To investigate molts and ornamental-plume development in herons and egrets, we examined 448 specimens of 10 North American species. We found no evidence for a prealternate molt, despite widespread opinion that such a molt occurs and includes the ornamental plumes. Our data indicate that these plumes emerge during the later stages of the definitive prebasic molt in August–November, grow slowly through January– February, and are retained until replacement during the following prebasic molt. The preformative (traditionally termed “first-prebasic”) molt shows substantial variation in extent. In 91.9% of 86 first-year individuals collected between November and May, this molt included the development of ornamental plumes that were similar in form, but shorter in length, than those of adults. Male Great Blue (Ardea herodias) and Little Blue (Egretta caerulea) herons developed longer ornamental plumes than females, presumably a result of sexual-selection strategies.

There are few records of functionally female birds exhibiting partial to total male plumages. On 26 March 2004, we collected a female Brown-headed Cowbird (Molothrus ater) at Fort Hood, Texas, with a presumably functional ovary and whose back and belly exhibited the glossy, greenish-black plumage typical of after-hatch-year males. This individual is a unique specimen because (with the exception of partial albinism) no aberrant plumages have been reported for Brown-headed Cowbirds.

Proportions of juvenile birds in migrant populations at coastal stopover sites are often higher than proportions of juveniles at inland stopover sites, a phenomenon called the “coastal effect.” The northern Great Plains forms the western boundary of the migratory ranges for many Neotropical woodland migrants. Moreover, woodland habitat is scarce in this region, consisting primarily of natural riparian corridor woodlands (hereafter corridors) and planted woodlots and shelterbelts around farmsteads and agricultural fields (hereafter woodlots). Due to the scarcity of woodland habitat, one might expect that adults—by virtue of their experience and better-developed navigational abilities—would avoid the Great Plains during fall migration, thus producing age structures in migrant populations similar to those found at coastal sites. We tested this “inland coast” hypothesis for Neotropical migrants captured during fall migration at corridor and woodlot stopover sites in southeastern South Dakota. We classified migrants into three groups based on whether our South Dakota study sites were peripheral (western edge of migratory range within South Dakota), near-peripheral (western edge in, or just west of, Wyoming or Montana), or central (western edge well west of Montana and Wyoming) to their regular migratory ranges. We captured higher juvenile proportions of peripheral (86.5 ± 10.4%, 2 species) and near-peripheral (85.6 ± 4.5%, 7 species) migrants than central migrants (79.6 ± 7.2%, 5 species), but the difference was not significant (P = 0.11). The proportion of juveniles was inversely correlated with the distance of our study sites from the western edge of a given species' migratory range (r = 0.476, P = 0.085). The proportion of juvenile Neotropical migrants at our study sites was near the upper end of proportions recorded for other inland sites in North America, but was slightly lower than those recorded at coastal sites. Our results are, therefore, only partially consistent with the inland coast hypothesis, suggesting that factors other than geographic location also shape age structures at our study sites. The mean proportion of juveniles (for species captured ≥13 times in both habitats; n = 10) was significantly greater (P = 0.002) in the woodlot (89.1 ± 7.0%) than in corridors (73.8 ± 12.5%). The differential age structure in the two habitats suggests that habitat characteristics may influence age structure of the migrant community, but mechanisms for such an influence are currently unknown.

We examined selection of grit-ingestion sites by Black Brant (Branta bernicla nigricans) on South Humboldt Bay, California in relation to particle size and calcium content. We hypothesized that Brant site selection was dependent primarily upon calcium content and secondarily upon distribution of substrate particle size. We (1) mapped grit-ingestion sites, (2) ranked their importance by Brant abundance and individual movement probabilities between sites, (3) characterized Brant gizzard grit and compared it with grit available at ingestion sites, and (4) compared calcium content and particle-size distribution between ingestion sites and unused sites, and between primary and secondary ingestion sites. Brant repeatedly congregated at specific, discrete sites during the 2 years of observation. The distribution of gizzard-grit particle size was right-skewed toward larger particles (>0.5 mm) relative to the proportional availability of particle sizes in the substrate. We found no significant differences in calcium content or particle size between sites where grit was ingested and unused sites. Within used sites, the calcium content of substrates at the primary ingestion site was significantly higher than at the secondary ingestion sites, as ranked by Brant abundance and between-site movement probabilities. Our findings from the field corroborate previous laboratory results, and confirm that calcium is a significant ecological factor for this species.

