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Effects of band-tailed pigeon behavior on estimates of population parameters Kautz, Jerry Edward 1977

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E F F E C T S O F B A N D - T A I L E D P I G E O N B E H A V I O R ON E S T I M A T E S O F P O P U L A T I O N P A R A M E T E R S A THESIS S U B M I T T E D IN P A R T I A L F U L F I L L M E N T O F T H E R E Q U I R E M E N T S F O R T H E D E G R E E O F M A S T E R O F S C I E N C E i n T H E F A C U L T Y O F G R A D U A T E S T U D I E S Department of Zoology by J E R R Y E D W A R D K A U T Z B.S. C o l o r a d o State U n i v e r s i t y , 1970 We accept this thesis as conforming to the r e q u i r e d standard T H E 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 September, 1977 Jerry Edward Kautz, 1977 In presenting th is thes is in p a r t i a l fu l f i lment of the requirements for an advanced degree at the Un ivers i ty of B r i t i s h Columbia, I agree that the L ibrary sha l l make it f ree ly ava i l ab le for reference and study. I fur ther agree that permission for extensive copying of th is thes is for scho la r 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 fo r f inanc ia l gain sha l l not be allowed without my wri t ten permission. Department of ^£?a?/c?4 c/ The Univers i ty of B r i t i s h Columbia Vancouver 8, Canada Date ^ 0c A 7 7 i i A B S T R A C T Du r i n g the s ummers of 1973 and 1974 a study was conducted in the R i o Grande V a l l e y of C o l o r a d o to determine whether t r a p samples of band-t a i l e d pigeons (Columba fasciata) are randomly drawn f r o m the population. Counts and trap samples at the same site and time of day did not give s i g n i f i c a n t l y different estimates (P>0.05) of tagged p r o p o r t i o n or imma-ture p r o p o r t i o n . T h e r e f o r e , counts were rep r e s e n t a t i v e of trap samples. A n a l y s i s of count data indicated that trapping would sample the population feeding at a site randomly with r e s p e c t to tagged pr o p o r t i o n , but not with r e s p e c t to immature pro p o r t i o n . Immature pro p o r t i o n s d i f f e r e d s i g n i f i -cantly (P< 0.05) at different times of day at many feeding s i t e s , at d i f f e r -ent t i m e s of y e a r at the same feeding site, and at different feeding sites at the same time of year. Tagged proportions in counts d e c r e a s e d with distance f r o m the tagging site, but the d e c r e a s e was not u n i f o r m f r o m site to site and appeared to depend upon flight patterns of bandtails. F r e -quency d i s t r i b u t i o n s of distance between captures of pigeons caught twice in C o l o r a d o were s i g n i f i c a n t l y different (P< 0,001) for i m m a t u r e s and adults and for adult m a l e s and f e m a l e s . Immatures d i s p e r s e d long d i s -tances m o r e often than adults and adult m ales had a s m a l l e r feeding range than females. The frequency d i s t r i b u t i o n of recapture distances f o r adult pigeons banded and r e c a p t u r e d i n the same yea r was s i g n i f i c a n t l y different (P< 0. 001) than that f o r adults banded and r e c a p t u r e d i n different y e a r s . i i i T agged p r o p o r t i o n s in hunter k i l l samples and count samples d i d not d i f f e r s i g n i f i c a n t l y (P>0.05), but immature proportions did d i f f e r s i g n i f i c a n t l y (P< 0.05). It is concluded that c a p t u r e - r e c a p t u r e methods can be used to calculate an index of population s i z e , but c a r e must be u s e d in s e l e c t i o n of t r a p sites and i n i n t e r p r e t a t i o n of population data. T r a p data and hunter k i l l data should not be used to estimate immature p r o p o r t i o n s . i v T A B L E O F C O N T E N T S Page A B S T R A C T ? . i i T A B L E O F C O N T E N T S i v L I S T O F T A B L E S v i L I S T O F F I G U R E S v i i i A C K N O W L E D G E M E N T S x I N T R O D U C T I O N 1 S T U D Y A R E A . 3 M E T H O D S 6 T r a p p i n g and M a r k i n g 6 Intensive Study A r e a 6 Statewide 10 Counts 11 Hunter Bag Checks 16 Data A n a l y s i s 16 R E S U L T S 18 S t a t i s t i c a l P r p p e r t i e s of Counts 18 C o m p a r i s o n of Counts and T r a p Samples . 23 C o m p a r i s o n of Hunter Bags and Counts 26 C o m p a r i s o n of T r a p Samples 28 Spatial and T e m p o r a l V a r i a t i o n in Immature P r o p o r t i o n s . 31 Spatial V a r i a t i o n i n Tagged P r o p o r t i o n s 34 V T a b l e of Contents (Continued) Page DISCUSSION 53 C r i t i c i s m of the Data . , . 53 F e e d i n g and F l o c k i n g B e h a v i o r 56 E s t i m a t i o n of Po p u l a t i o n P a r a m e t e r s 60 L I T E R A T U R E C I T E D 67 v i L I S T O F T A B L E S Table Page I Summary of band-tailed pigeon trapping by cannon net, R io Grande V a l l e y , C o l o r a d o , 197 3-74 . 7 II Summary of band-tailed pigeon counts at m a j o r feeding s i t e s , Rio Grande V a l l e y , C o l o r a d o , 1973-74 . . 12 III T e s t s of independence on daily sets of band-tailed pigeon counts 19 IV C h i square tests of homogeneity on d a i l y sets of band-tailed pigeon counts 22 V C o m p a r i s o n s of immature proportions of band-t a i l e d pigeons i n counts and tr a p samples 24 VI C o m p a r i s o n s of tagged proportions of adult band-t a i l e d pigeons i n counts and tr a p samples 25 VII C o m p a r i s o n of immature proportions and tagged proportions of adults i n hunter bag checks and counts . . 27 VIII C o m p a r i s o n of band-tailed pigeon composition of p a i r e d trap samples 29 IX 1973 tagged proportions of adult band-tailed pigeons at m a j o r count sites 35 X 1974 tagged proportions of adult band-tailed pigeons at m a j o r count sites by time p e r i o d 36 v i i L i s t of T a b l e s (Continued) T a b l e Page XI A l l sightings of tagged band-tailed pigeons which were id e n t i f i e d at A l b e r t a Lake and T r e a s u r e Mountain . . . . 46 XII Capture data and J o l l y - S e b e r estimates of population p a r a m e t e r s to show the effects of using two t r a p locations under four, d i f f e r e n t time schedules 63 XIII Capture data for adult band-tailed pigeons trapped and banded at Longmont, C o l o r a d o 65 X I V J o l l y - S e b e r estimates of population p a r a m e t e r s f o r adult band-tailed pigeons captured and banded at Longmont, C o l o r a d o , 65 v i i i L I S T O F F I G U R E S F i g u r e Page 1 Map of intensive study a r e a showing band-tailed pigeon count loca t i o n s , t r a p s i t e s , and flight paths 4 2 C o m p a r i s o n of adult band-tailed pigeon weight d i s t r i -bution i n p a i r e d t r a p samples 30 3 Immature proportions of b a n d - t a i l e d pigeons vs. time of y e a r at feeding sites i n 1974 , 32 4 F r e q u e n c y d i s t r i b u t i o n of distances between banding loc a t i o n and r e c a p t u r e l o c a t i o n for C o l o r a d o band-t a i l e d pigeon r e c a p t u r e s . . . , 37 5 Tagged proportions of band-tailed pigeons vs. distance between tagging and counting l o c a t i o n for pigeons tagged i n 1973 39 6 1974 tagged proportions of adult band-tailed pigeons tagged at T r u j i l l o and Hannah E a s t vs. distance between tagging and counting locations 40 7 1974 tagged proportions of band-tailed pigeons tagged at Davis vs. distance between tagging and counting locations 41 ix L i s t of F i g u r e s (Continued) F i g u r e Page 8 1974 tagged proportions of band-tailed pigeons tagged at Spur ling vs. distance between tagging and counting locations 42 9 R e l a t i v e frequency d i s t r i b u t i o n s of distances between banding.and recapture locations for band-tailed pigeons banded as adults and i mmatures . 48 10 R e l a t i v e frequency d i s t r i b u t i o n s of distances between banding and recapture locations f o r band-tailed pigeons banded as adult males and adult females 50 11 R e l a t i v e frequency d i s t r i b u t i o n s of distances between banding and recapture locations for adult band-tailed pigeons banded and r e c a p t u r e d in the same y e a r and banded and r e c a p t u r e d in different y e a r s . 51 A C K N O W L E D G E M E N T S Many people helped with v a r i o u s phases of this study. I a m gra t e f u l to a l l of them and would e s p e c i a l l y like to thank the following. Dr. C l a i t E . B r a u n of the C o l o r a d o D i v i s i o n of W i l d l i f e was i n s t r u -mental i n getting support for the f i e l d work, let me use the C o l o r a d o band-t a i l e d pigeon recapture data, helped with the f i e l d work, o f f e r e d encour-agement and c r i t i c i s m , and reviewed the t h e s i s . Howard Funk, S m a l l Game R e s e a r c h C h i e f of the C o l o r a d o D i v i s i o n of W i l d l i f e p r o v i d e d ad-m i n i s t r a t i v e a s s i s t a n c e and helped with f i e l d work. M a r i e A. Kautz helped with the f i e l d work, reviewed the t h e s i s , and of f e r e d support. My s u p e r v i s o r , . Dr. C a r l J . W a l t e r s , and committee members, Dr. C h a r l e s J . K r e b s and Dr. J.N.M. Smith, reviewed the thesis and offere d h e l p f u l advice and c r i t i c i s m . Dr. Da v i d C. Bowden of C o l o r a d o State U n i v e r s i t y gave advice on s t a t i s t i c a l a n a l y s i s . M i k e Z g a i n e r , Ronald D e s i l e t , Steve B r o c k , Mike German, Jack Reneau, Bob T r e d e r , and K a r e n Steenhof of the C o l o r a d o D i v i s i o n of Wil d l i f e a l l helped with baiting t r a p sites and trapping pigeons. M a r k Schwindt helped with the computer a n a l y s i s . F i n a n c i a l support f o r the f i e l d work was pr o v i d e d by the C o l o r a d o D i v i s i o n of W i l d l i f e through F e d e r a l A i d to W i l d l i f e R e s t o r a t i o n P r o j e c t W-88-R. 1 I N T R O D U C T I O N The band-tailed pigeon (Columba fasciata) i s a m i g r a t o r y game b i r d o c c u r r i n g i n mountain f o r e s t s of w e s t e r n N o r t h A m e r i c a , C e n t r a l A m e r i c a , and northwestern South A m e r i c a (Goodwin 1967). Two r a c e s are r e c o g n i z e d north of M e x i c o , a C o a s t a l r a c e o c c u r r i n g on the P a c i f i c C o a s t f r o m southern B r i t i s h C o l u m b i a to B a j a C a l i f o r n i a and an I n t e r i o r r ace o c c u r r i n g on both slopes of the Rocky Mountains south of Wyoming ( A m e r i c a n Ornithologist's Union 1957), Though management agencies have attempted to census bandtails, no method has been s u c c e s s f u l i n p r o v i d i n g an accurate density estimate. Methods t r i e d on the West Coast have included pre-hunting season counts at m i n e r a l springs and tidewater areas (Oregon and Washington), p r e -season s u r v e y counts ( C a l i f o r n i a ) , winter ground counts ( C a l i f o r n i a ) , c a l l counts (Washington), and hunter questionnaire h a r v e s t surveys ( B r i t i s h C o lumbia, Washington, Oregon, and C a l i f o r n i a ) . Although none give density e stimates, c a l l counts and p r e s e a s o n counts at m i n e r a l springs and tidewater areas have shown p r o m i s e as indices of abundance ( J e f f r e y 1977). The only census method t r i e d extensively on the I n t e r i o r population is a s y s t e m a t i c tabulation of sightings by f i e l d w o r k e r s (Neff 1951; B r a u n 1973; B r a u n et a l . 1975). Neff (1951) suggested this method could be used as an index of band-tailed pigeon population s i z e , but l a t e r w o r k e r s have 2 not agreed ( B r a u n 1973), C a l l counts have been t r i e d i n C o l o r a d o , Utah, and A r i z o n a , but pigeons were hear d c a l l i n g at only one a r e a i n A r i z o n a ( J e f f r e y 1977). T r a p p i n g and banding of band-tailed pigeons was begun i n 1969 i n C o l o r a d o as a part of a cooperative study of the In t e r i o r population ( B r a u n 1972). A f t e r s e v e r a l y e a r s of banding, r e c a p t u r e rates were high enough to c o n s i d e r the use of c a p t u r e - r e c a p t u r e methods to estimate numbers of bandtails. However, it was not known whether the n e c e s s a r y assumptions of random sampling (Seber 1973) were s a t i s f i e d by the trapping methods. T h i s study was designed to answer the following questions; Do the trapping methods used in C o l o r a d o sample band-tailed pigeons randomly and p r o -vide unbiased estimates of population p a r a m e t e r s ? If not, what p r o c e -dures can be followed to derive estimates with b i a s e s which are t o l e r a b l e f o r management purposes? 3 S T U D Y A R E A The South F o r k - M o n t e V i s t a a r e a i n the Rio Grande R i v e r drainage of s o u t h - c e n t r a l C o l o r a d o ( F i g . 