W E E N , THE L O N G - B I L L E D MARSH S E E N AND THE B E D - H I N G E D B L A C K B I R D AT P I T T MEADOWS, B R I T I S H COLOMBIA by C r a i g S t e v e n R u n y a n B . S c , U n i v e r s i t y o f C o l o r a d o , 1970 A T H E S I S SUBMITTED I N P A R T I A L F U L F I L L M E N T OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF S C I E N C E i n THE F A C U L T Y OF GRADUATE S T U D I E S D e p a r t m e n t o f Z o o l o g y We a c c e p t t h i s t h e s i s a s c o n f o r m i n g , t o t h e r e q u i r e d s t a n d a r d THE U N I V E R S I T Y OF B R I T I S H C O L U M B I A M a y , 1979 © C r a i g S t e v e n R u n y a n In presenting th i s thes is in pa r t i a l fu l f i lment of the requirements for an advanced degree at the Un ivers i ty of B r i t i s h Columbia, I agree that the L ibrary sha l l make it f ree l y ava i l ab le for reference and study. I fur ther agree that permission for extensive copying of th is thesis for scho lar ly purposes may be granted by the Head of my Department or by his representat ives. It is understood that copying or pub l i ca t ion of th is thes is for f inanc ia l gain sha l l not be allowed without my writ ten pe rm i ss ion . Department of Zoology The Univers i ty of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date April 12, 1979 i i ABSTRACT T h e o b j e c t i v e s o f t h e s t u d y w e r e t o d e t e r m i n e t h e y e a r - r o u n d d i s t r i b u t i o n a n d h a b i t a t s e l e c t i o n o f f o u r m a r s h p a s s e r i n e s p e c i e s , a s d e s c r i b e d by v e g e t a t i o n t y p e a n d i t s p h y s i c a l c h a r a c t e r i s t i c s , a n d t o i n v e s t i g a t e i n t e r s p e c i f i c c o m p e t i t i o n a s a f a c t o r i n t h e h a b i t a t s e l e c t i o n o f t h e L o n g - b i l l e d M a r s h W r e n a n d t h e R e d - w i n g e d B l a c k b i r d . F u l f i l l m e n t o f t h e s e o b j e c t i v e s s h o u l d h e l p t h e B . C . F i s h a n d W i l d l i f e B r a n c h t o a s s e s s t h e e f f e c t s o f t h e i r management p l a n s o n m a r s h p a s s e r i n e s -I d e t e r m i n e d t h e a b u n d a n c e o f f o u r p a s s e r i n e s p e c i e s i n d i f f e r e n t v e g e t a t i o n t y p e s v i a m a r s h c e n s u s t r a n s e c t s o v e r t h e p e r i o d o f one y e a r . N e s t i n g h a b i t a t a n d b r e e d i n g i n f o r m a t i o n o n m a r s h w r e n s a n d r e d w i n g s was o b t a i n e d v i a n e s t s t u d y p l o t s . The r e s u l t s w e r e : - A r e a s t r a v e r s e d f r o m t h e c e n t r a l a n d d e e p e s t m a r s h o u t w a r d t o w a r d s h i g h e r g r o u n d a r e i n h a b i t e d b y r e d w i n g s , m a r s h w r e n s . Common Y e l l o w t h r o a t s , and Song S p a r r o w s , r e s p e c t i v e l y . - H a b i t a t s o f w r e n s a n d r e d w i n g s a r e s p a t i a l l y a n d t e m p o r a l l y s e g r e g a t e d . W r e n s u s e t h e " D e n s e S p i r a e a " ( H a r d h a c k s h r u b ) h a b i t a t e x t e n s i v e l y , w h i l e r e d w i n g s u s e i t h a r d l y a t a l l i n t h e m a r s h . S i m i l a r l y , r e d w i n g s a r e a b u n d a n t i n S c i r E U s c y p e r i n u s ( H a i r y -s e e d e d B u l r u s h ) , w h e r e a s w r e n s s e l d o m u s e t h i s h a b i t a t . B o t h w r e n s a n d r e d w i n g s u s e o t h e r v e g e t a t i o n t y p e s , b u t r e d w i n g s u s e t hem i n t h e l a t e s p r i n g , w h e r e a s w r e n s u s e t h e m i n t h e summer . - B o t h w r e n s a n d r e d w i n g s h a v e l o w e r r e p r o d u c t i v e s u c c e s s when n e s t i n g i n c l o s e p r o x i m i t y t h a n when n e s t i n g a p a r t . T h i s s u p p o r t s t h e h y p o t h e s i s t h a t i n t e r s p e c i f i c c o m p e t i t i o n e x i s t s a n d i n d i c a t e s t h a t s e l e c t i o n may f a v o u r h a b i t a t s e g r e g a t i o n . , - I a l s o f o u n d m u t u a l s u p p r e s s i o n o f r e p r o d u c t i v e s u c c e s s when t h e e f f e c t s o f d i f f e r e n t v e g e t a t i o n t y p e s w e r e r e m o v e d . The r e s u l t s w e r e 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 h o w e v e r , p o s s i b l y due t o s m a l l s a m p l e s i z e s . - O f t h e o b s e r v e d d i f f e r e n c e s b e t w e e n t h e p h y s i c a l n e s t s i t e p a r a m e t e r s o f w r e n s a n d r e d w i n g s , v e g e t a t i o n h e i g h t a n d p r e s e n c e a n d / o r d e p t h o f w a t e r r e q u i r e f u r t h e r i n v e s t i g a t i o n a s f a c t o r s i n t h e h a b i t a t s e l e c t i o n o f t h e t w o s p e c i e s . - B r e n - w r e n c o m p e t i t i o n d o e s n o t a p p e a r t o a f f e c t w r e n n e s t i n g s u c c e s s i n t h e p r e s e n t s t u d y m a r s h . Managemen t r e c o m m e n d a t i o n s a r e g i v e n b a s e d on t h e o b j e c t i v e o f m a i n t a i n i n g a n d p o s s i b l y e n h a n c i n g b i r d s p e c i e s d i v e r s i t y i n t h e s t u d y m a r s h . i v T A B L E OF CONTENTS &J&SJTHACT .•••••••••••••••*•••-•••••*•••*•»•••••*/••••'•*••••'••«• 1 i L I S T OF TABLES • <•••••••••**••••••••••••*••••••*• •. • • • V i L I S T OF F I G U R E S . ^ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v i i ACKNOWLEDGEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i x INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 O b j e c t i v e s . . . . . . . . * . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 L i t e r a t u r e R e v i e w . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 R e s e a r c h H y p o t h e s e s . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 METHODS 10 S t u d y A r e a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 M a j o r P l a n t S p e c i e s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 I n t r o d u c t i o n And L i m i t a t i o n s O f M e t h o d s . . . . . . . . . . . . . . . . . 24 C e n s u s T r a n s e c t s ............................^.......... . 26 N e s t S t u d y P l o t s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 fi£S UIi TS • • •••••••*•••• • • • ******** * ^ 0 G e n e r a l R e s u l t s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 S i n t e r H a b i t a t S e l e c t i o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 C o m p a r a t i v e N e s t i n g I n f o r m a t i o n . . . . . . . . . . . . . . . . . . . . . . . 4 3 P h y s i c a l N e s t S i t e P a r a m e t e r s ............^............ 44 V e g e t a t i o n T y p e S e l e c t i o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 C e n s u s T r a n s e c t s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 N e s t S u b s t r a t e . . . . . . . . . . . . . . . . . . . • . . . * . . . * , . , , • . . . . . « . 52 S u b s t r a t e U t i l i z a t i o n - Maps O f N e s t P l o t s 61 S u b s t r a t e U t i l i z a t i o n - A n a l y s i s . . . . . . . . . . . . . . . . . . . . 87 Sum HI & IT y • • * • • • • • * • * • • • . 99 C o m p e t . i t . i o n • • • • . 101 H c e n - R e d w i n g . . . . . . » . . . . . . . . . . . . . . . . . . . . . , . . • • • . . • • • - • • • 101 Wren— R r e n . . . . . . . . . . . . . . • • , . » . , . . , . , , . . . . , « , . • • » , . . . . 1 0 8 DXS CO SSXO N . . . . . . • • • • • < » • , • • • . • • « * • • • • . • 113 B i o l o g i c a l I m p l i c a t i o n s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 R e v i e w O f H y p o t h e s e s 113 C o m p a r i s o n s W i t h O t h e r S t u d i e s . . . . . . . . . . . . . . . . . . . . . . . . 1 1 4 H a b i t a t S e g r e g a t i o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 C o m p e t i t i o n - - - . - . . - . . , . - • . . . - - - . . . - - - . - • . » . - . . - - - - • • 117 F a c t o r s O t h e r T h a n I n t e r s p e c i f i c C o m p e t i t i o n . . . . . . . . . . 120 F a c t o r s O p p o s i n g S e g r e g a t i o n . . . . . . . . . . . . . . . . . . . . . . ~ . . . 124 C l o s i n g S t a t e m e n t 126 Management I m p l i c a t i o n s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 L I T E B S T O R E C I T E D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 A P P E N D I X 135 v i L I S T OF T A B L E S T a b l e I . D i s t r i b u t i o n o f V e g e t a t i o n T y p e s i n T r a n s e c t s 29 T a b l e I I . V e g e t a t i o n A r e a s i n N e s t S t u d y P l o t s . . . . . . . . . 37 T a b l e I I I . C o m p a r a t i v e P h y s i c a l N e s t S i t e P a r a m e t e r s . . . . 4 5 T a b l e I V . N e s t N u m b e r s i n D i f f e r e n t V e g e t a t i o n i n N e s t S t u d y P l o t s 88 T a b l e V . C h r o n o l o g y o f Wren N e s t S u b s t r a t e C h o i c e . . . . . 9 6 T a b l e V I . C h r o n o l o g y o f R e d w i n g S u b s t r a t e C h o i c e . . . . . . . 97 T a b l e V I I . N e s t S u c c e s s v s . v e g e t a t i o n T y p e Osed a s N e s t S u b s t r a t e ....•,,.•>•, M . . <r* *.« 98 T a b l e V I I I . C l o s e s t R e d w i n g N e s t D i s t a n c e C a t e g o r y v s . Wren N e s t S u c c e s s . . . . . . . . . . . . . . . . . . . . . . . . 106 T a b l e I X . C l o s e s t H a r s h Wren N e s t D i s t a n c e v s . R e d w i n g N e s t S u c c e s s . . . . . . . . . . . . . . . . . - , . . . . . . . . . . . . 107 T a b l e X . M u t u a l S u p r e s s i o n o f N e s t i n g . S u c c e s s i n D i f f e r e n t V e g e t a t i o n T y p e s . . . . . . . . . . . . . . . . . . . 109 T a b l e X I . C l o s e s t Wren N e s t D i s t a n c e v s . W r e n N e s t S u c c e s s F o r A l l N e s t s . . . . . . . . . . . . . . . . . . . . . . . . 1 1 0 T a b l e X I I . C l o s e s t Wren N e s t D i s t a n c e v s . Wren N e s t S u c c e s s f o r N e s t s C l o s e r T h a n 50 m F r o m a R e d w i n g N e s t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 v i i L I S T OF F I G U R E S F i g u r e 1. S t u d y A r e a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 F i g u r e 2 . S c i r p u s a c u t u s ( H a r d - s t e m m e d B u l r u s h ) . . . . . . . . . 14 F i g u r e 3 . S c i r p u s c y p e r i n u s . ( H a i r y - s e e d e d B u l r u s h ) . . . . . . 16 F i g u r e 4 . C a r e x r o s t r a t a and C a r e x s i t c h e n s i s (Low S e d g e ) 18 F i g u r e 5 . T y p h a l a t i f o l i a ( B r o a d - l e a v e d C a t t a i l ) . . . . . . . . 20 F i g u r e 6. S p i r a e a d o u g l a s i i ( H a r d h a c k ) . . . . . . . . . . . . . . . . . . 22 F i g u r e 7 . L o c a t i o n o f H a r s h C e n s u s T r a n s e c t s . . . . . . . . . . . . 27 F i g u r e 8 . T i m e C a t e g o r i e s f o r M a r s h C e n s u s e s . . . . . . . . . . . . 31 F i g u r e 9 . L o c a t i o n o f M a r s h N e s t S t u d y P l o t s ( S h a d e d A r e a s ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 5 F i g u r e 1 0 . E a r l y W i n t e r R e d w i n g A b u n d a n c e on M a r s h C e n s u s e s 41 F i g u r e 1 1 . N o n - b r e e d i n g S e a s o n M a r s h C e n s u s R e s u l t s by V e g e t a t i o n T y p e f o r M a r s h Wren a n d R e d - w i n g e d B l a c k b i r d 4 8 F i g u r e 1 2 . B r e e d i n g S e a s o n M a r s h C e n s u s R e s u l t s by V e g e t a t i o n T y p e f o r M a r s h Wren and R e d - w i n g e d B l a c k b i r d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 0 F i g u r e 1 3 . L a t e S p r i n g a n d Summer C e n s u s R e s u l t s i n S . a c u t u s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3 F i g u r e 14 . L a t e S p r i n g a n d Summer C e n s u s R e s u l t s i n S . c y p e r i n u s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 F i g u r e 1 5 . N o n - b r e e d i n g S e a s o n M a r s h C e n s u s R e s u l t s b y V e g e t a t i o n T y p e f o r Y e l l o w t h r o a t a n d S o n g v i i i S p a r r o w . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 F i g u r e 1 6 . B r e e d i n g S e a s o n M a r s h C e n s u s R e s u l t s b y V e g e t a t i o n T y p e f o r Y e l l o w t h r o a t a n d S o n g S p cLTTlTOtf • 59 F i g u r e 1 7 . L e g e n d : V e g e t a t i o n C o v e r M a p s , B e s t S t u d y P l o t s 62 F i g u r e 1 8 . N e s t D i s t r i b u t i o n i n P l o t A , L a t e S p r i n g . . . . . . 64 F i g u r e 1 9 . N e s t D i s t r i b u t i o n i n P l o t A , Summer . . . . . . . . . . . 66 F i g u r e 2 0 . N e s t D i s t r i b u t i o n i n P l o t B , L a t e S p r i n g . . . . . . 68 F i g u r e 2 1 . . . N e s t D i s t r i b u t i o n i n P l o t B , Summer . . . . . . . . . . . 70 F i g u r e 2 2 . N e s t D i s t r i b u t i o n i n P l o t C , L a t e S p r i n g . . . . . . 72 F i g u r e 2 3 . N e s t D i s t r i b u t i o n i n P l o t D , L a t e S p r i n g . . . . . . 74 F i g u r e 2 4 . N e s t D i s t r i b u t i o n i n P l o t D , Summer . . . . . . . . . . . 76 F i g u r e 2 5 . N e s t D i s t r i b u t i o n i n P l o t E , L a t e S p r i n g . . . . . . 78 F i g u r e 2 6 . N e s t D i s t r i b u t i o n i n P l o t E , Summer . . . . . . . . . . . 8 0 F i g u r e 2 7 . N e s t D i s t r i b u t i o n i n P l o t F , L a t e S p r i n g . . . . . . 82 F i g u r e 2 8 . N e s t D i s t r i b u t i o n i n P l o t F , Summer . . . . . . . . . . . 84 F i g u r e 2 9 . W e i g h t e d N e s t D i s t r i b u t i o n s b y V e g e t a t i o n , E n t x i r © S 6 • * • • * • • » • * • • • • • * * * / * • • » • • ' • • • • • • »^ • • 39 F i g u r e 3 0 . W e i g h t e d N e s t D i s t r i b u t i o n s by V e g e t a t i o n ; L a t e S p r i n g . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 F i g u r e 3 1 . W e i g h t e d N e s t D i s t r i b u t i o n s b y V e g e t a t i o n , F i g u r e 3 2 - D i s t r i b u t i o n o f R e d w i n g N e s t O u t c o m e w i t h R e s p e c t t o I n t e r s p e c i f i c D i s t a n c e . . . . . . . . . . . . . 102 F i g u r e 3 3 . D i s t r i b u t i o n o f H r e n N e s t O u t c o m e w i t h R e s p e c t t o I n t e r s p e c i f i c D i s t a n c e . . . . . . . . . . . . . . . . . . . . . 104 ACKNOWLEDGEMENTS F u n d s f o r t h e f i e l d w o r k o f t h i s s t u d y w e r e p r o v i d e d by D u c k s U n l i m i t e d ( C a n a d a ) . S u p p l e m e n t a r y f u n d s w e r e a l s o p r o v i d e d b y t h e B . C . F i s h a n d m i d l i f e B r a n c h . I n a t i m e o f b u d g e t c u t s a n d a u s t e r i t y p r o g r a m s , t h i s c o m m i t m e n t t o w a r d s a n h o l i s t i c a p p r o a c h t o w i l d l i f e managemen t i s h i g h l y c o m m e n d a b l e . ' f B e y o n d t h e c a l l o f d u t y " i s an a p p r o p r i a t e c l i c h e t h a t a c c u r a t e l y d e s c r i b e s t h e e f f o r t s o f s e v e r a l o f t h e i n d i v i d u a l s who a s s i s t e d me . O u t s t a n d i n g among t h e s e a r e Torn B u r g e s s o f t h e B . C . F i s h a n d W i l d l i f e B r a n c h , f i e l d a s s i s t a n t s R o b i n B o b i n s o n a n d K a r l S t u r m a n i s , a n d my s u p e r v i s o r . D r . L e e G a s s , w h o s e h e l p a n d s u g g e s t i o n s , a s w e l l a s t h o s e o f t h e o t h e r members o f my c o m m i t t e e , w e r e i n v a l u a b l e . O f t h e many d i s c u s s i o n s w i t h c o l l e a g u e s o n my r e s e a r c h t o p i c , n o n e w e r e more f r u i t f u l t h a n t h o s e w i t h J a r o s l a v P i e m a n , w h o s e s t u d i e s o f t h e s e t w o s p e c i e s i n s p i r e d my own i n t e r e s t . N e i l G i l b e r t a n d D r . C . W e h r h a h n p r o v i d e d a d v i c e on s t a t i s t i c s . F i n a l l y , I t h a n k my w i f e a n d d e a r f r i e n d T a n a f o r h e r p a t i e n c e a n d s u p p o r t d u r i n g my r e s e a r c h p r o g r a m . 1 INTRODUCTION O b j e c t i v e s The o b j e c t i v e s o f t h i s s t u d y a r e : 1. To d e t e r m i n e t h e y e a r - r o u n d d i s t r i b u t i o n a n d h a b i t a t s e l e c t i o n * o f f o u r m a r s h p a s s e r i n e s p e c i e s a s d e s c r i b e d b y v e g e t a t i o n t y p e a n d i t s p h y s i c a l c h a r a c t e r i s t i c s . 2 . T o i n v e s t i g a t e i n t e r s p e c i f i c c o m p e t i t i o n b e t w e e n t h e L o n g - b i l l e d M a r s h W r e n , T e l m a t o d y t e s p a l u s t r i s , a n d t h e R e d - w i n g e d B l a c k b i r d , A g e l a i u s p h o e n i c e u s . a s a f a c t o r i n h a b i t a t s e l e c t i o n . I t i s h o p e d t h a t t h i s i n f o r m a t i o n w i l l a i d t h e B . C . F i s h a n d W i l d l i f e B r a n c h i n t h e i r management o f t h e P i t t W i l d l i f e M a n a g e m e n t A r e a (PWMA) . T h i s a r e a i s i n t e n d e d f o r m u l t i p l e r e c r e a t i o n a l u s e , a n d s p e c i e s d i v e r s i t y i s t h u s i m p o r t a n t . An u n d e r s t a n d i n g o f t h e h a b i t a t r e q u i r e m e n t s o f t h e m a r s h p a s s e r i n e s w i l l h e l p t o a v o i d a n y d r a s t i c r e d u c t i o n s i n t h e s e p o p u l a t i o n s r e s u l t i n g f r o m h a b i t a t m a n i p u l a t i o n s . , B e c a u s e t h e s t u d y m a r s h c o n t a i n s u n i f o r m s t a n d s o f d i v e r s e f l o r a , f r o m s e d g e s ( C y p e r a c e a e ) t o s h r u b s ( f i o s a c a e a ) , a n y o b s e r v e d d i f f e r e n c e i n u t i l i z e d v e g e t a t i o n t y p e w i l l l i k e l y r e f l e c t d i f f e r e n c e s i n h a b i t a t r e q u i r e m e n t s . * T h e t e r m s " S e l e c t e d " a n d ^ U t i l i z e d " b o t h r e f e r i n t h i s t h e s i s t o t h e " R e a l i z e d " a s o p p o s e d t o t h e " F u n d a m e n t a l " , o r t h a t o c c u p i e d i n t h e a b s e n c e o f c o m p e t i t i v e i n t e r a c t i o n s , h a b i t a t ( M i l l e r 1 9 6 7 ) . 2 L i t e r a t u r e Review Though other passerine species occasionally occur i n the study marsh (Runyan 1978), by f a r the most abundant species, i n order of decreasing abundance, are: Long-billed Marsh Wren, Red-winged Blackbird, Common Yellowthroat (Geothiypis t r i c h a s ) . and Song .Sparrow (Melospiza melodia) . Wrens, redwings, and Song Sparrows are present year-round, whereas yellowthroats are present during the breeding season only. I gathered detailed data primarily on wrens and redwings, and I w i l l review the l i t e r a t u r e f o r these two species. 