Although adult plumage in Cooper's Hawks (Accipiter cooperii) exhibits little or no sexual dichromatism, iris color reportedly changes from yellow or light orange in younger birds to shades of orange or red in older birds, especially in males. However, there is little quantitative data on this phenomenon. It has been suggested that male eye color may serve as a signal of age and hence reproductive fitness and thus offer a basis for nonrandom mating in Cooper's Hawks. In this study we examine the relationships between eye color and age, sex, and reproductive output for Cooper's Hawks in two breeding populations in British Columbia and North Dakota, 1999–2002, and compare these results to those previously published for a breeding population in Wisconsin, 1980–1995. Cooper's Hawks in British Columbia and North Dakota appear to acquire darker orange or red irides more frequently and more quickly than their counterparts at known and relative ages in Wisconsin. Females in all study sites are slower and less likely than males to acquire the darkest eye colors. Eye color is not a reliable predictor of age in individual male and female Cooper's Hawks, for researchers and perhaps for the birds themselves, because individual hawks of a given eye color displayed variation in known and relative ages in British Columbia and Wisconsin. There was no significant relationship between the eye color of males and their brood sizes in any of these three populations, and therefore no discernable support for the premise that male eye color per se signals male fitness, or functions as a sexual trait for assortative mating in this species.

We observed a male sparrow in May 1999 in Stow, Massachusetts, that showed hybrid characteristics resembling both Grasshopper Sparrow (Ammodramus savannarum) and Savannah Sparrow (Passerculus sandwichensis). During 1999 and 2000, this male sang a simplified Song Sparrow (Melospiza melodia) song. However, in 2001 it also sang a typical Savannah Sparrow song and frequently alternated between these two songs. We recorded songs and captured this individual in an area with numerous Song Sparrows and about three pairs of Savannah Sparrows. We compared mitochondrial DNA, morphological measurements, behavior, and audio spectrograms of this hybrid with similar data from Grasshopper, Savannah, and Song sparrows. Genetic analysis indicated that the hybrid's mother was almost certainly a Grasshopper Sparrow. The hybrid showed morphological traits that were within the range of both Savannah Sparrow and Song Sparrow, but generally were more consistent for Savannah Sparrow. We observed this individual frequently associating with Savannah Sparrows, attempting to copulate with a female Savannah Sparrow, carrying Savannah Sparrow fecal sacs, and feeding young Savannah Sparrows, lending additional support to Savannah Sparrow paternity. We conclude that this individual was a Grasshopper × Savannah sparrow hybrid that learned to imitate the songs of Song Sparrows at an early stage of development. Interestingly, the hybrid's exposed culmen was considerably longer than culmen measurements of any of the three species of sparrows under consideration.

We studied White-throated Jacamars (Brachygalba albogularis) at Manu National Park, Peru, finding a mean population density of 0.8 groups per km of suitable streamside habitat, and taking the first recordings of its song. Observations at nests provided the first evidence of cooperative breeding in the genus Brachygalba, as well as information on foraging tactics, prey selection, and provisioning behavior.

Female song rarely has been examined in suboscines. This paper describes the context and structure of female Least Flycatcher (Empidonax minimus) songs. During two years, we observed 4 of 19 females singing, and although singing occurred infrequently, it occurred predominantly at the nest during incubation and brooding. Analysis of five songs from one female showed that the mean of this female's songs fell below the distribution of male songs for the internote interval, the minimum and maximum frequency, the frequency range, and the frequency at maximum amplitude of the first note of the two-note song. These results differ from other studies showing no sex differences in song structure of tyrannid flycatchers, suggesting further analyses of female song are warranted.

Male Gambel's Quail (Callipepla gambelii) have strikingly ornate plumage. Yet, captive experiments indicate that removing multiple ornaments does not necessarily alter patterns of female mate choice or male-male competition. To test these unexpected results, I observed a wild population of banded quail for three seasons to determine ornamental and body size traits associated with pairing date and winners of male contests. I also documented mating behaviors (e.g., pairing date, mate fidelity, brood size). Consistent with captive studies, male mass, rather than ornate plumage, was the primary feature related to winners of male contests and early pairing. Heavier males paired earlier, regardless of age, but did not exhibit significantly larger ornaments. Adults of both sexes were heavier and paired earlier than yearlings. Early pairing also correlated positively with brood size, suggesting that heavy, early nesting birds experienced greater fitness. Mating behaviors were flexible across seasons. Social monogamy decreased from 83% in 1996 to 30% in 1998, while polygamy (sequential, long term pairings) increased, particularly among yearlings and adult males. Adult females were equally likely to exhibit social monogamy or polygamy each season. They also exhibited the highest frequency of early pairing and the greatest keel scores (a general measure of condition), suggesting their capacity for breeding was high. At least two adult females abandoned their first mate after hatching and re-paired, in an apparent attempt to double brood.

