Recording flight calls of migrating birds with one or more microphones provides information on identity of some birds aloft over each microphone and on the time course of their migration, or at least their calling. Doppler surveillance radar observations, on the other hand, provide information on the numbers and sizes of flying animals aloft over a wide area and on speeds, directions of travel, and height in favorable circumstances. Comparison of calls of Dickcissels (Spiza americana) from sound recording stations across south Texas in spring with images from the KBRO NEXRAD (WSR-88D) radar operated by the National Weather Service showed a surprising correspondence between the two kinds of data, both temporally over the course of a night and geographically across about 115 km. Highly significant correlations between call rates and radar reflectivity were obtained for seven sound recording stations but not for two other stations that were too distant for the radar to receive echoes from birds migrating at the normal heights for passerines.

The number of visits parents make to their nest during chick rearing is a commonly used measure of the amount of food delivered to nestlings and an index of the quality of parental care. Use of the number of visits for these purposes assumes that parents feed nestlings when they visit and that there are no systematic differences in the amount of food delivered on each visit. These assumptions were tested in Tree Swallows (Tachycineta bicolor) breeding in nest boxes near Ithaca, New York. Video observations of parents inside their nest boxes showed that parents feed nestlings on 95–98% of visits to the nest. An average visit delivered 18.1 insects with a total dry mass of 24.1 mg, usually to a single nestling. Although females visited more frequently, the load they carried on each visit was not different than that carried by males. Load size did not differ with nestling age, brood size or the date of the feeding. Overall, there were few systematic differences in load size among nests. Therefore, the number of visits to the nest is a good measure of food delivery and parental care in Tree Swallows.

Seasonal variations in occurrence of the Blue-and-yellow (Ara ararauna), Red-and-green (A. chloroptera), and Scarlet (A. macao) Macaw were evaluated in the floodplain rainforest of the Manu Biosphere Reserve, southeast Peru. One-hour surveys of macaws were conducted while traveling along the Rio Manu in a motorized canoe during both the dry and rainy season. There was a significant three-fold decline in the number of macaws encountered during the dry season compared to the rainy season. Encounter rates also varied significantly among macaw species, and may be due to behavioral characteristics or habitat preferences of species. Rapid or short-term surveys used to establish trade quotas and the status of species may be susceptible to biases and inaccuracies resulting from seasonal variations and behavioral characteristics of psittacine species.

We describe a lightweight, portable, and inexpensive field aviary that was designed for observing Northern Bobwhite (Colinus virginianus) vigilance and feeding behavior. The general construction details of this aviary are easily modified to accommodate a variety of bird species and research objectives.

Golden Eagles (Aquila chrysaetos) were banded as nestlings, migrants, wintering birds, and resident breeders in three states of the U.S. Rocky Mountain West between June 1973 and January 1999. To January 2000, 6.2% of 325 eagles banded had been encountered as dead or injured birds or live captures. Median age of all encounters was 2.25 yr. Sex ratio of Golden Eagles encountered was not different from sex ratio at banding. Eagles banded as migrants were encountered less frequently than those banded as nestlings, residents, or wintering eagles. Cumulative exponential distribution analysis of recoveries (dead eagles) by age indicated 50% of banded eagles were dead by 2 yr, 7 mo, 75% by age 5 yr, 1 mo, and 95% by 11 yr, 1 mo, with a maximum predicted age of 33 yr, 10 mo. Distance from banding to encounter site was <90 km for 90% of encounters, and all encounters of eagles banded as nestlings were within 200 km of their natal nest. Mean vector bearing of all encounters was 92.95°. Rayleigh tests for uniformity indicated encounters showed no directional bias, but only 22% of all encounters were westward. No encounters occurred on the slope of the Continental Divide opposite from banding. The largest proportion (40%) of Golden Eagles encountered died of unknown causes, and eagles less than one-year old may suffer the highest mortality rate. Considering the minimal contribution of recent nestling banding to the understanding of Golden Eagle demography and natural history, conservation and management of the species may be better served by focusing on more productive methods of research (color-marking, radio-tagging) rather than simply banding nestlings.