1) was s e l e c t e d f o r intensive study. The a r e a v a r i e s i n elevation f r o m about 2, 300 m at Monte V i s t a to over 4,000 m i n the San Juan Mountains west of Monte V i s t a . A c c o r d i n g to K u c h l e r (1964) the potential n a t u r a l vegetation types present are: Saltbrush-Greasewood ( c e n t r a l San L u i s V a l l e y ) , W h e a t g r a s s - N e e d l e g r a s s (edges of the San L u i s V a l l e y ) , J u n i p e r - P i n o n Woodland (Rio Grande V a l l e y and western foothills of the San L u i s V a l l e y ) , Southwestern S p r u c e - F i r F o r e s t (mountains), and A l p i n e Meadows and B a r r e n (mountains above t i m b e r l i n e ) . The R i o Grande V a l l e y f r o m South F o r k to Monte V i s t a and the San L u i s V a l l e y are l a r g e l y cultivated. The most common crops grown are s m a l l g r a i n s , hay, potatoes, and lettuce. C a t t l e , sheep, and hogs are fed in feedlots i n f a r m i n g a r e a s . B a n d - t a i l e d pigeons are sum-m e r residents i n this a r e a and are thought to nest p r i m a r i l y i n the Spruce-F i r f o r e s t at higher elevations ( B r a u n 197 3). They can be found feeding on waste g r a i n in fields and feedlots throughout the s p r i n g , summer, and f a l l , often i n la r g e f l o c k s . They migr a t e to wintering areas in northwestern M e x i c o i n late f a l l and r e t u r n to C o l o r a d o between late M a r c h and e a r l y May the following y e a r ( B r a u n et a l . 1975). The study a r e a was se l e c t e d because i t was known to be one of the most c e r t a i n areas i n C o l o r a d o for locating l arge feeding flocks of 4 LOCATION S 0 5 10 15 20 25 30 i . . . . i 1 1 1 1 1 1 KILOMETERS BAND-TAILED PIGEON COUNT AND TRAP LOCATIONS A Treasure Mountain J Weiler B Alberta Lake K Gjellum C Colville L Kolb D Trujillo M Spurting E Hannah West N Paulson F Hannah East 0 Wyland G Bauer P Monte Vista Dump H Davis 0 Bell 1 B.A.R. Cattle Co. •*> BAND-TAILED PIGEON FLIGHT PATHS TO FEEDING AREAS Figure 1. Map of intensive study area showing band-tailed pigeon count locations, trap sites, and flight paths. 5 bandtails f r o m s p r i n g to e a r l y f a l l . Pigeons i n this a r e a appear to be m o r e dependent on g r a i n than pigeons i n other a r e a s . The r e a s o n may be that oak (Quercus spp. ) i s r a r e in the a r e a and oak f l o w e r s and' acorns are the most important food of bandtails i n s p r i n g and f a l l (Neff 1947). Oak is common i n most of the band-tailed pigeon habitat i n C o l o r a d o , making the study a r e a somewhat a t y p i c a l . However, my observations i n the sum-m e r s of 1973 and 1974 indicated that band-tailed pigeons i n the a r e a u s e d native foods m o r e than p r e v i o u s l y suspected. Pigeons were found feeding on e l d e r b e r r i e s (Sambucus spp.) and t w i n b e r r i e s ( L o n i c e r a spp.) i n the S p r u c e - F i r f o r e s t s during the f a l l of both y e a r s . In the f a l l of 1973 few pigeons continued u s i n g g r a i n fi e l d s because native food was abundant. I also found pigeon droppings containing the r e m a i n s of b e r r i e s at most g r a i n feeding sites after the latter part of J u l y i n both y e a r s . T h i s i n d i -cates that some pigeons were eating both native foods and g r a i n during late summer and f a l l . Because documented s p r i n g and summer native foods of bandtails (Neff 1947; C. E . Braun, unpublished data) o c c u r within the study a r e a , i t i s l i k e l y that native foods are also used during this time of y e a r . T h e r e f o r e pigeons within the study a r e a d i f f e r f r o m pigeons i n other a r e a s only i n kinds and amounts of native foods used. It is my opinion based on extensive observations of pigeons throughout occupied habitats in C o l o r a d o that these d i f f e r e n c e s are m i n i m a l and have li t t l e effect on the p a r a m e t e r s studied. Thus I believe the r e s u l t s of this study are applicable to other areas in the I n t e r i o r where pigeons supplement native foods with waste g r a i n . 6 M E T H O D S Tr a p p i n g and M a r k i n g Intensive Study A r e a We trapped band-tailed pigeons at two types of sites on the intensive study a r e a during three time periods i n 19*73 and four time periods i n 1974 (Table I). P e rmanent bait sites were in areas bandtails had u s e d p r e v i o u s l y that had no fopd present other than g r a i n p r o v i d e d by us. Monte V i s t a Dump i n 1973 and Hannah E a s t and Davis i n 1974 were this type of s i t e . In 1973 we r e p l a c e d the g r a i n at the permanent site as it disappeared. In 1974 we p r o v i d e d about 11 kg whole c o r n ( Z e a mays) and about 38 kg whole b a r l e y (Hordeum vulgare) on alternate days throughout the summer. T e m p o r a r y t r a p sites were i n areas with waste g r a i n (typ-i c a l l y g r a i n fields) where pigeons were feeding. We p r e b a i t e d each t e m p o r a r y t r a p site with whole corn, whole b a r l e y , and/or f i e l d peas ( P i s u m sativum) two weeks to one month p r i o r to trapping. A t a l l bait sites where c o r n was being used, we switched f r o m whole to c r a c k e d c o r n just before trapping because pigeons r a p i d l y f i l l t h e i r crops on whole c o r n and qu i c k l y leave the t r a p si t e . We u s e d cannon nets s i m i l a r to those designed by D i l l and Thorns -b e r r y (1950) to t r a p pigeons. Nets were put i n place the evening before trapping, after most pigeons had left, and were operated throughout the T a b l e I. Summary of band- t a i l e d pigeon trapping by cannon net, Rio G r a n d V a l l e y , Colorado, 1973-74. Wing Tags T o t a l New Re p l a c e d L o c a t i o n Date T i m e catch color numbe r number Hannah West 18 Oct. 1973 915 16 0 1 Hannah E a s t 23 May 1973 715 70 Orange 47 0 845 64 Orange 25 0 26 May 1973 1100 70 Orange 58 0 1725 45 Orange 12 0 Bauer 24 May 1973 720 76 Orange 58 0 Welle r . 10 Aug. 1973 715 182 Yellow 68 0 1315 61 Yellow 24 0 1530 134 Yellow 48 0 Monte V i s t a Dump - 11 June 1973 1745 5 Yellow 1 0 1840 6 Yellow 5 0 11 Aug. 197 3 730 25 Yellow 13 0 B e l l 12 Aug. 1973 1630 22 Yellow 9 0 1800 30 Yellow 12 0 29 Aug. 197 3 715 29 Yellow 11 0 1973 T o t a l s 835 391 1 T a b l e I (Continued). L o c a t i o n Date T i m e T o t a l catch color Wing Tags New numbe r R e p l a c e d number T r u j i l l o Hannah E a s t Davis Spur! ing 1974 T o t a l s 25 May 1974 25 June 1974 28 May 1974 29 May 1974 30 J u l y 1974 23 Aug. 1974 29 J u l y 1974 12 Aug. 1974 615 1425 645 1030 650 915 1210 630 1200 650 645 1425 720 109 52 36' 88 83 26 25 120 91 136 86 77 102 1,031 B l a c k B l a c k B l a c k B l a c k White White White White White G r e e n Green 76 30 26 53 54 15 16 44 32 0 34 30 0 410 4 8 2 9 3 2 10 2 1 3 1 59 9 trap p i n g day. T r a p p e d pigeons were held i n b u r l a p bags u n t i l they could be p r o c e s s e d , and were r e l e a s e d i m m e d i a t e l y afterwards. A s e r i a l l y num-ber e d , si z e 5, U.S. F i s h and W i l d l i f e S e r v i c e band was placed on one leg of each unhanded pigeon that was r e l e a s e d . F o r r e c a p t u r e s , we r e c o r d e d the band numbers and took the same data as for unbanded b i r d s . Many pigeons were also tagged with two p l a s t i c patagium tags (Murton et a l . 1971), one on each wing. These tags were made of c o l o r e d v i n y l i n 1973 and c l e a r dichloromethane (with c o l o r painted on) i n 1974. The tags were . 25 m m thick, were 30 x 50 mm i n s i z e , and had unique 2 c h a r a c t e r num-be r s painted on them. Most tags of both types broke ne a r the point of attachment after a y e a r of use, but v i n y l tags la s t e d longer than the dichloromethane tags. F o r each pigeon trapped we r e c o r d e d age, sex, c r o p a c t i v i t y , and weight. Pigeons were c a t e g o r i z e d as immature (in the f i r s t c a l e n dar y e a r of l i f e ) , subadult (in the second calendar y e a r of l i f e ) , or adult (in the second or lat e r y e a r of l i f e ) . Immatures were separated f r o m adults by o v e r a l l d i f f e r e n c e s i n plumage (Ridgway 1916). We c l a s s e d as subadult a l l bandtails which had most of th e i r adult plumage but s t i l l r e t a i n e d one or m o r e juvenile s e c o n d a r i e s or wing coverts (White 1973). A n unknown p r o p o r t i o n of second y e a r b i r d s complete th e i r post-juvenile molt by summer, ther e f o r e some subadults were c l a s s e d as adults. F o r most purposes in this paper subadults are combined with adults. We separated older immature, subadult, and adult males f r o m f e -males by dif f e r e n c e s i n plumage c o l o r a t i o n of the head and b r e a s t 10 (Ridgway 1916). M a l e s are p u r p l i s h i n these areas and females are brownish. However, i n sunlight both sexes have a p i n k i s h cast to these feathers, making the females appear purplish-brown. "With experience we could e a s i l y sex most b i r d s , and the r e m a i n d e r were sexed by c l o a c a l c h a r a c t e r s ( M i l l e r and Wagner 1955). We c l a s s i f i e d pigeons which had w e l l developed c r o p glands (pro-ducing crop milk) as active, and a l l others as inactive ( Z e i g l e r 1971; M a r c h and S a d l e i r 1970). T h i s c l a s s i f i c a t i o n was made by palpation (Houston 1963), although some experience was r e q u i r e d . The pigeons were weighed with a p l a t f o r m s c a l e to the n e a r e s t 10 grams. Statewide C o l o r a d o D i v i s i o n of W i l d l i f e p e r s o n n e l trapped and banded pigeons throughout the C o l o r a d o band-tailed pigeon range f r o m 1969 through 1975. I used the r e c a p t u r e data they c o l l e c t e d f r o m 1970 through 1975 f r o m these bandings. T r a p p i n g methods were the same as on the intensive study a r e a except that i n a few situations funnel traps (Reeves et a l . 1968; Evans 1972) and drop traps (Braun 1976) were u s e d instead of cannon nets. Methods of sexing and aging were the same except that c l o a c a l sex c h a r a c -te r s were not used after 1969. A detailed d e s c r i p t i o n of the trapping methods used i n C o l o r a d o is given by B r a u n (1976). 11 Counts I counted bandtails f r o m J u l y through m i d - O c t o b e r i n 19V3 and f r o m e a r l y May through mid-September in 1974 (Table II). I had o r i g i n a l l y hoped to t r a v e l over randomly selected, standard routes through the study a r e a and count a l l bandtails seen. T h i s was not poss i b l e because the di s t r i b u t i o n of feeding flocks was so clumped that they were s e l d o m seen on the random routes. Instead i t was n e c e s s a r y to locate as many feeding sites as poss i b l e and count at them. At least twice a month during counting p e r i o d s , I s e a r c h e d the study a r e a f o r feeding f l o c k s . I also r e c e i v e d r e -ports of flocks f r o m a r e a r e s i d e n t s . Counts were made of a l l known study a r e a flocks that were large enough to warrant counting (30 or more pigeons i n the a r e a at a time). In 1973 the ti m i n g of counts was not sys t e m a t i c except that at least one day of counts was made at each t r a p site just be-for e trapping. In 1974 I t r i e d to count three times a month for a f u l l day at each s i t e . Pigeons were counted using a v a r i a b l e power (15-40x) spotting scope mounted on a t r i p o d . F o r each count I r e c o r d e d the time of day (Mountain Daylight T i m e ) , pigeon act i v i t y , total number of pigeons, number of i m -matures, number of tagged b i r d s , tag numbers, and est i m a t e d number of pigeons i n the v i c i n i t y . I counted a l l i n d i v i d u a l pigeons i n sight, r e c o r d e d the count, and then made another count, repeating this p r o c e s s throughout the day. The rate of counting v a r i e d with the number of pigeons using the site and t h e i r a c t i v i t y . If the flock was l a r g e , and was feeding i n g r a i n T a b l e II. Summary of band-tailed pigeon counts at m a j o r feeding s i t e s , R io Grande V a l l e y , C o l o r a d o , 1973-74. D i f f e r e n t ^ Number Pigeons tagged L o c a t i o n M a j o r food Dates of days Counts-^ c l a s s i f i e d i n d i v i d u a l s C o l v i l l e waste g r a i n 10. Sept.-27 Sept. 1973 7 32 489 7 Hannan West waste g r a i n 28 Sept. -18 Oct., 1973 10 59 1, 507 9 W e i l e r waste g r a i n 22 July-5 Sept. 1973 13 97 7,764 50 Monte V i s t a Dump bait g r a i n 23 July-12 Aug. 1973 6 48 924 3 B e l l waste g r a i n 21 July-30 Aug. 1973 15 63 1, 501 10 1973 T o t a l s 299 12, 185 T r e a s u r e Mountain native f r u i t 13 Aug.-5 Sept. 1974 3 25 398 10 A l b e r t a Lake native f r u i t 5 Sept. 1974 1 5 77 5 C o l v i l l e waste g r a i n 3 Sept.-6 Sept. 1974 2 19 219 12 T r u j i l l o waste g r a i n 11 May-26 May 1974 4 61 2,015 22 Hannah West waste g r a i n 12 Sept. -13 Sept. 1974 2 20 864 23 Table II (Continued). D i f f e r e n t -L o c a t i o n M a j o r food Dates Numbe r of days Counts—^ Pigeons c l a s s i f i e d tagged ind i v i d u a l s Hannah E a s t bait g r a i n 16 June-2 Aug. 1974 7 145 6,267 130 Davis bait g r a i n 22 May-12 Sept. 1974 14 336 11,115 190 B a r Cattle Co. waste g r a i n 29 June-18 J u l y 1974 2 14 1,086 29 Welle r waste g r a i n 23 May-10 June 1974 2 65 1,869 35 G j e l l u m waste g r a i n 19 June 1974 1 6 166 6 Kolb waste g r a i n 18 July-5 Aug. 1974 3 22 1,504 43 Spurling waste g r a i n 16 July-22 Aug. 1974 7 88 6,729 143 P a u l s o n waste g r a i n 12.Sept. -14 Sept. 1974 2 28 1,254 19 Wyland waste g r a i n , 15 Sept. -17 Sept. 1974 2 8 507 9 B e l l waste g r a i n 4 Sept. -12 Sept. 1974 2 21 498 3 1974 T o t a l s 863 34,568 'Onlycounts i n which one or more ind i v i d u a l s were c l a s s i f i e d a c c o r d i n g to tag status and age are included. ^ A l l tagged i n d i v i d u a l s i d e n t i f i e d are included whether in a count or not. 14 stubble where it was d i f f i c u l t to see i n d i v i d u a l s , counts were made as often as p o s s i b l e . A t permanent bait sites counts were made each time a group of pigeons fed. T h i s r e s u l t e d i n a mean frequency of counting f o r each tagged b i r d of about twice a day (2. 