Clearcutting is the preferred timber harvest method in bottomland hardwood forests because it is most likely to result in regeneration of preferred species. However, clearcutting generally has negative impacts on forest birds. Patch-retention harvesting may provide similar silvicultural benefits, but its effects on birds are unknown. We surveyed breeding birds in uncut control, clearcut, and patch-retention treatment areas (11–13 ha) for one season prior to harvest and two seasons postharvest in a bottomland hardwood forest in the Lower Coastal Plain of southeastern South Carolina. Bird observations recorded along line transects were analyzed using the software EstimateS to estimate species richness and program Distance to estimate densities. We found greater species richness and bird densities in the patch-retention treatment than in the clearcut in both postharvest seasons. We detected no forest-interior birds in the clearcut after the harvest, but by the second postharvest season in the patch-retention treatment, the density of forest-interior birds had returned to approximately half of its preharvest level. Thus, based on density response, patch-retention harvesting appears to be less detrimental to forest birds than clearcutting. However, additional work is needed to determine whether retained patches influence avian survival and productivity.

We examined the relationship of trends in fall–spring mass of 330 Northern Bobwhites (Colinus virginianus) with photoperiod, air temperature, energy requirements, and supplemental feeding in the Texas Panhandle during 2000–2003. Mass of bobwhites increased from September to December, at which point it peaked and then decreased through March. Mean monthly mass was negatively correlated with photoperiod (r =−0.89) and temperature (r =−0.79) and positively correlated with energy required (r = 0.79; estimated using air temperature). From September to March, bobwhites occupying areas where supplemental feed was provided (n = 246) were greater in mass (x̄ = 193.4 g, 95% CL = 191.6–195.1) than bobwhites in areas without supplemental feed (x̄ = 186.5 g, 95% CL = 184.0–189.0, n = 84), but mean monthly mass was different only during November (x̄ = 197.8 g, 95% CL = 195.3–200.3 for food-supplemented; x̄ = 188.0 g, 95% CL = 185.0– 191.0 for unsupplemented). Abiotic factors, such as photoperiod and temperature, are confounding factors when attempting to explain fall and winter trends of bobwhite mass. Temporal changes in activities (daily foraging, nocturnal roosting) and their energetic costs (e.g., thermoregulation) also complicate issues of trends in mass.

Data on historical extinction and current endangerment in non-passerine birds were used to assess associations between vulnerability to human impacts and genus size, range size, and insular endemism. Consistent with the results of previous studies, historical extinction was more frequent in species from monotypic genera, even when other factors were controlled for statistically. By contrast, current endangerment showed no such pattern when other factors were controlled for. Both historical extinction and current endangerment were more frequent in species with restricted ranges and for insular species. Moreover, insular species with restricted ranges were especially vulnerable to current endangerment. Changes between the patterns of historical extinction and current endangerment are likely due to changes in the nature of human impacts over the past 500 years, especially the recent trend toward wholesale habitat destruction.

Although offspring delay dispersal past the age of independence in many Thryothorus species, cooperative breeding has not been recorded in this genus. Here, I present the first observation of cooperative breeding in a Thryothorus wren (Buff-breasted Wren, T. leucotis). Of 41 offspring that delayed dispersal past the age of independence, 4 individuals stayed on their natal territory until their parent's next breeding attempt, indicating a low potential for cooperative breeding. Of these four individuals, one male provisioned 11- to 15-day-old nestlings and one female approached her parents' nest but was repeatedly driven away from it by her father. The retained female was apparently tolerated when in the vicinity of fledglings, but feeding was never positively confirmed.

