bluuebunny/crossref_metadata_2025_split huggingface dataset:
Use of Two Song Categories by Golden-Cheeked Warblers
Authors: Bolsinger Jeffrey S. 
Published: September 2019

Abstract
I tape-recorded and counted the songs of color-banded Golden-cheeked Warblers (Dendroica chrysoparia) on Fort Hood, Texas in 1993 and 1994 to determine whether males use a two-category song system common to many wood-warbler species. More than 97% of all songs I documented belonged to two categories: A and B. A songs were higher in frequency, shorter, less complex, and were delivered at lower rates than B songs. Males used A songs primarily early in the nesting season, when near females, and from the interior of territories. In contrast, B songs were more common later in the nesting season, at dawn, and when males sang near territory boundaries. Songs delivered near territory edges were usually sung from one or two preferred perches on each male's territory that often coincided with the edge of a cliff or a break in the forest canopy. Based on these data, and in contrast to the implications of an early account of Golden-cheeked Warbler song use, this species shares the song system used by many wood-warbler species. Furthermore, the patterns of song use that I observed suggest that males do not sing randomly with respect to time or location on territory, and monitoring efforts that assume random singing across time and space may result in inaccurate or biased estimates of population sizes and habitat preferences.
The Diet of the Magnificent Frigatebird During Chick Rearing
Authors: Calixto-Albarrán Itzia , Osorno José-Luis 
Published: September 2019

Abstract
We describe the diet of the Magnificent Frigatebird Fregata magnificens at Isla Isabel off the Pacific coast of Mexico based on 158 regurgitates (555 prey items) from males, females, chicks, and juveniles. The diet included 50 species of fishes (21 identified to genus only), 1 species of squid, and 2 species of crustaceans. Diplectum pacificum and Anchoa lucida were the most frequent species of fish in the frigatebird's diet. No differences in prey composition or prey size were found between males and females, but females disgorged 62% more food. This difference mirrors the bigger size (15% larger than males) and larger contribution of females to chick feeding. Flying juveniles consumed prey in different proportions than the adults and disgorged marginally more food. Juveniles may obtain food in different patches than adults and complement this source with maternal feedings, or they may be more likely to regurgitate. Diet composition of males, females, and flying juveniles changed during the 4-month period of this study, but the mass of regurgitates did not change as the breeding season progressed, suggesting that availability of prey species changes over time. Most of the diet of this population probably comes from opportunistic feeding on fisheries, because the variety of fishes disgorged is remarkably similar to the published list of fishes discarded by prawn-fishing boats in the area. If our assumption is true, kleptoparasitism and direct fishing are only marginally represented in the diet of this population.
Nocturnal and Diurnal Foraging Activity of Hawaiian Albatrosses Detected With a New Immersion Monitor
Authors: Fernández Patricia , Anderson David J. 
Published: September 2019

Abstract
We used a new immersion monitor to study the foraging movements of two species of albatrosses that nest in the Hawaiian Islands. The monitors showed that breeding male Black-footed Albatrosses (Phoebastria nigripes) land on the water more frequently during the day than at night. Breeding male Laysan Albatross (Phoebastria immutabilis) behavior was more variable and also showed a diurnal bias. We found no evidence of a nocturnal foraging bias in either species; in particular, these species do not seem to be limited to live capture of nocturnally available squid. Such squid may, nonetheless, contribute to the diet as a result of scavenging.
Effects of Forest Fragment Size and Successional Stage on Mixed-Species Bird Flocks in Southeastern Brazil
Authors: Maldonado-Coelho Marcos , Marini Miguel Â 
Published: September 2019

AbstractWe analyzed patterns of species richness, size, structure, and composition of mixed-species flocks in relation to forest fragment size and forest successional stage during dry and rainy seasons, at the state of Minas Gerais, southeastern Brazil. Three forest fragments (1.7, 50, and 200 ha) were used for fragment size analysis, and two fragments (200 and 300 ha) were used for successional stage analysis. Fragment size and season affected flock richness, size, stability, and composition. In the 1.7-ha fragment, flock species richness, size, and stability were significantly different only during the rainy season. Fragment successional stage also influenced flock richness and size, although season did not. Flock composition also had changes related to fragment successional stage. Fragment geometry seems to be an important factor influencing flock structure and composition.
The Spatial Response of Male Hooded Warblers to Edges in Isolated Fragments
Authors: Norris D. Ryan , Stutchbury Bridget J. M. , Pitcher Trevor E. 
Published: September 2019