19 - 2. 31) at the permanent bait s i t e s , and g e n e r a l l y l e s s i n g r a i n fi e l d s (1.33 - 2.37, most around 1.5 -1.6). Bandtails spend a major p r o p o r t i o n of t h e i r time p e r c h i n g and re s t i n g when i n feeding a r e a s . They alternate these a c t i v i t i e s with feeding, and a l l or most of the b i r d s in the a r e a r e s t or feed at the same time. I counted pigeons feeding on bait s i t e s , i n plowed f i e l d s , i n g r a i n stubble, i n li v e s t o c k feedlots, and i n patches of b e r r i e s . I also counted them while they were p e r c h i n g on fence w i r e s , on telephone w i r e s , and in t r e e s . The v i s i b i l i t y of pigeons is different i n each of these situations, as is t h e i r rate of movement, and each situation presents different counting p r o b l e m s . In an attempt to standardize, I adopted the following p r o c e d u r e s ; (1) p i -geons were counted i n o r d e r as the f i e l d of view of the spotting scope was pas s e d a c r o s s a group of b i r d s or as the b i r d s moved into the f i e l d of view of the scope while it was held stationary, (2) the count was stopped when the entire group had been passed over with the scope, the b i r d s had stopped moving into the f i e l d of view, or the b i r d s were i n t e r r u p t e d enough to make it l i k e l y that individuals would be counted twice i n the same count. Individuals were not included i n the counts if they could not be seen c l e a r l y enough to be c a t e g o r i z e d as tagged or untagged and immature or adult.(generally l e s s than ten percent of the pigeons seen). 15 I dist i n g u i s h e d immature band-tailed pigeons f r o m adults i n the counts by the drab c o l o r , lack of a neck c r e s c e n t , and s m a l l s i z e of the immature. At about three months of age immatures lose these c h a r a c -t e r s and begin to r e s e m b l e adults (White 1973), so it is p o s s i b l e that some immatures i n September and October were c l a s s i f i e d as adults. Imma-tures can s t i l l be r e c o g n i z e d in trap samples and hunter bag samples at this time of y e a r and this presents d i f f i c u l t i e s i n the c o m p a r i s o n of these samples with counts. To determine tag status I checked one wing of each pigeon. If a tag was unreadable and the pigeon could be aged, the c o l o r of the tag was r e -corded, and the b i r d was included i n the count. F o r tagged b i r d s which were seen out of o r d e r or between counts and were not a l r e a d y included i n a count that day, I r e c o r d e d the tag number sepa r a t e l y . P e r i o d i c a l l y , I watched tagged pigeons to determine whether or not they had lost the other tag. I attempted to c l a s s i f y pigeons as " c e n t r a l , " " a v e r a g e , " or " p e r i -p h e r a l " a c c o r d i n g to their b e h a v i o r i n feeding (Murton, Coombs, and T h e a r l e 1972). A t many sites this was not possible because the feeding f l o c k was too large or could not be seen c l e a r l y . However, I could not re c o g n i z e these b e h a v i o r types at any of the sites where fl o c k s i z e was s m a l l and v i s i b i l i t y was good. If there were too many pigeons to feed on the bait site at once, the b i r d s alternated feeding, and none appeared to use " p e r i p h e r a l " feeding lo c a t i o n s . It is po s s i b l e that food was not l i m i t -ing f o r band-tailed pigeons on the study a r e a and these b e h a v i o r patterns 16 were not e x p r e s s e d . It is also p o s s i b l e that bandtails do not use these feeding locations f o r d e t e r m i n i n g who feeds at a c e r t a i n s i t e . Hunter Bag Checks We checked the b a n d - t a i l e d pigeon hunting bag of a l l hunters we could locate i n the intensive study a r e a and at B a y f i e l d , C o l o r a d o between September 7 and 19, 1974. Wing envelopes were also d i s t r i b u t e d to a l l hunters who obtained b a n d - t a i l e d pigeon p e r m i t s i n the San L u i s V a l l e y of C o l o r a d o . These hunters were requested to send one wing f r o m each pigeon they shot to the C o l o r a d o D i vis ion of W i l d l i f e , - F o r each wing o r b i r d checked i n the hunter bag we r e c o r d e d the tag status and age. Wings were separated into i mmature and adult categories using the c h a r a c t e r s of White (1973), and pigeons in bag checks were aged a c c o r d i n g to o v e r a l l plumage c h a r a c t e r s (Ridgway 1916; White 1973). A f t e r e l i m i n a t i n g d u p l i -cation, data f r o m wing samples were combined with data f r o m bag checks. Data A n a l y s i s Groups of counts were combined to compute immature and tagged p r o p o r t i o n s f o r v a r i o u s time p e r i o d s . Rather than assume any frequency d i s t r i b u t i o n f o r these count p r o p o r t i o n s , I computed e m p i r i c a l standard deviation estimates u s i n g the f o r m u l a of Snedecor and C o c h r a n (1967:515) for unequal s i z e d c l u s t e r p r o p o r t i o n s . In most ca s e s , I then c a l c u l a t e d standard e r r o r s and confidence i n t e r v a l s f o r the o v e r a l l proportions u s i n g those standard deviation e s timates. When there were l e s s than two tags 17 o r i m m a t u r e s i n the pooled counts, I us e d b i n o m i a l confidence i n t e r v a l s ( F i s h e r and Yates 1963:65), To test independence of counts at the same site within the same day, I u s e d s e r i a l c o r r e l a t i o n coefficients (Box and Jenkins 1970:32) and c h i square tests of independence (Snedecor and C o c h r a n 1967:239)• I com-par e d the d i s p e r s i o n of immature and tagged proportions i n counts to the b i n o m i a l d i s t r i b u t i o n u s i n g the chi square test of homogeneity (Snedecor and C o c h r a n 1967:240) with the si g n i f i c a n c e l e v e l s of Haldane (1945). The normal, deviate (Z test, Snedecor and C o c h r a n 1967:101, 152) was u s e d to test f o r s i g n i f i c a n t d i f f e r e n c e s between proportions when sample s i z e s were l a r g e , and d i r e c t c o m p a r i s o n of b i n o m i a l confidence i n t e r v a l s ( F i s h e r and Yates 196 3:65) was u s e d when they were s m a l l . To test d i f f e r e n c e s between frequency d i s t r i b u t i o n s , I used the chi square test (Snedecor and C o c h r a n 1967:239), and to compare mean weights i n tr a p samples I us e d student's t test (Snedecor and C o c h r a n 1967:105). A l l tests were made at the 0.05 s i g n i f i c a n c e l e v e l unless otherwise s p e c i f i e d . Distances between count and tr a p sites i n the intensive study a r e a ( F i g . 1) were m e a s u r e d on a U.S. G e o l o g i c a l Survey topographic map (1:250,000). I ca l c u l a t e d distances between banding and recapture l o c a -tions f o r a l l C o l o r a d o band-tailed pigeon r e c a p t u r e s using the la t i t u d i n a l and longitudinal coordinates of the trap sites to the n e a r e s t minute (Robinson and Sale 1969:33). I ca l c u l a t e d J o l l y - S e b e r estimates of popula-tion p a r a m e t e r s a c c o r d i n g to the equations given i n Seber (1973:200-203, 219). 1 8 RESULTS Statistical Properties of Counts Throughout this paper I have assumed that each count is a random sample of all band-tailed pigeons feeding at a count location on a count day. Because this assumption is necessary to use count estimates of population parameters and their variances for comparisons between sites and days, I tested its validity. For each day of counts, I tested for count inde-pendence using a chi square test and a first order serial correlation co-efficient. I tested for random sampling in each day using a chi square test of homogeneity. A chi square test of independence was conducted on immature pro-portions and tagged proportions of adults for each count day with more than five useable counts and an overall proportion greater than zero. More than half (26 of 50) of the tests on immature proportions were significant (P<0.05), and the results were similar for both years (Table III), indi-cating that there were significant differences in immature proportions at different times of day. Of the tests on tagged proportions of adults, only a few were significant (6 of 53) at the five percent level, and both years were similar. This means that there was generally not significant hourly variation in tagged proportion of adults at a site on a given day. T a b l e III. T e s t s of independence on d a i l y sets of band-tailed pigeon counts. Values are the number of days i n each category. F i r s t O r d e r S e r i a l C o r r e l a t i o n C o e f f i c i e n t S i g n i f i c a n t ^ Not sig n i f i c a n t T o t a l Immature P r o p o r t i o n s C h i square Significant Not significant T o t a l T agged P r o p o r t i o n s of Adults C h i square Significant Not s i g n i f i c a n t T o t a l Immature P r o p o r t i o n s C h i square Significant Not s i g n i f i c a n t T o t a l Tagged P r o p o r t i o n s of Adults C h i square Sign i f i c a n t Not s i g n i f i c a n t T o t a l 1973 5 3 8 0 9 9 5 12 17 0 2 2 0 11 11 0 13 13 1974 7 11 18 2 13 15 9 24 33 1 3 4 3 33 36 4 36 40 1/ P < 0 . 05 si g n i f i c a n c e l e v e l . 20 Because of the way counts were made, i n d i v i d u a l band-tailed p i -geons often appeared i n m o re than one count during one day. Since the number of i n d i v i d u a l pigeons feeding at a site i n one day was s m a l l , d u p l i -cation of individuals was expected in a large number of r andom counts. However, since i n d i v i d u a l band-tailed pigeons often a r r i v e d at the feeding s i t e , r e m a i n e d u n t i l they obtained enough food, and left, c o r r e l a t i o n i n counts which were close together i n time could r e s u l t . T o test this p o s s i -b i l i t y , . ! u s e d s e r i a l c o r r e l a t i o n c o e f f i c i e n t s . S e r i a l c o r r e l a t i o n coefficients were c a l c u l a t e d f o r the same count days as chi square tests of independence. M o r e than one q u a r t e r (14 of 50) of the f i r s t o r d e r co e f f i c i e n t s c a l c u l a t e d f o r immature proportions were sig n i f i c a n t (P< 0. 05) with the pattern being consistent f o r both y e a r s (Table III). Twelve out of fourteen of the days with s i g n i f i c a n t s e r i a l c o r r e l a t i o n a l s o had s i g n i f i c a n t v a r i a t i o n i n immature proportions (chi square tests of independence, Tabl e III). Thus there was a time s e r i e s t r e n d in immature proportions at some sites on some days. Only four of 53 f i r s t o r d e r c o r r e l a t i o n coefficients c a l c u l a t e d f o r tagged proportions of adults were s i g n i f i c a n t (Table III), indi c a t i n g that s e r i a l c o r r e l a t i o n was not g e n e r a l l y present i n tagged p r o p o r t i o n s . T h e o r e t i c a l l y , random sampling with r e p l a c e m e n t f o r an attribute with two categories w i l l generate a b i n o m i a l frequency d i s t r i b u t i o n (Brownlee 196 5:30-35). Since I took i n d i v i d u a l counts throughout the day, I could calculate an e m p i r i c a l v a r i a n c e for the daily v a r i a t i o n in count p r o p o r t i o n s . T h i s could be c o m pared to the t h e o r e t i c a l b i n o m i a l v a r i a n c e 21 f o r the entire day's count, i n d i c a t i n g whether the d i s p e r s i o n was s i m i l a r to that expected with random sampling. The c h i square test of homoge-neity is a f o r m a l c o m p a r i s o n of this type. The test is two t a i l e d ; a s m a l l value indicates u n d e r - d i s p e r s i o n i n the counts,, and a large value indicates o v e r - d i s p e r s i o n . C h i square tests of homogeneity were computed for a l l count days with the following c h a r a c t e r i s t i c s : counts taken over a time p e r i o d of m o r e than one hour, m o r e than one immature or tagged i n d i v i d u a l counted, and m o r e than ten total i n d i viduals counted. About half (26 of 55) of the c h i square values for immature proportions were si g n i f i c a n t at the five percent l e v e l (Table IV), and most were too l a r g e . T h i s indicates that i m m a t u r e s were not randomly d i s t r i b u t e d among adults at feeding s i t e s . T e s t s on tagged proportions of adults r e s u l t e d i n a few m o r e s i g n i f i c a n t days (6 of 53) than was expected by chance at the five p ercent l e v e l (3), but the s i g n i f i c a n t days were evenly d i s t r i b u t e d between o v e r - and under-d i s p e r s i o n (Table IV). T h i s indicates that i n d i v i d u a l counts were a random sample of the tagged p r o p o r t i o n of the d a i l y adult feeding population. The combined r e s u l t s of this s e c t i o n indicate that counts of band-t a i l e d pigeons were not random samples of the immature p r o p o r t i o n of pigeons feeding at a site during a day. At some times of day i m m a t u r e proportions were much higher and at other times of day much lower than expected with chance v a r i a t i o n about the daily mean. However, counts were a random sample of the tagged p r o p o r t i o n of adults feeding at a site during one day. The r e m a i n i n g sections address the