White Terns (Gygis alba) are common in the northwestern Hawaiian Islands, but in the main Hawaiian Islands they are found only on Oahu, where they are listed as threatened by the State of Hawaii. I censused the White Tern population on Oahu from October 2001 to January 2003, and I investigated breeding success and seasonality during monthly visits to four sites. I observed a total of 694 adult White Terns on Oahu, of which approximately 500 (72%) were breeding birds. Active nests were present during all months, but most eggs were laid from January to April (65%), with a peak in egg laying during March (22%). Nest success was 74%, and pairs produced a mean of 0.98 fledglings/year. One pair fledged successive young less than three months apart. The incubation period at one nest was 35 days, and the fledging periods at two nests were 43 and 47 days. The White Tern population on Oahu has increased from a single breeding pair in 1961 to approximately 250 pairs in 2002, a growth rate of 14% per year. White Terns on Oahu exist entirely in urban and suburban areas, and their reproduction is not inhibited by the numerous predators and sources of disturbance.

I reviewed Greater Sandhill Crane (Grus canadensis tabida) reproductive success at Malheur National Wildlife Refuge in southeastern Oregon, 1966–1989, during which time predators were removed in 12 years and not removed in 12 years. Of 1,024 comparable crane nests found in those years, compared to those during nonremoval years, nests during years when some predators were removed had greater nesting success, more young fledged/100 pairs, lower mortality rates of young, and higher annual recruitment rates. The most important limiting factor for cranes at Malheur NWR was low annual recruitment resulting primarily from predation on eggs and prefledged young. Coyotes (Canis latrans) were the primary predator on eggs and young, but in some years Common Ravens (Corvus corax) and raccoons (Procyon lotor) took a large number of eggs.

Studies using artificial nests to assess rates or patterns of nest predation have increased during recent decades. However, the critical assumption that temporal or spatial patterns of relative predation rates of artificial nests parallel those of natural nests has begun to be questioned. We compared the daily survival rate for 365 artificial nests with that estimated for 295 open nests of passerines, and analyzed the trends in survival rates for both nest types among three breeding seasons and three species of nest plants in the central Monte Desert, Argentina. Daily survival rate for artificial nests (0.737) was significantly lower than that for natural nests (0.925). Trends in survival rates of artificial nests over years and among species of nest plants only partially reflected those of natural nests. Our results support the well established finding that artificial nests may not accurately estimate actual rates of nest predation. Artificial nests may provide an additional source of data to natural nests when testing ecological hypotheses, but artificial nest experiments should be carefully designed (i.e., realistic) and should attempt to identify predators of artificial and natural nests to validate the experimental results.

Until recently, little information was available on patterns of brood parasitism by Brown-headed Cowbirds (Molothrus ater) in the southeastern United States, a region into which cowbirds expanded their range only during the last half of the Twentieth Century and where their abundance is relatively low. We compiled parasitism data from several published and unpublished studies conducted in Georgia and South Carolina from 1993–2000 to examine levels of brood parasitism and determine frequent host species. The combined dataset included 1,372 nests of 24 species reported in the literature to have been parasitized by cowbirds. The parasitism rate on all species combined was 8.2%. Considering only those species that served as hosts in these studies (n = 12), the parasitism rate was 9.3%. Seven species were parasitized at rates ≥10%. Based on the extent of parasitism (among studies and locations), their relative abundance, and the sample size of nests, Prairie Warblers (Dendroica discolor), Hooded Warblers (Wilsonia citrina), Yellow-breasted Chats (Icteria virens), and Indigo Buntings (Passerina cyanea), all shrub nesters, appear to be the most important cowbird hosts in the region. Parasitism on some species reported as frequent hosts elsewhere was extremely low or not documented. We conclude that the impact of brood parasitism on the seasonal fecundity of hosts in the region probably is minimal, but additional work is warranted on species of concern, such as the Painted Bunting (Passerina ciris).

We studied nest site selection by Semipalmated Plovers (Charadrius semipalmatus) to compare microhabitat characteristics at nest and random sites, and to compare successful and unsuccessful nests on the northern shore of Akimiski Island, Nunavut, during 2002. Nesting birds selected sites with more pebbles and less vegetative cover than randomly available in the environment. Nest sites also had smaller percentage of bare mud than random sites. Plovers selected sites within 100 m of Arctic Terns (Sterna paradisaea) more often than expected based on the distribution of random sites in the study area. Twenty-three of 41 (56%) nests hatched successfully. None of the microhabitat features that we measured predicted nest success. All 10 nests near the colony of Arctic Terns hatched, suggesting that interspecific associations are more reliable than habitat features for predicting nest success.