1. Vegetation Type Selection During the breeding season, wrens and redwings use a wide variety of vegetation for nesting substrate, including c a t t a i l (Typhaceae), sedges, 1 and shrubs (Bent 1948, 1958), though they appear to prefer c a t t a i l . Redwings also use trees (Bent 1958) . The two species overlap extensively i n t h e i r use of substrate vegetation. Burt (1970) found that a l l substrates used by wrens were also used by redwings; however, Burt did not use h i s data to explore the p o s s i b i l i t y of temporal differences. Though wrens are sometimes most abundant i n sedges (Scirpus, or bulrush, Allen 1914; Carex, Burt 1970) or grasses (Spartina, Kale 1965) compared to other available vegetation, they seem to prefer c a t t a i l (Typha spp^ ),..., Welter (1935) found most nests 1 I use the term "sedge" throughout t h i s thesis i n reference to the; sedge family (Cyperaceae) , which includes the genera S.cirpus (bulrush) and Carex (sedge) . , ,; j 3 a t t a c h e d t o T y p h a , t h o u g h C a r e x was a l s o a b u n d a n t w i t h i n w r e n t e r r i t o r i e s . I n b o t h e a s t e r n a n d w e s t e r n W a s h i n g t o n m a r s h e s , T y p h a was p r e f e r r e d o v e r S c i r p u s a c u t u s , a n d n e s t s i n S c i r ^ u s s l i p p e d down s t e m s a n d / o r w e r e b l o w n l o o s e more o f t e n t h a n n e s t s i n T y p h a ( V e r n e r 1 9 6 5 , V e r n e r a n d E n g e l s e n 1 9 7 0 ) . , E x t e n s i v e s t u d i e s i n a b r a c k i s h m a r s h i n V a n c o u v e r h a v e f o u n d w r e n s n e s t i n g i u T y p h a t h r o u g h o u t t h e s e a s o n , p r e f e r r i n g i t , i n t h e s p r i n g , t o t h e p r e v i o u s y e a r ' s g r o w t h o f S c i r p u s . I n t h e s u m m e r , when new S c i r p u s g r o w t h i s a v a i l a b l e , w r e n n e s t d e n s i t i e s w e r e f a i r l y e q u a l i n b o t h p l a n t s ( P i e m a n , p e r s . c o m m . ) . The o n l y s t u d y i n w h i c h T y p h a was a v a i l a b l e a n d was n o t u t i l i z e d b y w r e n s was by B u r t ( 1 9 7 0 ) . B o t h r e d - w i n g e d a n d y e l l o w - h e a d e d ( X a n t h o c e p h a l u s x a n t h o c e p h a l u s ) • b l a c k b i r d s u t i l i z e d t h e T y p h a e x t e n s i v e l y , a n d f r e q u e n t l y o b s e r v e d a g g r e s s i o n t o w a r d s w r e n s i n h i s s t u d y s u g g e s t s t h e b l a c k b i r d s may h a v e e x c l u d e d w r e n s f r o m t h a t v e g e t a t i o n . T h o u g h no d e t a i l e d i n f o r m a t i o n i s a v a i l a b l e o n s h r u b - n e s t i n g b y w r e n s . W e l t e r ( 1 9 3 5 ) , B e n t ( 1 9 4 8 ) , a n d V e r n e r (1965) m e n t i o n t h e p h e n o m e n o n . The l a t t e r r e f e r s t o w r e n s n e s t i n g i n S p i r a e a d o u g l a s i i n e a r S e a t t l e , W a s h i n g t o n , a n a b u n d a n t s h r u b i n t h e p r e s e n t s t u d y m a r s h . . R e d w i n g s a l s o seem t o f a v o r c a t t a i l o v e r s e d g e s , a s n e s t i n g s u b s t r a t e . B u r t * s (1970) s t u d y i s t h e o n l y one i n w h i c h b o t h p l a n t f a m i l i e s a p p e a r t o be e q u a l l y i m p o r t a n t t o r e d w i n g s . C a t t a i l d o m i n a t e s t h e s t u d i e s o f A l l e n (1914) a n d C a s e a n d H e w i t t (1963) . . . . R e d w i n g s p r e f e r r e d T y p h a o v e r S c i r p u s i n a m a r s h x n t h e i n t e r i o r o f B r i t i s h C o l u m b i a , a n d s e v e r a l o f t h e i r n e s t s s l i d down o r t i l t e d t o o n e s i d e on S c i r p u s s t e m s ( F o w l e 1 9 4 2 ) . 4 F o w l e e x p l a i n e d t h i s i n t e r m s o f T y j J h a ' s s u p e r i o r n e s t s u p p o r t i n g p r o p e r t i e s . H o l m (1973 ) f o u n d r e d w i n g n e s t s w e r e more s u c c e s s f u l i n Ty.pjia t h a n S c i r p u s , a n d t h e l a t t e r g e n u s , t h o u g h a s e q u a l l y a b u n d a n t a s T y j j h a , was s e l d o m u s e d by r e d w i n g s i n P i e m a n ' s s t u d y . S e v e r a l a u t h o r s a l s o g i v e e v i d e n c e f o r a p r e f e r e n c e f o r m o d e r a t e t o s p a r s e d e n s i t y T y p h a s t a n d s o v e r d e n s e s t a n d s ( A l l e n 1 9 1 4 , Ho lm 1 9 7 3 , L i n s d a l e 1 9 3 8 ) . N e s t i n g i n s h r u b s by r e d w i n g s was i n v e s t i g a t e d i n one e a s t e r n s a l t m a r s h i n w h i c h t a l l s h o r e l i n e s h r u b s a n d r o b u s t h e r b a c e o u s p l a n t s s u p p o r t e d 9556 o f a l l n e s t s ( S e a n l e y a n d Webb 1 9 6 3 ) . S m i t h (1943) s u g g e s t s a h i g h e r s u c c e s s r a t e i n some " b r u s h y " c o m m u n i t i e s due t o g r e a t e r c o n c e a l m e n t . The i m p o r t a n c e o f w a t e r l e v e l s , h o w e v e r , c a n n o t be o v e r l o o k e d . O f 21 r e d w i n g n e s t s i n s h r u b s f o u n d by Ho lm ( 1 9 7 3 ) , a l l h a d w a t e r b e n e a t h , a n d i n a d r y y e a r when w a t e r was a b s e n t f r o m t h e a r e a , r e d w i n g s d i d n o t n e s t t h e r e . N e s t i n g s u c c e s s a n d b r e e d i n g d e n s i t y o f r e d w i n g s h a s a l s o b e e n f o u n d t o b e g r e a t e r i n m a r s h h a b i t a t t h a n i n u p l a n d s ( f i o b e r t s o n 1 9 7 2 ) . B o b e r t s o n o b s e r v e d a l o w e r i n c i d e n c e o f n e s t p r e d a t i o n i n m a r s h e s t h a n i n u p l a n d s , a n d he c i t e d t h e p r e s e n c e o f w a t e r a s a n i m p o r t a n t f a c t o r t h a t l i m i t s p r e d a t i o n . 2 . S p a t i a l S e g r e g a t i o n T h e n e s t s i t e s o f w r e n s a n d r e d w i n g s a p p e a r t o b e s p a t i a l l y s e g r e g a t e d , t h o u g h t h e i r t e r r i t o r i e s a r e n o t c o m p l e t e l y m u t u a l l y e x c l u s i v e ( O r i a n s a n d W i l l s o n 1 9 6 4 , W i l l s o n 1 9 6 7 , B u r t 1 9 7 0 , P i e m a n 1 9 7 7 a ) . D i f f e r e n c e s i n c h o s e n p h y s i c a l c h a r a c t e r i s t i c s a t n e s t s i t e s may c a u s e s e g r e g a t i o n . F o r e x a m p l e , w r e n s p r e f e r 5 d e n s e r v e g e t a t i o n , a t l e a s t i n t h e p r e s e n c e o f r e d w i n g s ( P i e m a n , p e r s - comm. ; ) . A g g r e s s i v e i n t e r a c t i o n s b e t w e e n w r e n s a n d r e d w i n g s , h o w e v e r , may b e t h e mos t i m p o r t a n t d r i v i n g f o r c e b e h i n d t h e i r s e g r e g a t i o n ( P i e m a n 1 9 7 7 a ) -3 . I n t e r s p e c i f i c C o m p e t i t i o n C o m p e t i t i o n c a n be a n i m p o r t a n t f a c t o r i n h a b i t a t s e l e c t i o n ( H i l d e n 1 9 6 5 ) . I n t e r s p e c i f i c c o m p e t i t i o n may r e s t r i c t s p e c i e s t o h a b i t a t t o w h i c h t h e y a r e b e s t a d a p t e d , w h i l e , i n t r a s p e c i f i c c o m p e t i t i o n may f o r c e i n d i v i d u a l s i n t o more m a r g i n a l h a b i t a t ( S v a r d s o n 1 9 4 9 ) . T h u s , much o f t h e d e s c r i p t i o n o f h a b i t a t s r e p r e s e n t s " R e a l i z e d " a s o p p o s e d t o " F u n d a m e n t a l " h a b i t a t ( M i l l e r 1 9 6 7 ) . I n t e r f e r e n c e c o m p e t i t i o n , w h e r e o n e s p e c i e s i s k e p t f r o m a r e s o u r c e by a n o t h e r , i s c o m m o n l y e n c o u n t e r e d i n b i r d s p e c i e s ( M i l l e r o p . c i t . ) a n d i s f a i r l y e a s y t o d e t e c t i n t y p i c a l s h o r t - t e r m s t u d i e s ( J a e g e r 1 9 7 4 ) . I n a d d i t i o n t o o b s e r v a t i o n s o f i n t e r s p e c i f i c a g g r e s s i o n , e v i d e n c e may t a k e t h e f o r m o f t w o s p e c i e s h a v i n g a n e g a t i v e e f f e c t o n e a c h o t h e r . T h i s i s s i m i l a r t o M a c A r t h u r ' s (1972) p r a c t i c a l d e f i n i t i o n f o r c o m p e t i t i o n : " O r g a n i s m s c o m p e t e i f an i n c r e a s e i n a n y one s p e c i e s h a r m s t h e o t h e r . • » The r e l a t i o n s h i p mus t a l s o b e r e c i p r o c a l t o f i t t h i s d e f i n i t i o n o f c o m p e t i t i o n . R e d w i n g s a g g r e s s i v e l y d i s p l a c e w r e n s . O b s e r v a t i o n s o f r e d -w i n g c h a s e s ( O r i a n s a n d W i l l s o n 1 9 6 4 , N e r o 1 9 5 6 , B u r t 1 9 7 0 , P i e m a n , p e r s . comm.) a n d a p p a r e n t d i s p l a c e m e n t o f w r e n t e r r i t o r i e s ( V e r n e r 1 9 7 5 a , B u r t 1970) a r e common. B u r t ( p p . c i t . ) o b s e r v e d b o t h w r e n s a n d r e d w i n g s m o v i n g i n t o c e n t r a l ( d e e p e r w a t e r ) m a r s h h a b i t a t a f t e r Y e l l o w - h e a d e d B l a c k b i r d s h a d cpmpleted nesting. Based on subsequent nest d i s t r i b u t i o n , redwings appeared to push wrens back toward the periphery, leaving themselves sole occupants of the c e n t r a l marsh. Yellow-headed Blackbirds are even more aggressive towards wrens than are redwings (Burt op. c i t . ) , and both species probably a f f e c t wren d i s t r i b u t i o n . In Verner*s (1975a) study, wren t e r r i t o r y contracted a f t e r the appearance of Yellow-headed and Sed-winged Blackbirds and re-expanded afte r the blackbirds completed nesting and l e f t the immediate area. The only wren nest simultaneously active with the blackbird nests was abandoned. This wren nest was located within 10 m from both a yellowhead and a redwing nest. &n interference mechanism used by wrens against blackbirds i s destruction of eggs (Alien 1914, Pieman 1977a) and nestlings (Pieman op. c i t . ) . A s i g n i f i c a n t (28%) proportion of 51 redwin nests observed by A l l e n (1914) contained broken eggs. Because he observed wren-redwing egg destruction, he believed most of these eggs were broken by wrens. Pieman (1977a) also observed t h i s destruction by wrens of the contents of both natural and experimentally placed redwing nests. Burt (1970) and Pieman (1977a) observed lower redwing nesting success close to wren nests. The l a t t e r study showed that the successful proportion of nests i n successive wren^redwing distance categories was p o s i t i v e l y correlated with the means of the distances i n each category. The successful proportion of a l l redwing nests withi 10 m of the nearest wren nest was very low (.11 f o r N = 30, Pieman, pers. comm.). 7 M a r s h w r e n s a l s o d e s t r o y e g g s a n d y o u n g o f o t h e r w r e n s , a n d t h i s i n t r a s p e c i f i c c o m p e t i t i o n m i g h t be a n i m p o r t a n t f a c t o r i n _ t h e n e s t i n g s u c c e s s o f d e n s e w r e n p o p u l a t i o n s a n d f o r t h o s e i n d i v i d u a l s who n e g l e c t t h e i r n e s t s o w i n g t o c o n t i n u a l r e d w i n g h a r a s s m e n t ( P i e m a n , p e c s . c o m m . ) . e R e s e a r c h H y p o t h e s e s I e s t a b l i s h e d t h r e e h y p o t h e s e s c o n c e r n i n g c o m p a r i s o n s b e t w e e n w r e n s a n d r e d w i n g s . T h e s e w e r e b a s e d o n a v a i l a b l e i n f o r m a t i o n f r o m t h e l i t e r a t u r e a n d t h e f o l l o w i n g c o n s i d e r a t i o n s . F i r s t , m o s t o f t h e p r e v i o u s s t u d i e s on w r e n s a n d r e d w i n g s h a v e b e e n c o n d u c t e d i n m a r s h e s w h e r e o n l y h e r b a c e o u s e m e r g e n t s s u c h a s c a t t a i l a n d s e d g e w e r e a v a i l a b l e . O v e r l a p , b o t h i n t e r m s o f d i s t r i b u t i o n o f t e r r i t o r i e s , a n d v e g e t a t i o n u s e d a s n e s t i n g s u b s t r a t e , h a s b e e n o b s e r v e d . P a r t o f t h e o v e r l a p i n v e g e t a t i o n t y p e c o u l d be e x p l a i n e d by, d i f f e r e n c e s i n . u se o v e r t i m e . T h e o n l y p r e v i o u s s t u d y p r o v i d i n g e x t e n s i v e c o m p a r a t i v e d a t a on t h e t w o s p e c i e s i n d i v e r s e v e g e t a t i o n ( B u r t 1970) d o e s n o t e x a m i n e p o s s i b l e t e m p o r a l d i f f e r e n c e s i n s u b s t r a t e u s e . T h o u g h c l o s e s c r u t i n y o f B u r t ' s t h e s i s r e v e a l s some t e m p o r a l d i f f e r e n c e s , t h e s e c o u l d h a v e b e e n l i m i t e d by t h e f a c t t h a t b r e e d i n g by r e d w i n g s a n d w r e n s i n h i s I o w a m a r s h was c o n f i n e d t o a t w o - m o n t h p e r i o d . T h e p r e s e n t s t u d y m a r s h o f f e r s n o t o n l y a v a r i e t y o f s e d g e v e g e t a t i o n b u t a w i d e l y d i s t r i b u t e d e m e r g e n t s h r u b , a n d t h i s c o u l d p r o v i d e a d d i t i o n a l o p p o r t u n i t y f o r d i v e r g e n c e o f h a b i t a t s e l e c t i o n b e t w e e n t h e t w o s p e c i e s . T h e t e m p e r a t e c l i m a t e a l s o p r o v i d e s f o r a l o n g e r n e s t i n g s e a s o n a n d i n c r e a s e d o p p o r t u n i t y f o r t e m p o r a l s e g r e g a t i o n t h a n i n o t h e r a r e a s . S e c o n d , t h o u g h t h e p h y s i c a l c h a r a c t e r i s t i c s o f t h e u t i l i z e d v e g e t a t i o n c a n s u g g e s t d i f f e r e n c e s i n h a b i t a t r e q u i r e m e n t s , s u c h a s n e s t s u p p o r t a n d p r o t e c t i o n f r o m p r e d a t o r s a n d t h e e l e m e n t s , i n t e r s p e c i f i c c o m p e t i t i o n c a n a l s o i n f l u e n c e d i s t r i b u t i o n . E v i d e n c e f o r c o m p e t i t i v e m e c h a n i s m s e x i s t s f o r m a r s h e s c o n t a i n i n g m o s t l y s e d g e s , b u t i t i s u s e f u l t o i n v e s t i g a t e t h e i n f l u e n c e o f c o m p e t i t i o n i n t h e p r e s e n t s t u d y m a r s h , w h i c h c o n t a i n s a u n i q u e f l o r a l d i v e r s i t y . T h i r d a n d l a s t , c o m p e t i t i o n b e t w e e n i n d i v i d u a l s o f t h e same s p e c i e s may a l s o a f f e c t t h e i r d i s t r i b u t i o n and may h a v e a c o m b i n e d e f f e c t w i t h i n t e r s p e c i f i c c o m p e t i t i o n . I f r e d w i n g s a f f e c t w r e n n e s t i n g s u c c e s s , t h e y may do s o by c a u s i n g w r e n s t o n e g l e c t t h e i r n e s t s , l e a v i n g t h e m more v u l n e r a b l e t o d e s t r u c t i o n b y , o t h e r w r e n s . I f t h a t were t h e c a s e , one w o u l d e x p e c t ^ t h a t a c o m b i n a t i o n o f l o w w r e n - r e d w i n g n e s t d i s t a n c e s a n d l o w w r e n - w r e n d i s t a n c e s w o u l d c a u s e n e s t f a i l u r e . , T h e h y p o t h e s e s a r e : 1. " S e g r e g a t i o n " h y p o t h e s i s . T h e r e i s h a b i t a t s e g r e g a t i o n b e t w e e n r e d w i n g s a n d m a r s h w r e n s , d e m o n s t r a t e d by e i t h e r u t i l i z a t i o n o f d i f f e r e n t v e g e t a t i o n t y p e s o r t h e same t y p e s a t d i f f e r e n t t i m e s . 2 . " M r e n - r e d w i n g c o m p e t i t i o n " h y p o t h e s i s . C l o s e r i n t e r s p e c i f i c d i s t a n c e s a r e r e l a t e d t o l o w e r n e s t i n g s u c c e s s f o r b o t h s p e c i e s . 3. " H r e n - w r e n c o m p e t i t i o n " h y p o t h e s i s . Wren n e s t i n g f a i l u r e , f o r n e s t s l o c a t e d c l o s e r t o r e d w i n g n e s t s , i s r e l a t e d t o s m a l l w r e n - w r e n n e s t d i s t a n c e s . 10 METHODS S t u d y A r e a The P i t t W i l d l i f e Management A r e a (PWMA) i s l o c a t e d i n t h e P i t t V a l l e y a p p r o x i m a t e l y 50 km e a s t o f V a n c o u v e r a n d i s b o r d e r e d on t h e n o r t h a n d w e s t by P i t t L a k e and R i v e r , on t h e e a s t by t h e 0* .B.C. R e s e a r c h F o r e s t , and on t h e s o u t h b y t h e a g r i c u l t u r a l l a n d s o f t h e P i t t a n d A l o u e t t e P o l d e r s ( F i g . 1 ) . I t c o n s i s t s o f 1460 h a (3600 a c r e s ) o f p r i m a r i l y s l o u g h , d y k e d m a r s h , wet meadow, a n d b o g h a b i t a t s . The p r e s e n t w a t e r r e g i m e i s i n f l u e n c e d b y p r e c i p i t a t i o n , d y k e s t o k e e p o u t a t i d a l r i v e r and l a k e , and t h e w a t e r s h e d o f t h e O . B . C . R e s e a r c h F o r e s t . H i g h w a t e r o c c u r s f r o m May t h r o u g h J u l y , l o w w a t e r f r o m A u g u s t t h r o u g h O c t o b e r , a n d f l u c t u a t i n g w a t e r f r o m November t h r o u g h A p r i l . The s u c c e s s i o n o f t h e a r e a i s t o w a r d a r e l a t i v e l y u n p r o d u c t i v e bog h a b i t a t ( B a r n a r d 1 9 7 5 ) . The management i n t e n t i o n s o f t h e B . C . F i s h and W i l d l i f e B r a n c h r e v o l v e a r o u n d i n c r e a s i n g o v e r a l l p r o d u c t i v i t y o f t h e a r e a , b e l i e v e d t o be c u r r e n t l y l i m i t e d by, t h e mar,sh-bog s u c c e s s i o n . The f i r s t s t e p i n c h a n g i n g t h e a r e a i n t o a r e l a t i v e l y p r o d u c t i v e mar sh i s g a i n i n g c o n t r o l o f t h e w a t e r r e g i m e , f o l l o w e d by a l t e r i n g t h e e x i s t i n g v e g e t a t i o n , e i t h e r a s a d i r e c t c o n s e g u e n c e o f a new w a t e r r e g i m e o r t h r o u g h m a n i p u l a t i o n s s u c h a s b u r n i n g . The w a t e r r e g i m e i s t o be c o n t r o l l e d by f u r t h e r d y k i n g w i t h i n t h e management a r e a , t h e f i r s t p h a s e o f w h i c h was c o m p l e t e d i n 1978 . 11 Figure 1. Study Area ISL "PIT r L/IK£ Study Area (Pitt Wildlife Management Area) Agricultural Area APPROX. S C A L E : ^50 M MAP AFTER J E R E M A 1976 1 3 Major Plant Species The major marsh plant species considered i n t h i s study are i l l u s t r a t e d and b r i e f l y described i n Figures 2-6. They are l i s t e d in approximate successional order from deepest to shallowest water. 14 F i g u r e 2 . S c i r p u s a e u t u s { H a r d - s t e m m e d B u l r u s h ) - a s s o c i a t e d w i t h d e e p e r w a t e r o f c e n t r a l m a r s h - s t e m s n o t c o m p l e t e l y c o l l a p s e d o v e r w i n t e r - new g r o w t h t o 2 m i n J u n e a n d J u l y 16 16 F i g u r e 3 . S c i r p u s c y p e r i n u s ( H a i r y - s e e d e d B u l r u s h ) - l o w - l y i n g ( . 5 m) l e a v e s u n t i l J u n e a n d J u l y when f l o w e r i n g s t e m s s h o o t up t o 2 m 18 F i g u r e 4 . C a r e x r o s t r a t a a n d C a r e x s i t c h e n s i s (Low S e d g e ) - s p e c i e s s i m i l a r t o e a c h o t h e r i n a p p e a r a n c e - s h o r t e s t o f t h e m a j o r v e g e t a t i o n t y p e s ( . 