following questions; 22 Ta b l e IV. C h i square tests of homogeneity on da i l y sets of band - t a i l e d pigeon counts. Values are the number of days i n each category. Significant y Not Too l a r g e Too s m a l l s i g n i f i c a n t T o t a l 1973 Immature proportions Tagged proportions of adults 8 1 0 0 13 21 10 1974 Immature proportions 17 16 34 Tagged proportions of adults 38 43 1/ P < 0.05 si g n i f i c a n c e l e v e l . Did trapping and hunting sample the daily feeding populations randomly? Were daily feeding populations a random sample of some larger popula-tion? Comparison of Counts and Trap Samples Counts were made at each trap location sometime during the four days before trapping. I compared these counts to trap samples to deter-mine whether there were significant differences in immature proportions or tagged proportions of adults. The comparisons of immature propor^ tions in counts and trap samples are shown in Table V. For days in which there were no significant differences (P>0.05) between counts, I used all counts from the closest previous day or days for the comparison. Where there were significant differences between counts, I used the largest count on the closest previous day taken within one half hour of the trap time. Four of thirteen comparisons (30 percent) of immature proportions were significant (P<0.05). In two comparisons the count proportion was larger than the trap proportion,, and in two the count proportion was smaller. This could indicate that trap samples did not give unbiased estimates of immature proportions, or that immafure proportions varied from day to day at the same time of day. Comparisons of tagged proportions of adults in counts and trap sam-ples are shown in Table VI. I used the pooled tagged proportion of all counts from the closest previous day or days for the comparison. Since some pigeons in the trap samples had only one tag, they were tallied as Table V. C o m p a r i s o n s of immature proportions of band-tailed pigeons i n counts and trap samples. Counts T r a p Samples  T o t a l Immature T o t a l Immature i n d i - p r o p o r - i n d i - p r o p o r -Site Sample vidua Is tion Sample viduals tion Welle r 10 Aug. 197 3, 700 186 .73 10 Aug. 1973, 715 182 .78 We Her 9 Aug. 1973, 1315 209 .47 10 Aug. 1973, 1315 61 . 1 8 ^ W e l l e r 9 Aug. 1973, 1505 138 .37 10 Aug. 1973, 1530 134 . 31 Monte V i s t a Dump 7 Aug. 1973, 750 40 . 20 11 Aug. 1973, 730 25 .32 B e l l 12 Aug. 1973, 1615 25 . 52 12 Aug. 1973, 1630 22 . 50 B e l l 28 Aug. 1973, 716 33 .67 29 Aug. 1973, 715 29 .45 Hannah West 16 -18 Oct. 197 3 259 . 50 18 Oct. 1973, 915 16 .44 Spur l i n g 28 Jul y 1974, 653 191 .40 29 July 1974, 645 86 . 31 Spur l i n g 28 J u l y 1974, 1430 159 .18 29 July 1974, 1445 77 .471/ Davis 26 J u l y 1974, 631 86 . 13 30 July 1974, 630 120 . 2 5 ^ Davis 26 J u l y 1974, 1230 32 .06 30 J u l y 1974, 1200 91 . 03 Spurling 9 Aug. 1974, 720 228 .42 12 Aug. 1974, 720 102 . 51 Davis 23 Aug. 1974, 648 101 .60 23 Aug. 1974, 650 136 .4ZV y S i g n i f i c a n t l y d i f f e r e n t (P< 0. 05). Table VI. Comparisons" of tagged proportions of adult band-tailed pigeons in counts and trap samples. Counts Trap Samples Site Sample Total adults Tagged proportion— Sample Total adults Tagged proportion Weiler 8 -10 Aug. 1973 942 .005 10 Aug. 1973, 715 40 0.0 Weiler 8 -10 Aug. 1973 942 .005 10 Aug. 1973, 1315 50 0.0 Weiler 8 -10 Aug. 1973 942 .005 10 Aug. 1973, 1530 93 0.0 Hannah West 16 -17 Oct. 1973 125 .024 18 Oct. 1973, 915 9 0.0 Trujillo 24 May- 1974 935 .025 25 May 1974, 615 109 .009 Trujillo 24 May 1974 935 . 025 25 May 1974, 1425 52 .019 Davis 27 May 1974 1180 .016 28 May 1974, 650 83 .024 Davis 27 May 1974 1180 .016 29 May 1974, 915 26 .039 Davis 27 May 1974 1180 .016 29 May 1974, 1210 25 .040 Hannah East 24 June 1974 667 .072 25 June 1974, 645 36 .111 Hannah East 24 June 1974 667 . 072 25 June 1974, 1030 87 .069 Spurling 28 July 1974 1123 .025 29 July 1974, 645 59 .068 Spurling 28 July 1974 1123 . 025 29 July 1974, 1445 41 .098 Davis 26 July 1974 1005 . 094 30 July 1974, 630 90 . 100 Davis 26 July 1974 1005 . 094 30 July 1974, 1200 88 . 091 Spurling 9 Aug. 1974 898 .059 12 Aug. 1974, 720 50 . 080 Davis 21 Aug. 1974 817 .129 23 Aug. 1974, 650 79 .089 None of the tagged proportions are significantly different (P>0.05) in the counts and trap samples. 26 half a tag. The total number of tags in the trap sample was then rounded up to the nearest whole number. This is because the probability is 0. 5 that a visible pigeon with only one tag will be recorded as tagged in a count. None of the seventeen comparisons showed significant differences (P>0.05). This indicates that trap samples provided unbiased estimates of the tagged proportion of adult band-tailed pigeons feeding at the trap site, and that band-tailed pigeons did not learn to avoid being trapped by avoiding the trap. However, they might have avoided the trap area en-tirely, thus not appearing in the counts. Comparisons of Hunter Bags and Counts There were no significant differences (P>0.05) in the tagged pro-portions of adult band-tailed pigeons in hunter bags and counts (Table VII). Consequently, pigeons trapped previously had the same probability of being shot as pigeons not trapped previously. All of the immature proportions were higher in counts than in hunter bags, one significantly so (Table VII). The difference may have been greater than indicated in the data because of the possibility of classifying an immature as an adult in counts at this time of year. This indicates that adults present in a hunting area had a higher probability of being shot than did immatures. A possi-ble cause is that adults spent less time at feeding sites and were more actively involved in flying between trees and food than immatures. Thus adults at a site may have had a higher probability than immatures of flying within range of a hunter. T a b l e VII. C o m p a r i s o n of immature proportions and tagged proportions of adults in hunter bag checks and counts. Immature P r o p o r t i o n Tagged P r o p o r -tion of Adults Sample N p r o p o r t i o n N p r o p o r t i o n Counts, 4 Sept. 1974, Steffanson 429 .40 256 . 027 Bag, 7-8 Sept. 1974, Steffanson 44 .36 28 0. 0 Counts, . 14 Sept. 1974, P a u l s o n 1181 .47 y .29 626 .048 Bag, 17-19 Sept. 1974, P a u l s o n and Wyland 41 29 . 034 Counts, 7 Sept. 1974, B a y f i e l d , Colo. 163 .65 ... • • • Bag, 7 Sept. 1974, B a y f i e l d , Colo. 21 . 52 ... y S i g n i f i c a n t l y different (P< 0.05). 28 C o m p a r i s o n of T r a p Samples T o test f or site to site d i f f e r e n c e s i n population p a r a m e t e r s , I com-par e d t r a p samples taken within a few days of each other at about the same time of day. The re s u l t s (Table VIII and F i g . 2) indicate there was some s p a t i a l v a r i a t i o n i n the p a r a m e t e r s compared. P i g e o n samples trapped at W e i l e r i n 1973 were composed of s i g n i f i c a n t l y (P<0.05) m o r e im m a t u r e s , li g h t e r adults, and fewer banded adults than pigeons trapped at the Monte V i s t a Dump. Adult pigeons trapped at Davis i n J u l y 1974 were composed of m o re males, m ore b i r d s with active c r o p s , and h e a v i e r b i r d s than those trapped at S p u r l i n g . In both of these situations, sites which had a l a r g e r feeding flock of pigeons attracted f r o m a l a r g e r a r e a ( W e i l e r and Spurling) were compared to sites with a s m a l l e r feeding flock attracted f r o m a s m a l l e r a r e a (Monte V i s t a Dump and Da v i s ) . In con-t r a s t , the other two comparisons were between sites with s i m i l a r num-ber s of pigeons (Hannah E a s t and Bauer; T r u j i l l o and Davis) and the only s i g n i f i c a n t d i f f e r e n c e (P< 0. 05) was between the mean weights at T r u j i l l o and Davis in May 1974 (the weight di s t r i b u t i o n s were not s i g n i f i c a n t l y different). In both cases with d i f f e r e n c e s i n s i z e of feeding flock, the s m a l l e r site was u p s t r e a m ( c l o s e r to nesting areas) f r o m the l a r g e r s i t e , flights of pigeons were o b s e r v e d between the two s i t e s , and the pigeons at the s m a l l e r site were he a v i e r , o l d e r , and had higher f r e q u e n c i e s of active c r o p s . T h i s suggests that there was a b e h a v i o r a l cause f o r o b s e r v e d d i f f e r e n c e s . P o s s i b i l i t i e s are competition for food at the site c l o s e r to T a b l e VIII. C o m p a r i s o n of band-tailed pigeon composition of p a i r e d trap samples. P r o p o r - P r o p o r t i o n of Adults Number tion No. of Second A c t i v e T r a p Sample caught immature adults year M a l e c r o p Banded Hannah E a s t , 23 May 197 3., 715 70 y • • • 70 . 06 .76 .04 . 33 Bauer, 24 May 197 3, 720 76 * • • 76 . 08 .75 .09 . 24 We lie r , Monte V i s t a Dump, 10 Aug. 1973, 11 Aug. 1973, 715 730 182 25 .78 2/ . 32 40 17 .25 0.0 .78 1.0 .79^ .76 .13 .65 T r u j i l l o , 25 May 1974, 615 109 • • * 109 .06 .94 . 31 .28 Da v i s , 28 May 1974, 650 83 • • • 83 .04 .98 .25 . 35 Spur l i n g , D a v i s , 29 J u l y 1974, 30 July 1974, 645 630 86 120 . 31 ;25 59 90 .29 .2.1 .75 2y .89 .29*/ •2/ .53 . 32 . 36 y P r o p o r t i o n 0. 0 i n both samples, no c o m p a r i s o n made. y S i g n i f i c a n t l y diffe rent (P< 0. 05). 3/ C r o p a c t i v i t y was not d e t e r m i n e d for two of the adults i n this sample. 1/ C r o p a c t i v i t y was not d e t e r m i n e d for one of the adults i n this sample. 30 20-, 15} a H a n n a h East , 23 MAY 7 3 , 715. ( N = 70 , X - 3 5 8 ,S.E. = 3.63) • Bauer , 2 4 M A V 7 3 , 7 2 0 ( N = 7 6 , x = 3 5 5 , S.E. = 3.02) n i l l l , Ik Ol 20-, 15-10-5H • W e i l e r , 10 AUG 7 3 , 7 1 5 l/V = 40 , X = 322.8 ,S .E=4.68) U Monte V i s t a D u m p , 1J AUG 73, 7 3 0 (N=17, X -348.2 .S.L . -4 .39) JLL i B IL K Z UJ Q: a.15-5H 0-1 • T ru j i l lo , 25 MAY*., 615 (N=107, X=365.3, S. £ . = 2.54) • Davis, 28M/AY74, 6 5 0 (A/-83, X=373.5 , S . £ .=2 .98) In. J i E L 20-, 1 5 H o - i • Spurling,29JULY74, 645>(N=58,X«358.4 ,S.E.-3.78) • D a v i s , 3 0 j U / - Y 7 4 , 6 3 0 (N=90, X=371.2 , S . £ .=2 .70) 1 D 250 F i g u r e 2. I ' 1 1 ' I i i I i i i 300 350 WEIGHT IN GRAMS 400 Comparison of adult band-tailed pigeon weight distribution in paired trap samples. Both the distributions and means at Weiler and Monte V i s t a Dump in 19V 3 and Spurling and Davis in 1974 are significantly different (P<0.05). The means at T r u j i l l o and Davis in 1974 are significantly different (P = 0. 05). 31 nesting areas and m o re wi l l i n g n e s s by s m a l l e r , l e s s e x p e r i e n c e d b i r d s to wander. The s i g n i f i c a n t d i f f e r e n c e i n banded p r o p o r t i o n of adults at W e l l e r and Monte V i s t a Dump may be due to unequal s p a t i a l d i s t r i b u t i o n of banding effort i n previous y e a r s (next section). Spatial and T e m p o r a l V a r i a t i o n in Immature P r o p o r t i o n s The r e s u l t s r e p o r t e d above of chi square tests of independence and s e r i a l c o r r e l a t i o n c o e f f i c i e n t s c a l c u l a t e d f o r immature proportions i n d i -cated there was often s i g n i f i c a n t h o u r l y v a r i a t i o n (P<^0.05) i n immature proportions at the same site on the same day. I also c o m p a r e d immature proportions between si t e s and days in 1974 ( F i g . 3). In an attempt to standardize I u s e d only days for which counts were made during a l l or m ost of the day. Because few days in 1973 s a t i s f i e d this c r i t e r i o n , com-pa r i s o n s were not made f o r that y e a r . I c a l c u l a t e d o v e r a l l i mmature proportions and confidence i n t e r v a l s f o r each site f o r each day. Inspec-ti o n of F i g u r e 3 shows a s i g n i f i c a n t i n c r e a s e (P< 0.05) i n i m m a t u r e p r o -portions over time at sites where more than one day of counts was made. T h i s i n c r e a s e i s expected because newly fledged young are constantly joining the population during the time of y e a r shown. By i n s p e c t i o n ( F i g . 3) one can see that there were sig n i f i c a n t d i f f e r e n c e s (P<0.0 5) i n i m -mature proportions between sites at about the same time of y e a r . E v e n sites which were close enough that many of the same tagged b i r d s were seen at each site had s i g n i f i c a n t d i f f e r e n c e s in immature proportions at the same time of y e a r . F o r example, there are highly s i g n i f i c a n t 32 Figure 3. Immature proportions of band-tailed pigeons vs. time of year at feeding sites in 1974. Proportions are shown for all days during which counts were taken over all or most of the day at the same site. d i f f e r e n c e s (P<0.05) i n the i m m a ture proportions at Hannah E a s t , D a v i s , and S p u r l i n g at the end of J u l y and f i r s t of August. T h e r e are also s i g n i f i cant d i f f e r e n c e s (P< 0.05) between C o l v i l l e and Hannah West during the e a r l y part of September, and these sites are only 5 k m apart. Observations at W e i l e r i n 1973 indicated that adults stopped feeding at that site (presumably to feed on native food) at a much m o r e r a p i d rate than immatures did. B y September 5 the immature p r o p o r t i o n there had r a p i d l y r i s e n to 0. 