The ability to accurately determine age of nestlings is useful in studies of reproductive performance of small birds. Because of a resurgence of interest in nest-box studies of reproductive performance of Prothonotary Warblers (Protonotaria citrea), we closely monitored the growth and development of 766 nestlings from 190 nests over the 1999 and 2000 breeding seasons. Distinguishing characteristics of known-age warbler nestlings are provided, including mass measurements, aspects of plumage development, and behavioral notes in sufficient detail that investigators can determine the age of young Prothonotary Warblers with only one or two visits to a given nest.

Snowy Plovers (Charadrius alexandrinus) are small, partially migrant shorebirds that are broadly distributed across North America. Snowy Plover distribution west of the Rocky Mountains has been well described. However, distribution and abundance east of the Rocky Mountains has not received much attention despite current status and ESA listing concerns for Snowy Plovers in the southeastern United States and the Caribbean. Thus, a first step in developing a monitoring program for Snowy Plovers is to understand the species' distribution. We summarize information on distribution and abundance of Snowy Plovers in the eastern United States, Caribbean, and Bahamas. Breeding and winter distribution maps for the continental United States were generated from a database of 3563 records from 388 sites in continental North America constructed from International Shorebird Survey (ISS), Christmas Bird Count (CBC), unpublished field data, and published accounts. Comparison of maximum counts per site (1980–present) indicated the number of breeding Snowy Plovers was greatest in Kansas and Oklahoma, while the greatest number of wintering birds occurred in the Laguna Madre of Texas and Mexico. Snowy Plovers concentrate at sites in Oklahoma and Texas during migration, with higher concentrations on the upper Texas coast in spring compared to fall migration. Data regarding historic abundance and trends are limited but suggest that Snowy Plovers in the eastern United States may have experienced regional population declines and may have suffered a range contraction in Texas. Serious concerns about the conservation status of Snowy Plovers in the eastern United States, the Caribbean, and the Bahamas indicate an immediate need for systematic surveys and up-to-date population estimates.

We compared the results of point-count and mist-net surveys during the breeding and post-breeding seasons in four Missouri Ozark habitats: mature upland forest, mature riparian forest, 9- to 10-yr-old upland forest and 3- to 4-yr-old upland forest created by clearcutting. We determined whether differences in abundance estimates among habitats or between breeding and post-breeding seasons varied with survey method (i.e., habitat × method, season × method, or habitat × season × method interaction effects). The habitat × method interaction was significant for 13 of 16 species. The general pattern was for canopy or sub-canopy species to be detected by point counts more often in the mature-forest habitats, and to be detected by mist nets more often in the young-forest habitats. The season × method interaction was significant for 6 species largely because there was a greater decrease from breeding to post breeding season in mist-net captures than point-count detections. Two species had a significant habitat × season × method interaction. Differences in the patterns in abundance among habitats and between seasons, by survey method, are indicative of bias in the survey methods. Individuals planning bird surveys should recognize these biases and select the method that best samples the segment of the community they are surveying and that is least likely to confound treatment effects. Often this may require the use of multiple survey methods.

An Egyptian Nightjar (Caprimulgus aegyptius) specimen was salvaged on 5 September 2000 from the landing gear of a DC-10 airliner that had landed at Langley Air Force Base, Virginia. The bird likely collided with the plane during its stop the previous day in Kuwait City, Kuwait, within the typical range of this nightjar. This incident illustrates the importance of proper documentation of specimens and shows that aircraft transport of avian specimens can occur.

Using museum specimens from Mexico, Canada, and the western United States, we examined sexual dimorphism in the Wilson's Warbler (Wilsonia pusilla), a Nearctic-Neotropic migrant (Passeriformes: Parulidae). On average, males had longer tails, wing chords, and eighth and ninth primaries than females. Three methods for quantifying cap plumage showed that differences in cap size and pattern alone could not definitively separate the sexes. Discriminant functions are presented for sexing individuals using cap category, cap length, wing chord, tail length, and ninth primary length. More specific functions are provided for samples from Alaska and eastern Mexico. For each group, equations are included for assigning individual probabilities of belonging to either sex.