5 m - 1 m) 20 F i g u r e 5 . Ty pha l a t i f o l i a ( B r o a d - l e a v e d C a t t a i l ) - p r e s e n t i n a f e w r e l a t i v e l y s m a l l p a t c h e s - some s t e m s n o r m a l l y l e f t s t a n d i n g o v e r w i n t e r - new g r o w t h t o 2 m i n J u n e a n d J u l y 22 P i g u r e 6 - S p i r a e a d o u q l a s i i ( H a r d b a c k ) - e m e r g e n t p e r e n n i a l s h r u b a s s o c i a t e d w i t h h i g h e r g r o u n d - 1-3 m t a l l 24 I n t r o d u c t i o n And L i m i t a t i o n s O f M e t h o d s A n y a t t e m p t t o d e t e r m i n e t h e a b u n d a n c e o f a n a n i m a l ; s p e c i e s i s l i m i t e d by t h e o b s e r v e r ' s a b i l i t y t o c o n s i s t e n t l y d e t e c t i n d i v i d u a l s . B i r d s a r e h i g h l y m o b i l e a n d h a v e b e h a v i o r p a t t e r n s t h a t v a r y w i t h t h e s e a s o n , h a b i t a t , w e a t h e r , a n d c o u n t l e s s o t h e r f a c t o r s , a n d t h e s e c h a r a c t e r i s t i c s c a n s e r i o u s l y r e d u c e t h e i r d e t e c t a b i l i t y a n d t h e a c c u r a c y o f e s t i m a t e s o f a b u n d a n c e ( D a v i s 1 9 6 5 , B e l l e t a l . 1 9 7 3 ) . I t i s i m p o r t a n t t o k e e p t h e s e l i m i t a t i o n s i n m i n d r e g a r d l e s s o f w h a t s t u d y t e c h n i q u e s o n e c h o o s e s . F o r t h i s s t u d y , t h e r e a r e t w o b a s i c t y p e s o f i n f o r m a t i o n r e q u i r e d ^ 1. C o m p a r i s o n s , f o r e a c h s p e c i e s , among a b u n d a n c e s i n d i f f e r e n t v e g e t a t i o n t y p e s t h r o u g h o u t t h e y e a r . ; 2 . D e t a i l e d n e s t i n g i n f o r m a t i o n on r e d w i n g s a n d w r e n s , i n c l u d i n g a m e a s u r e o f n e s t i n g s u c c e s s . To p r o v i d e t h i s i n f o r m a t i o n , I : o b t a i n e d i n d i c e s o f a b u n d a n c e f r o m b o t h y e a r - r o u n d c e n s u s t r a n s e c t s a n d r e p e a t e d n e s t c o u n t s a n d m o n i t o r i n g o f n e s t c o n t e n t s . , , T h e s e s t u d y t e c h n i q u e s h a v e v a r i o u s a d v a n t a g e s a n d d i s a d v a n t a g e s , a n d I w i l l b r i e f l y d i s c u s s t h o s e m o s t p e r t i n e n t t o t h i s s t u d y * The m a i n a d v a n t a g e t o t h e c e n s u s t r a n s e c t m e t h o d i s t h a t a l a r g e a r e a c a n be c o v e r e d w i t h a min imum amoun t , o f e f f o r t ( K e n d e i g h 1 9 4 4 , E m l e n 1 9 7 1 ) . T h e m a i n d i s a d v a n t a g e i s t h a t t h e m e t h o d r e l i e s o n t h e d e t e c t a b i l i t y o f t h e b i r d s , w h i c h m i g h t v a r y b e t w e e n h a b i t a t s a n d s e a s o n s ( E m l e n 1 9 7 1 , S a v a r d 1978) . . - • 25 One a d v a n t a g e t o t h e s e c o n d m e t h o d , r e p e a t e d n e s t c o u n t s , i s t h a t t h e e s t i m a t e i s much c l o s e r t o t h e a b s o l u t e a b u n d a n c e t h a n t h a t o f t h e c e n s u s t r a n s e c t ( K e n d e i g h 1 9 4 4 ) . A n o t h e r a d v a n t a g e i s t h a t i n a d d i t i o n t o p r o v i d i n g t h e d e s i r e d n e s t i n g i n f o r m a t i o n o n w r e n s a n d r e d w i n g s , t h e r e p e a t e d n e s t c o u n t s m e t h o d o f f e r s a d i f f e r e n t i n d e x o f a b u n d a n c e f o r c o m p a r i s o n w i t h t h e i n d e x , p r o v i d e d b y c e n s u s t r a n s e c t s d u r i n g t h e b r e e d i n g s e a s o n . I f b o t h t e c h n i q u e s r e s u l t i n t h e same o b s e r v e d d i f f e r e n c e s o f a b u n d a n c e among d i f f e r e n t h a b i t a t s a n d s e a s o n s , we may more r e a s o n a b l y a s s u m e t h a t t h e v a r i a t i o n o f d e t e c t a b i l i t y due t o t h e s e f a c t o r s i s n e g l i g i b l e . N e s t c o u n t s were a l s o s u b j e c t t o v a r i a t i o n i n n e s t d e t e c t a b i l i t y , b u t t h i s was m i n i m i z e d b y a d j u s t i n g s e a r c h e f f o r t * We i n c r e a s e d t h e e f f o r t l a t e r i n t h e g r o w i n g s e a s o n when n e s t s may h a v e b e e n more c o n c e a l e d b y t h e t a l l e r and . more d e n s e v e g e t a t i o n . B e c a u s e o n l y t h e c e n s u s t r a n s e c t m e t h o d was u s e d d u r i n g t h e f a l l a n d w i n t e r s e a s o n s , n o c h e c k on t h e v a r i a t i o n o f d e t e c t a b i l i t y was p r o v i d e d f o r t h o s e s e a s o n s . I d e s c r i b e t h e t w o m e t h o d s i n more d e t a i l i n t h e f o l l o w i n g two s e c t i o n s . 26 C e n s u s T r a n s e c t s A l t h o u g h t h e s t u d y f o c u s e d o n r e d w i n g s a n d w r e n s , i n o r d e r t o m a x i m i z e t h e u n d e r s t a n d i n g o f t h e p a s s e r i n e c o m m u n i t y I g a t h e r e d some d a t a a l s o o n y e l l o w t h r o a t s a n d S o n g S p a r r o w s . F o r t h i s p u r p o s e , I d e t e r m i n e d t h e y e a r - r o u n d a b u n d a n c e o f e a c h o f t h e f o u r p a s s e r i n e s p e c i e s i n d i f f e r e n t v e g e t a t i o n t y p e s a l o n g f o u r m a r s h c e n s u s t r a n s e c t s . T h e s e t r a n s e c t s w e r e e s t a b l i s h e d i n w i d e l y s p a c e d a r e a s i n w h i c h h a b i t a t m a n i p u l a t i o n was p l a n n e d a n d t h a t c o n t a i n e d f a i r l y u n i f o r m p a t c h e s o f t h e m a j o r v e g e t a t i o n t y p e s ( F i g . 7) . I u s e d f i e l d o b s e r v a t i o n s a n d a e r i a l p h o t o s t o c l a s s i f y t h e t r a n s e c t e d a r e a s i n t o f o u r v e g e t a t i o n t y p e s : " D e n s e S p i r a e a " - o v e r 50% o f a r e a c o v e r e d b y S p i r a e a d o u g l a s i i . r e m a i n d e r by p a t c h e s o f C a l a m a q r o s t i s c a n a d e n s i s o r C a r e x s p e c i e s . " S e d g e - S p i r a e a " - l e s s t h a n 50% o f a r e a c o v e r e d b y S p i r a e a d o u g l a s i i . m a j o r p o r t i o n b y p a t c h e s o f S . c y p e r i n u s a n d C a r e x s p p . " S c i r p u s a c u t u s " - p u r e s t a n d s o f S . a c u t u s . " S c i r p u s c y p e r i n u s " - p u r e s t a n d s o f S . c y p e r i n u s . T a b l e X g i v e s t h e d i s t r i b u t i o n o f t h e v e g e t a t i o n t y p e s i n t h e f o u r t r a n s e c t s e x p r e s s e d i n km o f t r a n s e c t p a s s i n g t h r o u g h t h a t p a r t i c u l a r t y p e . 27 F i g u r e 7. L o c a t i o n o f M a r s h C e n s u s T r a n s e c t s TABLE I. DISTRIBUTION OF VEGETATION TYPES IN TRANSECTS Transect Total 1 2 3 4 Distance Dense Spiraea .50 km .00 .52 .60 1.62 Sedge-Spiraea .36 .08 .00 .00 .44 Scirpus acutus .44 .32 .00 .00 .76 Scirpus cyperi nus .10 .12 .00 .00 .22 Total Distance 1.40* .52 .52 .60 3.04 Figures represent one-way distance. Censuses included detections during both forward and return trips (two-way). 30 T r a n s e c t l i n e s were w a l k e d a n d b i r d s c e n s u s e d e v e r y two weeks f r o m J a n u a r y 1 t o D e c e m b e r 3 1 , 1977- I i n c r e a s e d t h e f r e q u e n c y o f c e n s u s e s d u r i n g t h e e a r l y b r e e d i n g p e r i o d ( M a r c h -Hay) t o o n c e e v e r y t e n d a y s . To a l l o w f o r p o s s i b l e d a i l y v a r i a t i o n s i n h a b i t a t u s e , I a l t e r n a t e d t h e t i m e s o f d a y when c e n s u s e s w e r e p e r f o r m e d . F o r t h i s p u r p o s e , a d a y was d i v i d e d i n t o f o u r d a y l i g h t t i m e i n t e r v a l s o f d i f f e r e n t l e n g t h s i n d i f f e r e n t s e a s o n s , a s s h o w n i n F i g u r e 8 . T h e s e a r e s i m i l a r t o t h e d i v i s i o n s i n a d a y made by V e r n e r ( 1965b ) f o r m a r s h w r e n a c t i v i t y . I w a l k e d e a c h t r a n s e c t d u r i n g a d i f f e r e n t t i m e i n t e r v a l on e a c h s u c c e s s i v e v i s i t . T h i s s t i l l a l l o w s f o r c o m p a r i s o n s b e t w e e n t r a n s e c t s ( and v e g e t a t i o n t y p e s ) a s l o n g a s a l l t h e t r a n s e c t t i m e s a r e r o t a t e d e q u i t a b l y ( S h i e l d s 1 9 7 7 ) . T r a n s e c t s i n t h e m o r n i n g c a t e g o r i e s were w a l k e d a s c l o s e t o t h e b e g i n n i n g o f t h e t i m e i n t e r v a l a s p o s s i b l e a n d t h o s e i n t h e a f t e r n o o n c a t e g o r i e s , c l o s e t o t h e end o f t h e i n t e r v a l . I d e f i n e d s e a s o n s a s f o l l o w s : L a t e W i n t e r J a n . - F e b . E a r l y S p r i n g M a r . - A p r . ( 15 L a t e S p r i n g A p r . 15 - May Summer J u n e - J u l y F a l l S e p t . - O c t . E a r l y W i n t e r N o v . - D e c . The b e g i n n i n g o f " L a t e S p r i n g " c o i n c i d e s w i t h t h e s t a r t o f e g g l a y i n g f o r m a r s h w r e n s a n d t h e end o f "Summer" w i t h t h e e n d o f m o s t o f t h e m a r s h p a s s e r i n e n e s t i n g a c t i v i t y . The f r e q u e n c y o f t r a n s e c t s a n d t h e d u r a t i o n o f t h e s e a s o n s were t h u s c h o s e n s o t h a t e a c h t r a n s e c t b e c o v e r e d d u r i n g e a c h o f t h e f o u r d a y l i g h t t i m e c a t e g o r i e s i n a n y s e a s o n . 31 . F i g u r e 8- T i m e C a t e g o r i e s f o r H a r s h C e n s u s e s 3 o l M o n t h s J F M A M J J A S O N 0 T3 t-l a ts s 4-1 CO u u ni 0. 0400 0600 0300 1000 1200 1400 1600 1S00 L a t e M o r n i n g E a r l y A f t e r n o o n 33 A s E m l e n (1971) p o i n t s o u t , t h e v a r i a t i o n i n c e n s u s r e s u l t s w i t h o b s e r v e r a n d w e a t h e r c a n be s u b s t a n t i a l . To r e d u c e t h e s e s o u r c e s o f v a r i a b i l i t y , I p e r f o r m e d a l l c e n s u s e s m y s e l f a n d o n l y on d a y s w i t h o u t r a i n o r h i g h w i n d s . A v e r a g e p r o g r e s s a l o n g t r a n s e c t s was 1.2 k m / h r , i n c l u d i n g b r i e f s t o p s a b o u t e v e r y 4 0 m. T h e s e s t o p s were n o t o n l y n e c e s s a r y b e c a u s e o f t h e i n t e r f e r e n c e b e t w e e n t h e n o i s e o f my own m o v e m e n t s t h r o u g h t h e v e g e t a t i o n a n d b i r d d e t e c t i o n , b u t a l s o e n a b l e d me t o m o n i t o r and t a k e i n t o a c c o u n t b i r d m o v e m e n t s , w h i c h c o u l d c a u s e t h e c o u n t i n g o f a n i n d i v i d u a l m o r e t h a n o n c e . I f o u n d t h i s m e t h o d t o be s a t i s f a c t o r y , e v e n t h o u g h o t h e r a u t h o r s s t r e s s t h e i m p o r t a n c e o f m o v i n g r a p i d l y t o a v o i d " d o u b l e c o u n t s " ( E m l e n 1 9 7 1 , S a v a r d 1 9 7 8 ) . A s i n E m l e n ( 1 9 7 1 ) , I u s e d • p i s h i n g ' s o u n d s t o a t t r a c t b i r d s a n d t h u s m a x i m i z e d e t e c t i o n . T h e s e s o u n d s w e r e made e v e r y 80 m ( e v e r y s e c o n d s t o p ) , s i n c e I f e l t t h a t m a k i n g them a n y more f r e q u e n t l y w o u l d c a u s e e x c e s s i v e b i r d movement a n d i n c r e a s e t h e r i s k o f d o u b l e c o u n t s . D e t e c t i o n s , e i t h e r b y h e a r i n g o r s i g h t , o f a l l p a s s e r i n e s w i t h i n 100 m e i t h e r s i d e o f t h e t r a n s e c t w e r e r e c o r d e d a l o n g w i t h s e x , i f p o s s i b l e , a n d w h e t h e r s i n g i n g , c a l l i n g , o r s i l e n t . I r e c o r d e d d e t e c t i o n s a l o n g b o t h f o r w a r d a n d r e t u r n t r i p s . A s i n d i c e s o f a b u n d a n c e , I u s e d c o u n t s o f s i n g i n g m a l e s d u r i n g t h e s p r i n g a n d summer a n d t o t a l d e t e c t i o n s d u r i n g t h e f a l l a n d w i n t e r . B i r d s d e t e c t e d on d y k e s o r f l y i n g o v e r a n d n o t l a n d i n g i n t h e m a r s h v e g e t a t i o n w e r e n o t i n c l u d e d i n t h e s e f i g u r e s . 34 N e s t S t u d y P l o t s Two a s s i s t a n t s a n d I g a t h e r e d n e s t i n g h a b i t a t a n d b r e e d i n g d a t a on m a r s h w r e n s a n d r e d w i n g s f r o m a t o t a l a r e a o f 27 h a , d i v i d e d i n t o s e v e n n e s t s t u d y p l o t s ( F i g . 9 ) . Y e l l o w t h r o a t s a n d S o n g S p a r r o w s w e r e much l e s s n u m e r o u s i n t h e p l o t s t h a n w r e n s a n d r e d w i n g s , a n d t h e i r n e s t s a r e m o r e d i f f i c u l t t o l o c a t e . A l t h o u g h some i n f o r m a t i o n o n y e l l o w t h r o a t s a n d s p a r r o w s was o b t a i n e d d u r i n g n e s t s t u d i e s , we g a t h e r e d no d e t a i l e d n e s t i n g d a t a f o r t h e s e t w o s p e c i e s . The c r i t e r i a I u s e d i n c h o o s i n g t h e p l o t s w e r e t h a t t h e y b e w i d e l y s p a c e d t o y i e l d u n b i a s e d i n f o r m a t i o n on t h e t o t a l m a r s h a n d t h a t t h e m a j o r v e g e t a t i o n t y p e s be s a m p l e d a d e q u a t e l y when a l l t h e p l o t s a r e t a k e n t o g e t h e r . B e c a u s e o f i t s i m p o r t a n c e a s n e s t i n g s u b s t r a t e i n p r e v i o u s s t u d i e s , p a t c h e s o f c a t t a i l , n o t i n c l u d e d i n t r a n s e c t s , were i n c l u d e d i n t h e n e s t p l o t s . T h e t o t a l a r e a s s t u d i e d o f e a c h p l a n t s p e c i e s u s e d a s n e s t i n g s u b s t r a t e * a r e s i m i l a r i n s i z e , w i t h t h e e x c e p t i o n o f c a t t a i l , t h e p a t c h e s o f w h i c h w e r e r e l a t i v e l y s m a l l a n d f e w i n number ( T a b l e I I ) . I c a l c u l a t e d t h e s e a r e a s f r o m v e g e t a t i o n c o v e r maps o f t h e p l o t s p r o d u c e d w i t h t h e a i d o f a e r i a l p h o t o s a n d p a c i n g w i t h c o m p a s s i n t h e f i e l d ( K e l l e r a n d S p a t c h e r 1 9 6 5 ) . T h e s e maps a r e s h o w n a l o n g w i t h t h e d i s t r i b u t i o n o f n e s t s i n F i g u r e s 1 7 - 2 8 o f t h e R e s u l t s s e c t i o n . He e s t a b l i s h e d f u r t h e r r e f e r e n c e p l o t s t o a s s i s t i n r e c o r d i n g n e s t l o c a t i o n s b y m a r k i n g 1 S i rens a n d r e d w i n g s d i d n o t u s e C . c a n a d e n s i s a t a l l a n d C a r e x s p p . r a r e l y a s n e s t i n g s u b s t r a t e . 35 F i g u r e 9. L o c a t i o n o f M a r s h N e s t S t u d y P l o t s ( S h a d e d A r e a s ) 37 TABLE II. VEGETATION AREAS IN NEST STUDY PLOTS Vegetation N e s t P l o t Total A B C D E F G Spiraea douglasii 1.9ha 0.3 3.1 0.5 0.8 0 0 6.6 Scirpus acutus 0 3.5 0 1.3 1.7 0.6 0 7.1 S_. cyperinus 0 1.1 0 1.0 2.0 0.2 0.4 4.7 Typha latifolia 0 0 0 0.4 0.6 0.2 0.6 1.8 Graminae spp. 0 0.5 0.8 0.1 0.4 1.4 0 3.2 Carex spp. 2.1 0.5 0.1 0.4 0.1 0 0 2.8 Total Vegetation 4.0 5.5 4.0 3.7 5.6 2.4 1.0 26.2 Open Water 0 0.4 0 0.2 0.2 0 0 0.8 38 t h e a r e a o u t i n t o 5 0 - m e t e r s q u a r e g r i d s w i t h w i l l o w s h o o t s , b l u e f l a g g i n g , a n d a 3 0 - m e t e r t a p e . E a c h p l o t was v i s i t e d o n c e p e r w e e k , b y t h e same o b s e r v e r , f r o m M a r c h 1 t o a u g u s t 1. We p e r i o d i c a l l y a s s i s t e d one a n o t h e r t o e n s u r e c o n s i s t e n c y o f m e t h o d s . N e s t s w e r e l o c a t e d by a c r i s s - c r o s s s e a r c h o f t h e g r i d s a t 2 5 - m e t e r i n t e r v a l s a n d b e h a v i o u r a l o b s e r v a t i o n s o f b i r d s . S e a r c h l i n e s were w a l k e d a t 2 0 - m e t e r i n t e r v a l s i n t h e summer s e a s o n s , s i n c e t h e h i g h e r a n d d e n s e r v e g e t a t i o n made n e s t s l e s s v i s i b l e t h a n t h e y w e r e d u r i n g t h e l a t e s p r i n g . M o r e t i m e was a l s o s p e n t o b s e r v i n g n e s t i n g b e h a v i o u r a s a c l u e t o n e s t l o c a t i o n s d u r i n g t h e summer s e a s o n . We r e c o r d e d n e s t l o c a t i o n s o n a map o f t h e a r e a , m a r k e d t h e n e s t s w i t h a s m a l l p i e c e o f t a p e , a n d k e p t r e c o r d s o f e a c h n e s t . I n f o r m a t i o n g a t h e r e d i n c l u d e d v e g e t a t i o n t y p e u s e d a s n e s t i n g s u b s t r a t e , p r e s e n c e a n d number o f e g g s , a n d p r e s e n c e o f y o u n g i n t h e n e s t . We d i d n o t c o u n t m a r s h w r e n n e s t l i n g s o w i n g t o t h e a m o u n t o f d i s t u r b a n c e c a u s e d b y h a n d l i n g t h e y o u n g i n t h e c l o s e d n e s t . S i m i l a r l y f o r r e d w i n g s , we c o u n t e d n e s t l i n g s i f p o s s i b l e , b u t i n i n s t a n c e s i n w h i c h y o u n g b i r d s r e q u i r e d h a n d l i n g , we made no e x t r a e f f o r t t o d e t e r m i n e n u m b e r s . T h u s , a s u c c e s s f u l n e s t o f e i t h e r s p e c i e s was d e f i n e d a s o n e c o n t a i n i n g o n e o r more y o u n g o n e week o l d o r o l d e r , a d e f i n i t i o n a l s o u s e d by M e a n l y a n d Webb ( 1 9 6 3 ) . We a l s o r e c o r d e d t h e f o l l o w i n g p h y s i c a l p a r a m e t e r s a t e a c h b r e e d i n g n e s t s i t e w i t h i n s t u d y p l o t s , a s w e l l a s f o r 25 m i s c e l l a n e o u s b r e e d i n g n e s t s i n t h e m a r s h b u t o u t s i d e t h e p l o t s ; 1. N e s t h e i g h t : b o t t o m o f n e s t t o m a r s h b o t t o m ( s o i l 39 l a y e r , whether water present beneath the nest or not) . 2. Nest v i s i b i l i t y ; l a t e r a l v i s i b i l i t y of nest as i n f l u e n c e d by the amount of c o n c e a l i n g v e g e t a t i o n ; recorded as an index o f v e g e t a t i o n d e n s i t y ; measured upon completion of nest c o n s t r u c t i o n using a c i r c l e counting t e c h n i q u e . 1 3.. V e g e t a t i o n h e i g h t : maximum l e v e l above s o i l or marsh bottom a t t a i n e d by stems and/or l e a v e s of p l a n t t o which nest i s a t t a c h e d ; measured upon completion of nest c o n s t r u c t i o n 4. Water depth: water beneath nest averaged over the n e s t ' s a c t i v e p e r i o d . 5. D i s t a n c e to n e a r e s t open water: open water g r e a t e r than .5 m i n approximate diameter.. 