I examined short and long term responses of breeding bird communities to the systematic creation of early successional habitat resulting from forest management at a 1,120-ha study site in the Ridge and Valley Province of Pennsylvania, from 1998 through 2002. Species richness and abundances of all species combined and of early successional species increased from precut (1998–1999) to postcut eras (2001–2002) in a treated sector (aspen, Populus spp., and mixed oak, Quercus spp., areas combined), an uncut control sector, and the total study site (treated and control sectors combined) after the fourth cutting cycle. Abundances of a woodland species (Red-eyed Vireo, Vireo olivaceus) and four early successional species (e.g., Field Sparrow, Spizella pusilla) also increased. Over the past 15 years, which spans the third and the fourth cutting cycles at the study site, three woodland species increased significantly in both treated and control sectors (Red-eyed Vireo) or in the treated sector only (Ovenbird, Seiurus aurocapillus, and American Redstart, Setophaga ruticilla). The population of an early successional species (Indigo Bunting, Passerina cyanea) increased significantly in both treated and control sectors. Population trends of three woodland and three early successional species at the study site paralleled statewide or provincial increases in these species over the past two decades. My study has shown that the management of early successional habitats in extensively forested areas will be of benefit for the long term conservation of both early successional and mature forest bird species within a forested landscape.

The White-backed Woodpecker (Dendrocopos leucotos) is one of the rarest European woodpeckers and its populations have declined markedly during the last century in many European countries. The objective of our study was to investigate the selection of nesting and feeding trees by the subspecies D. l. lilfordi, a field not previously investigated. We conducted this study in a mountain area of central Italy characterized by wide and homogeneous tracts of beech- (Fagus sylvatica) forested slopes. The rate at which we detected the species was highly correlated with the mean trunk dbh of the stand; the more mature the stand, the greater the number of woodpecker detections. The White-backed Woodpecker was dependent upon trees that were mature, dead, or in an advanced degree of decay for both nesting and foraging. The habitat specialization of the species suggests that forest stand management should promote longer harvesting rotations, preserve dead and decaying trees, create new foraging sites, and prevent excessive fragmentation of forested landscapes.

We studied the diet of Imperial Cormorants (Phalacrocorax atriceps) and Rock Shags (P. magellanicus) at Bahía Bustamante, Argentina, between 1992 and 1994. We analyzed pellet casts (1887 from Imperial Cormorants and 799 from Rock Shags) and regurgitations of stomach contents (260 from Imperial Cormorants and 24 from Rock Shags). Imperial Cormorants and Rock Shags fed on at least 22 and 21 different types of prey, respectively. The main prey species during all study years were fish: Engraulis anchoita for Imperial Cormorants and Patagonothen sp. for Rock Shags. For both species, the consumption of the main food categories as estimated by pellet analysis was similar among years. A significant relationship was found between Imperial Cormorant and Rock Shag diets during the three years, while the diet overlap index was relatively high. During all years, Imperial Cormorants consumed a significantly larger proportion of pelagic or demersal fish than did Rock Shags, while Rock Shags consumed benthic fish in a greater proportion than did Imperial Cormorants. Mean maximum diving depth, determined using capillary tube depth gauges, of Imperial Cormorants (24.4 m ± 18.8 SD) was significantly greater but more variable than that of Rock Shags (9.3 m ± 4.1 SD).

Communal roosts are important resources for local populations of the Black Vulture (Coragyps atratus), but these roosts are increasingly becoming the focus for complaints of wildlife damage. We studied movements of Black Vultures between communal roosts in Florida using mark-resight methods. We marked 416 Black Vultures with patagial tags at two communal roosts in Orange County, Florida. A total of 1,245 resightings of 226 individuals were recorded over a 3-year period. Black Vultures made one-way movements between communal roosts of up to 152 km, and two-way movements (i.e., birds left a site and subsequently returned) between communal roosts of up to 144 km. Patterns of resightings indicated that some Black Vultures use several roosts over wide geographic ranges during parts of their lives. Long distance exchanges between roosts and high nightly turnover of membership at roosts leads to concerns that control of nuisance Black Vulture roosts has the potential to impact nontarget populations in a geographic area well beyond a given communal roost.