The Bridled White-eye is a little known species endemic to the Mariana Islands in the tropical Pacific. Based on observations of social behavior and on movements of color-banded individuals, I evaluated which of four flocking strategies the Bridled White-eye appeared to use: (1) group territoriality, (2) permanent membership flocks, (3) site-dependent flocks, and (4) temporary flocks. Banded birds declined in frequency of occurrence from a single banding site and exhibited no clear defense of territorial boundaries. Many banded birds remained in the study area for up to 14.5 mo. Small groups of at least three birds were family groups, although larger groups of ca. 50 birds also foraged together and then dispersed into smaller flocks. Plotted resightings of individual banded birds suggested that home ranges of individuals were overlapping. These observations led to the conclusion that the Bridled White-eye exhibited flocking characteristics intermediate between permanent membership and site-dependent flocks.

It has been suggested that the cohesion of mixed species flocks relies heavily on conspicuous species that act as an attractive nucleus for other birds. I evaluated the role of the White-flanked Antwren as a nuclear species in mixed-species flocks of gallery forests of eastern Colombia, and tested experimentally the hypothesis that the conspicuous wing-flashes of males contribute to interspecific cohesion. Although most of the species present in my study site showed a high propensity to flock heteroespecifically, interspecific associations of the White-flanked Antwren tended to be short. The white flanks of male White-flanked Antwrens were not critical for maintaining a particular number of species inside the flocks, for spacing out the individuals in the interspecific groups, or for prolonging the duration of the interspecific associations. The wing-flashes of the White-flanked Antwren provide an example of how assumptions about nuclear roles in species with conspicuous traits may lead to wrong conclusions about the dynamics of mixed-species flocking. My results suggest that although this antwren may be important for recruiting new members in forest flocks, it does not promote the maintenance of those associations.

Lesser Antillean Bullfinches Loxigilla noctis were observed opening packets of sugar on the grounds of a hotel on the west coast of Barbados. We presented closed sugar packets at 40 sites in 10 areas on the west coast, near the site where opening was originally observed, to determine whether the foraging behavior was locale-specific. Bullfinches only touched, opened, and fed from sugar packets at the original opening site, suggesting that the behavior pattern was specific to that location.

Griffon Vultures (Gyps fulvus) are responsible for most cases of usurpation of nests of Bearded Vultures (Gypaetus barbatus). However, little is known about how both species interact during reproduction. We studied territorial behaviour during the breeding season in four Bearded Vulture pairs in the eastern Pyrenees of northeastern Spain. Frequency of agonistic behavior was positively correlated with Griffon Vulture colony size. However, no significantly higher frequency of aggressive interactions was found that suggested actual competition for nest sites between these species. Nonetheless, Bearded Vulture pairs maintained a continuous defence of the area immediately surrounding their nests throughout the breeding season. Our data suggest that the Bearded Vulture's territorial behavior was more closely associated with defence of breeding space than with specific defence of actual nest sites.

We observed foraging behavior and success of gulls (Larus spp.) at spawning runs of eulachon (Thaleichthyes pacificus; Osmeridae) in Berners Bay, Alaska, in spring 1996–1998. Adults foraged more effectively (≥56% of dives were successful) than immatures (≤56%) when diving for fish, but there was little difference in the effectiveness of piracy (≤23% success for all gull species and age classes). The hypothesis that larger birds would be better pirates and less likely to lose prey to pirates was not well supported, although smaller species seldom attacked larger ones. Age classes less successful at foraging were more likely to act as pirates, but this relationship did not hold among species or between years. The frequency of piracy attempts was positively correlated with the availability of fish captured by other birds.

We examined predation rates on natural and artificial Common Wood-Pigeon (Columba palumbus) nests with camouflaged cameras, with uncamouflaged cameras, and without cameras in Villatobas, Central Spain. Total daily nest survival probability was considerably higher in uncamouflaged-camera nests than in the two other types of nests, while there were no differences between the camouflaged-camera and the control nests. Survival probability of natural nests was similar to that of camouflaged-camera and control nests and significantly lower than that of uncamouflaged-camera nests. Any significant differences among nest types applied only to predation by Black-billed Magpies (Pica pica); predation rates by the garden dormouse (Elyomis quercinus) were similar in all experimental treatments. The results suggest that the presence of an uncamouflaged camera can affect Black-billed Magpies, which may become wary and avoid nests equipped with uncamouflaged cameras. The influence of photographic equipment on predation intensity in different species is an important factor that should be taken into account in studies using artificial nests. The use of control nests is recommended to evaluate the potential effects of the camera.