1 T h i s technique i s s i m i l a r t o that i n Sestak (1971) f o r measuring l e a f area. I t c o n s i s t s of p l a c i n g h o r i z o n t a l l y , on the top o f the n e s t , a 50 m s t i c k with 20 painted c i r c l e s of 1 cm i n diameter evenly spaced a l o n g the s t i c k ' s l e n g t h . The number of c i r c l e s l e s s than h a l f - c o v e r e d by v e g e t a t i o n , i n c l u d i n g those completely v i s i b l e , i s recorded. The s t i c k i s viewed at a d i s t a n c e of 2 m from the nest on the s i d e of the n e s t with the l e a s t amount of surrounding v e g e t a t i o n . 40 RESULTS G e n e r a l R e s u l t s In t h i s s e c t i o n , I present wren and redwing r e s u l t s t h a t do not d i r e c t l y r e l a t e to my r e s e a r c h h y p o t h e s e s , but f a l l w i t h i n the s tudy o b j e c t i v e s * 1. Winter H a b i t a t s e l e c t i o n W e l t e r (1935) , i n one o f the e a r l i e s t l i f e h i s t o r y s t u d i e s o f the marsh wren, s t a t e s : "The marsh wren, u n l i k e the r e d w i n g , seeks s h e l t e r i n the marsh r a t h e r than depending upon f l i g h t f o r safety .*! Observed w i n t e r h a b i t a t use by the two s p e c i e s p r o b a b l y r e f l e c t s t h a t d i f f e r e n c e . Redwings were n e a r l y absent from the s t u d y marsh i n the e a r l y w i n t e r p e r i o d , a t l e a s t d u r i n g the d a y l i g h t h o u r s c o v e r e d i n the p r e s e n t s tudy ( F i g . 10) . I observed redwings i n the marsh p r i m a r i l y i n the e a r l y morning and l a t e a f t e r n o o n i n l a t e w i n t e r , 1 and l a r g e f l o c k s were seen u t i l i z i n g the a g r i c u l t u r a l areas d u r i n g these p e r i o d s . O r i a n s (1961) observed a s i m i l a r p r e - n e s t i n g p a t t e r n t o u t i l i z a t i o n o f the marsh by r e d w i n g s . Marsh wrens were p r e s e n t on ly i n the marsh o r on dykes a d j a c e n t to the marsh throughout the e n t i r e y e a r . 1 On l a t e w in ter c e n s u s e s , of 54 redwings d e t e c t e d i n the marsh, 39 were d e t e c t e d d u r i n g the e a r l y morning p e r i o d and 19 d u r i n g the l a t e a f t e r n o o n p e r i o d . 41 Figure 10. Early winter Redwing Abundance on Harsh Censuses 3.0 Birds km 2.0 1.0 Early Winter Average (Nov. - Dec.) Average over remainder of Fall - Winter Seasons 43 2 . C o m p a r a t i v e N e s t i n g I n f o r m a t i o n R e d w i n g s a n d w r e n s e x h i b i t e d d i f f e r e n c e s i n t h e d u r a t i o n o f t h e t o t a l n e s t i n g s e a s o n and i n t e m p o r a l d i s t r i b u t i o n o f n e s t i n g a c t i v i t y w i t h i n t h e s e a s o n . The o b s e r v e d n e s t i n g p e r i o d f o r r e d w i n g s was a f u l l month s h o r t e r t h a n t h a t f o r m a r s h w r e n s . The f i r s t r e d w i n g c l u t c h was c o m p l e t e d on A p r i l 28 and t h e l a t e s t on J u l y 1 3 , w h e r e a s t h e c o r r e s p o n d i n g d a t e s f o r w r e n s we re A p r i l 13 a n d J u l y 2 9 . The f i r s t m a l e wren t o c o m p l e t e a n o n - b r e e d i n g o r " dummy" n e s t d i d s o by M a r c h 1 4 , b u t e g g s w e r e n o t p r e s e n t i n t h a t t e r r i t o r y u n t i l A p r i l 19. M o s t r e d w i n g s f i n i s h e d e g g - l a y i n g i n t h e l a t e s p r i n g p r i o r t o J u n e 1* ( 6 8 % o f 69 n e s t s o b s e r v e d b o t h i n a n d o u t s i d e n e s t s t u d y p l o t s ) , w h e r e a s an e g u a l number o f w r e n s f i n i s h e d e g g - l a y i n g b o t h b e f o r e a n d a f t e r J u n e 1 ( 51% b e f o r e , 4 9% a f t e r , N = 1 1 5 ) . , T h e d e n s i t y o f w ren b r e e d i n g n e s t s i n s t u d y p l o t s was a p p r o x i m a t e l y t w i c e t h a t o f r e d w i n g s . D e n s i t i e s c a l c u l a t e d by d i v i d i n g t h e number o f a l l b r e e d i n g n e s t s f o r t h e e n t i r e n e s t i n g p e r i o d by t h e t o t a l a r e a o f t h e v e g e t a t i o n i n s t u d y p l o t s w e r e 4 . 0 a n d 2 . 2 n e s t s / h a f o r w r e n s a n d r e d w i n g s r e s p e c t i v e l y . The maximum u t i l i z e d d e n s i t i e s ( number o f s i m u l t a n e o u s l y a c t i v e n e s t s p e r t o t a l a r e a o f m a l e t e r r i t o r i e s ) o c c u r r e d a b o u t May 10 a n d w e r e 2 . 6 a n d 1.8 n e s t s / h a f o r w r e n s a n d r e d w i n g s r e s p e c t i v e l y . * J u n e 1 d i v i d e s t h e n e s t i n g s e a s o n r o u g h l y i n t w o , and t h e t w o p e r i o d s c o r r e s p o n d t o t h e l a t e s p r i n g a n d summer s e a s o n s d e f i n e d i n t h e m e t h o d s s e c t i o n . 44 R e d w i n g s , u n l i k e w r e n s , h a d d i f f e r e n t c l u t c h s i z e s i n t h e l a t e s p r i n g t h a n i n t h e s u m m e r . T h r e e a n d f o u r e g g s w e r e e q u a l l y common r e d w i n g c l u t c h e s o v e r a l l , w i t h a s i g n i f i c a n t d i f f e r e n c e b e t w e e n l a t e s p r i n g a n d summer a v e r a g e c l u t c h s i z e s . T h e a v e r a g e o f 32 l a t e s p r i n g n e s t s was 3 . 8 v e r s u s an a v e r a g e o f 14 summer n e s t s o f 2 . 9 (p < . 0 0 0 1 , S t u d e n t ' s t ) . F i v e e g g s w e r e t h e mos t common c l u t c h s i z e f o r w r e n s w i t h a n o v e r a l l a v e r a g e o f 4 . 8 (N = 9 6 ) . I o b s e r v e d n o s i g n i f i c a n t d i f f e r e n c e b e t w e e n t h e l a t e s p r i n g a n d summer s e a s o n s (p > . 1 5 , S t u d e n t ' s t ) . , U s i n g t h e d e f i n i t i o n o f a s u c c e s s f u l n e s t a s one p r o d u c i n g a n y n u m b e r o f y o u n g s u r v i v i n g s e v e n o r more d a y s a f t e r h a t c h i n g , I f o u n d t h a t 56% o f a l l w r e n n e s t s (N = 89) a n d 56% o f a l l r e d w i n g n e s t s (N = 39) w e r e s u c c e s s f u l . N e i t h e r s p e c i e s h a d d i f f e r e n t s u c c e s s i n t h e l a t e s p r i n g t h a n i n t h e summer s e a s o n s (p > . 2 0 f o r e a c h s p e c i e s , F i s h e r E x a c t P r o b a b i l i t y ) w 3 . P h y s i c a l N e s t S i t e P a r a m e t e r s The p h y s i c a l c h a r a c t e r i s t i c s o f w r e n n e s t s i t e s a r e d i s t i n c t l y d i f f e r e n t f r o m t h o s e o f r e d w i n g s i t e s ( T a b l e I I I ) . W r e n s p l a c e d t h e i r n e s t s much h i g h e r a n d i n t a l l e r v e g e t a t i o n t h a n r e d w i n g s . T h e g r e a t e r v i s i b i l i t y o f w r e n n e s t s p r o b a b l y r e f l e c t s t h e f a c t t h a t t h e y w e r e p l a c e d h i g h e r o f f t h e g r o u n d a n d i s t h u s o f l i m i t e d u s e a s a c o m p a r a t i v e i n d e x o f v e g e t a t i o n d e n s i t y . Wren n e s t s w e r e p l a c e d o v e r s h a l l o w e r w a t e r o n t h e a v e r a g e t h a n r e d w i n g n e s t s , a n d 43% w e r e o v e r d r y g r o u n d t h r o u g h o u t t h e n e s t ' s a c t i v e p e r i o d , v e r s u s 14% f o r r e d w i n g s ( F i s h e r E x a c t P r o b a b i l i t y = . 0 0 0 1 ) . W r e n s t e n d e d t o p l a c e n e s t s n e a r e r t o v e g e t a t i o n e d g e s t h a n r e d w i n g s . R e d w i n g s o f t e n p l a c e d TABLE III. COMPARATIVE PHYSICAL NEST SITE PARAMETERS Marsh Wren Redwing Significance of Difference Nest* Ht. Nest Visibil ity Veg. Ht. Avg. Water Depth Distance to Veg. Edge Distance to Open Water % of Nests Within .5 m Open Water 92.5 cm ± 2.4** 32.7 cm ± 1.5 12.7 circles ± 0.4 9.1 circles ± 0.5 157.4 cm ± 3.1 6.3 cm (105)*** 5.9 m (115) 8.2 m ••.(90) (100) 97.1 cm ± 2.9 12.5 cm (64) 13.9 m (63) 6.3 m (50) 24% (50) .0000 (Student's t) .0000 (Student's t) .0000 (Student's t) .0000 (Mann-Whitney U) .0000 (Mann-Whitney U) .096 (Mann-Whitney U) .0000 (Fisher Exact Prob.) * See Methods section for definition of parameters ** Standard Error of Mean *** 46 n e s t s i n t h e m i d s t o f e x t e n s i v e S c i r p u s p a t c h e s , w h e r e a s w r e n s o f t e n p l a c e d t h e i r s i n S p i r a e a o r T . l a t i f g l i a v e r y c l o s e t o C a r e x o r S^. c y p e r i n u s p a t c h e s . T h i s i s i n d i r e c t c o n t r a s t t o t h e s t u d y by B u r t ( 1 9 7 0 ) o f a m a r s h w i t h s i m i l a r - s i z e d v e g e t a t i o n p a t c h e s , i n w h i c h 58% o f r e d w i n g n e s t s were w i t h i n 20 f t o f a v e g e t a t i o n e d g e , c o m p a r e d w i t h 35% o f w r e n n e s t s . The a v e r a g e d i s t a n c e t o o p e n w a t e r was s i m i l a r f o r b o t h s p e c i e s , b u t t h e d i s t r i b u t i o n o f t h e d i s t a n c e s s h o w s t h a t a g r e a t e r n u m b e r o f r e d w i n g n e s t s w e r e f o u n d w i t h i n . 5 m o f o p e n w a t e r . Many o f t h e r e d w i n g n e s t s w e r e p l a c e d i n s i n g l e S . c y p e r i n u s p l a n t s s u r r o u n d e d by o p e n w a t e r . O t h e r a u t h o r s ( B u r t 1 9 7 0 , N e r o 1 9 5 6 , W i e n 1965) h a v e a l s o r e c o r d e d a t e n d e n c y f o r r e d w i n g s t o p l a c e n e s t s i n c l o s e p r o x i m i t y t o o p e n w a t e r . 47 V e g e t a t i o n T y p e S e l e c t i o n I n o r d e r t o t e s t t h e - w r e n - r e d w i n g " S e g r e g a t i o n " h y p o t h e s i s , I , u s e d t h e r e s u l t s o f t w o m e a s u r e s o f u t i l i z e d v e g e t a t i o n o r h a b i t a t * One m e a s u r e o f u t i l i z e d h a b i t a t was r e l a t i v e a b u n d a n c e i n d i f f e r e n t v e g e t a t i o n t y p e s v i a c e n s u s t r a n s e c t s . T h e o t h e r was t h e n e s t i n g s u b s t r a t e c h o s e n by w r e n s and r e d w i n g s , a s r e c o r d e d i n n e s t s t u d y p l o t s . I p r e s e n t t h e r e s u l t s o f t h e s e t w o m e a s u r e s s e p a r a t e l y w i t h a f i n a l summary o r s y n t h e s i s . C e n s u s t r a n s e c t r e s u l t s f o r y e l l o w t h r o a t s and S o n g S p a r r o w s a r e a l s o p r e s e n t e d . 1. C e n s u s T r a n s e c t s One d i f f e r e n c e b e t w e e n t h e h a b i t a t s o f w r e n s a n d r e d w i n g s i s c l e a r , a n d i t s t a n d s o u t i n b o t h t h e b r e e d i n g ( s p r i n g a n d summer) a n d n o n - b r e e d i n g ( f a l l a n d w i n t e r ) s e a s o n s . Of t h e v e g e t a t i o n t y p e s s a m p l e d by c e n s u s t r a n s e c t s , w r e n s w e r e m o s t a b u n d a n t i n t h e " D e n s e S p i r a e a " h a b i t a t , w h i c h was r a r e l y o c c u p i e d by r e d w i n g s ( F i g s . 11 a n d 1 2 ) . * Wrens u s e d p r i m a r i l y h a b i t a t c o n t a i n i n g S p i r a e a w i t h summer a n d f a l l u s e o f S c i r p u s s p p . , w h i l e r e d w i n g s u s e d a l m o s t e x c l u s i v e l y h a b i t a t c o n t a i n i n g s e d g e s ( S c i r p u s s p p . ) . S p i r a e a i s p a r t i c u l a r l y i m p o r t a n t t o w r e n s a s w i n t e r h a b i t a t ( F i g . 1 1 ) . * R e s u l t s o f t h e c e n s u s t r a n s e c t s a r e p r e s e n t e d i n t a b l e f o r m i n t h e A p p e n d i x . 48 F i g u r e 1 1 . N o n - b r e e d i n g S e a s o n M a r s h C e n s u s R e s u l t s b y V e g e t a t i o n T y p e f o r M a r s h Wren a n d R e d - w i n g e d B l a c k b i r d Long - billed Marsh Wren 10 Total Birds k m F * E W LW Dense Spiraea F EW LW Sedge -Spiraea F E W LW s_ acutus F EW LW cyperinus 1 0 h Total Birds km 5r l_J_i F EW LW Red - winged Blackbird UL F EW LW F EW LW F EW LW Dense Spiraea Sedge -Spiraea S. acutus cyperinus ** 'Seasons as defined in methods section : F - F a l l , EW - Early Winter, LW - Late Winter The means of all census transects over the entire fall - winter period were significantly different in different vegetation types for both species ( p * .001 for each species, Kruskal - Wallis one-way analysis of var iance) . 50 F i g u r e 1 2 . B r e e d i n g S e a s o n H a r s h C e n s u s B e s u l t s by V e g e t a t i o n T y p e f o r H a r s h Wren a n d R e d - w i n g e d B l a c k b i r d 51 Males k m 20 15 10 E S * L S S Dense Spiraea Long-billed Marsh Wren _L ES LS S Sedge-Spiraea ES LS S acutus ES LS S _s_ cyperinus Males k m 10 -1_L ES LS S Dense Spiraea Red - winged Blackbird * * ES LS S Sedge -Spiraea ES LS S _s^  acutus i l l ES LS S cyperinus Seasons as defined in methods section: ES - Early Spring, LS - Late Spring, S - Summer The means of all census transects over the entire spring - summer period were significantly different in different vegetation types for both species ( p < 005 for each species, Kruskal - Wallis one - way analysis of variance). 52 T e m p o r a l s e g r e g a t i o n may r e d u c e t h e o v e r l a p i n t h e use o f S . a c u t u s a n d c y p e r i n u s b y t h e two s p e c i e s . Wren a b u n d a n c e i n t h e s e s e d g e s i n c r e a s e s s h a r p l y i n s u m m e r , c o r r e s p o n d i n g w i t h a s t a t i s t i c a l l y i n s i g n i f i c a n t d e c l i n e i n r e d w i n g a b u n d a n c e ( F i g s . 13 a n d 1 4 ) . , S o n g S p a r r o w s a n d y e l l o w t h r o a t s s h a r e h a b i t a t c o n t a i n i n g S p i r a e a w i t h w r e n s a n d a r e m o s t a b u n d a n t i n " D e n s e S p i r a e a " ( F i g s . 15 a n d 1 6 ) . T h e y a r e a b s e n t f r o m t h e p u r e s e d g e t y p e s , w i t h t h e e x c e p t i o n o f some f a l l d i s p e r s a l ( F i g . 1 5 ) . , S o n g S p a r r o w s a l s o u t i l i z e d y k e s w i t h s h r u b s b o r d e r i n g some m a r s h a r e a s , a h a b i t n o t s h a r e d t o a n y e x t e n t by wrens , o r y e l l o w t h r o a t s ( B u n y a n 1 9 7 8 ) . , T h e i n c r e a s e i n y e l l o w t h r o a t a b u n d a n c e i n " D e n s e S p i r a e a " t h a t t a k e s p l a c e i n summer (p < . 0 5 , M a n n - W h i t n e y 0) c o i n c i d e s w i t h a d e c r e a s e i n w r e n a b u n d a n c e (p < . 0 0 2 , M a n n - W h i t n e y 0 ) . : 2 . N e s t S u b s t r a t e I n t h e f o l l o w i n g s e c t i o n , I show w r e n a n d r e d w i n g n e s t s i t e l o c a t i o n s i n r e l a t i o n t o v e g e t a t i o n i n v e g e t a t i o n c o v e r maps o f t h e s t u d y p l o t s . T h e h a b i t a t s o f w r e n s a n d r e d w i n g s a r e d i s c u s s e d w i t h r e f e r e n c e to , t h e s e m a p s , w i t h m e n t i o n a l s o o f y e l l o w t h r o a t a n d Song S p a r r o w o b s e r v a t i o n s * T h e s u b s e g u e n t s e c t i o n p r o v i d e s a m o r e r i g o r o u s a n a l y s i s o f t h e . i m p o r t a n c e o f t h e d i f f e r e n t v e g e t a t i o n t y p e s f o r w r e n a n d r e d w i n g n e s t i n g s u b s t r a t e . 53 Figure 13. Late Spring and Summer Census Results i n acutus Males km 15 10 Long-billed Marsh Wren (p <.002, Mann - Whitney U ) Late Spring Summer Red-winged Blackbird (p > .31, Mann - Whitney U ) 10 -Males km 5 -Late Spring Summer 55 F i g u r e 14. L a t e S p r i n g a n d Summer C e n s u s R e s u l t s i n S . c y p e r i n u s Males km 10 -Long-billed Marsh Wren (p <.02, Mann - Whitney U ) Late Spring Summer Males km 10 Red-winged Blackbird (p > ! 0 , Mann - Whitney U ) Late Spring Summer 57 F i g u r e 1 5 . N o n - b r e e d i n g S e a s o n M a r s h C e n s u s R e s u l t s b y V e g e t a t i o n T y p e f o r Y e l l o w t h r o a t a n d S o n g S p a r r o w Common Yellowthroat Birds km 5 A 3 2 1 F EW LW * Dense Spiraea F EW LW Sedge -Spiraea F EW LW _s^  acutus F EW LW cyperinus Song Sparrow Birds km 5 A 3 2 1 F EW LW Dense Spiraea F EW LW Sedge -Spiraea EW LW _S_^  acutus EW LW cyperinus Seasons as defined in methods section: F - F a l l , EW - Early Winter, LW - Late Winter 59 F i g u r e 1 6 . B r e e d i n g S e a s o n H a r s h C e n s u s R e s u l t s by V e g e t a t i o n T y p e f o r Y e l l o w t h r o a t a n d S o n g S p a r r o w Common Yellowthroat 10.0 Males k m 5.0 -1 ES LS S * Dense Spiraea ES LS S Sedge-Spiraea ES LS S acutus ES LS S cyperinus 5.0 Males k m Song Sparrow ES LS S Dense Spiraea ES LS S Sedge -Spiraea ES LS S _s, acutus ES LS S cyperinus Seasons as defined in methods section: ES -Ear ly Spring, L S - L a t e Spring, S -Summer 61 a . S u b s t r a t e U t i l i z a t i o n - Haps O f N e s t P l o t s T h e l o c a t i o n o f b r e e d i n g n e s t s i n e a c h o f t h e s i x m a i n n e s t p l o t s i s shown f o r b o t h l a t e s p r i n g a n d summer i n F i g u r e s 1 7 - 2 8 . P l o t C was t h e o n l y p l o t i n w h i c h n e i t h e r s p e c i e s n e s t e d d u r i n g t h e summer s e a s o n * W i t h o n l y one e x c e p t i o n , w ren n e s t s l o c a t e d w i t h i n 10 ra o f one a n o t h e r were n o t s i m u l t a n e o u s l y a c t i v e . P l o t G i s n o t shown b e c a u s e I d i d n o t map o u t i t s v e g e t a t i o n a s r i g o r o u s l y a s t h e o t h e r p l o t s . T h i s 1 ha p l o t of a f a i r l y u n i f o r m m i x t u r e o f T . l a t i f p l j . a a n d S. c y p e r i n u s was one s e c t i o n o f t h e l a r g e s t s i n g l e s t a n d o f T . l a t i f o i i a . w h i c h was more a b u n d a n t i n t h e p l o t t h a n S . c y p e r i n u s , i n t h e PWMA. Wrens a n d r e d w i n g s a p p e a r t o h a v e d i f f e r e n t v e g e t a t i o n p r e f e r e n c e s . W i t h t h e e x c e p t i o n o f c a t t a i l , t h e p r e f e r r e d v e g e t a t i o n o f r e d w i n g s i s s e d g e ( S c i r p u s s p p . ) , w h i l e t h a t o f w r e n s i s t h e S p i r a e a s h r u b . N e s t d i s t a n c e s b e t w e e n t h e t w o s p e c i e s a r e s m a l l e s t whe re S p i r a e a a n d S. c y p e r i n u s meet ( F i g s . 23 a n d 2 4 ) . E e d w i n g n e s t s w e r e a b s e n t f r o m p l o t s c o m p o s e d s o l e l y o f S p i r a e a , , C a r e x s p p . , a n d g r a s s e s ( F i g s . 18 , 19 , a n d 22) . B o t h s p e c i e s n e s t i n T. l a t i f o l i a a n d , t o a l e s s e r e x t e n t , i n a c u t u s > b u t a t d i f f e r e n t t i m e s d u r i n g t h e s e a s o n , Wren s u t i l i z e d b o t h p l a n t s i n t h e summer ( a f t e r J u n e 1 ) , w h i l e r e d w i n g s u t i l i z e d t h e m i n t h e ' l a t e s p r i n g ( F i g s . 