We trapped 994 hawks during spring migration in years between 1953 and 1972. We obtained sufficient numbers to comment on age or sex differences, or both, in the timing of migration of six species. Adults migrated earlier in most species, presumably because most adults but few juveniles breed. Adult male Sharp-shinned Hawks (Accipiter striatus) migrated significantly before adult females and the larger (presumably female) Red-tailed Hawks (Buteo jamaicensis) migrated significantly earlier than smaller individuals. Juvenile female Sharp-shinned Hawks and Cooper's Hawks (A. cooperii) migrated before males, probably because more juvenile females than males breed.

We compared the definitive prebasic molt schedules of Yellow Warblers (Dendroica petechia) at two northern temperate breeding sites: the Vermont Institute of Natural Science (Vermont) in Woodstock, Vermont, and North Point (James Bay) on the southwestern coast of James Bay, Ontario. The two sites are separated by 8° of latitude. Yellow Warblers initiated molt significantly earlier in Vermont than at James Bay, with respective mean onset dates of 29 June and 20 July, but durations and rates of molt did not differ significantly between populations at the two sites. Mean individual molt durations spanned 44.5 days in Vermont and 40.0 days at James Bay. Molt rate of females differed significantly between the two sites, but male rates were similar. Based on number of primaries growing simultaneously, Yellow Warblers in both Vermont and James Bay appear to undergo a rapid and intense molt. The earlier and slightly more protracted molt of Yellow Warblers in Vermont may result from their earlier spring arrival and longer breeding season.

We documented the breeding behavior and diet of a Philippine Eagle (Pithecophaga jefferyi) pair from July 1999 to January 2000 in an isolated forest in Central Mindanao. We observed eight distinct courtship displays and several activity patterns on the nest. Copulation started two months prior to egg laying and continued until the first month of incubation, with a mean of 1.5 copulations per day. Seventy-four percent of the time devoted to incubation was by the female. The incubation period lasted 58 days. Throughout the incubation and early brooding phases the male provided food for the female and the young. Diet consisted of 17 prey items of four vertebrate taxa, mostly mammals, with civet cats (Family Viverridae) and flying lemur (Cynocephalus volans) representing the bulk of the diet.

We observed a young male Red-cockaded Woodpecker (Picoides borealis) about 35 days old being fed by adults associated with a neighboring territory. A survey of biologists studying this species revealed similar acts of adoption had been observed elsewhere, but the behavior appeared to be very rare. Adoption generally implies a cost to adults because care is provided to unrelated young, but the situation is complicated in cooperative breeders such as the Red-cockaded Woodpecker. Adopted birds can help breeding adults raise additional young, and the adopted male we observed remained as a helper in its adopted territory and fed young the following breeding season.

I observed a population of White-winged Trumpeters (Psophia leucoptera) in undisturbed lowland moist forest in Peru. During 2,460 h of focal observations, I observed one instance of infanticide that occurred when a permanent group killed the 7-day-old chick of an intruding group that was using a portion of its territory. Trumpeter groups defend large, year round, contiguous territories that barely provide groups with enough food to meet their caloric requirements during the dry season when fruit abundance is low. There may be a selective advantage to such infanticidal behavior if it helps prevent the formation of a new group on a resident group's territory, and the concomitant loss of space that would accompany such an event.

We evaluated the moisture-facilitated nest depredation hypothesis in a semiarid environment in the Southern High Plains of Texas during 1999 and 2000. Scaled Quail (Callipepla squamata) provided an excellent model species for this evaluation because they typically suffer significant nest mortality and inhabit semiarid to xeric environments. We monitored 102 nests until they either hatched or were predated. Nest mortalities occurred on 30 days and precipitation fell on 51 days during the two-year study. Stepwise logistic regression revealed a predictive relationship for a model with central precipitation on the day of nest predation as a predictor. However, in contrast to our predictions, the equation indicates precipitation is negatively associated with nest predation in this data set. Thus, our data do not support the moisture-facilitated nest depredation hypothesis for Scaled Quail in the semiarid, Southern High Plains of Texas.

The Cave Swallow (Petrochelidon fulva), first discovered breeding in Texas in 1915, originally was thought to be confined to sinkholes in central and western Texas. During our survey of bridges in Brazos County, Texas, we discovered Cave Swallows modify and use old Barn Swallow (Hirundo rustica) nests, a previously unreported behavior. The presence of Barn Swallows (or old Barn Swallow nests) may facilitate colonization of new areas by Cave Swallows.

We observed a Yellow-crowned Night-Heron (Nyctanassa violacea) with its belly partly submerged in water, rapidly swaying its body laterally while holding its head and most of the extended neck still above the water. This behavior was observed several times with “Stand and Wait, Walk Slowly, Stand and Wait” foraging among three episodes of the “Submerge and Sway” mode. This body swaying motion appeared to flush out a frog that the heron captured during the second episode.