87 and a m a x i m u m of about 50 b i r d s were at the site at any one time (as opposed to 200-400 at the end of J u l y ) . It was my i m -p r e s s i o n that the i mmatures feeding at W e i l e r were r e s t i n g i n t r e e s along the Rio Grande R i v e r throughout the day rather than r e t u r n i n g with the adults to the mountains after feeding. If this were the case, they would have been slow i n following the adults to new s i t e s . In the e a r l y f a l l of 1974 the immature p r o p o r t i o n was highest at the sites farthest f r o m the mountains ( B e l l and Paulson,. F i g s . 3 and 1) i n d i c a t i n g that i m m a t u r e s may have been concentrating i n areas that adults were l e s s l i k e l y to use. These i m m a t u r e s may have also been staying i n the San L u i s V a l l e y rathe than r e t u r n i n g to the mountains, but this was not investigated. These r e s u l t s indicate that after l e a v i n g the nest, i m m a t u r e s do not behave s i m i l a r l y to adults with r e g a r d to movements or r e s t i n g and that they are not randomly d i s t r i b u t e d among adults over time of day at the same site or over space during the same time of y e a r . 34 Spatial V a r i a t i o n i n Tagged P r o p o r t i o n s In both 1973 and 1974 there were sig n i f i c a n t d i f f e r e n c e s (P<_0.05) in tagged proportions among count s i t e s , i n d i c a t i n g that tagged band-tailed pigeons did not m i x completely throughout the study a r e a (Tables IX and X). Spatial v a r i a t i o n i n tagged proportions and movement patterns of bandtails are examined i n d e t a i l i n this section. B ecause b a n d - t a i l e d pigeons have a nesting t e r r i t o r y and fl y to s u r -rounding areas to feed ( G l o v e r 1953; P e e t e r s 1962), I expected the p r o b a -b i l i t y of recapture of banded pigeons to be a d e c r e a s i n g function of distance f r o m the banding location. The frequency d i s t r i b u t i o n of distances between banding l o c a t i o n and reca p t u r e l o c a t i o n for a l l band-tailed pigeons banded and r e c a p t u r e d i n C o l o r a d o f r o m 1969 through 1975 ( F i g . 4) supports this hypothesis. Because trapping i n C o l o r a d o was not d i s t r i b u t e d evenly over distance, this graph gives only a rough approximation of the p r o b a b i l i t y of recap t u r e v e r s u s distance. Data presented i n F i g . 4 indicate that; (1) bandtails had a strong tendency to r e t u r n to the same feeding location, (2) movements between feeding sites within about 60 k m of each other were common, ind i c a t i n g that sites this close together may be within the feeding range of most pigeons, (3) movements f r o m 60 k m up to 160 k m were l e s s common, and (4) beyond about 160 k m movements were r a r e and the f r e -quency of movements d e c r e a s e d only s l i g h t l y with distance. A m o re d i r e c t m e a s u r e of the v a r i a t i o n i n p r o b a b i l i t y of recapture with distance is the v a r i a t i o n i n tagged proportions between count sites Table IX. 1973 tagged proportions of adult band-tailed pigeons at major count s i t e s . A l l Counts Counts after Aug. 14 No. Orange tagged No. Tagged L o c a t i o n adults p r o p o r t i o n adults p r o p o r t i o n C o l v i l l e 411 . 012 (.002 - . 022)-^ 411 .046 (.033 - .060) Hannah West 1005 .037 (.027 - .047) 1005 .046 (.035 - .057) W e i l e r 5186 .010 (. 007 - . 013) 239 .079 (.056 - . 103) Monte V i s t a Dump 729 0.0 (0.0 - .005) • o • ZJ • • • * • e • o e B e l l 1025 .001 (0.0 - .005) 145 0.0 (0.0 - .026) u Mean (0.95 confidence i n t e r v a l ) . u No counts made at this site during this time period. Table X . 1974 tagged proportions of adult band-tailed pigeons at major count sites by time period. 11 May to 24 May 8 June to 24 June 27 June to 28 July 1 Aug. to 17 Sept. No. Tagged No. Tagged No. Tagged No. Tagged Location adults proportion adults proportion adults proportion adults proportion Treasure Mountain y 347 055 (.033-. 077)S/ Alberta Lake 61 131 (. 091 - . 171) Colvil le 190 089 (. 041 - . 138) Truj i l lo 1927 .024(.018-.031) ...1/ ... Hannah West 149)^ 634 098(.073-. 122) Hannah East 2955 .063(.054-. 072) 2229 . 130 ( 112-. 848 092(.074-. 110) Davis 812 .026 (.015-.037) 1660 . 117 (. 103-. 131)5/ 3188 .098 ( 089-. 108) 2231 131 (. 119-. 144)5/ B A R Cattle Co . 1008 .052( 035-. 068) Weiler 1083 .017 (.010-.023) 781 .061 (.038-. 085) ... Gjel lum 165 .048 (. 006-. 091) Kolb 1354 .049( 037-. 060) 088)5/ Spurling 2138 .029( 020-. 037) 1875 075 (.062-. Paulson 679 050 (.036-. 064) Wyland 245 029 (. 004-. 053) Be l l 301 030 (.016-. 043) y No counts made at this site during this time period. u Mean (0.95 confidence interval). Tags were placed on pigeons at this site just prior to this time period. 37 241 C H 2410 2 4 0 0 J 110 9 0 8 0 70 60H LU CL >-o LU so o LU QC 40n| LL. 30H 20-1(H h226 493 tei 167 '99 18 14 6 ' 5 0 100 150 2 0 0 250 3 0 0 3 5 0 4 0 0 4 5 0 DISTANCE I N KM F i g u r e 4. F r e q u e n c y d i s t r i b u t i o n of d i s t a n c e s between banding l o c a t i o n and r e c a p t u r e l o c a t i o n f o r C o l o r a d o b a n d - t a i l e d pigeon r e -c a p t u r e s . A l l 5,192 i n d i v i d u a l s r e c a p t u r e d between 1970 and 1975 and banded between 1969 and 1975 a r e i n c l u d e d . C l a s s w i d t h v a r i e s , b a r height i s f r e q u e n c y p e r k i l o m e t e r i n c l a s s w i d t h , a c t u a l c l a s s f r e q u e n c y i s shown above each b a r . 38 ( F i g s . 5-8). Data in these graphs indicate that the high frequency in the z e r o c l a s s of F i g u r e 4 was an a r t i f a c t of sampling. However, there is s t i l l strong evidence that band-tailed pigeons u s e d the same feeding sites over and over. Data presented in the f i g u r e s also indicate that the p r o b a -b i l i t y of r e c a p t u r e was not a smooth function of the distance between the tagging and r e c a p t u r e l o c a t i o n s . F o r example in F i g u r e 5c C o l v i l l e had a s i g n i f i c a n t l y higher (P<0.05) tagged p r o p o r t i o n than Hannah West, yet it was f a r t h e r f r o m the tag site. M o s t s i m i l a r anomalies can be explained b y the i n f e r r e d movement patterns of the bandtails in the study a r e a . F i g u r e 1 shows band-tailed pigeon flight patterns which I i n f e r r e d f r o m the following: our r e c o r d e d sightings of pigeons f l y i n g within the study a r e a , my observations of pigeons f l y i n g to and f r o m feeding sites i n the study a r e a , and r e p o r t s of flight patterns by others f a m i l i a r with p i -geons in the study a r e a . G l o v e r (1953) o b s e r v e d that bandtails often f o l -lowed w a t e r c o u r s e s in their l o c a l movements,, an o b s e r v a t i o n repeated in this study. We a l s o found that pigeons u s e d some of the same flight paths y e a r after y e a r . Pigeons a r r i v e d at the feeding sites in s m a l l groups or singles, but often left in l a r g e groups (20-50 or more) which broke up into p r o g r e s s i v e l y s m a l l e r groups with distance f r o m the feeding si t e . Many s i m i l a r i t i e s in tagged p r o p o r t i o n s at count sites separated by l a r g e distances and d i f f e r e n c e s in tagged p r o p o r t i o n s at count sites separated by s m a l l distances can be explained by pigeon flight paths be-tween nesting a r e a s and feeding s i t e s . The g r a i n f i e l d s northwest of Monte V i s t a were used by pigeons f r o m a much l a r g e r a r e a of breeding 39 0.04-1 0.034 0.02 o.oH o i . a * I 0.0-> r 0.020-0.015-Q 0.010 h-QC Q0.005-|X 5 CL O o.o CC CL Q 0.100-1 UJ O 0.075-1 CD I—- 0.050-| 0.025-0.0J e 1973 COUNTS PROPORTION of ADULTS TAGGED at HANNAH EAST Q. E O a — .95 Confidence Limits X Overall Proportion 1 *r-r "T T 1974 COUNTS PROPORTION of ADULTS TAGGED at HANNAH EAST in 19 73 o u < v- O o r o COUNTS 14 AUG to 18 OCT 1973 PROPORTION of ADULTS TAGGED at WELLER o - * - * T -0.254-,-0.20 0.15H 0.10 0.05 0.0-" If D COUNTS 14 AUG to 18 OCT 1973 PROPORTION of IMMATURES TAGGED at WELLER 20 i • y 0 10 20 30~ 40 50 DISTANCE BETWEEN TAG SITE AND COUNT LOCATION (KM) —i 60 F i g u r e 5. Tagged p r o p o r t i o n s of b a n d - t a i l e d pigeons v s . d i s t a n c e be-tween tagging and counting l o c a t i o n f o r pigeons tagged i n 1973. 40 0.06 0.05-1 0.04 0.03-0.02-0.01-o °-° QC 0.125 o CL Q 0.100-^ * 0.075-I Q LU o CD 0.025 o LU O c o 0.050 0.0-I i i / \ COUNTS 8 JUNE to 24 JUNE 1974 — .95 Confidence Limits X Overall Proportion B i <~ r COUNTS 27 JUNE to 28 JULY 1974 O O) CO J 0.125 0.100-^  0.075H 0.050H 0.025H o.o-J 2 * c -r _ COUNTS 1 AUG to 17SEPT 1974 o Q <5 o S DISTANCE BETWEEN TAG SITE AND COUNT LOCATION (KM) 3~0 i F i g u r e 6. 1974 tagged p r o p o r t i o n s of adult b a n d - t a i l e d pigeons tagged at T r u j i l l o and Hanna E a s t vs. d i s t a n c e between tagging and counting l o c a t i o n s . T h r e e t i m e p e r i o d s a r e shown; u n t i l 24 June tags had been put on on l y at T r u j i l l o . 41 0.10 0.08-0.06-0.04-0.02 0.0-> *6_ A COUNTS 8 JUNE to 24 JUNE 1974 TAGGED PROPORTION of ADULTS — .95 Confidence Limits X Overall Proportion 0.08 ^ 0.06 O p:o.o4 QC o QC o.o-a. '0.02-P0.10-go.08-j2o.06-| 0.04 0.02-0.0-o u • B 2i a. k COUNTS 27 JUNE to 28 JULY 1974 TAGGED PROPORTION of ADULTS o X o u * * r COUNTS 1 AUG to 17 SEPT 1974 TAGGED PROPORTION of ADULTS -i r 0.025-, 0.020 0.015-0.010-0.005-0.0-a. I") COUNTS 1 AUG to 17 SEPT 1974 •1 L / TAGGED PROPORTION of IMMATURES r — ' — # — • — a * - * - 1 1 * — i • 1 . L 0 10 20 30 40 50 60 DISTANCE BETWEEN TAG SITE AND COUNT LOCATION (KM) F i g u r e 7. 1974 tagged p r o p o r t i o n s of b a n d - t a i l e d pigeons tagged at D a v i s v s . d i s t a n c e between tag g i n g and count i n g l o c a t i o n s . T h r e e t i m e p e r i o d s a r e shown. 0.04-, 0.03J A o ° ' 0 U ^ 0-01-1 O o a o J QC 0 * 0.08-, Q CD <tf" 0.04 O) c a 0.02J 0.0. O) c 3 a. c o 3 o o. * * T3 C o Q COUNTS 1 AUG to 17SEPT 1974 TAGGED PROPORTION of ADULTS — .95 Confidence Limits = X Overall Proportion S 3 -•- O C c c C 0 £ 1 | X o a. e C > o 4) cfi COUNTS 1 AUG to 17SEPT 1974 TAGGED PROPORTION of IMMATURES 4) O c c o X I 10 I 20 r * =r-30 40 50 c 3 o 5 o 4> * 1 60 DISTANCE BETWEEN TAG SITE AND COUNT LOCATION (KM) Figure 8. 1974 tagged proportions of band-tailed pigeons tagged at Spurling vs. distance between tagging and counting locations. habitat than any other of the feeding sites in the study a r e a . T h i s is r e f l e c t e d in the tagged p r o p o r t i o n s at Davis being m o r e s i m i l a r to tagged pr o p o r t i o n s at the sites northwest of Monte V i s t a than to tagged proportions at the Hannah sites ( F i g . 7a-d). Pigeons u s i n g the feeding a r e a s n o r t h -west of Monte V i s t a came f r o m both the San Juan Mountains and the L a G a r i t a Mountains, pigeons feeding at Davis came p r i m a r i l y f r o m the P i n o s C r e e k drainage of the San Juan Mountains, while pigeons feeding at the Hannah sites came f r o m the L a G a r i t a Mountains and the South F o r k and m a i n R i o Grande drainages of the San Juan Mountains ( F i g . 1). T h e r e -f o r e , the pigeons tagged at Davis commonly fed at Davis and at sites northwest of Monte V i s t a , but did not often feed at the Hannah sit e s . The s i m i l a r p r o p o r t i o n s of b i r d s tagged at Hannah E a s t and T r u j i l l o in counts at the two Hannah sites and A l b e r t a Lake ( F i g . 6c) probably r e s u l t e d be-cause these sites were s i m i l a r distances f r o m the breeding a r e a s of many of the pigeons tagged at Hannah E a s t and T r u j i l l o . A s i m i l a r explanation is p o s s i b l e f o r the s i m i l a r p r o p o r t i o n s of pigeons tagged at Davis in counts at Davis, A l b e r t a Lake,.and T r e a s u r e Mountain ( F i g . 7c). The s i m i l a r tagged p r o p o r t i o n s at Spurling and B e l l in F i g u r e 8 could be due to both sites being s i m i l a r distances f r o m breeding a r e a s of most pigeons feeding at B e l l . The si g n i f i c a n t d i f f e r e n c e (P< 0.05) between C o l v i l l e and Hannah West in p r o p o r t i o n of pigeons tagged at W e i l e r ( F i g . 5c) seems to be an exception to explanations by flight patterns. A p o s s i b l e cause is that pigeons f r o m the L a G a r i t a Mountains were not feeding at the W e i l e r site 44 during the time of trapping, or at the C o l v i l l e site during counts there. I know that pigeons were feeding at Hannah West during the counts at C o l v i l l e , and I d i d not see pigeons at C o l v i l l e f l y i n g to or f r o m the d i r e c -tion of the L a G a r i t a Mountains. However, I do not know whether p i -geons were coming f r o m the L a G a r i t a Mountains to feed at W e i l e r . Another d i f f e r e n c e d i f f i c u l t to explain by flight patterns is the large d i f f e r e n c e i n tagged proportions between T r u j i l l o and the two Hannah sites i n F i g u r e 5b. It is p o s s i b l e that pigeons feeding at Hannah E a s t during trapping in 1973 and at T r u j i l l o during counting i n 1974 (late May both years) were composed p r i m a r i l y of p r e - n e s t i n g b i r d s which l a t e r d i s -p e r s e d . It is a l s o p o s s i b l e that many of the pigeons seen at T r u j i l l o avoided Hannah West and Hannah E a s t because they a s s o c i a t e d those sites with trapping i n 1973, I have no data to support e i t h e r explanation, but the fact that 31 percent of the adult pigeons trapped at T r u j i l l o on 25 May 1974 in the m o r n i n g sample had active crops,. is. c o n t r a r y to the f i r s t explanation, and the fact that there is no evidence of avoidance of other t r a p sites is c o n t r a r y to the second. To aid in my choice of a drop off point i n frequency of r e c a p t u r e s over distance ( F i g . 