2 0 , 2 1 , 2 3 - 2 8 ) . T e m p o r a l s e g r e g a t i o n was p a r t i c u l a r l y a p p a r e n t i n T . l a t i f o l i a . F o u r r e d w i n g n e s t s were f o u n d i n t h e c a t t a i l - d o m i n a t e d P l o t G d u r i n g t h e l a t e s p r i n g s e a s o n when no w r e n s w e r e d e t e c t e d w i t h i n 200 m o f t h e p l o t . One w ren b r e e d i n g n e s t a p p e a r e d much l a t e r i n J u l y . T h o u g h a f e w m a l e and f e m a l e r e d w i n g s w e r e s t i l l s e e n 62 F i g u r e 17. L e g e n d : V e g e t a t i o n C o v e r M a p s , N e s t S t u d y P l o t s Legend: 1. Vegetation + + + + + + + + + • o o • • • n o a n n " V V V V v v V v v Spiraea douglasii (Hardhack) Graminae spp. Typha latifolia (Broad-leaved Cattail) Scirpus acutus (Hard-stemmed Bulrush) Scirpus cyperinus (Hairy-seeded Bulrush) Carex spp. (Low Sedge) Open Water 2. Breeding Nests Wren • Redwing Scale of maps: 1 cm = 16.7 meter Seasons: Late Spring - prior to June 1 Summer - June 1 and after 64 F i g u r e : 1 8 . B e s t D i s t r i b u t i o n i n P l o t ft. L a t e S p r i n g („5 i v v V V W W v w v v v v v v v v v v w w v w v v v v v v v v v v v v v v v v v V V V V V V v v v v v v v v v v v 70 3, V V V V V V V V W W W W w w w v w w w w v w w v v w w v w w v w v W W W V V W W V V V W V W V v v w w w v v w w w v v w w w v v w w w v v v W V w w w w w w w v V v v w w w w V V V W V V V V V V V w w w w w w w w w V W W V W V V v v w w w 66 F i g u r e 1 9 . N e s t D i s t r i b u t i o n i n P l o t ft. Summer A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A ) f.tf; „: . i w . -. *.i 0 I 68 F i g u r e 20. B e s t D i s t r i b u t i o n i n P l o t B , L a t e S p r i n g 70 F i g u r e 2 1 . N e s t D i s t r i b u t i o n i n P l o t B , Summer 72 Figure 22- Best Dis t r i b u t i o n i n Plot C, Late Spring 7 3 74 Figure 23. Nest Dis t r i b u t i o n i n Plot D, Late Spring 76 F i g u r e 2 4 . N e s t D i s t r i b u t i o n i n P l o t D , Summer 78 Figure 25. Nest Dis t r i b u t i o n in Plot B, Late Spring 80 Figure 26. Nest Dis t r i b u t i o n i n Plot E, Summer 82 F i g u r e 2 7 . N e s t D i s t r i b u t i o n i n P l o t F , L a t e S p r i n g 84 Figure 28. Nest Distribution i n Plot F, Summer 86 w i t h i n a n d i m m e d i a t e l y a d j a c e n t t o t h e p l o t none o f t h e s e n e s t e d i n t h e p l o t . I n a p a t c h o f T . l a t i f o l i a i n t h e n o r t h e r n c o r n e r o f P l o t D ( F i g s . 23 a n d 2 4 ) , a m a l e w r e n b u i l t a "dummy" n e s t ( n o t u s e d f o r b r e e d i n g ) e a r l y i n t h e l a t e s p r i n g . A r e d w i n g t h e n e s t a b l i s h e d a t e r r i t o r y i n w h i c h t w o f e m a l e s n e s t e d , a n d w r e n a c t i v i t y i n t h a t t e r r i t o r y , a n d i n t h e s u r r o u n d i n g a r e a w i t h i n 100 m o f t h e p l o t b o u n d a r y , c e a s e d u n t i l l a t e J u n e , a f t e r t h e b l a c k b i r d s c o m p l e t e d t h e i r n e s t i n g . y e l l o w t h r o a t s a n d S o n g S p a r r o w s w e r e a l s o d e t e c t e d i n t h e p l o t s , p r i m a r i l y i n S p i r a e a s t a n d s ( P l o t s A a n d C ) . T h o u g h we f o u n d n o n e s t s , we o b s e r v e d r e c e n t l y f l e d g e d y e l l o w t h r o a t y o u n g i n t h e p l o t s on t h r e e o c c a s i o n s . One S o n g S p a r r o w n e s t was l o c a t e d i n P l o t C . T e r r i t o r i e s o f y e l l o w t h r o a t s a n d w r e n s d e t e r m i n e d by t h e l o c a t i o n s o f m a l e s o n g , a p p e a r e d t o be s e g r e g a t e d . Wrens n e s t i n g i n t h e S p i r a e a o f A a n d C n o r m a l l y c h o s e s i t e s b e s i d e C a r e x p a t c h e s i n t h e e a s t e r n p o r t i o n o f A a n d t h e s o u t h e r n p o r t i o n o f C . Y e l l o w t h r o a t s e s t a b l i s h e d m o s t o f t h e i r t e r r i t o r i e s i n t h e w e s t e r n a n d n o r t h e r n p a r t s o f A a n d C r e s p e c t i v e l y , w h e r e g r a s s e s were more a b u n d a n t , a n d t h e g r o u n d was n o t i c e a b l y h i g h e r . 87 b. S u b s t r a t e U t i l i z a t i o n - A n a l y s i s How important are the d i f f e r e n t v e g e t a t i o n types to redwings and wrens as n e s t i n g s u b s t r a t e ? To answer that question, I examined the percentages of a l l n e s t s i n each of the p l a n t s p e c i e s (Table IV) weighted by d i v i d i n g by the area of t h a t p l a n t s p e c i e s covered (Fig- 29). When c o n s i d e r i n g the e n t i r e breeding season, Spiraea h a b i t a t was much more important to wrens than t o redwings, and the two S c i r p u s spp. were more important t o redwings than to wrens ( F i g . 29). I observed the same r e l a t i o n s h i p i n the a n a l y s i s o f census t r a n s e c t s ( F i g - 12). Typha was the most important p l a n t used f o r nest s u b s t r a t e f o r both redwings and wrens. By s e p a r a t i n g t h e a n a l y s i s i n t o the l a t e s p r i n g and summer ne s t i n g seasons ( F i g s . 30 ad 31), temporal s e g r e g a t i o n emerges. Wrens use T. l a t i f o l i a and S. acutus p r i m a r i l y i n the summer when the redwing use has decreased. The r e s u l t s of census t r a n s e c t s suggested t h i s same temporal s e g r e g a t i o n i n the use of S«. acutus and c y p e r i n u s ( F i g - 12). Wrens r a r e l y used S. c y p e r i n u s as n e s t i n g s u b s t r a t e , and there was no temporal s e g r e g a t i o n from redwings i n t h i s v e g e t a t i o n type ( F i g s . 30 and 31). I t h i n k the main reason f o r t h i s d i s c r e p a n c y between the census t r a n s e c t r e s u l t s and the n e s t s u b s t r a t e r e s u l t s f o r S. c y p e r i n u s i s that the t o t a l census t r a n s e c t sample s i z e f o r S. c y p e r i n u s was r e l a t i v e l y s m a l l (see Table I ) . TABLE IV. NEST NUMBERS IN DIFFERENT VEGETATION IN NEST STUDY PLOTS Spiraea douglasii S. acutus S. cyperinus T. latifolia Carex spp. Total Wren Total 57 nests* 16 5 27 0 105 Late Spring 41 3 0 6 50 Summer 16 13 5 21 55 Redwing Total 1* 20 22 14 2 59 Late Spring 1 18 6 13 2 40 Summer 0 2 16 1 0 19 Nests containing eggs or young 89 Figure 29. Weighted Nest Distributions by Vegetation, Entire Season K.O 12.0 °/o 10.0 Nests in Vegetation Area Vegetation (ha) 8.0 6.0 A.O 2.0 Wren Redwing Spiraea S. acutus S. cyperinus Typha 91 Figure 30- Weighted Nest Distributions by Vegetation, Late Spring 24.0 Nests in Vegetation Area Vegetation (ha) 16.0 12.0 8.0 4.0 Wren Redwing Spiraea S. acutus S. cyperinus Typha 9 3 F i g u r e 3 1 . w e i g h t e d N e s t D i s t r i b u t i o n s b y V e g e t a t i o n , Summer 24.0 0 / 20.0 Nests in Vegetation Area Vegetation (ha) 16.0 12.0 8.0 4.0 Redwing Wren Spiraea S. acutus S. cyperinus Typha 95 S e v e r a l a u t h o r s e m p h a s i z e t h e i m p o r t a n c e o f e x a m i n i n g t h o s e h a b i t a t s i n w h i c h s e x u a l p a i r i n g o c c u r s f i r s t a s a n i n d i c a t i o n o f s u i t a b i l i t y o f t e r r i t o r i e s ( S v a r d s o n 1 9 4 9 , V e r n e r 1964 a n d 1 9 7 5 b ) . T h e n u m b e r s i n T a b l e s V a n d V I r e p r e s e n t t h i s same i d e a i n t e r m s o f t h e o r d e r i n w h i c h d i f f e r e n t s u b s t r a t e s a r e c h o s e n f o r b r e e d i n g n e s t s . . F i v e - d a y t i m e i n t e r v a l s w e r e e x a m i n e d , s t a r t i n g f r o m t h e d a t e o f t h e f i r s t c o m p l e t e c l u t c h b y e a c h s p e c i e s , a n d t h e n u m b e r o f n e s t s i n e a c h s u b s t r a t e was w e i g h t e d fey t h e s u b s t r a t e a r e a s a m p l e d . W r e n s c h o s e S p i r a e a f i r s t w h i l e r e d w i n g s c h o s e Ty p h a , a r e s u l t c o n s i s t e n t w i t h t h e o v e r a l l s u b s t r a t e u s a g e f o r t h e l a t e s p r i n g s e a s o n ( F i g . 3 0 ) . T h o u g h t h e o v e r a l l d i f f e r e n c e i n n e s t i n g s u c c e s s b e t w e e n n e s t s i n d i f f e r e n t v e g e t a t i o n t y p e s i s s i g n i f i c a n t o n l y f o r r e d w i n g n e s t s (p < . 0 5 , C h i - s g u a r e d ) , t h e r e i s a n i n d i c a t i o n t h a t b o t h w r e n s a n d r e d w i n g s h a d t h e g r e a t e s t n e s t i n g s u c c e s s i n t h e t w o s u b s t r a t e s t h e y u s e d m o s t o f t e n a n d t h e l e a s t s u c c e s s i n S . a c u t u s ( T a b l e V I I ) . F l o o d i n g c a u s e d f i v e o f t h e e i g h t r e d w i n g f a i l u r e s i n S . a c u t u s , a n d t h i s c a u s e o f n e s t f a i l u r e a l o n e s u f f i c i e n t l y e x p l a i n s t h e d i f f e r e n c e i n r e d w i n g n e s t i n g s u c c e s s i n d i f f e r e n t v e g e t a t i o n t y p e s . » F l o o d i n g a l s o c a u s e d t h e f a i l u r e o f one o f t w o r e d w i n g n e s t s p l a c e d i n C a r e x s i t c h e n s i s . A l l o f t h e 11 w r e n n e s t s i n S . a c u t u s w e r e l o c a t e d i n n e s t P l o t B , a n d s i x o f t h e s e v e n f a i l u r e s w e r e a s s o c i a t e d w i t h e x t e n s i v e n e s t d e s t r u c t i o n . T h i s d e s t r u c t i o n r a n g e d f r o m a l a r g e h o l e i n t h e n e s t , t o t h e m i s s h a p e n n e s t b e i n g f o u n d i n t h e w a t e r a s i f * I f f l o o d e d r e d w i n g n e s t s i n S . a c u t u s a r e i g n o r e d , t h e d i f f e r e n c e s i n T a b l e V I I a r e n o l o n g e r s t a t i s t i c a l l y s i g n i f i c a n t f o r e i t h e r s p e c i e s * 96 TABLE V. CHRONOLOGY OF WREN NEST SUBSTRATE CHOICE 1st 5 days 2nd 5 days 3rd 5 days Spi raea douglasi i _S. acutus T. latifolia * (No. nests in veg. type/Area veg. type sampled) x 10 nests ha x 10 4.5 6.1 2.8 5.6 TABLE VI. CHRONOLOGY OF REDWING SUBSTRATE CHOICE 1st 5 days 2nd 5 days 3rd 5 days S. acutus nests ha x 10 4.2 4.2 cyperinus 2.1 2.1 6.2 T. latifolia 5.6 16.7 38.9 * (No. nests in veg. type/Area veg. type sampled) x 10 93 TABLE V I I . NEST SUCCESS VS. VEGETATION TYPE USED AS NEST SUBSTRATE Spiraea douglasi i S_. acutus S_. cyperinus X- l a t i f o l i a 51%* 36% insu f f i c i en t g g % W r e n (N = 47) (N = 11) ' ( ^ = 5 ) ( N = 2 9 ) i n su f f i c i en t sample (N = 1) 75% 56% Redwing sample ( N ^ ' l l ) (N =°16) (N=°9 ) * Percentage of nests in that vegetation type succeeding in fledging one or more young. 99 i t , a n d t h e s t e m t o w h i c h i t was a t t a c h e d , had b e e n p u s h e d d o w n . A l a r g e p r e d a t o r , s u c h a s t h e e v e r p r e s e n t N o r t h w e s t e r n C r o w , i s s u s p e c t e d . 3. Summary Wrens u s e d i f f e r e n t v e g e t a t i o n t y p e s t h a n t h o s e t y p e s u s e d by r e d w i n g s , o r t h e same t y p e s b u t a t d i f f e r e n t t i m e s . T h i s r e s u l t was c o n s i s t e n t f o r t w o m e t h o d s u s e d d u r i n g t h e s p r i n g a n d summer s e a s o n s : c e n s u s t r a n s e c t s t h a t c e n s u s e d s i n g i n g m a l e s a n d n e s t c o u n t s i n n e s t s t u d y p l o t s . T h i s s u p p o r t s t h e " S e g r e g a t i o n " h y p o t h e s i s . W r e n s a p p e a r t o p r e f e r h a b i t a t c o n t a i n i n g S p i r a e a , w i t h t h e e x c e p t i o n o f a p r e f e r e n c e f o r T . l a t i f o l i a d u r i n g summer n e s t i n g . R e d w i n g s p r e f e r S c i r p u s s p p . , w i t h t h e e x c e p t i o n o f t h e l a t e s p r i n g , when t h e y p r e f e r T . l a t i f o l i a f o r n e s t i n g . T h e y r a r e l y u s e t h e " D e n s e S p i r a e a " h a b i t a t p r e f e r r e d b y w r e n s . B o t h w r e n s a n d r e d w i n g s u t i l i z e d S . a c u t u s a n d T . l a t i f o l i a . b u t a t d i f f e r e n t t i m e s . T h i s t e m p o r a l s e g r e g a t i o n t o o k t h e f o r m o f r e d w i n g u s e f i r s t , f o l l o w e d by w r e n u s e , f o r b o t h h a b i t a t s . A s s h o w n i n o t h e r s t u d i e s , T y p h a i s i m p o r t a n t a s n e s t i n g s u b s t r a t e f o r b o t h s p e c i e s , b o t h i n r e l a t i v e u s e a n d n e s t i n g s u c c e s s . I d i d n o t e x a m i n e t h e w i n t e r u s e o f t h e T y p h a h a b i t a t . S o n g S p a r r o w s a n d y e l l o w t h r o a t s s h a r e t h e s h r u b p o r t i o n o f , t h e : w r e n ' s h a b i t a t , a n d a p a t t e r n o f v e g e t a t i o n u s e b y t h e f o u r p a s s e r i n e s p e c i e s i n r e l a t i o n t o s u c c e s s i v e s t a g e s f r o m t h e c e n t r a l m a r s h a p p e a r s . A r e a s t r a v e r s e d f r o m t h e c e n t r a l a n d d e e p e s t m a r s h o u t w a r d t o w a r d s h i g h e r g r o u n d , a r e i n h a b i t e d by r e d w i n g s , w r e n s , y e l l o w t h r o a t s , a n d S o n g S p a r r o w s i n t h a t o r d e r . 100 A l l e n ( 1914 ) r e p o r t s a s i m i l a r p a t t e r n . 101 Compe t i t i on I n t h i s s e c t i o n , I p r e s e n t t h e r e s u l t s o f t e s t s o f t h e t w o r e s e a r c h h y p o t h e s e s t h a t e x a m i n e t h e r o l e o f i n t e r f e r e n c e c o m p e t i t i o n i n t h e h a b i t a t s e l e c t i o n o f w r e n s a n d r e d w i n g s . 1. W r e n - B e d w i n g I e x a m i n e d t h e e f f e c t o f w r e n - r e d w i n g n e s t d i s t a n c e on t h e n e s t i n g s u c c e s s o f e a c h s p e c i e s . S i n c e i n d i v i d u a l w r e n s a n d r e d w i n g s n o r m a l l y m a i n t a i n r o u g h l y t h e same t e r r i t o r y t h r o u g h o u t t h e b r e e d i n g p e r i o d ( V e r n e r 1 9 6 5 a , K a l e 1 9 6 5 , A l i e n 1 9 1 4 , B e n t 1958) t, t h e w r e n - r e d w i n g n e s t d i s t a n c e f o r a n y n e s t was d e f i n e d a s t h a t b e t w e e n i t a n d a n y b r e e d i n g n e s t o f t h e o t h e r s p e c i e s w h i c h i s a c t i v e a n y t i m e b e f o r e , d u r i n g , o r up t o t w o weeks f o l l o w i n g t h e a c t i v e p e r i o d o f t h e n e s t i n q u e s t i o n . I e x c l u d e d f l o o d e d r e d w i n g n e s t s f r o m t h e a n a l y s i s o f r e d w i n g n e s t i n g s u c c e s s . The d i s t r i b u t i o n s o f n e s t s u c c e s s e s a n d f a i l u r e s a t d i f f e r e n t min imum w r e n - r e d w i n g n e s t d i s t a n c e s ( F i g s . 32 a n d 3 3 ) * s u g g e s t t h a t w r e n s a n d r e d w i n g s h a v e l o w e r s u c c e s s a t w r e n -r e d w i n g d i s t a n c e s c l o s e r t h a n 50 m a n d 25 m r e s p e c t i v e l y . I n d i v i d u a l s o f b o t h s p e c i e s d o , i n f a c t , h a v e s i g n i f i c a n t l y l o w e r s u c c e s s when t h e y n e s t c l o s e r t o i n d i v i d u a l s o f t h e o t h e r s p e c i e s t h a n t h e s e s u g g e s t e d c u t - o f f p o i n t s ( T a b l e s V I I I a n d I X ) . , T h i s s u p p o r t s t h e " W r e n - B e d w i n g C o m p e t i t i o n " h y p o t h e s i s . * The s c a l e o n t h e x - a x i s o f F i g u r e 32 i s l a r g e r t h a n t h a t o f F i g u r e 33 b e c a u s e t h e t e r r i t o r y , a n d t h u s t h e a r e a o f i n f l u e n c e , o f a w r e n i s n o r m a l l y much s m a l l e r t h a n t h a t o f a r e d w i n g . 102 Figure 32. D i s t r i b u t i o n of Redwing Nest outcome with Respect to I n t e r s p e c i f i c Distance Failure Success 2 2 1 nest 1 1 1 2 1 _ l I I I I , L_ 1 1— 10 20 30 AO 50 60 70 80 Distance to Nearest Wren Breeding Nest (m) 104 F i g u r e 33. D i s t r i b u t i o n of Wren Nest Outcome w i t h Bespect to I n t e r s p e c i f i c D i s t a n c e Failure 2 nests 1 1 2 1 1 1 1 1 2 1 Success 1 122 1 2 1 1 1 3 1 1 1 _ i i i i i i i i i i i i 1— 10 20 30 40 50 60 70 80 90 100 110 120 130 Distance to Nearest Redwing Nest ( m ) TABLE VIII. CLOSEST REDWING NEST DISTANCE CATEGORY VS. WREN NEST SUCCESS Redwing Nest Distance < 50 m > 50 m Wren 13 nests 18 Success (50%) (75%) Wren 13 6 Failure (50%) (25%) Total 26 24 Statistics: Accept differences in nest success at .05 level (Fisher Exact Probability of null hypothesis = .03) TABLE IX. CLOSEST MARSH WREN NEST DISTANCE VS. REDWING NEST SUCCESS Wren Nest Distance < 25 m >25 m Redwing 2 nests 13 Success (28.6%) (72.2%) Redwing 5 5 Failure (71.4%) (27.8%) Total 7 18 Statistics: Accept differences in nest success at .05 level (Fisher Exact Probability of null hypothesis = .03) 108 The n a t u r e o f r e d w i n g n e s t f a i l u r e s c l o s e t o w r e n n e s t s s u p p o r t s t h e i d e a t h a t w r e n s w e r e t h e c a u s e . None o f t h e f o u r r e d w i n g n e s t s t h a t w e r e c l o s e r t h a n 15 m t o a w r e n n e s t s u c c e e d e d . Two o f t h e s e n e s t s w e r e i n T . l a t i f o l i a , a n d two w e r e i n c y p e r i n u s , p l a n t s i n w h i c h r e d w i n g s w e r e , on t h e a v e r a g e , more s u c c e s s f u l ( T a b l e V I I ) . E g g s o r y o u n g were m i s s i n g f r o m a l l f i v e o f t h e f a i l e d n e s t s c l o s e r t h a n 25 m t o a w r e n n e s t , and I f o u n d t w o b r o k e n e g g s on t h e g r o u n d b e n e a t h o n e o f t h e n e s t s . None o f t h e s e n e s t s h a d b e e n o b v i o u s l y d i s r u p t e d ( t i l t e d , n e s t m a t e r i a l d i s r u p t e d , o r f a l l e n d o w n ) . E v i d e n c e f o r t h e c a u s e o f t h e 13 w r e n n e s t f a i l u r e s c l o s e t o n e s t s o f r e d w i n g s was i n c o n c l u s i v e - A l l o f t h e s e n e s t s l o s t e g g s o r y o u n g , a n d 6 o f t h e 13 w e r e o b v i o u s l y d i s r u p t e d ( t o p o f n e s t m i s s i n g o r n e s t k n o c k e d d o w n ) . T h i s p a t t e r n o f m u t u a l s u p p r e s s i o n o f n e s t i n g s u c c e s s i s a l s o f o u n d when t h e e f f e c t s o f d i f f e r e n t v e g e t a t i o n t y p e s on n e s t i n g s u c c e s s a r e r e m o v e d ( T a b l e X ) . T h e r e s u l t s a r e , h o w e v e r , s t a t i s t i c a l l y i n s i g n i f i c a n t , p o s s i b l y due t o l o w s a m p l e s i z e s . T h u s , t h e r e l a t i o n s h i p b e t w e e n v e g e t a t i o n a n d i n t e r s p e c i f i c e f f e c t s on n e s t i n g s u c c e s s r e m a i n s u n r e s o l v e d . 2 . W r e n - W r e n O v e r a l l , w r e n - w r e n c o m p e t i t i o n d o e s n o t a p p e a r t o a f f e c t t h e o u t c o m e o f w r e n n e s t s . C o n s i d e r i n g a l l w r e n n e s t s , t h e d i s t a n c e b e t w e e n a n e s t a n d t h a t o f t h e c l o s e s t c o n s p e c i f i c n e s t t h a t i s s i m u l t a n e o u s l y a c t i v e d o e s n o t a f f e c t t h e s u c c e s s o f t h e n e s t ( T a b l e X I ) . 