Little is known about the breeding biology of Bridled White-eyes (Zosterops conspicillatus), especially the federally endangered Rota Bridled White-eye (Z. c. rotensis). Here, we report on the breeding behavior, nest-site characteristics, and nest dimensions of Rota Bridled White-eyes. From 1997 to 1999, we found 20 Rota Bridled White-eye nests in Elaeocarpus joga (35%), Hernandia labyrinthica (30%), Merrilliodendron megacarpum (20%), and introduced Acacia confusa (15%) trees between 320 and 460 m in elevation. Nests were 2.5–12.8 m above the ground (n = 18) in trees 3.3–14.6 m tall (n = 16). Clutch size ranged from one to two eggs (n = 7) and the breeding season was from at least December through August. Nest dimensions (n = 4) were 36–44 × 57.7–60.8 mm (outer height × diameter) and 25–29 × 44.6–47.7 mm (cup depth × diameter).

We quantified the diet of the Chilean Hawk (Accipiter chilensis) by analyzing 495 prey remains collected during two breeding seasons (2001–2002 and 2002–2003) in an Andean Nothofagus forest of Nevados de Chillán, northern Patagonia. The diet was almost exclusively birds (97.8% of all prey remains), with relatively few rodents (1.6%) and insects (0.6%). At least 19 vertebrate species composed the prey remains (1 small mammal and 18 bird species), with Austral Thrush (Turdus falcklandii), White-crested Elaenia (Elaenia albiceps), Black-chinned Siskin (Carduelis barbata), Fire-eyed Diucon (Xolmis pyrope), and Thorn-tailed Rayadito (Aphrastura spinicauda) being the most common. All identified vertebrate prey are known to use forest habitats; 47% (n = 9) are forest specialists. Prey that inhabit both forest and shrublands accounted for 82% of the remains, and 18% of prey remains were of forest specialists. Our results indicate that during the breeding season, Chilean Hawks in Nevados de Chillán are pre-eminent, bird-eating predators that feed primarily on forest-dwelling birds.

For 4 consecutive evenings in southern Nicaragua, a group of three Yellow Tyrannulets (Capsiempis flaveola) roosted in the same plant, and always arrived approximately 45 min before last light. Pre-roosting behavior appeared stereotyped and included mutual preening and a peculiar manner of hopping over one another. These three birds presumably left the roost around first light each morning.

A Red-tailed Hawk (Buteo jamaicensis; estimated mass 1,000–1,200 g) failed to kill a Red-breasted Merganser (Mergus serrator; estimated mass 1,150 g) that it captured in shallow water (<25 cm), but evidently dispatched a starving Red-necked Grebe (Podiceps grisegena; mass 645–660 g). These observations are pertinent to estimating the upper mass limit for successful foraging in water.

We observed an adult Gray Jay (Perisoreus canadensis) that had captured an adult Black-capped Chickadee (Poecile atricapillus) in Algonquin Provincial Park, Ontario, Canada, during winter. Aerial pursuit of small, adult birds and an instance of capture and predation of a juvenile bird by a Gray Jay have been reported previously. Here, we present the first documented case of capture of a seemingly uninjured, adult bird.

A number of authors have qualitatively described the songs of Vermilion Flycatchers (Pyrocephalus rubinus) given during flight display, but no spectrograms or quantitative analyses are available. We present such a description based on displays of 14 different males. Our analysis confirms the impressions of earlier authors that the flight song is closely similar to that given by perched birds, but also revealed an important difference: most flight display songs also included an extra element known as the peent vocalization. The peent is also an alarm call, given during male-male and male-female interactions, as well as during foraging bouts. Besides reporting on the common use of peent vocalizations by perched Vermilion Flycatchers, we now describe the frequency and use of peent vocalizations in flight display songs.