4) as an i n d i c a t o r of the feeding range of most band-t a i l s , I used tag sighting data f r o m the intensive study a r e a . Sightings of the same tagged pigeons at sites which were close together were common, as is r e f l e c t e d i n the tagged p r o p o r t i o n s in F i g u r e s 5-8. Unfortunately my study a r e a was not large enough to have any m a j o r count sites m o r e 45 than about 60 k m apart, so I have no good sighting data over distance as evidence of the feeding range of pigeons. Ta b l e XI shows a l l sightings of tagged pigeons which were i d e n t i f i e d at A l b e r t a L a k e and T r e a s u r e Mountain. These sites were s e l e c t e d be-cause they are the farthest f r o m other m a j o r count sites and t r a p p i n g lo c a t i o n s . G i v e n the d i s t r i b u t i o n of count sites and the number of days counts were made at v a r i o u s s i t e s , these data indicate that movements between feeding sites up to 60 k m apart were common enough and clos e enough together i n t i m e to be within the feeding range of many pigeons. F o r example,. BR9 was commonly seen at Hannah E a s t throughout the summer, was seen on the 15th of August at S p u r l i n g and was sighted five days l a t e r at T r e a s u r e Mountain, 59 k m away. WA8 was seen at five d i f f e r e n t feeding sites on the study a r e a , the farthest separated ones being.Kolb and T r e a s u r e Mountain at 58 km, and W e l l e r and T r e a s u r e Mountain at 56 km. WL3 was seen at Davis s i x days before it was seen at T r e a s u r e Mountain, a distance of 40 km. WX4 was seen at C o l v i l l e the day af t e r - i t was seen 29 k m away at A l b e r t a Lake. I used frequency d i s t r i b u t i o n s of distances between C o l o r a d o banding and recapture locations to compare movements of adults to i m -matures, and adult m ales to adult f e m a l e s . Because most immatures were trapped a f t e r 1 August, I used only bandings after that day i n each y e a r f o r the immature-adult c o m p a r i s o n . The r e s u l t s ( F i g . 9) show that i m m a t u r e s had a higher p r o b a b i l i t y of being r e c a p t u r e d at the longer distances and adults had a higher p r o b a b i l i t y at the s h o r t e r distances 46 Table XI. A l l sightings of tagged band-tailed pigeons which were identified at Alberta Lake and Treasure Mountain. T a g 1/ 2/ number—' Sex—' Tagging Date/Site Sightings Date:!/ - Number of Sightings/Site B20 B27 B34 WH5 WX4 B E I BL5 BR9 OR6 WA8 M M M M M 25 June 1974 Hannah East 25 June 1974 Hannah East 1 5 July - 1 Hannah East ] 5 July - 4 Hannah East | 34 km 23 July - 1 5 Sept. - 2 Hannah East Alberta Lake | 34 k m - ' | 5 Sept. - 2 Alberta Lake 25 June 1974 Hannah East 5 August - 1 Alberta Lake 34 km 29 May 1974 Davis 30 July 1974 Davis I 36 km 34 km 11 June - 4 Davis 17 July - 1 Davis 5 Sept. - 2 -Alberta Lake [ 17 June - 2 Davis 26 July - 2 Davis 29 June - 3 B A R Cattle Co . 5 Sept. - 1 Alberta Lake — 36 kr 6 Sept. - 1 Colvil le J 29 km 26 May 1974 Truj i l lo 35 k m 1 3 Sept. - 5 -Hannah West 27 June - 1 Hannah East 23 July - 2 Hannah East | 37 km 25 May 1974 Truj i l lo 28 June - 1 Davis 1 August - 3 Davis | 40 km 29 June - 1 B A R Cattle Co . 20 August - 1 Treasure Mtn. I I 17 July - 2 Davis 1 3 August - 1 Treasure Mtn. ] 35 km J 25 June 1974 Hannah East 15 July - 8 Hannah East 1 5 August - 1 Spurling | 59 km 23 July - 4 Hannah East 20 August - 1 Treasure Mtn. 37 k m 26 May 197 3 Hannah East 22 July - 1 Weiler 6 Sept. - 2 Treasure Mtn. 56 kr 37 km 28 May 1974 Davis 56 km 10 June - 1 I— Welle r 15 July - 6 Hannah East 20 August - 1 L Treasure Mtn. 17 June - 4 Davis 18 July - 1 Kolb 40 km 5 Sept. - 1 Treasure Mtn. J | 37 k m 1 2 Sept. - 2 Hannah West 15 July - 2 Hannah East 56 km 26 July - 4 Davis 2 August - 3 Hannah East 15 Sept. - 1 Treasure Mtn. 28 June - 2 Davis 23 July - 2 Hannah East 58 km 52 km Table XI (Continued). T a g 1/ 2/ numb e r - Sex—' Tagging Date/Site Sightings Date.?./ - Number of Sightings/Site WL3 WM8 WP3 WR1 WT1 WX1 M M M 17 June - 3 Davis 18 July - 2 Kolb 29 May 1974 11 June - 1 Davis Davis 17 July - 2 Davis 14 August - 3 20 August - 4 Davis Treasure Mtn, | 40 km | 29 May 1974 10 June - 2 13 August - 1 Davis Weller Treasure Mtn. | 56 km | 40 k m I 28 June - 2 Davis 26 July - 1 Davis 58 k m ^ 30 July 1974 20 August - 1 Davis Treasure Mtn. | 40 k m | 30 July 1974 Davis | 40 km 1 3 August - 1 Treasure Mtn. 30 July 1974 Davis 30 July 1974 Davis 1 August - 3 Davis | 40 k m 20 August - 3 Treasure Mtn. 1 August - 2 13 August - 3 Davis Treasure Mtn. I 40 km I yFirst letter stands for tag color: B = black, O = orange, and W = white. 2/ — ' A l l tagged pigeons identified at these two sites were adults. 3/ —' A l l sightings were in 1974 except those of OR6 which were in 1973. i / D i stance between sites. 48 48-46 H 44J 26-1 24-i 22-\ 20- | LU 1 H o 14-10H 0 -LEGEND • ADULT (N =793 RECAPTURES) M IMMATURE (N = 495 RECAPTURES) [L IrpJrlrlrlrlrlrB 0 1i"o 1 2 5 2 3 5 341o" % 5iS 67o" 7 s 5 896 T o 6 ^ 1 ^ - V ^ ^ 1 ! f e % - 2 & - l 1 o - 3 & - 3 4 ^ o -DISTANCE IN KILOMETERS F i g u r e 9. R e l a t i v e f r e q u e n c y d i s t r i b u t i o n s of d i s t a n c e s between banding and r e c a p t u r e l o c a t i o n s f o r b a n d - t a i l e d pigeons banded as adul t s and i m m a t u r e s . Includes a l l i n d i v i d u a l s banded a f t e r 1 August i n e a c h y e a r between 1969 and 1975 and r e c a p t u r e d between 1970 and 197 5 i n C o l o r a d o . The two d i s t r i b u t i o n s a r e s i g n i f i c a n t l y d i f f e r e n t ( P < 0.001) by a c h i square t e s t . 49 (1 - 20 km). This is probably due to a stronger tendency of immatures to disperse than adults. Adult males and females had the same probability of being recaptured at longer distances, but females moved further between feeding sites within their feeding range and had a stronger tendency to use the same feeding site repeatedly (Fig. 10). I also used frequency distributions to compare movements of pi-geons recaptured in the year of banding to pigeons recaptured after the year of banding. I excluded the zero distance class from this comparison because trapping took place more often at the same site in the same year than in different years. Recaptures in the same year were distributed more evenly across the short distances (1 - 60 km) and did not occur as often in the middle distances as recaptures in different years (Fig. 11). These differences are likely an artifact of sampling because the sampling distribution of distances between banding sites was not the same each year. The similarity between these two distributions (Fig. 11) is re-markable, considering that the pigeons migrated to Mexico between each summer of trapping. The comparison between years of tagged propor-tions in counts (Figs. 5a and b) is not so similar, but the proportions are quite low. In summary, the results of this section are consistent with the fol-lowing model of band-tailed pigeon feeding behavior: during the nesting season, bandtails are more likely to feed at sites close to nesting areas than far away. They choose between feeding sites at the same distance in the same drainage in a random manner, but once a site has been used 50 4 8 n 46 -44 • 42 J 28 • 26 24 . 22 • h~ 1 8 -s Ol6-cc 12 • 10 • 8 H 2 ^ 0 J LEGEND • MALE (N = 2 2 2 3 RECAPTURES U FEMALE fA/ = 2 1 1 6 RECAPTURES) 0 1 - 1 1 - 2 1 - 3 1 - 4 1 - 5 1 - 6 1 - 71 - 8 1 - 9 1 - 1 0 1 - 1 2 1 - 1 4 1 - 161 - 1 8 1 - 2 0 1 - 2 4 1 - 281- 3 2 1 - 3 6 1 - 4 0 1 - ' 10 2 0 3 0 4 0 5 0 6 0 70 8 0 9 0 100 120 140 160 180 2 0 0 .240 280 320 3 6 0 4 0 0 4 4 0 DISTANCE IN KILOMETERS F i g u r e 10. R e l a t i v e f r e q u e n c y d i s t r i b u t i o n s of d i s t a n c e s between banding and r e c a p t u r e l o c a t i o n s f o r b a n d - t a i l e d pigeons banded as adult m a l e s and adult f e m a l e s . Includes a l l a d u l t s banded between 1969 and 197 5 and r e c a p t u r e d between 1970 and 197 5 i n C o l o r a d o . The d i s t r i b u t i o n s a r e s i g n i f i c a n t l y d i f f e r e n t ( P < 0. 001) by a c h i square t e s t . 51 5 0 -4 8 H 4 6 • 22-1 20 -^ UJ a. 1 4 . 1 0 -8-1 64 2 J 0 J LEGEND • SAME YEAR (575 RECAPTURES) • DIFFERENT YEAR C1798 RECAPTURES) I- 1 1 - 2 1 -10 2 0 3 0 3 1 -4 0 4 1 - 5 1 -5 0 60 rlj J n r l r l r i ^ r » [ l imn i^ 61 - 71 - 81 - 91 70 8 0 9 0 1 0 1 - 1 2 1 - 1 4 1 - 1 6 1 - 1 8 1 - 2 0 1 - 2 4 1 - 2 8 1 - 3 2 1 - 3 6 1 - 4 0 1 -100 120 140 1 6 0 . 180 200 240 280 320 3 6 0 4 0 0 4 2 0 DISTANCE IN KILOMETERS F i g u r e 11. R e l a t i v e f r e q u e n c y d i s t r i b u t i o n s of d i s t a n c e s between banding and r e c a p t u r e l o c a t i o n s f o r adult b a n d - t a i l e d pigeons banded and r e c a p t u r e d i n the same y e a r and banded and r e c a p t u r e d i n d i f f e r e n t y e a r s . Includes a l l i n d i v i d u a l s banded between 1969 and 1975 and r e c a p t u r e d between 1970 and 1975 except those r e c a p t u r e d at the banding s i t e . The d i s t r i b u t i o n s a r e s i g n i f i c a n t l y d i f f e r e n t ( P < 0.001) by a c h i square t e s t . there is a strong tendency to use it again. Bandtails tend to follow water-courses to feeding areas, and feeding areas which require flights across drainages are not as likely to be used as feeding areas which require only a direct flight along a watercourse. Immature band-tailed pigeons are not dispersed randomly among adults at feeding areas in time or space, but they often use the same feeding areas as adults. Immatures are also more likely to disperse to new areas than adults. . Females travel further than males to feed, but are more likely to use one site repeatedly. 53 DISCUSSION C r i t i c i s m of the Data My a s s e s s m e n t of flight paths was based on s c a t t e r e d data f r o m band-t a i l e d pigeon sightings in the study a r e a , not data c o l l e c t e d s p e c i f i c a l l y to show a l l flight patterns. Thus the data are incomplete and may be b i a s e d because most human a c t i v i t y was along roadways, many of which follow drainages. However, repeated observations of pigeon flights in the same places y e a r after y e a r indicate that at least some of the paths habitually used by pigeons were a c c u r a t e l y d e s c r i b e d . F o r example, pigeons were consistently o b s e r v e d c r o s s i n g the highways at the bridge a c r o s s the Rio Grande R i v e r in D e l Norte and at the c r o s s i n g at Citizen's D i t c h west of Monte V i s t a . They were not seen c r o s s i n g at other places nearby on the r e s p e c t i v e highways. Without a l a r g e r study a r e a and a m o re even d i s t r i b u t i o n of the num-ber of counts over distance, the meaning of my data on re sightings of p i -geons with r e g a r d to t h e i r feeding range i s questionable. Because there were no sightings indicating that a pigeon was feeding at one site, then another up to 60 k m f r o m the f i r s t , then back at the f i r s t over a short time i n t e r v a l (Table XI), the b i r d s could have been moving to a new feeding a r e a and not making r e g u l a r long distance movements. I do not think this was the case because droppings containing native b e r r i e s were common at 54 the feeding sites farthest f r o m the mountains. However, to measure band-t a i l e d pigeon feeding ranges adequately it would be d e s i r a b l e to monitor the movements of radio tagged pigeons. T h i s could also provide better data on flight paths and site s e l e c t i o n . T h e r e are s e v e r a l p o s s i b l e p r o b l e m s with my tagged p r o p o r t i o n s . They were low in many cases in Table VI and F i g u r e s 5a and 5b, and in these cases the lack of, or presence of sig n i f i c a n t d i f f e r e n c e s may not be meaningful. E v e n though many ma l e s and females feed at different t i m e s of day (Br a u n et a l . 1975), there were few significant d i f f e r e n c e s in tagged pr o p o r t i o n s f r o m the same day. T h i s may be because the tagged p r o p o r -tions and count s i z e s were not large enough to detect such d i f f e r e n c e s , or the r e s u l t of tags being p l a c e d on pigeons in p r o p o r t i o n to the use of the sites by the sexes in the population. Another p o s s i b l e weakness in the tagged p r o p o r t i o n s r e s u l t e d f r o m not knowing whether some tagged pigeons avoided the trapping a r e a s because they a s s o c i a t e d the sites with trapping. C o m p a r i s o n of tagged proportions at feeding sites which were close to-gether indicates that tagged pigeons d i d not use nearby sites instead, but it is p o s s i b l e they could have avoided a large a r e a around the trap site completely. The high tagged proportions at T r e a s u r e Mountain and A l b e r t a Lake ( F i g s . 