109 TABLE X. MUTUAL SUPRESSION OF NESTING SUCCESS IN DIFFERENT VEGETATION TYPES % Success Stati sti cal Vegetation • Significance Species Type Used Small* Large (Fisher Exact For Nesting Interspecific Interspecific Distances Di stances Probability) Redwing S. cyperinus 33.3% 80.0% (3)** (10) .10 T. latifolia 25.0% 66.7% .18 (4) (3) Wren Spiraea 33.3% 68.4% .07 (6) (19) T. latifolia 53.3% 100% .10 (15) (3) * Cutoff points are 25 m and 50 m for redwing and wren nests respectively * Sample size TABLE XI. CLOSEST WREN NEST DISTANCE VS. WREN NEST SUCCESS FOR ALL NESTS Wren Nest Distance 25 m* > 25 m Wren 17 nests 26 Success (68%) (54.2%) Wren 8 22 Failure (32%) (45.8%) Total 25 48 Statistics: p = .19, Fisher Exact Probability * The use of other cut-off points yielded similar results 111 S i m i l a r l y , s m a l l w r e n - w r e n n e s t d i s t a n c e was n o t r e l a t e d t o n e s t s u c c e s s , e v e n when r e d w i n g n e s t s w e r e w i t h i n 50 m, t h e d i s t a n c e p r e v i o u s l y d e t e r m i n e d t o b e t h e r a d i u s o f i n f l u e n c e o f r e d w i n g s on w r e n s ( T a b l e X I I ) - - I n f a c t , t h e r e s u l t s , t h o u g h n o t s i g n i f i c a n t , s u g g e s t t h a t s m a l l w r e n - w r e n n e s t d i s t a n c e s a r e a s s o c i a t e d w i t h g r e a t e r n e s t i n g s u c c e s s t h a n l a r g e r d i s t a n c e s . , T h i s w o u l d be j u s t t h e o p p o s i t e f r o m t h e r e s u l t p r e d i c t e d by t h e " W r e n - W r e n C o m p e t i t i o n " h y p o t h e s i s , w h i c h c a n n o t t h e r e f o r e b e a c c e p t e d . 112 TABLE XII. CLOSEST WREN NEST DISTANCE VS. WREN NEST SUCCESS FOR NESTS CLOSER THAN 50 M FROM A REDWING NEST Wren Nest Distance < 25 m > 25. m Wren 6 nests 7 Success (60%) (46.7%) Wren 4 8 Failure (40%) (53.3%) Total 10 15 Statistics: p = .40, Fisher Exact Probability 113 D I S C U S S I O N B i o l o g i c a l I m p l i c a t i o n s 1- R e v i e w O f H y p o t h e s e s I n t h i s s t u d y I e v a l u a t e d t h r e e h y p o t h e s e s a b o u t c o m p a r i s o n s b e t w e e n w r e n s a n d r e d w i n g s . F i r s t , b e c a u s e t h i s s t u d y m a r s h c o n t a i n s a u n i q u e d i v e r s i t y o f v e g e t a t i o n , i n t h e " S e g r e g a t i o n " H y p o t h e s i s , I h y p o t h e s i z e d t h a t w r e n s a n d r e d w i n g s w o u l d be s e g r e g a t e d by t h e use o f d i f f e r e n t v e g e t a t i o n t y p e s o r t h e same t y p e s b u t a t d i f f e r e n t t i m e s . T h e r e s u l t s o f t w o d i f f e r e n t s t u d y m e t h o d s s u p p o r t e d t h i s h y p o t h e s i s . The g r e a t e s t d e g r e e o f s e g r e g a t i o n was e x h i b i t e d i n t h e c o n t r a s t i n g r e s u l t s t h a t w r e n s w e r e mos t a b u n d a n t i n h a b i t a t c o n t a i n i n g d e n s e s t a n d s o f t h e s h r u b S p i r a e a  d o u g l a s i i a n d t h a t r e d w i n g s w e r e r a r e l y f o u n d i n t h i s h a b i t a t . S e c o n d , o f t h e p o s s i b l e u l t i m a t e f a c t o r s ( H i l d e n 1965) t h a t i n f l u e n c e t h e h a b i t a t s e l e c t i o n o f w r e n s a n d r e d w i n g s , I c h o s e t o e x a m i n e i n t e r s p e c i f i c c o m p e t i t i o n , a s d e f i n e d b y t w o s p e c i e s h a v i n g a n e g a t i v e e f f e c t on one a n o t h e r { M a c f t r t h u r 1 9 7 2 ) . T h e r e s u l t s o f m o n i t o r i n g n e s t i n g s u c c e s s i n r e l a t i o n t o i n t e r s p e c i f i c n e s t d i s t a n c e s s u p p o r t e d t h i s h y p o t h e s i s , w h i c h s t a t e s t h a t c l o s e r i n t e r s p e c i f i c d i s t a n c e s a r e r e l a t e d t o l o w e r n e s t i n g s u c c e s s f o r b o t h s p e c i e s . S h e n t h e e f f e c t s o f d i f f e r e n t v e g e t a t i o n t y p e s on n e s t i n g s u c c e s s w e r e r e m o v e d , I o b s e r v e d t h e same r e l a t i o n s h i p b e t w e e n i n t e r s p e c i f i c d i s t a n c e s a n d n e s t s u c c e s s . The r e s u l t s o f t h e l a t e r a n a l y s i s , h o w e v e r , were n o t s i g n i f i c a n t s t a t i s t i c a l l y , p o s s i b l y due t o l o w s a m p l e s i z e s . 114 The t h i r d h y p o t h e s i s s t a t e s : " W r e n n e s t i n g f a i l u r e , f o r n e s t s l o c a t e d c l o s e r t o r e d w i n g n e s t s , i s r e l a t e d t o s m a l l w r e n -w r e n d i s t a n c e s . " I n t h i s h y p o t h e s i s , I e x a m i n e d t h e p o s s i b i l i t y t h a t h a r a s s m e n t o f w r e n s by r e d w i n g s c o u l d c a u s e w r e n s t o n e g l e c t t h e i r n e s t s , l e a v i n g t h e s e n e g l e c t e d n e s t s more v u l n e r a b l e t o i n t r a s p e c i f i c n e s t d e s t r u c t i o n , fly r e s u l t s d i d n o t s u p p o r t t h i s h y p o t h e s i s , n o r w e r e s m a l l i n t r a s p e c i f i c n e s t d i s t a n c e s , t a k i n g a l l w r e n n e s t s i n t o a c c o u n t , a s s o c i a t e d w i t h l o w w r e n n e s t i n g s u c c e s s . 2 . C o m p a r i s o n s W i t h O t h e r S t u d i e s a . H a b i t a t S e g r e g a t i o n I t i s s u r p r i s i n g t h a t w r e n n e s t s w e r e mos t a b u n d a n t i n t h e s h r u b . S p i r a e a ( a l o n g w i t h c a t t a i l i n t h e summer o r l a t e r ; n e s t i n g s e a s o n ) a n d t h a t r e d w i n g s r a r e l y u s e d S p i r a e a a s n e s t i n g s u b s t r a t e . I f r e d w i n g s a r e e v o l u t i o n a r i l y more r e c e n t m a r s h i n h a b i t a n t s t h a n w r e n s ( A l i e n 1 9 1 4 , B u r t 1 9 7 0 ) , o n e w o u l d e x p e c t w r e n s t o be b e t t e r a d a p t e d t o n e s t i n g i n s e d g e ( p r i m a r i l y S c i r p u s a n d C a r e x s p p . ) a n d c a t t a i l , w h i c h t y p i f y m a r s h v e g e t a t i o n , t h a n a r e r e d w i n g s . The d i v e r s i t y o f r e d w i n g n e s t i n g s u b s t r a t e ( B e n t 1958) a n d t h e r e d w i n g ' s a d a p t a b i l i t y t o a w i d e r r a n g e o f h a b i t a t s ( u p l a n d a s w e l l a s marsh ) t h a n t h a t o f w r e n s a l s o s u g g e s t t h a t r e d w i n g s w o u l d be more l i k e l y t o u s e s h r u b s t h a n w r e n s . T h e r e s u l t s o f o t h e r s t u d i e s may h e l p e x p l a i n why t h i s was n o t t h e c a s e a n d p u t t h e h a b i t a t s e g r e g a t i o n I o b s e r v e d i n t o a b r o a d e r p e r s p e c t i v e . 115 O f t h e few p r e v i o u s s t u d i e s i n v o l v i n g w r e n s a n d r e d w i n g s , B u r t (1970 — T h i s a n d a l l s u b s e q u e n t r e f e r e n c e s t o B u r t a r e b a s e d o n h i s 1970 M . S c . t h e s i s . ) a n d P i e m a n ( T h i s a n d a l l s u b s e q u e n t r e f e r e n c e s t o P i e m a n a r e b a s e d on h i s P h . D . t h e s i s i n p r o g r e s s , u n l e s s o t h e r w i s e s t a t e d . ) p r o v i d e t h e m o s t e x t e n s i v e c o m p a r a t i v e i n f o r m a t i o n o n t h e t w o s p e c i e s . , B u r t ' s I o w a s t u d y m a r s h c o n t a i n e d a v a r i e t y o f s e d g e v e g e t a t i o n d i s t r i b u t e d i n p a t c h e s s i m i l a r i n s i z e t o t h e p a t c h e s i n t h e p r e s e n t s t u d y m a r s h , a n d he o b s e r v e d e x t e n s i v e o v e r l a p i n t h e t y p e s o f v e g e t a t i o n u s e d f o r n e s t i n g by w r e n s a n d r e d w i n g s . T h i s was p a r t i c u l a r l y t r u e i n t h o s e p o r t i o n s o f t h e s t u d y a r e a i n w h i c h Y e l l o w - h e a d e d B l a c k b i r d s were p r e s e n t . I n t h e l a r g e s t p o r t i o n o f B u r t ' s m a r s h , i n w h i c h w r e n s , r e d w i n g s , and y e l l o w h e a d s n e s t e d i n t h e l a r g e s t n u m b e r s , 96% o f a l l w r e n n e s t s a n d 52% o f a l l r e d w i n g n e s t s w e r e p l a c e d i n C a r e x l a c u s t r i s ( L a k e s e d g e ) . T h u s , t h e d e g r e e o f s e g r e g a t i o n , a s m e a s u r e d by o v e r l a p i n t h e t y p e s o f v e g e t a t i o n u s e d f o r n e s t i n g s u b s t r a t e i s much s m a l l e r i n B u r t ' s s t u d y t h a n i n m i n e . The p r e s e n c e o r a b s e n c e o f y e l l o w h e a d s , h o w e v e r , may b e a c r u c i a l f a c t o r when c o m p a r i n g t h e h a b i t a t s o f w r e n s a n d r e d w i n g s . Y e l l o w h e a d s a r e o n l y p r e s e n t i n my s t u d y m a r s h i n t h e f o r m o f a s m a l l ( 6 - 1 2 i n d i v i d u a l s ) c o l o n y , a n d i t i s u n l i k e l y t h a t t h e c o l o n y a f f e c t s w r e n o r r e d w i n g d i s t r i b u t i o n s . The c o l o n y , t h o u g h s e e n i n o t h e r l o c a t i o n s o f my m a r s h , w a s n e v e r s e e n i n my n e s t s t u d y p l o t s . T h e r e i s s u b s t a n t i a l e v i d e n c e s u p p o r t i n g t h e i d e a t h a t y e l l o w h e a d s a f f e c t b o t h r e d w i n g a n d w r e n d i s t r i b u t i o n s . I n B u r t ' s s t u d y , a l t h o u g h t h e h a b i t a t o f w r e n s a n d r e d w i n g s o v e r l a p p e d e x t e n s i v e l y i n t h e p r e s e n c e o f y e l l o w h e a d s , r e d w i n g s 116 a n d w r e n s s h o w e d m a r k e d s e g r e g a t i o n a f t e r y e l l o w h e a d s c o m p l e t e d t h e i r r e l a t i v e l y s h o r t n e s t i n g p e r i o d . B e d w i n g s e s t a b l i s h e d t h e m s e l v e s i n c a t t a i l p a t c h e s f o r m e r l y o c c u p i e d b y y e l l o w h e a d s , w h i l e w r e n s , a f t e r a n i n i t i a l movement i n t o t h e c a t t a i l , r e t u r n e d t o t h e l a k e s e d g e . T h i s s u g g e s t s t h a t r e d w i n g s w e r e e x c l u d e d f r o m h a b i t a t by y e l l o w h e a d s , an i d e a a l s o s u g g e s t e d b y H i l l e r ( 1 9 6 8 ) . B u r t , H e r o (1956) , a n d H i e n (1965) a l l p r o v i d e e v i d e n c e t h a t a " t y p i c a l " f e a t u r e ( a s s o c i a t i o n w i t h o p e n w a t e r ) o f y e l l o w - h e a d e d h a b i t a t i s p r e f e r r e d b y r e d w i n g s i n t h e a b s e n c e o f y e l l o w h e a d s . B u r t ' s r e s u l t s a l s o s u g g e s t t h a t , i n m a r s h e s f r o m w h i c h y e l l o w h e a d s a r e a b s e n t , r e d w i n g s e x c l u d e w r e n s f r o m c e r t a i n t y p e s o f h a b i t a t i n a manner s i m i l a r t o t h e e x c l u s i o n o f w r e n s a n d r e d w i n g s by y e l l o w h e a d s i n o t h e r m a r s h e s . T h i s c o u l d e x p l a i n t h e more m a r k e d s e g r e g a t i o n b e t w e e n t h e t w o s p e c i e s i n my m a r s h , w h e r e y e l l o w h e a d s do n o t r e s t r i c t t h e i r r a n g e o f h a b i t a t , t h a n i n B u r t ' s m a r s h . A l s o , t h e s t r o n g a f f i n i t y f o r c e n t r a l m a r s h l o c a t i o n s c o u l d o v e r r i d e o t h e r f a c t o r s i n e x p l a i n i n g t h e r e d w i n g ' s r e l a t i v e a b s e n c e f r o m t h e more p e r i p h e r a l S p i r a e a h a b i t a t i n my m a r s h . The h y p o t h e s i s t h a t r e d w i n g s e x c l u d e w r e n s f r o m h a b i t a t c o u l d be t e s t e d i n t h e f i e l d b y e x p e r i m e n t a l l y r e m o v i n g r e d w i n g s f r o m s e d g e v e g e t a t i o n a n d o b s e r v i n g t h e s u b s e q u e n t d i s t r i b u t i o n o f w r e n s . P i e m a n , w h o s e r e s e a r c h t o o k p l a c e i n a b r a c k i s h , f o r e s h o r e m a r s h t h a t i s q u i t e d i f f e r e n t f r o m b o t h B u r t ' s a n d my s t u d y m a r s h e s , r a i s e s t h e q u e s t i o n o f p h y s i c a l f e a t u r e s o f t h e v e g e t a t i o n a s a c o n t r i b u t i n g f a c t o r t o t h e h a b i t a t s o f w r e n s a n d r e d w i n g s . P i e m a n ' s s t u d y m a r s h c o n t a i n e d a u n i f o r m s t a n d o f 117 c a t t a i l i n w h i c h b o t h w r e n s a n d r e d w i n g s n e s t e d i n t h e e a r l y p a r t o f t h e s e a s o n , c o m p l i m e n t e d by a g r o w t h o f s e d g e s ( p r i m a r i l y S c i r p u s sp* ) t h a t was s e a w a r d f r o m t h e c a t t a i l s t a n d a n d became a v a i l a b l e l a t e r i n t h e s e a s o n . O n l y w r e n s n e s t e d i n t h i s s e d g e v e g e t a t i o n . I n a d d i t i o n , y e l l o w h e a d s , n o r m a l l y a s s o c i a t e d w i t h f r e s h - w a t e r m a r s h e s ( B e n t 1 9 5 8 ) , w e r e a b s e n t f r o m h i s m a r s h . T h o u g h b o t h w r e n s a n d r e d w i n g s u s e d t h e same v e g e t a t i o n i n P i e m a n ' s m a r s h , t h e y were s p a t i a l l y s e g r e g a t e d , a n d w r e n s , when n e s t i n g n e a r r e d w i n g n e s t s , t e n d e d t o n e s t i n h i g h e r , d e n s e r v e g e t a t i o n t h a n r e d w i n g s . I f g r e a t e r v e g e t a t i o n h e i g h t a n d d e n s i t y a r e i m p o r t a n t f e a t u r e s o f e i t h e r f u n d a m e n t a l o r r e a l i z e d w r e n h a b i t a t ( M i l l e r 1 9 6 7 ) , i t c o u l d h e l p t o e x p l a i n my o b s e r v a t i o n s i n P i t t Meadows o f a p r e f e r e n c e b y w r e n s f o r S p i r a e a a s o p p o s e d t o t h e s e d g e v e g e t a t i o n p r e f e r r e d by r e d w i n g s . I w i l l d i s c u s s t h e i m p o r t a n c e o f p h y s i c a l f e a t u r e s o f t h e v e g e t a t i o n l a t e r i n t h i s d i s c u s s i o n i n t h e " O t h e r F a c t o r s " s e c t i o n . b . C o m p e t i t i o n I n t e r f e r e n c e c o m p e t i t i o n , a s d e f i n e d b y t w o s p e c i e s h a v i n g a n e g a t i v e e f f e c t o n e a c h o t h e r , a p p e a r s t o be a n u l t i m a t e f a c t o r s e l e c t i n g f o r h a b i t a t s e g r e g a t i o n b e t w e e n L o n g - b i l l e d M a r s h H r e n s a n d B e d - w i n g e d B l a c k b i r d s i n P i t t M e a d o w s . F o r more s o l i d e v i d e n c e , one s h o u l d u n d e r t a k e e x p e r i m e n t a l w o r k s u c h a s r e m o v a l o r a d d i t i o n o f one o f t h e s p e c i e s , w i t h a p p r o p r i a t e c o n t r o l s , a n d o b s e r v a t i o n o f a n y c h a n g e s i n n e s t i n g s u c c e s s . I d i d n o t do t h i s i n t h e p r e s e n t s t u d y , b u t e v i d e n c e f o r w r e n s h a v i n g a n e g a t i v e e f f e c t o n r e d w i n g s was a d d e d t o t h a t p r o v i d e d by o t h e r 118 i,. a u t h o r s ( f t l l e n 1 9 1 4 , B u r t 1 9 7 0 , P i e m a n 1 9 7 7 a ) . a d d i t i o n a l l y , I h a v e p r e s e n t e d e v i d e n c e f o r r e d w i n g s h a v i n g a n e g a t i v e e f f e c t o n w r e n s . A g g r e s s i v e n e s s by r e d w i n g s on w r e n s h a s b e e n o b s e r v e d i n o t h e r s t u d i e s , b u t t h e s e s t u d i e s h a v e p r o v i d e d no f u r t h e r s u p p o r t i v e e v i d e n c e f o r w r e n s b e i n g a f f e c t e d by r e d w i n g s . The a g r e e m e n t o f my r e s u l t s w i t h t h o s e o f o t h e r s s u p p o r t s t h e i d e a . t h a t , i n g e n e r a l , i n t e r s p e c i f i c c o m p e t i t i o n i s a n i m p o r t a n t f a c t o r i n f l u e n c i n g h a b i t a t s e l e c t i o n by w r e n s a n d r e d w i n g s . I n t e r s p e c i f i c c o m p e t i t i o n c a u s i n g s e g r e g a t i o n b e t w e e n w r e n s a n d r e d w i n g s c o u l d , i n c o m b i n a t i o n w i t h o t h e r f a c t o r s , i n f l u e n c e t h e s e s p e c i e s * n e s t i n g s t r a t e g i e s . T h e o r i e s o n how p o l y g y n y , o r t h e m a t i n g o f one m a l e w i t h more t h a n o n e f e m a l e , c o u l d h a v e e v o l v e d i n m a r s h w r e n s a n d r e d w i n g s h a v e f o c u s e d p r i m a r i l y on t h e i m p o r t a n c e o f p h y s i c a l f e a t u r e s i n t h e b i r d ' s h a b i t a t a n d how t h e s e c o u l d i n f l u e n c e t h e s e l e c t i o n f o r p o l y g y n y ( V e r n e r 1 9 6 4 ; O r i a n s 1 9 6 1 , 1 9 6 9 , a n d 1 9 7 0 ) . P i e m a n ( p e r s . comm.) h a s b e e n w o r k i n g o n t h e h y p o t h e s i s t h a t i n t e r s p e c i f i c c o m p e t i t i o n a l s o p l a y s a f u n d a m e n t a l r o l e i n t h e e v o l u t i o n o f p o l y g y n y i n w r e n s a n d r e d w i n g s * My r e s u l t s s a y n o t h i n g a b o u t t h e o c c u r r e n c e o f p o l y g y n y v e r s u s monogamy o r c o l o n i a l i t y o f m a r s h p a s s e r i n e s , b u t t h e y d o s u p p o r t t h e h y p o t h e s i s t h a t i n t e r s p e c i f i c c o m p e t i t i o n r e s t r i c t s t h e r a n g e o f w r e n a n d r e d w i n g h a b i t a t s , a n d c o u l d t h u s r e s u l t i n t h e c o n t a g i o u s n e s t i n g o f b o t h s p e c i e s . O t h e r f a c t o r s c o u l d c o m b i n e w i t h c o m p e t i t i o n t o s e l e c t f o r p o l y g y n y o v e r o t h e r s y s t e m s o f n e s t i n g . F o r e x a m p l e . P i e m a n ( p e r s . comm*) b e l i e v e s t h a t r e d w i n g p o l y g y n y e v o l v e d a s a c o m p r o m i s i n g s t r a t e g y b e t w e e n t h e n e e d f o r m u t u a l n e s t d e f e n s e a g a i n s t w r e n s , f a v o u r i n g c o l o n i a l i t y , a n d l i m i t e d f o o d 1 19 r e s o u r c e s , f a v o u r i n g t e r r i t o r i a l i t y . The f a c t t h a t t h e maximum 1977 d e n s i t i e s 1 o f a c t i v e n e s t s o f b o t h w r e n s and r e d w i n g s were l o w e r i n my m a r s h ( 2 . 6 n e s t s / h a f o r w r e n s , 1 . 8 n e s t s / h a f o r r e d w i n g s ) t h a n i n P i e m a n ' s m a r s h ( 7 . 0 n e s t s / h a f o r w r e n s , 3 . 