6c and 7c) may indicate that this type of avoidance existed. T h i s would r e s u l t in negatively b i a s e d tagged proportions at the trapping s i t e s . Only a s m a l l number of counts were made in n a t u r a l feeding a r e a s ( A l b e r t a Lake and T r e a s u r e Mountain) because they were d i f f i c u l t to locate. If there were individuals in the population which only used natural feeding areas, they would have been neglected in this study. However the high tagged proportions at Alberta Lake and Treasure Mountain may indi-cate that this was not the case. If I were to repeat this study, I would develop a more durable tag so that larger numbers of tags would be retained from one year to another, and I would do trapping and counting over two summers at a similar inten-sity as I did in 1974. Since trapping data can be used to monitor popula-tions from year to year, I really need better data showing the change in tagged proportions over distance from year to year than is shown in Figure 5b. I would also spend more time attempting to locate natural feeding areas so different portions of the population could be identified if they exist. I had hoped to make comparisons between tagged proportions at permanent bait sites and waste grain feeding sites. Because my two permanent bait sites (Davis and Hannah East in 1974) were so far sepa-rated from the waste grain sites being actively used at the same time (Fig. 1 and Table II) these comparisons were not warranted. It would have been desirable to locate permanent bait sites near waste grain feeding sites with enough food to hold pigeons until the bait sites were being actively used. 56 F e e d i n g and F l o c k i n g B e h a v i o r My e s t i m a t i o n that the feeding range of the band-tailed pigeon is on the o r d e r of 60 k i l o m e t e r s i s i n agreement with Braun's (1972) estimate. If the feeding range is this l a r g e , it may be the r e a s o n for observations that pigeons are e r r a t i c i n d i s t r i b u t i o n (Neff 1947) and may have l e d to postulation of nomadic breeding for this species i n some a r e a s ( G u t i e r r e z et a l . 1975). My observations indicate the l o c a t i o n and size of summer feeding f l o c k s i s e r r a t i c , but because of the l a r g e home range, these d i f f e r e n c e s do not n e c e s s a r i l y r e f l e c t e r r a t i c population s i z e s . T h e r e is no documented movement of a summer population of bandtails to a new bre e d i n g a r e a i n response to v a r i a t i o n i n food supply. M a r c h and S a d l e i r (1972) postulated that b a n d - t a i l e d pigeons feeding i n r a i l r o a d y a r d s six k i l o m e t e r s f r o m nesting habitat were not breeding because of the distance and because they fed in f l o c k s . T h i s led them to postulate that breeding did not start u n t i l native foods became available in e a r l y June, but data on cro p a c t i v i t y ( M a r c h and McKeown 1973) i n d i -cated that nesting was underway in late A p r i l and e a r l y May. S i m i l a r reasoning led Neff and N e i d r a c h (1946) to suggest that b r e e d i n g was not yet underway by pigeons s t i l l feeding i n f l o c k s i n e a r l y June. My observations indicate that many of the pigeons feeding in large f l o c k s i n C o l o r a d o have active c r o p s and are nesting, even when the flo c k s are feeding many kilom-eters f r o m nesting habitat. 57 Murton, Coombs, and T h e a r l e (1972) were able to show changes in the size of feeding f l o c k s of f e r a l pigeons (Cohimba l i v i a ) with changes in the amount of food provided. It was my i m p r e s s i o n that the size of feeding f l o c k s of band-tailed pigeons a l s o v a r i e d with the amount of food a v a i l a b l e , but no m e a s u r e of food a v a i l a b i l i t y was made. It would be p o s s i b l e to do so by manipulating a r t i f i c i a l bait sites or by m e a s u r i n g the amount of food at waste g r a i n feeding a r e a s . The habitual use of the same flight paths by bandtails has long been r e c o g n i z e d and u s e d to advantage by hunters ( E i n a r s e n 1953; Neff 1947; M ace and B a t t e r s o n 1961). Because they use common flight paths and feeding a r e a s , some pigeons are often seen together. However, they are also often seen with other pigeons f r o m different a r e a s . Because they a r r i v e at the feeding a r e a s alone or in s m a l l groups, there is no evidence that i n d i v i d u a l s f l o c k together in a cohesive s o c i a l unit, The f l o c k s appear to be aggregations caused by common use of feeding a r e a s . B r a u n (1972) postulated the existence of d i s c r e t e subpopulations of pigeons in C o l o r a d o based upon p r e l i m i n a r y a n a l y s i s of banding and r e -capture data. M y data indicate that interchange between sites d e c r e a s e s with distance, but there is no i n d i c a t i o n of d i s c r e t e boundaries between subpopulations. B a s e d on this and p r e v i o u s work with the C o l o r a d o r e -capture data, I think Braun's subpopulation d i v i s i o n s are an a r t i f a c t of his d i s t r i b u t i o n of sampling points and incomplete knowledge of feeding s i t e s . T h e r e a r e some int e r r u p t i o n s i n b a n d - t a i l e d pigeon d i s t r i b u t i o n in C o l o -rado where d i s c o n t i n u i t i e s i n pigeon habitat occur, but these are 58 scattered. Braun's c o n c l u s i o n that management of bandtails can be done by a r e a because of the s m a l l interchange between areas i s v a l i d , but the d i v i s i o n of a r e a s should be based on human v a r i a b l e s such as land use, hunting p r e s s u r e and l o g i s t i c s of management operations. However, popu-lations of f e r a l pigeons a r t i f i c i a l l y r educed in l o c a l i z e d areas were r a p -i d l y r e p l a c e d by i m m i g r a n t s (Murton, T h e a r l e , and Thompson 1972) and the fact that bandtails often move long distances ( F i g . 4) indicates that they might r e a c t s i m i l a r l y , M u r t o n et a l . (1971) present data indicating that flock feeding in the wood pigeon (Columba palumbus) causes some ind i v i d u a l s i n the f l o c k to have a higher s u r v i v a l p r o b a b i l i t y by having higher feeding e f f i c i e n c y . They suggest that a s o c i a l h i e r a r c h y exists in which c e r t a i n m e m b e r s of the flock are subordinate and when food becomes l i m i t i n g , they leave the fl o c k , feed alone, and t h e i r s u r v i v a l chances d e c r e a s e . T h i s work was done in winter, and since food is much more abundant in summer and wood pigeons feed alone or in s m a l l f l o c k s (Murton 1965) it apparently does not apply then. S o c i a l competition for food in f l o c k s has a l s o been proposed for f e r a l pigeons (Murton, Coombs and T h e a r l e 1972). Though I made no observations of competitive behavior in this study, the finding that i n d i -v iduals trapped at sites u p s t r e a m with li t t l e food were h e a v i e r , o l d e r , and had m o r e active c r o p s than i n d i v i d u a l s t rapped downstream at sites with l a r g e amounts of food might indicate competition f o r food i n this s p e c i e s . P a s t studies showed that the sex of pigeons in C o l o r a d o t r a p samples during the breeding season averaged 68 percent male p r i o r to 1000 h r s . , 64 59 percent female between 1000 and 1600, and equal p r o p o r t i o n s after 1600 (Brau n et a l . 1975). T h i s diffe r e n c e is probably because the male i n c u -bates and broods the eggs and nestli n g s between about 1000 and 1700 and the female does so during the evening, night, and e a r l y m o r n i n g (Neff and N i e d r a c h 1946; P e e t e r s 1962). Thus d u r i n g this part of the b r e e d i n g cycle i n C o l o r a d o the female has one p e r i o d of roughly seven hours to feed and the male has two per i o d s of roughly four hours each. P e r h a p s the longer continuous time p e r i o d available f o r females to feed explains the l a r g e r feeding range of females in this study. In agreement with my r e s u l t s , previous authors r e c o g n i z e d that the p r o p o r t i o n of immature band-tailed pigeons in counts, t r a p samples, and hunter bag samples was not n e c e s s a r i l y r e p r e s e n t a t i v e of o v e r a l l popula-tion c omposition ( B r a u n et a l . 1975; G l o v e r 1953; M a r c h and Sa d l e i r 1972; Fit z h u g h 1974; S i l o v s k y 1969; Smith 1968). On the West Coast a lower i m -mature p r o p o r t i o n was obse r v e d during the f a l l hunting season in Oregon and C a l i f o r n i a than i n winter in C a l i f o r n i a ( M a c G r e g o r and Smith 1955; Smith 1968). F i t z h u g h (1974) ob s e r v e d a lower p r o p o r t i o n of older imma-ture s in f a l l hunter samples than h i s e a r l i e r trap samples had suggested should be present i n the population. D i f f e r e n t i a l m i g r a t i o n of adults and immatures has been suggested as one reason for these d i f f e r e n c e s ( B r a u n et a l . 1975; SiloVsky 1969; Smith 1968). G l o v e r (1953) suggested that the decrease in immature p r o p o r t i o n i n C a l i f o r n i a f l o c k s which he obse r v e d in the f a l l may have been due to adults t e r m i n a t i n g nesting and joining the f l o c k s . M a r c h and S a d l e i r (1972) observed that the k i l l of i m m a t u r e s at 60 m i n e r a l springs on the West Coast was low and suggested this was due to the i r lower m i n e r a l need. B r a u n et a l . (1975) ob s e r v e d that immature pro p o r t i o n s were higher in the hunter wing survey than in trap samples. They suggest that the diffe r e n c e is due to a higher p r o b a b i l i t y of imma-ture s being shot than adults, but this is c o n t r a r y to my finding that imma-ture p r oportions were lower in hunter bags than in the f l o c k s . E s t i m a t i o n of Population P a r a m e t e r s Because band-tailed pigeon densities in C o l o r a d o are low, because feeding flock s i z e appears to v a r y with the clumping of food supply, and because both fl o c k s and i n d i v i d u a l s are d i f f i c u l t to locate, d i r e c t counts are not valuable as an estimate of population density. The r e s u l t s of this study have shown that due to spatial v a r i a t i o n in tagged p r o p o r t i o n s and our lack of knowledge of the land a r e a f r o m which pigeons at a. feeding a r e a are drawn,, c a l c u l a t i o n of population densities using m a r k and r e c a p t u r e techniques would be d i f f i c u l t . T h e r e f o r e a good e s t i m a t o r of pigeon den-sity i n C o l o r a d o is s t i l l not a v a i l a b l e . I recommend that the J o l l y - S e b e r (Seber 1973) m a r k and r e c a p t u r e technique be u s e d only as an index to population si z e f o r management purposes in C o l o r a d o , The assumption of the J o l l y - S e b e r technique that is d i f f i c u l t to satisfy with bandtails is that a l l b i r d s , whether m a r k e d or unmarked, have the same pr o b a b i l i t y of being captured (Seber 1973). Because of the de-c r e a s e in tagged p r o p o r t i o n s with distance f r o m the trap site and the v a r i a t i o n i n feeding f l o c k l o c a t i o n and size f r o m y e a r to y e a r , it would be difficult to devise a system for monitoring the banded proportion in a study area. Even when it is possible to trap at the same site year after year, variation in the availability of food supplies and flock size may mean that the feeding flock is being drawn from a different size breeding range each year. If a population estimation method is developed which allows the probability of recapture to decrease with distance at a known rate and mortality and birth to occur, it would be possible to compute a probability of recapture curve from Colorado recapture data and use it to estimate population densities in areas where several different trap sites were used each year. Because recapture tagged proportions decrease with distance from the banding site, using banding information from trapping at two or more sites will result in biased Jolly-Seber estimates. The bias will increase in general with increasing distance between the trap locations used, but the amount and type of bias will be highly variable depending upon tem-poral variation in the use of the same sites. For example, consider two sites used for trapping in a three year program. The sites are spaced at such a distance that the probability of recapture of an individual at site 2 which was tagged at site 1 is half the probability of recapture at site 1. The opposite applies to an individual tagged at site 2. Otherwise assume that: sampling is random with respect to tagged and untagged individuals, a constant number of individuals are trapped and released each year (400), survival probability is constant (0. 5), probability of a live tagged indi-vidual being trapped at the same site is constant (0. 