6 n e s t s / h a f o r r e d w i n g s ) h a s a d i r e c t b e a r i n g o n t w o o f P i e m a n ' s ( p e r s . comm. ) h y p o t h e s e s . The f i r s t i s t h a t , a t l o w e r w r e n d e n s i t i e s , t h e i m p a c t o n w r e n s o f r e d w i n g s s h o u l d e x c e e d t h a t o f o t h e r w r e n s . T h o u g h t h e s i t u a t i o n s a r e n o t s t r i c t l y c o m p a r a b l e , s i n c e r e d w i n g s a l s o o c c u r r e d a t l o w e r d e n s i t i e s i n my m a r s h , t h i s was t h e c a s e i n my s t u d y . T h e s e c o n d h y p o t h e s i s i s b a s e d p r i m a r i l y o n P i e m a n ' s c o r r e l a t e d o b s e r v a t i o n s o f a g r e a t e r i m p a c t o f w r e n s on r e d w i n g s i n 1976 t h a n i n 1977 a n d a l o w e r w r e n d e n s i t y i n 1976 t h a n i n 1 9 7 7 . He p r e d i c t s t h a t w r e n s c o u l d h a v e a n i m p a c t on r e d w i n g s e v e n a t l o w w r e n d e n s i t i e s b e c a u s e t h e d e c r e a s e i n i n t r a s p e c i f i c s t r i f e a s s o c i a t e d w i t h t h e s e l o w d e n s i t i e s w o u l d l e a v e more t i m e f o r w r e n s t o i n t e r f e r e w i t h c o m p e t i n g r e d w i n g s . T h e f a c t t h a t I o b s e r v e d t h i s w r e n - r e d w i n g i m p a c t a t t h e l o w w r e n d e n s i t i e s i n my m a r s h s u p p o r t s t h i s h y p o t h e s i s . A p o s s i b l e a l t e r n a t i v e e x p l a n a t i o n o f t h e i m p a c t o f w r e n s on r e d w i n g s c o u l d , h o w e v e r , be f o u n d i n t h e f a c t t h a t r e d w i n g d e n s i t i e s w e r e a l s o l o w e r i n my m a r s h t h a n i n P i e m a n ' s . I f r e d w i n g s h a v e some f o r m o f m u t u a l n e s t d e f e n s e , l o w e r r e d w i n g d e n s i t i e s c o u l d r e d u c e t h e e f f e c t i v e n e s s o f t h i s d e f e n s e ( p r i m a r i l y r e d w i n g - w r e n c h a s e s ) , a n d i n c r e a s e t h e d e t r i m e n t a l i m p a c t o f w r e n s o v e r t h a t f o u n d i n * n u m b e r o f s i m u l t a n e o u s l y a c t i v e n e s t s p e r t o t a l a r e a o f m a l e t e r r i t o r i e s . 120 s i t u a t i o n s with higher redwing densities. 3. Factors Other Than I n t e r s p e c i f i c Competition There are undoubtedly other forces a f f e c t i n g wren-redwing segregation besides competition with each other* The nesting success of both species varied with vegetation type (Table VII). Although these differences were not s i g n i f i c a n t s t a t i s t i c a l l y (p > -05), I believe that vegetation e f f e c t s are important. In the extreme, i f the only concern to a nesting wren were that she avoid redwings, she should be more successful i n any s u i t a b l e habitat devoid of redwings. There was i n fact one study plot (Plot C) i n the present study the edge of which was located 300 m from the nearest redwing t e r r i t o r y . Brens i n three of the other plots with redwings were more successful on the average than those i n t h i s plot, so other influences must be considered. Thus f a r , I have discussed the "ultimate" f a c t o r s influencing habitat s e l e c t i o n as opposed to "proximate" f a c t o r s . The d i s t i n c t i o n between the two types of factors i s stated by Hilden (1965) as follows: "In habitat s e l e c t i o n , the former (ultimate)* are e s s e n t i a l for the survival:of the species, and constitute the underlying reasons determining why each species breeds i n i t s s p e c i f i c environment. The l a t t e r (proximate), on the other hand, only serve to release the s e t t l i n g reaction and need not necessarily have any b i o l o g i c a l significance to the species as such." In spite of t h i s d i s t i n c t i o n , proximate factors can often suggest the ultimate factor behind the habitat selection (Hilden 1 My terms in parentheses. 121 1 9 6 5 , V e r n e r 1 9 7 5 b ) . F o r e x a m p l e , i f i n t e r s p e c i f i c c o m p e t i t i o n i s t h e m o s t i m p o r t a n t u l t i m a t e f a c t o r i n f l u e n c i n g h a b i t a t s e l e c t i o n i n w r e n s a n d r e d w i n g s , t h e p r e s e n c e o f t h e o t h e r s p e c i e s w o u l d l i k e l y s e r v e a s t h e a v o i d a n c e c u e , o r p r o x i m a t e f a c t o r . Some o f my r e s u l t s s u g g e s t t h e b i r d s c u e o n f a c t o r s o t h e r t h a n t h e p r e s e n c e o r a b s e n c e o f t h e o t h e r s p e c i e s . F i r s t , w r e n s a r e mos t a b u n d a n t b y f a r i n t h e S p i r a e a s h r u b h a b i t a t i n e a r l y w i n t e r ( F i g . 11) when r e d w i n g s a r e n e a r l y a b s e n t f r o m t h e m a r s h . I f t h e g r e a t e r a b u n d a n c e o f w r e n s i n S p i r a e a h a b i t a t i s c a u s e d e x c l u s i v e l y b y t h e a v o i d a n c e o f r e d w i n g s , t h e y s h o u l d u t i l i z e o t h e r h a b i t a t s i n t h e a b s e n c e o f r e d w i n g s . S e c o n d , i f S p i r a e a i s o n l y i m p o r t a n t t o w r e n s i n w i n t e r , i n s p r i n g t h e y m i g h t a t t e m p t t o u s e a n d s u b s e q u e n t l y be e x p e l l e d b y r e d w i n g s f r o m t h e b u l r u s h s p e c i e s o f t h e c e n t r a l m a r s h . B a s e d on c e n s u s r e s u l t s ( F i g . 12) a n d l o c a t i o n s o f s p r i n g w r e n t e r r i t o r i e s i n n e s t s t u d y p l o t s , t h i s d i d n o t o c c u r . 1 S r e n s s i m p l y i n c r e a s e d i n a b u n d a n c e i n t h e S p i r a e a . T h e r e i s a t h i r d r e s u l t t h a t p u t s i n j e o p a r d y t h e h y p o t h e s i s t h a t w r e n s c h o o s e h a b i t a t p r i m a r i l y i n r e s p o n s e t o t h e a b s e n c e o f r e d w i n g s . An o b v i o u s p h y s i c a l f a c t o r t h a t a c c o m p a n i e d w r e n movement i n t o T y p h a l a t i f o l i a a n d S c i r p u s s p p . i n t h e s u m m e r , i n a d d i t i o n t o d e c r e a s i n g r e d w i n g a b u n d a n c e , was a n i n c r e a s e i n t h e h e i g h t o f t h e n e s t s u b s t r a t e v e g e t a t i o n o v e r t h e h e i g h t i n t h e s p r i n g n e s t i n g s e a s o n (p < . 0 0 5 f o r b o t h T . l a t i f o l i a a n d S . a c u t u s . S t u d e n t ' s t ) . W h a t , t h e n , a r e some f e a t u r e s o f t h e 1 T h e r e was e v i d e n c e , h o w e v e r , s u g g e s t i n g t h a t one m a l e w r e n e s t a b l i s h e d a n e a r l y t e r r i t o r y i n T . l a t i f o l i a a n d was f o r c e d t o a b a n d o n t h e t e r r i t o r y b e c a u s e o f r e d w i n g p r e s e n c e . 122 h a b i t a t t h a t m i g h t e x p l a i n t h e a b o v e r e s u l t s a n d o f f e r a l t e r n a t i v e s o r c o m p l e m e n t s t o i n t e r s p e c i f i c c o m p e t i t i o n a s u l t i m a t e c a u s e s o f s e g r e g a t i o n ? G o o d s o n g b i r d h a b i t a t mus t p r o v i d e r e l i a b l e n e s t s u p p o r t . T h i s i s p a r t i c u l a r l y c r u c i a l i n m a r s h v e g e t a t i o n , w h i c h i s o f t e n s t r u c t u r a l l y w e a k . B e c a u s e o f w i d e l y f l u c t u a t i n g w a t e r l e v e l s i n many m a r s h e s , i t w o u l d a l s o be t o a b i r d ' s a d v a n t a g e t o n e s t s u f f i c i e n t l y h i g h i n t h e v e g e t a t i o n t o a v o i d f l o o d i n g . When c o n s i d e r i n g n e s t s u p p o r t , t h e c o m b i n e d w e i g h t o f t h e n e s t a n d t h e b i r d i s i m p o r t a n t . W r e n s w e i g h a b o u t o n e - f o u r t h a s much a s r e d w i n g s , a n d t h e n e s t s o f t h e t w o s p e c i e s w e i g h a p p r o x i m a t e l y t h e s a m e . 1 T h u s , w r e n s c a n a f f o r d t o n e s t h i g h e r a n d d o , i n f a c t , do s o i n a l l t h e d i f f e r e n t v e g e t a t i o n t y p e s o f t h e p r e s e n t s t u d y m a r s h . W i t h t h e e x c e p t i o n o f T y p h a s p p . , t y p i c a l m a r s h v e g e t a t i o n , w h i c h i s p r i m a r i l y s e d g e s , i s n o t r o b u s t a n d p r o b a b l y o f f e r s p o o r s u p p o r t f o r p a s s e r i n e n e s t s ( V e r n e r 1 9 6 5 , V e r n e r a n d E n g e l s e n 1 9 7 0 , F o w l e 1 9 4 2 , H o l m 1 9 7 3 ) , p a r t i c u l a r l y f o r t h o s e n e s t s p l a c e d h i g h i n t h e v e g e t a t i o n l i k e t h o s e o f w r e n s . S h r u b s , l i k e S p i r a e a d o u g l a s i i , a r e r o b u s t a n d , a s i s t h e c a s e w i t h S p i r a e a , o f t e n s t a n d t a l l e r t h a n s e d g e s a n d o t h e r e m e r g e n t s . T h u s , when w r e n s move i n t o T . l a t i f o l i a a n d S c i r p u s s p p , i n summer t h e y may i n d e e d b e r e s p o n d i n g t o a n i n c r e a s e i n v e g e t a t i o n h e i g h t . T h i s i s f u r t h e r s u p p o r t e d b y t h e f a c t t h a t t h e f o u r w r e n b r e e d i n g n e s t s p l a c e d i n t h e p r e v i o u s y e a r ' s * N e s t s i n t h e f i e l d a p p e a r t o b e made o f t h e same a m o u n t s o f m a t e r i a l , a n d I t o o k t h e d r y w e i g h t s o f t w o s a m p l e n e s t s . The w r e n n e s t w e i g h e d 7 3 . 2 g , c o m p a r e d t o 7 0 . 3 g f o r t h e r e d w i n g n e s t . 123 g r o w t h o f S . a c u t u s i n t h e s p r i n g w e r e i n t a l l e r p l a n t s o f t h i s s p e c i e s t h a n t h o s e i n w h i c h r e d w i n g s w e r e n e s t i n g d u r i n g t h e same p e r i o d (p < . 0 3 , S t u d e n t ' s t ) . The h e a v i e r r e d w i n g , when u s i n g s e d g e v e g e t a t i o n , mus t n e s t c l o s e r t o t h e w a t e r t h a n w r e n s t o o b t a i n a d e q u a t e n e s t s u p p o r t * at t h e s e l o w e r l e v e l s S c i r p u s s t e m s a n d l e a v e s a r e c l o s e t o g e t h e r , a n d r e d w i n g s h a v e a m p l e s u r f a c e f o r n e s t a t t a c h m e n t s . S i n c e S c i r p u s i s s h o r t e r t h a n t h e S p i r a e a p r e f e r r e d by w r e n s , v e g e t a t i o n h e i g h t may be a c u e u s e d b y b o t h s p e c i e s , a n d t h e u l t i m a t e r e a s o n s f o r s e l e c t i n g d i f f e r e n t h e i g h t s o f v e g e t a t i o n c o u l d be n e s t s u p p o r t and a v o i d a n c e o f f l o o d i n g . P r o t e c t i o n f r o m p r e d a t o r s a n d t h e w e a t h e r c o u l d i n f l u e n c e t h e s e l e c t i o n o f h a b i t a t by t h e two s p e c i e s . P i e m a n o b s e r v e d w r e n s n e s t i n g i n h i g h e r , more d e n s e v e g e t a t i o n t h a n r e d w i n g s o n l y i n s i t u a t i o n s i n w h i c h t h e two s p e c i e s n e s t e d n e a r t o o n e a n o t h e r , s u g g e s t i n g t h a t t h e s e v e g e t a t i o n f e a t u r e s a r e o n l y i m p o r t a n t t o w r e n s f o r p r o t e c t i o n f r o m r e d w i n g s . I n s p i t e o f t h i s r e s u l t , h i g h d e n s i t y a n d h e i g h t o f v e g e t a t i o n c o u l d p r o t e c t w r e n s a n d t h e i r n e s t s f r o m w e a t h e r a n d b o t h l a n d a n d a v i a n p r e d a t o r s . S p i r a e a d o u q l a s i i h a s b o t h t h e s e p r o p e r t i e s , a n d w r e n s s e l d o m u s e a n y o t h e r h a b i t a t i n t h e w i n t e r , s u g g e s t i n g t h e i m p o r t a n c e o f t h i s h a b i t a t t o p r o t e c t i o n f r o m t h e e l e m e n t s . B e d w i n g s a r e more p r o n e t o c h a s i n g p r e d a t o r s , p a r t i c u l a r l y o t h e r b i r d s , t h a n w r e n s , a n d v e g e t a t i o n t h a t i s s h o r t e r a n d l e s s d e n s e a t t h e u p p e r v e g e t a t i o n l e v e l s may be more s u i t a b l e t o t h e m . S c i r p u s s p p . h a v e t h e s e p r o p e r t i e s a n d y e t c a n h i d e n e s t s f r o m t h e v i e w o f l a n d p r e d a t o r s t h a t r e l y o n s i g h t f o r d e t e c t i o n o f n e s t s . We saw e a r l i e r t h a t l a t e r a l v i s i b i l i t y o f r e d w i n g n e s t s 124 was l e s s t h a n t h a t o f w r e n n e s t s ( T a b l e I I I ) . The a s s o c i a t i o n o f r e d w i n g s w i t h d e e p e r w a t e r a n d o p e n w a t e r n e a r t o n e s t s may b e t h e k e y f e a t u r e t h a t a t t r a c t s r e d w i n g s t o c e n t r a l m a r s h h a b i t a t s . T h i s a t t r a c t i o n may r e f l e c t t h e p r o t e c t i o n f r o m m a m m a l i a n p r e d a t o r s t h a t w a t e r a f f o r d s r e d w i n g s . L o w e r w a t e r l e v e l s a n d f e w e r o p e n w a t e r p a t c h e s i n . S p i r a e a h a b i t a t i n t h e m a r s h may a l s o h e l p e x p l a i n t h e a b s e n c e o f r e d w i n g s f r o m t h i s h a b i t a t , e v e n t h o u g h r e d w i n g s f r e q u e n t l y n e s t i n t r e e s a n d s h r u b s i n o t h e r a r e a s . I n f a c t , r e d w i n g n e s t s h a v e b e e n r e c o r d e d i n S p i r a e a , p r i m a r i l y g r o w i n g on d y k e s b e s i d e s l o u g h s a n d d i t c h e s , i n P i t t Meadows i n p r e v i o u s y e a r s ( B . C . P r o v i n c i a l Museum n e s t r e c o r d s c h e m e ) . 4 . F a c t o r s O p p o s i n g S e g r e g a t i o n L i m i t s t o t h e d e g r e e o f s e g r e g a t i o n b e t w e e n w r e n s a n d r e d w i n g s mus t e x i s t . H a t e r l e v e l s a r e p r o b a b l y i m p o r t a n t i n t h i s r e g a r d . I f r e d w i n g s move t o o f a r i n t o d e e p e r w a t e r , t h e y a r e f o r c e d t o a t t e m p t t o a t t a c h t h e i r n e s t s t o t h e t h i n , f l i m s y s t e m s t h a t a r e c h a r a c t e r i s t i c o f h i g h e r p o r t i o n s o f s e d g e s . S i m i l a r l y , i f w r e n s move t o o f a r away f r o m w a t e r t o t h e e x t r e m e o f n e s t i n g e x c l u s i v e l y on d r y l a n d , t h e y n o l o n g e r h a v e t h e p r o t e c t i o n f r o m p r e d a t o r s t h a t w a t e r p r o b a b l y a f f o r d s t h e m , a n d "i t h e y r e m o v e t h e m s e l v e s f r o m a f o o d s o u r c e ( a q u a t i c i n v e r t e b r a t e s ) t h a t i s n o r m a l l y i m p o r t a n t i n t h e i r d i e t ( W e l t e r 1 9 3 5 , V e r n e r a n d E n g e l s o n 1 9 7 0 ) . 125 A n o t h e r p o s s i b l e f o r c e o p p o s i n g w r e n - r e d w i n g s e g r e g a t i o n i s t h e i n t r a s p e c i f i c i n t e r f e r e n c e ( n e s t d e s t r u c t i o n ) p r o b a b l y e x p e r i e n c e d b y w r e n s ( P i e m a n 1 9 7 7 b ) . T h i s w o u l d t e n d t o s e l e c t f o r w r e n s t h a t w o u l d n e s t f u r t h e r f r o m o t h e r w r e n s a n d c l o s e r t o r e d w i n g s , p a r t i c u l a r l y i f w r e n d e n s i t y i s h i g h . T h i s w r e n - w r e n i n t e r f e r e n c e was n o t a n i m p o r t a n t f a c t o r f o r t h e w r e n p o p u l a t i o n s t u d i e d h e r e , e v e n when w r e n s n e s t e d c l o s e t o o r w i t h i n r e d w i n g t e r r i t o r i e s , w h e r e t h e y m i g h t be e x p e c t e d t o n e g l e c t n e s t s b e c a u s e o f r e d w i n g h a r a s s m e n t . S i n c e w r e n d e n s i t i e s i n t h i s m a r s h w e r e t h e l o w e s t y e t r e p o r t e d ( W e l t e r 1 9 3 5 , V e r n e r 1 9 6 5 a , P i e m a n p e r s . c o m m . ) , t h i s i n t e r f e r e n c e may s t i l l be i m p o r t a n t f o r d e n s e r p o p u l a t i o n s . A s i l l u s t r a t e d by a p r e v i o u s d i s c u s s i o n o f t h e e f f e c t s o f y e l l o w h e a d s , c o m p e t i t i o n w i t h o t h e r s p e c i e s c o u l d o p p o s e s e g r e g a t i o n o f w r e n s f r o m r e d w i n g s . The Common Y e l l o w t h r o a t may a f f e c t o b s e r v e d w r e n h a b i t a t . I h a v e a l r e a d y d e m o n s t r a t e d t h a t w r e n s a n d y e l l o w t h r o a t s s h a r e t h e same " D e n s e S p i r a e a " h a b i t a t w i t h some s u g g e s t i o n o f b o t h s p a t i a l a n d t e m p o r a l s e g r e g a t i o n w i t h i n t h a t h a b i t a t . I a l s o o b s e r v e d a m a l e w r e n c h a s i n g a m a l e y e l l o w t h r o a t . Y e l l o w t h r o a t s , a member o f t h e Wood W a r b l e r ( P a r u l i d a e ) f a m i l y , a r e l i k e l y b e t t e r a d a p t e d t h a n w r e n s t o t h e s l i g h t l y d r i e r c o n d i t i o n s i n w h i c h t h e y a r e f o u n d , a n d , t o t h e e x t e n t t h a t t h e y c o m p e t e w i t h w r e n s f o r f o o d a n d / o r s p a c e , t h e y may make i t a d v a n t a g e o u s f o r w r e n s t o r e f r a i n f r o m n e s t i n g t o o f a r away f r o m damp a r e a s . 126 5- C l o s i n g S t a t e m e n t I n t h e p r e c e d i n g d i s c u s s i o n I h a v e t r i e d t o p o i n t o u t t h a t , t h o u g h I p r o v i d e e v i d e n c e w h i c h s u p p o r t s t h e h y p o t h e s i s t h a t c o m p e t i t i o n i s a n i m p o r t a n t u l t i m a t e c a u s e o f w r e n - r e d w i n g s e g r e g a t i o n , o t h e r f a c t o r s , i n d e p e n d e n t o f i n t e r s p e c i f i c i n t e r a c t i o n s , mus t n o t be i g n o r e d . The o b s e r v e d d i f f e r e n c e s b e t w e e n t h e h a b i t a t s o f t h e t w o s p e c i e s a n d t h e l a c k o f e x p e r i m e n t a l work in t h e p r e s e n t s t u d y t o d e t e r m i n e t h e u l t i m a t e f a c t o r s o f h a b i t a t s e l e c t i o n , s u g g e s t t h a t p h y s i c a l f a c t o r s o f t h e h a b i t a t s r e q u i r e f u r t h e r i n v e s t i g a t i o n . B o t h i n t e r s p e c i f i c a n d i n t r a s p e c i f i c c o m p e t i t i o n p r o b a b l y c o m b i n e w i t h o t h e r f a c t o r s t o i n f l u e n c e h a b i t a t s e l e c t i o n , a n d t h e r e l a t i v e i m p o r t a n c e o f e a c h o f t h e f a c t o r s d i f f e r s w i t h d i f f e r e n t m a r s h s i t u a t i o n s . 127 Management I m p l i c a t i o n s M a n a g e m e n t i m p l i c a t i o n s w i l l be d i s c u s s e d w i t h t h e o b j e c t i v e i n mind o f a v o i d i n g a n y d r a s t i c r e d u c t i o n s i n p o p u l a t i o n s i z e o f a n y o f t h e m a r s h p a s s e r i n e s p e c i e s - The m a r s h p a s s e r i n e c o m m u n i t y i s o n l y o n e c o m p o n e n t i n a c o m p l e x w e t l a n d s y s t e m , l o c a t e d i n a n a r e a w h i c h i s t o b e managed f o r m u l t i p l e - u s e , a n d o v e r a l l s p e c i e s d i v e r s i t y s h o u l d be a n i m p o r t a n t c o n s i d e r a t i o n . F o r t h i s r e a s o n , a n y p o l i c i e s t h a t I r e c o m m e n d w o u l d be u n d e r t a k e n o n l y i f no s e r i o u s c o n f l i c t e x i s t s b e t w e e n them a n d e i t h e r t h e management p l a n s o r t h e w e l f a r e o f o t h e r marsh s p e c i e s . N a t u r e s t u d y i s p r o b a b l y t h e m o s t i m p o r t a n t r e c r e a t i o n a l u s e made o f mar sh p a s s e r i n e s . F o r s c i e n t i f i c s t u d y , I b e l i e v e t h e p a s s e r i n e c o m m u n i t y a n d t h e u n i q u e c h a r a c t e r i s t i c s o f t h i s p a r t i c u l a r m a r s h , n o t t h e l e a s t o f w h i c h i s an a b i l i t y t o c o n t r o l w a t e r l e v e l s , a r e i m p o r t a n t . H o w e v e r , t h i s i m p o r t a n c e i s l i m i t e d by t h e e x t e n t t o w h i c h t h e a r e a w i l l b e u s e d f o r r e c r e a t i o n a l p u r p o s e s * H e c o m m e n d a t i o n s b a s e d on a n o v e r a l l w i l d l i f e i n v e n t o r y o f t h e a r e a h a v e b e e n g i v e n p r e v i o u s l y ( H u n y a n 1978) . I b a s e my r e c o m m e n d a t i o n s o n t h e o b s e r v e d h a b i t a t s t h a t t h e s p e c i e s o c c u p y . T h e u l t i m a t e c a u s e o f t h i s h a b i t a t s e l e c t i o n , w h e t h e r i t be c o m p e t i t i o n o r p h y s i c a l h a b i t a t r e q u i r e m e n t s , i s n o t known w i t h e n o u g h c e r t a i n t y t o u t i l i z e i n a s s e s s i n g management p o l i c i e s * I t may, i n a n y c a s e , b e u n n e c e s s a r y . F r o m t h e s e o b s e r v e d h a b i t a t s , t h e d i v e r s i t y o f m a r s h v e g e t a t i o n t h a t e x i s t s i n t h e PWMA seems i m p o r t a n t t o m a r s h p a s s e r i n e s . 