2), and survival and capture probabilities are equal among all individuals, A set of banding data and Jolly-Seber population estimates for four trapping sequences under these assumptions are shown in Table XII. In case A the data are unbiased and the estimates are unbiased. In case B the estimated sur-vival rate and estimated number of marked individuals alive are half their true values, the estimated number of animals joining is one and one half times as large as it should be, and the population size and probability of capture are unchanged. The effect is much more drastic and all population parameters are estimated incorrectly in case C. In case D the estimates of total marked and survival probability are unbiased but . both population size and number joining are one third again as large as in case A. From this example it is clear that the amount of bias in Jolly-Seber estimates is highly dependent on temporal variation in the use of two or more trap sites. The safest procedure for getting reasonable esti-mates is to use the same site each year. For the Jolly-Seber estimation technique to be used as an index to yearly variation in population parameters of band-tailed pigeons in Colo-rado, I recommend that certain precautions be taken during trapping. Trapping should be done at the same site (or sites less than 5 km apart) to prevent a decrease in the probability of retrap due to distance from the trap site. In order to accomplish this it may be necessary to use artificial bait sites or specially planted grain field feeding sites. Flight patterns of the pigeons using the trapping area each year should be monitored to give an idea of the size of the range from which the population is being drawn. Table XII. Capture data and J o l l y - S e b e r estimates of population parameters to show the effects of usin g two t r a p locations under four different time schedules. Banding data were constructed assuming a constant number of individuals captured, random sampling, and constant proba-b i l i t i e s of s u r v i v a l (0. 5) and recapture (0.2) for a l l individuals,except that the p r o b a b i l i t y of re c a p t u r e at one site of in d i v i d u a l s banded at the other site is half of n o r m a l . Banding Data E s t i m a t e s of Population P a r a m e t e r s T r a p Number caught and Recaptures by yea r of last capture T o t a l P o p u l a -S u r v i v a l proba- Number Capture proba-Case lo c a t i o n Y e a r r e l e a s e d 1 2 m a r k e d tion size b i l i t y j oining b i l i t y A 1 1 1 1 2 3 400 400 400 40 16 40 200 2000 . 50 1000 . 20 B 1 2 2 1 2 3 400 400 400 20 8 40 100 2000" .25 1500 .20 C 1 2 1 1 2 3 400 400 400 20 18 20 380 7600 .95 380 .05 D Both Both Both 1 2 3 4 0 0 ^ 400 400 30 12 30 190 2533 .48 1330 . 16 y 200 an i m a l s caught and r e l e a s e d at each site during each y e a r . 64 Because of differences in behavior patterns, immature populations should be estimated separately. Either trapping should be done throughout the day to get representative samples of each sex, or separate population esti-mates should be made for each sex. Trapping should be done only over a time period of a few days each year at each site to prevent the birds from learning trap avoidance and to satisfy the assumption of instantaneous sampling (Seber 1973). Tables XIII and XIV give capture data and estimates of population parameters for adult band-tailed pigeons trapped at one site near Long-mont, Colorado. Al l of the above recommendations were followed except that trapping took place over a two to three month time period in some years and flight patterns were not monitored. Because the area from which pigeons were drawn might have varied from year to year, the change in estimates of population size might not be indicative of changes in population densities. If flight patterns of pigeons coming to and leaving this feeding site had been monitored, there would be some indication of the proper interpretation of the estimates. The Jolly-Seber technique also gives estimates of survival proba-bility (1 - (mortality + emigration)) and number joiningfbirth -f immigra-tion) (Table XIV), therefore these will be available for the small areas where Jolly-Seber estimation is used. It is also possible to estimate survival rates over a large area using hunter kill recoveries of banded pigeons. To use band recoveries it is necessary that all pigeons have the Table XIII. Capture data for adult band-tailed pigeons trapped and banded at Longmont, C o l o r a d o . Number Number Recaptures by Y e a r of L a s t Capture Y e a r caught r e l e a s e d 1970 1971 1972 1973 1974 1970 324 304 1971 303 300 36 1972 258 257 25 43 1973 . 167 166 4 11 30 1974 162 162 3 5 7 15 1975 189 186 3 3 10 8 14 Table XIV. J o l l y - S e b e r estimates of population p a rameters for adult band-tailed pigeons captured and banded at Longmont, Colorado. S u r v i v a l Standard E r r o r of P r o p o r t i o n T o t a l Population p roba- Numbe r Population S u r v i v a l Number Y e a r m a r k e d m a r k e d size b i l i t y joining size p r o b a b i l i t y joining 1970 0 .68 . 11 1971 . 12 205 1728 .48 27 364 .08 162 1972 .26 227 860 .65 442 150 . 15 162 197 3 . 27 269 997 • 79 87 5 243 .26 379 1974 • 19 308 1661 548 197 5 . 20 66 same s u r v i v a l and r e c o v e r y rate (Seber 197 3). Because of the l i k e l i h o o d of lower s u r v i v a l rates and different p r o b a b i l i t i e s of being shot i n imma-t u r e s , immature bandings should not be used i n such c a l c u l a t i o n s . The n e c e s s i t y that a l l pigeons have the same r e c o v e r y rate i m p l i e s that hunting must be random with r e g a r d to banded b i r d s . Banding p r o g r a m s should be planned with this objective in mind. Because of the d i f f e r e n c e s i n immature proportions among sites and time s of day, because of different p r o b a b i l i t i e s of imm a t u r e s and adults appearing in the hunter bag, and because only four to eight t r a p samples are n e c e s s a r y to t r a p 400 band-tailed pigeons, it would be d i f f i c u l t to ob-tain c o r r e c t e s t imates of f a l l i m mature pr o p o r t i o n s by routine trapping or hunter bag checks. F o r example, depending on whether trapping had been done at Hannah West or P a u l s o n i n September 1974 ( C o l v i l l e didn't have enough pigeons to w a r r a n t trapping), the daily immature p r o p o r t i o n of pigeons u s i n g the t r a p site would have v a r i e d between 0.25 and 0.47 de-pending on which site was used ( F i g . 3). And, the h o u r l y v a r i a t i o n at Hannah West on 13 September i n counts of over 50 pigeons was 0.20 to 0.35 while at P a u l s o n on 14 September it was 0.37 to 0.63. T h e r e f o r e the immature p r o p o r t i o n could have v a r i e d between 0.20 and 0.63 de-pending upon the site and time of day used for a trap sample. The f a l l i m m ature p r o p o r t i o n can best be e s t i m a t e d for an a r e a f r o m separate population e s timates of adults and immatures. However, if behavior d i f f e r e n c e s disappear by winter it might be pos s i b l e to estimate the imma-ture p r o p o r t i o n s in winter populations using trap samples. 67 L I T E R A T U R E C I T E D A m e r i c a n Ornithologist's Union. 1957. C h e c k - l i s t of N o r t h A m e r i c a n b i r d s . 5th ed. L o r d B a l t i m o r e P r e s s , B a l t i m o r e . 691 p. Box, G.E.P., and G. M. Jenkins. 1970. T i m e s e r i e s a n a l y s i s : f o r e -casting and c o n t r o l . Holden-Day, San F r a n c i s c o . 553 p. Braun, C. E . 1972. Movements and hunting m o r t a l i t y of C o l o r a d o band-t a i l e d pigeons. T r a n s . N. Am. "Wildl. Nat. Resour. Conf. 37: 326-334. . 1973. D i s t r i b u t i o n and habitats of band - t a i l e d pigeons i n C o l o -rado. P r o c . West. A s s o c . State Game F i s h Comms. 53:336-344. . 1976. Methods f o r locating, trapping and banding band-tailed pigeons in C o l o r a d o . Colo. Div. W i l d l . Spec. Rep. 39. 20 p. , D. E . Brown, J . C. P e d e r s o n , and T. P. Zapatka, 1975. Resul t s of the F o u r C o r n e r s cooperative band-tailed pigeon i n v e s t i -gation. U..S. F i s h W i l d l . Serv. R e sour. P u b l / 126. 20 p. Brownlee, K. A. 1965. S t a t i s t i c a l theory and methodology in science and engineering. 2nd ed. John Wiley & Sons, New Yo r k . 590 p. D i l l , H. H. , and W. H. T h o r n s b e r r y . 1950. A cannon-projected net trap for capturing waterfowl. J . W i l d l . Manage. 14:132-137. E i n a r s e n , A. S. 1953. P r o b l e m s of the band - t a i l e d pigeon. P r o c . West. A s s o c . State Game F i s h Comms. 33:140-146. Evans, J . 1972. Ba n d t a i l pigeon trapping techniques i n A r i z o n a . A r i z . Game F i s h Dept. F e d . A i d P r o j . W-53-R-22, Work P l a n 3 Job 5, Spec. Rep. 20 p. F i s h e r , R. A., and F. Yates. 1963. S t a t i s t i c a l tables for b i o l o g i c a l , a g r i c u l t u r a l , and m e d i c a l r e s e a r c h . 6th ed. - Hafner,.New York. 146 p. Fitzhugh, E . L. 1974. Chronology of c a l l i n g , egg layin g , c r o p gland a c t i v i t y , and bre e d i n g among w i l d band-tailed pigeons i n A r i z o n a , Ph.D. T h e s i s , Univ. A r i z . , Tucson. 74 p. 68 G l o v e r , F. A. 1953. A nesting study of the band-tailed pigeon (Columba f. fasciata) in n o rthwestern C a l i f o r n i a . C a l i f . F i s h Game 39: 397-407. Goodwin, D. 1967. Pigeons and doves of the world. B r i t i s h Museum, London. 446 p. G u t i e r r e z , R. J . , C. E . Braun, and T. P. Zapatka. 1975. Reproductive biology of the band-tailed pigeon in C o l o r a d o and New Mex i c o . Auk 92:665-677. 2 Haldane, J.B.S. 1945. The use of X as a test of homogeneity i n a (nx 2)-fold table when expectations are s m a l l . B i o m e t r i k a 33:234-238. Houston,. D. B. 1963. A contribution to the ecology of the b a n d - t a i l e d pigeon, C o l umba f a s c i a t a , Say. M.S. T h e s i s , Univ. Wyo. , L a r a m i e . 74 p. Je f f r e y , R. G. , C h a i r m a n . 1977. Ba n d - t a i l e d pigeon (Columba fas c i a t a ). P ages 210-245. i n G. C. Sanderson, ed. Management of m i g r a t o r y shore and upland game b i r d s in N o r t h A m e r i c a . International A s s o c i a t i o n of F i s h and W i l d l i f e A g e n c i e s , Washington, D. C. K u c h l e r , A. W. 1964. P o t e n t i a l n a t u r a l vegetation of the conterminous United States. Am. Geogr. Soc. Spec. P u b l . 36. 116 p. Mace, R. U., and W. M. Batt e r s o n . 1961. Resu l t s of a band-tailed pigeon banding study at Nehalem, Oregon. P r o c . West. A s s o c . State Game F i s h Comms. . 41:151-153. M a c G r e g o r , W. G. , and W. M. Smith. 1955. Nes t i n g and r e p r o d u c t i o n of the band-tailed pigeon i n C a l i f o r n i a . C a l i f . F i s h Game 41:315-326. M a r c h , G. L. , and B. A. McKeown. 1973. S e r u m and p i t u i t a r y p r o l a c t i n changes in the band-tailed pigeon (Columba fasciata) in r e l a t i o n to the r e p r o d u c t i v e c y c l e . Can. J . P h y s i o l . P h a r m a c o l . 51:583-589. , and R.M. F. S. S a d l e i r . 1970. Studies on the b a n d - t a i l e d pigeon (Columba fasciata) in B r i t i s h Columbia. I. Seasonal changes in gonadal development and c r o p gland a c t i v i t y . Can. J, - Z o o l . 48: 1353-1357. ,. and . 1972. Studies on the band-tailed pigeon (Columba fasciata) in B r i t i s h Columbia. II. Food r e s o u r c e and m i n e r a l - g r a v e l l i n g a c t i v i t y . Syesis 5:279-284. 69 M i l l e r , W. J . , and F. H. "Wagner. 1955. Sexing mature C o l u m b i -f o r m e s by c l o a c a l c h a r a c t e r s . Auk 72:279-285. Murton, R. K. 1965. The wood-pigeon. C o l l i n s , London. 256 p. , C . F . B . Coombs, and R. J . P. T h e a r l e . 1972. E c o l o g i c a l studies of the f e r a l pigeon Columba l i v i a v a r . II. F l o c k behavior and s o c i a l o r ganization. J . Appl. E c o l . 9:875-889-, A. J . Isaacson, and N. J . Westwood. 1971. The s i g n i f i c a n c e of g r e g a r i o u s feeding behavior and a d r e n a l s t r e s s in a population of wood-pigeons Columba palumbus. J . Z o o l . 165:53-84. „ R.J.P. T h e a r l e , and J . Thompson. 1972. E c o l o g i c a l studies of the f e r a l pigeon Columba l i v i a v a r . I. Population, b r e e d i n g biology, and methods of c o n t r o l . J . A p p l . E c o l . 9:835-874. Neff, J . A. 1947. Habits, food, and economic status of the band-tailed pigeon. U.S. F i s h W i l d l . Serv. N. Am. F a u n a 58. 76 p. 1951. Inventory of band-tailed pigeon populations in A r i z o n a , C o l o r a d o , and New Mexico: 1951. U.S. F i s h W i l d l . Serv., Denver W i l d l . Res. Lab. Rep. (Nov. 1951). 37 p. , and R. J . N i e d r a c h . 1946. Nesting of the band-tailed pigeon in C o l o r a d o . Condor 48:72-74. P e e t e r s , H. J . 1962. Nuptial behavior of the band-tailed pigeon in the San F r a n c i s c o B a y a r e a . Condor 64:445-470. Reeves, H. M. , A, D. G e i s , and F. C. K n i f f i n . 1968. M o u r n i n g dove capture and banding. U.S. F i s h W i l d l . Serv.. Spec. S c i . Rep.-W i l d l . 117. 63 p. Ridgway, R. 1916. The b i r d s of N o r t h and Middle A m e r i c a . U.S. N a t l . Mus. B u l l . 50(7). 543 p. Robinson, A. H. , and R. D. Sale. 1969. E l e m e n t s of cartography. 3rd ed. John Wi l e y & Sons, New Y o r k . 415 p. Seber, G.A. F. 1973. The e s t i m a t i o n of a n i m a l abundance and r e l a t e d p a r a m e t e r s . Hafner, New Y o rk. 506 p. Silovsky, G. D. 1969. D i s t r i b u t i o n and m o r t a l i t y of the P a c i f i c C o a s t band-tailed pigeon. M.S. T h e s i s , Oreg. State Univ. , C o r v a l l i s . 70 p. 70 Smith, W. A. 1968. The band-tailed pigeon in C a l i f o r n i a . C a l i f . F i s h Game 54:4-16. Snedecor, G. W. , and W. G. C o c h r a n . 1967. S t a t i s t i c a l methods. 6th ed. Iowa State Univ. P r e s s , Ames. 593 p. White, J . A. 1973. Molt of C o l o r a d o band-tailed pigeons. M.S. T h e s i s , C o l o. State Univ. , F t . C o l l i n s . 34 p. Z e i g l e r , D. L . 1971. C r o p - m i l k c y c l e s i n band-tailed pigeons and l o s s e s of squabs due to hunting pigeons i n September. M.S. T h e s i s , Oreg. State Univ., C o r v a l l i s . 48 p. Typed and Reproduced by T Y P E - I N K F o r t C o l l i n s 

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