128 O f t h e f o u r p a s s e r i n e s p e c i e s , y e l l o w t h r o a t s a n d w r e n s w o u l d l i k e l y b e t h e mos t s e n s i t i v e t o v e g e t a t i o n c h a n g e s , p a r t i c u l a r l y s i n c e management e f f o r t s w i l l p r o b a b l y r e d u c e t h e q u a n t i t y o f t h e s h r u b S p i r a e a d o u q l a s i i . Y e l l o w t h r o a t s a r e m o s t c o m m o n l y s e e n i n t h e P i t t Meadows r e g i o n o f a l l t h e p o p u l a r a r e a s f o r b i r d s t u d y i n t h e V a n c o u v e r B i r d C h e c k l i s t a r e a ( C a m p b e l l 1974) a n d , t h o u g h i t may b e o b s e r v e d i n s m a l l n u m b e r s i n a f e w a r e a s o f C o q u i t l a m a n d S u r r e y , t h e PWHA o f f e r s t h e m o s t a c c e s s i b l e y e l l o w t h r o a t h a b i t a t ( M . S c h o u t e n , p e r s . c o m m . ) . a f e w s i n g i n g m a l e s u s e t h e g r a s s y d y k e s i n t h e P i t t P o l d e r , b u t a r e o t h e r w i s e r e s t r i c t e d t o t h e S p i r a e a d o u g l a s i i - C a l a m a q r g s t i s c a n a d e n s i s a s s o c i a t i o n . P r e s e r v a t i o n o f some a r e a s o f t h i s h a b i t a t h a s t h u s p r e v i o u s l y b e e n r e c o m m e n d e d . S p i r a e a i s a l s o u s e d e x t e n s i v e l y by w r e n s , t h o u g h t h e y a r e s i m i l a r l y a b u n d a n t i n T y p h a . E n c o u r a g e m e n t , i f p o s s i b l e , o f T . l a t i f o l i a w o u l d l i k e l y o f f s e t a n y l o s s e s e x p e r i e n c e d by w r e n s due t o e x t e n s i v e r e m o v a l o f S p i r a e a . S o n g S p a r r o w s a n d B e d - w i n g e d B l a c k b i r d s w o u l d , i n my o p i n i o n , b e l e s s s e n s i t i v e t o v e g e t a t i o n c h a n g e s . I n a d d i t i o n t o t h e " D e n s e S p i r a e a " h a b i t a t . S o n g S p a r r o w s make u s e o f t h e n u m e r o u s " s h r u b b y " d y k e s i n t h e PWMA. B e d w i n g s i n h a b i t more o p e n m a r s h a r e a s w i t h s t a n d i n g w a t e r , t h e h a b i t a t s f o r w h i c h c u r r e n t management i s a i m e d . The o n l y s i t u a t i o n i n w h i c h t h e r e d w i n g p o p u l a t i o n m i g h t s u f f e r w o u l d b e one i n w h i c h o n l y S . a c u t u s was a v a i l a b l e a s n e s t i n g s u b s t r a t e , a n d w a t e r l e v e l s w e r e k e p t h i g h . T h i s w o u l d f o r c e r e d w i n g s t o n e s t h i g h e r w h e r e , p a r t i c u l a r l y i n jS. a c u t u s , n e s t s u p p o r t i s i n f e r i o r t o t h a t a t l o w e r l e v e l s o f t h e m a r s h v e g e t a t i o n w h e r e r e d w i n g s n o r m a l l y 129 n e s t . An a d d i t i o n a l o p t i o n i s s t i l l a v a i l a b l e t o r e d w i n g s i n e v e n t h i s e x t r e m e s i t u a t i o n , s i n c e t r e e s e x i s t n e a r b y , a n d r e d w i n g s o f t e n n e s t i n t r e e s i n o t h e r l o c a t i o n s ( B e n t 1 9 5 8 , C a s e a n d H e w i t t 1963) a n d h a v e b e e n o b s e r v e d n e s t i n g i n t r e e s i n r e s p o n s e t o f l o o d i n g o f s e d g e n e s t i n g a r e a s i n I o w a ( B u r t 1 9 7 0 ) . Some e n h a n c e m e n t o f p a s s e r i n e p o p u l a t i o n s may r e s u l t f r o m c u r r e n t management p l a n s t o s t a b i l i z e w a t e r l e v e l s a n d a p o s s i b l e f u t u r e f e r t i l i z a t i o n o f PWHA w a t e r . Many o f t h e r e d w i n g n e s t s p l a c e d i n S . a c u t u s w e r e f l o o d e d i n J u n e by w a t e r l e v e l s s u d d e n l y r i s i n g t o 1.3 m a b o v e s e a l e v e l ( a n a v e r a g e w a t e r d e p t h a t f l o o d e d n e s t s i t e s i n S-_ a c u t u s o f 30 c m ) . T h u s , s t a b i l i z i n g w a t e r l e v e l s a t a m o d e r a t e l e v e l i n t h e m a r s h c o u l d b e n e f i t r e d w i n g s . A s m a l l c o l o n y o f Y e l l o w - h e a d e d B l a c k b i r d s t h a t a p p e a r t o u t i l i z e t h e PWMA f o r n e s t i n g e a c h y e a r c o u l d a l s o b e n e f i t s T h i s y e l l o w h e a d c o l o n y i s e l u s i v e d u r i n g n e s t i n g , b u t t h e r e i s some e v i d e n c e t h a t i t n e s t e d i n S . a c u t u s i n 1977 ( R u n y a n 1978) a n d i n p r e v i o u s y e a r s ( R . R o b i n s o n , p e r s . c o m m . ) . T h e " c e n t r a l m a r s h " l o c a t i o n w o u l d be c o n s i s t e n t w i t h y e l l o w h e a d h a b i t a t r e p o r t e d i n o t h e r s t u d i e s . The w i d e l y f l u c t u a t i n g w a t e r l e v e l s o f t h e c e n t r a l m a r s h may be s e v e r e l y l i m i t i n g t h e n e s t i n g s u c c e s s o f t h i s s p e c i e s , a s n e s t s l i k e l y s u c c u m b t o t h e same f l o o d i n g e x p e r i e n c e d by r e d w i n g n e s t s i n S . a c u t u s . I f f e r t i l i z a t i o n o f t h e w a t e r , by a l l o w i n g a g r i c u l t u r a l r u n - o f f t o e n t e r t h e P U M A , i s e v e r a t t e m p t e d i t c o u l d i n c r e a s e a g u a t i c i n v e r t e b r a t e p o p u l a t i o n s . T h i s c o u l d o b v i o u s l y e n h a n c e m a r s h p a s s e r i n e p o p u l a t i o n s . 130 From t h e a b o v e d i s c u s s i o n , I r ecommend t h a t some e x t e n s i v e a r e a s o f S p i r a e a be c o n s e r v e d a n d t h a t T . l a t i f o l i a , i f p o s s i b l e , be e n c o u r a g e d . T h i s w o u l d h e l p t o r e t a i n d i v e r s i t y o f m a r s h p a s s e r i n e s a n d , t o t h e b e s t o f my k n o w l e d g e , w o u l d n o t c o n f l i c t w i t h o t h e r management p l a n s . 131 L ITERATURE C ITED A l l e n , A . A . 1 9 1 4 . The r e d - w i n g e d b l a c k b i r d ; a s t u d y i n t h e e c o l o g y o f a c a t t a i l m a r s h . L i n n a e a n S o c . N . Y . , P r o c . N o s . 2 4 - 2 5: 4 3 - 1 2 8 . B a r n a r d , A . E . 1 975 . A g e n e r a l s t u d y o f t h e p r i m a r y and s e c o n d a r y p r o d u c t i v i t y o f t h e n o r t h e r n P i t t Meadows w i t h s p e c i a l r e f e r e n c e t o t h e i r u se by w a t e r f o w l . U n p u b l i s h e d M.Sc. T h e s i s , U n i v e r s i t y o f B r i t i s h C o l u m b i a . 274 p p . B e l l , B. p.", C. K. C a t c h p o l e , K . J . C o r b e t t , a nd R . J . H o r n b y . 197 3- The r e l a t i o n s h i p b e t w e e n c e n s u s r e s u l t s a nd b r e e d i n g p o p u l a t i o n s o f some m a r s h l a n d p a s s e r i n e s . B i r d S t u d y 2 0 : 1 2 7 - 1 4 0 . B e n t , A . C . . 1 948 . L i f e h i s t o r i e s o f N o r t h A m e r i c a n n u t h a t c h e s , w r e n s , t h r a s h e r s , a n d t h e i r a l l i e s . U.S . N a t . B u s . , B u l l . 1 95 . 475 p p . B e n t , A . C . 1 9 5 8 . L i f e h i s t o r i e s o f N o r t h A m e r i c a n b l a c k b i r d s , o r i o l e s , t a n a g e r s , a n d a l l i e s . U.S . N a t - , Mus . , B u l l . 2 1 1 . 549 p p . B u r t , D e V e r e E. 1 9 7 0 . H a b i t a t s e l e c t i o n a n d s p e c i e s i n t e r a c t i o n s o f some ma r sh p a s s e r i n e s - M . S c . T h e s i s , I o w a S t a t e U n i v e r s i t y . 74 p p . C a m p b e l l , G. 1974. U n p u b l i s h e d r e p o r t t o A s s i s . D i r e c t o r , F i s h a n d H i l d l f e B r a n c h , D e p t . o f S e c . a n d C o n s e r v a t i o n - 21 p p . a n d map. C a m p b e l l , H. e t a l . 1 9 7 4 . V a n c o u v e r b i r d s . V a n c o u v e r N a t u r a l H i s t o r y S o c i e t y p u b l . 96 p p . C a s e , A . and H.O. H e w i t t . 1 9 6 3 . N e s t i n g and p r o d u c t i v i t y o f t h e r e d - w i n g e d b l a c k b i r d i n r e l a t i o n t o h a b i t a t . L i v i n g B i r d 2 : 7 - 2 0 . D a v i s , J . 1 9 6 5 . The 1 s i n g i n g m a l e * m e t h o d o f c e n s u s i n g b i r d s : a w a r n i n g . C o n d o r 6 7 ; 8 6 - 8 7 . E m l e n , J . T . 1 9 7 1 . P o p u l a t i o n d e n s i t i e s o f b i r d s d e r i v e d f r o m t r a n s e c t c o u n t s . Auk 8 8 : 3 2 3 - 3 4 2 . F o w l e , C. D a v i d . 1 9 4 2 . A p r e l i m i n a r y i n v e s t i g a t i o n o f c e r t a i n b i r d ' s n e s t s w i t h r e f e r e n c e t o t h e i r e n v i r o n m e n t a l r e l a t i o n s h i p s . U n p u b l i s h e d B -A. H o n o r s T h e s i s . H i l d e n , 0 - 1 965 . H a b i t a t s e l e c t i o n i n b i r d s . A n n . Z o o l . F e n n i c i 2 : 5 3 - 7 5 . 132 Holm, C H . 1973. Breeding sex r a t i o s , t e r r i t o r i a l i t y , and r e p r o d u c t i v e success i n the red-winged b l a c k b i r d ( A g e l a i u s < phoeniceus ). Ecology 54: 356-365. Jaeger, E.G. 1974. Competitive e x c l u s i o n : comments on s u r v i v a l and e x t i n c t i o n of s p e c i e s . B i o s c i e n c e 24(1): 33-39. •Jerema, R.S. 1976. Comparisons of a e r i a l and ground census methods f o r e s t i m a t i n g winter r a p t o r p o p u l a t i o n s i n P i t t Meadows, B.C. Unpublished BCIT student r e p o r t . 33 pp. Kale, H.W., I I . 1965. Ecology and b i o e n e r g e t i c s of the l o n g -b i l l e d marsh wren i n Georgia s a l t marshes. N u t t a l l O r n i t h . Club, Pub. No. 5, 142 pp., Kendeigh, S.C. 1944. Measurement of b i r d p o p u l a t i o n s . E c o l . Monogr. 14: 67-106. L i n s d a l e , J.M. 1938- Environmental responses of v e r t e b r a t e s i n the Great Basin. Amer- M i d i . Nat. 19: 1-206-HacArthur, R.H. 1972. Geographical ecology. Harper and Row, N. Y. 269 pp. Meanley, B. and J.S. Webb. 1963. Nesting ecology and r e p r o d u c t i v e r a t e of the red-winged b l a c k b i r d i n t i d a l marshes of the upper Chesapeake Bay r e g i o n . Chesapeake S c i . 4: 90-100. M i l l e r , R.S. 1967. P a t t e r n and process i n c o m p e t i t i o n . Adv. E c o l . Res. 4: 1-74. M i l l e r , R.S. 1968. C o n d i t i o n s o f competition between redwings and yellow-headed b l a c k b i r d s . J . Anim. E c o l . 37: 43-62. Nero, R.W. 1956. A behaviour study o f the red-winged b l a c k b i r d . I. Mating and n e s t i n g a c t v i t i e s . Wilson B u l l . 68: 5-37. Odum, E.P. 1971. Fundamentals of ecology. W.B. Saunders Co., P h i l a d e l p h i a , PA. 574 pp. Orians, G.H. 1961. The ecology of b l a c k b i r d (Agelaius) s o c i a l systems. E c o l . Monogr. 31: 285-312. O r i a n s , G.H. and M.F. W i l l s o n . 1964. I n t e r s p e c i f i c t e r r i t o r i e s of b i r d s . Ecology 54: 736-745. Orians, G.H. 1969. On the e v o l u t i o n of mating systems i n b i r d s and mammals. The American N a t u r a l i s t 103: 589-603. Orians, G.H. 1970. The adaptive s i g n i f i c a n c e of mating systems i n the I c t e r i d a e . Proc. XV. I n t e r n . O r n i t . Congr.: 389-398. 133 P i e m a n , J . 1 9 7 7 a - D e s t r u c t i o n o f e g g s by t h e l o n g - b i l l e d m a r s h w r e n T e l m a t o d y t e s p a l u s t r i s p a l u s t r i s . C a n . , J . Z o o l . ; 55 (11) : 1 9 1 4 - 1 9 2 0 . P i e m a n , J . 1 9 7 7 b . I n t r a s p e c i f i c n e s t d e s t r u c t i o n i n t h e l o n g -; b i l l e d m a r s h w r e n T e l m a t o d y t e s p a l u s t r i s p a l u s t r i s . C a n . J . Z o o l . 5 5 ( 1 2 ) : 1 9 9 7 - 2 0 0 3 . R o b e r t s o n , R . J . 1 9 7 2 . O p t i m a l n i c h e s p a c e o f t h e r e d - w i n g e d , b l a c k b i r d ( A g e l a i u s p h o e n i c e u s ) . I . N e s t i n g s u c c e s s i n , m a r s h a n d u p l a n d h a b i t a t * . C a n . J . Z o o l * 5 0 : 2 4 7 - 2 6 3 . R u n y a n , C . S . 1 9 7 8 . P i t t w i l d l i f e management a r e a , w i l d l i f e • i n v e n t o r y r e p o r t . U n p u b l . r e p o r t t o B - C - F i s h a n d W i l d l i f e B r a n c h . 99 p p . p l u s a p p . S a v a r d , J e a n - P i e r r e . 1 9 7 8 . B i r d s i n m e t r o p o l i t a n T o r o n t o : d i s t r i b u t i o n ^ r e l a t i o n s h i p s w i t h h a b i t a t f e a t u r e s , a n d n e s t , s i t e s . U n p u b l i s h e d H . S c . T h e s i s . 2 0 9 p p . S e s t a k , Z - e t a l . , ( e d . ) . 1 9 7 1 . P l a n t p h o t o s y n t h e t i c ^ p r o d u c t i o n , m a n u a l o f m e t h o d s . , D r . W. J u n k N - V . P u b l i s h e r s , The H a g u e , p - 5 2 0 . S h i e l d s , W . H . 1 9 7 7 . The e f f e c t o f t i m e o f d a y o n a v i a n c e n s u s r e s u l t s . Auk 9 4 : 3 8 0 - 3 8 3 . S m i t h , H . M . 1 9 4 3 . S i z e o f b r e e d i n g p o p u l a t i o n i n r e l a t i o n t o jegg l a y i n g a n d r e p r o d u c t i v e s u c c e s s i n t h e e a s t e r n R e d w i n g . , E c o l o g y 2 4 : 1 8 3 - 2 0 7 . S v a r d s o n , B . 1 9 4 9 - C o m p e t i t i o n a n d h a b i t a t s e l e c t i o n i n b i r d s . O i k o s 1 (2) : 1 5 8 - 1 7 3 . V e r n e r , J . 1 9 6 4 . E v o l u t i o n o f p o l y g a m y i n t h e l o n g - b i l l e d m a r s h w r e n . E v o l u t i o n 1 8 : 2 5 2 - 2 6 1 . V e r n e r , J . 1 9 6 5 a . B r e e d i n g b i o l o g y o f t h e l o n g - b i l l e d m a r s h w r e n . C o n d o r 6 7 : 6 - 3 0 . V e r n e r , J . 1965b* T i m e b u d g e t o f t h e m a l e l o n g - b i l l e d m a r s h w r e n d u r i n g t h e b r e e d i n g s e a s o n . C o n d o r 6 7 : 1 2 5 - 1 3 9 . V e r n e r , J . 1 9 7 5 a . I n t e r s p e c i f i c a g g r e s s i o n b e t w e e n y e l l o w -h e a d e d b l a c k b i r d s a n d l o n g - b i l l e d m a r s h w r e n . C o n d o r 7 7 : 3 2 9 - 3 3 1 . V e r n e r , J . 1 9 7 5 b - A v i a n b e h a v i o u r a n d h a b i t a t m a n a g e m e n t . P a p e r p r e s e n t e d a t t h e s y m p o s i u m o n management o f f o r e s t a n d r a n g e h a b i t a t s f o r nongame b i r d s , T u c s o n , A r i z o n a , Hay 6 - 9 , 1 9 7 5 - 20 p p . V e r n e r , J a n d G . f l . E n g e l s e n . , 1 9 7 0 . T e r r i t o r i e s , m u l t i p l e n e s t b u i l d i n g , a n d p o l y g y n y i n t h e l o n g - b i l l e d m a r s h w r e n . Auk 8 7 : 5 5 7 - 5 6 7 . ^3u H e l l e r , M . W . a n d C . £ . S p a t c h e r . 1 9 6 5 - B o l e o f h a b i t a t i n t h e d i s t r i b u t i o n a n d a b u n d a n c e o f m a r s h b i r d s . , I o w a S t a t e U n i v . , A g r i c . a n d Home E c o n . E x p e r . S t a t i o n , S p e c . B e p t . N o . 4 3- 31 p p . W e l t e r , W . A . 1 9 3 5 . The n a t u r a l h i s t o r y o f t h e l o n g - b i l l e d m a r s h w r e n . W i l s o n B u l l . 4 7 : 3 - 3 4 . W i e n , J . A . 1 9 6 5 . B e h a v i o u r a l i n t e r a c t i o n s o f r e d - w i n g e d b l a c k b i r d s a n d common g r a c k l e s on a common b r e e d i n g g r o u n d . Auk 3 2 : 3 5 6 - 3 7 5 . W i l l s o n , H . F . 1 9 6 7 . N o t e s on t h e i n t e r s p e c i f i c b e h a v i o r a l r e l a t i o n s h i p s o f m a r s h - n e s t i n g p a s s e r i n e s A u k 8 4 : 1 1 8 - 1 2 0 . A P P E N D I X fiesults of Harsh Census Transects 136 FALL AND WINTER MARSH CENSUS RESULTS,"DENSE SPIRAEA" Fall Early Winter Late Winter Long-billed Marsh Wren 5.8 ^ ± 1.52 km 7.1 ± 1.10 4.4 ± 0.96 Red-winged Blackbird 0.3* ± 0.26** 0.3 ± 0.35 0.5 ± 0.48 Song Sparrow 2.3 ± 0.66 1.0 ± 0.34 0.6 ± 0.36 Common Yellowthroat 4.3 ± 1 . 8 5 0.0 0.0 * Represents mean of total detections for all transects during respective period ** Standard error of mean, N = 12 137 SPRING AND SUMMER MARSH CENSUS RESULTS, "DENSE SPIRAEA" Early Spring Late Spring Summer Long-billed Marsh Wren 15. .1 males km - ± 3.07 18. .1 + 3. .63 11. .8 + 2. .72 Red-winged Blackbird 0. ,6* ± 0. 4 4 * * 1. .1 + 0. .57 0, .8 + 0, .42 Song Sparrow 0. .9 + 0. 33 1 , .2 + 0. .33 1 , .2 + 0, .44 Common Yellowthroat 0. .2 + 0. 16 5, .5 + 1, .40 10. .1 + 1 .16 * Represents mean of singing males for all transects during respective period ** Standard error of mean, N = 12 138 FALL AND WINTER MARSH CENSUS RESULTS, "SEDGE-SPIRAEA' Common Yellowthroat Fall Early Winter Late Winter Long-billed & 3 birds ± 2 3 0 * 2 * ± 1 > 3 7 } Q Q ± , Q 5 Marsh Wren km J i d ' l " i " 9 S d ° - 5 ± ° - 3 6 ° - 3 ± ° - 2 3 4 - 7 ± 2 - 0 1 Blackbird Song SDarrow 1.1 ± 0.80 0.0 0 . 7 ± 0 . 6 9 0.0 0.0 0.0 * Standard error of mean, N = 8 139 SPRING AND SUMMER MARSH CENSUS RESULTS, "SEDGE-SPIRAEA' Early Spring Late Spring Summer Long-billed n . 3 ma]es ± 2 . 3 1 * 1 2 . 8 ±1 .40 1 3 . 5 ± - 2 . 8 8 Marsh Wren km Red-winged Blackbird 5.0 ± 2.44 7.8 ± 2.95 3.8 ± 2.14 Song Sparrow 0.0 0.0 0.0 Common Yellowthroat 0.0 0.5 ± 0.25 3.3 ± 1.00 * Standard error of mean, N = 8 140 FALL AND WINTER MARSH CENSUS RESULTS, "SCIRPUS ACUTUS' Common Yellowthroat Fall Early Winter Late Winter Long-billed 4 > 4 birds ] g o.3 ± 0.22 0.0 Marsh Wren km Red-winged ? 3 5 6 8 Blackbird Song Sparrow 0.0 0.0 0.0 0.9 ± 0.77 0.0 0.0 * Standard error of mean, N = 8 141 SPRING AND SUMMER MARSH CENSUS RESULTS, "SCIRPUS ACUTUS" Red-winged Blackbird Common Yellowthroat Early Spring Late Spring Summer Long-billed males n.63* 4 . 7 ± 1.63 14 .8 ± 3.11 Marsh Wren km 7.3 ± 1.35 8.5 ± 1.48 6.4 ± 1.54 Song Sparrow 0.0 0.0 0.0 0.0 0.0 0.0 * Standard error of mean, N = 8 142 FALL AND WINTER MARSH CENSUS RESULTS, "SCIRPUS CYPERINUS" Fall Early Winter Late Winter Long-bi1 led Marsh Wren 3J birds ± 1 > 7 0 * 0.5 ± 0.52 0.0 Red-winged Blackbird 0.0 0.0 4.1 ± 1.99 Song Sparrow 0.6 ± 0.62 0.0 0.0 Common Yellowthroat 0.0 0.0 0.0 * Standard error of mean, N = 8 SPRING AND SUMMER MARSH CENSUS RESULTS, "SCIRPUS CYPERINUS Red-winged Blackbi rd Early Spring Late Spring Summer Long-billed 0 > 0 males ± ± Marsh Wren km 1.0 ± 1.03* 5.5 ± 3.04 1.8 ± 1 .27 Song Sparrow 0.0 0.0 0.0 5 ; ° ™ ™ t o-o 0.0 0.0 Yellowthroat * Standard error of mean, N = 8 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            data-media="{[{embed.selectedMedia}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
https://iiif.library.ubc.ca/presentation/dsp.831.1-0094587/manifest

Comment

Related Items