AbstractWe tested whether Hooded Warblers (Wilsonia citrina) avoided abrupt forest edges by radiotracking males breeding in small, isolated forest patches (0.5–2.0 ha) in northwest Pennsylvania. Because territory edges were synonymous with abrupt forest edges in all cases, we compared space use patterns with males radiotracked in a nearby continuous forest (150 ha), where we defined edge from territorial boundaries. Based on the proportion of edge to core area, males in both habitats avoided the area within 20 m of the edge, implying that males responded to the presence of territory edge rather than forest edge. Surprisingly, however, males in isolated fragments used the edge area significantly more than males in continuous forest, even when measured against the relative amount of edge area within each territory. Elevated levels of edge use were not related to distance of nests to edges, nest stage, or time of day. We conclude that the presence of physical edges is not the sole determinant of territorial space use in this species and there are likely additional social factors influencing occupancy rates in small, isolated woodlots. Therefore, definitions of forest-interior species based on edge use need to be reconsidered.
Demography of a Declining Population of Warbling Vireos in Coastal California
Authors: Gardali Thomas , Ballard Grant , Nur Nadav , Geupel Geoffrey R. 
Published: September 2019

AbstractWe investigated population trends, adult survival, and productivity indices of a breeding population of Warbling Vireos (Vireo gilvus) in north coastal California using capture-recapture data from 19 years of standardized mist-netting conducted at Point Reyes National Seashore. We found significant long-term declines in abundance of both breeding and migratory Warbling Vireos. In addition, we found a significant long-term decline of hatching-year birds captured during the breeding season. The number of new adults in a given year, defined as those birds not previously banded and assumed to be an index of adult recruitment, was significantly correlated with the capture rate of hatching-year birds in the previous year, suggesting a link between reproductive success and adult abundance and recruitment. Our analysis of capture-recapture data provided an estimate of 50.4% for adult annual survival, similar to estimates for other species in stable populations. We could detect no temporal trend in survival. Nest survivorship from areas near our netting site was relatively low. We suggest that the decline of breeding and migratory populations of Warbling Vireos observed in coastal California may be the result of low productivity on the breeding grounds.
Molt of the Gray Vireo
Authors: Voelker Gary 
Published: September 2019

AbstractUsing museum specimens, I document the molt cycles and molting grounds of the Gray Vireo (Vireo vicinior). During prebasic molts, adult female Gray Vireos replace their primaries in 57 days, whereas adult males take 70 days; all body plumage is replaced during this molt. Prebasic molts occur almost exclusively on the breeding grounds; just 3 of 41 specimens replacing primaries were collected away from breeding grounds. No molting specimens were collected from wintering areas. Prealternate molt occurs on the wintering grounds, and appears limited to the replacement of innermost secondaries and a limited molt of body plumage. By performing prebasic molt on breeding grounds, the Gray Vireo differs from several other western breeding passerine species that use desert regions of the southwestern United States and northwestern Mexico to exploit late summer food resources. The areas of these southwestern desert regions used by other species form a small portion of the breeding grounds, and encompass the entire wintering grounds, of Gray Vireos. I hypothesize that this contrast in molting regions is not due to differences in the general timing of prebasic molts among these species; rather, the contrast may be due to constraints imposed on Gray Vireos by a dietary shift to fruit during winter and the need to defend winter territories.
Nesting Effort of Northern Pintails in Alberta
Authors: Guyn Karla L. , Clark Robert G. 
Published: September 2019

Abstract
We studied nesting effort and success of Northern Pintails (Anas acuta) in southern Alberta. Annual nesting success estimates ranged from 6–18%. Clutch size averaged 7.2, and declined in a simple curvilinear fashion with nest initiation date. We found no relationship between egg size and clutch size or evidence from one year to the next of a trade-off between current and future investment in eggs. Within-year renesting rate ranged from 55%, based on a sample of 20 decoy-trapped females that lost their first nests to predators, to 85% based on a sample of 13 nest-trapped females forced to renest when we removed their clutches. Greater investment in initial clutches led to longer delays in laying replacement clutches. Because delays in renesting are costly (late-nesting females produce fewer offspring), females must contend with a trade-off between maximizing reproductive output in initial clutches versus the risk of delayed renesting if the first clutch should fail. We suggest that pintail reproductive traits have evolved primarily in response to short nesting seasons and variable environments.
Interactive Effects of Vegetation and Predators on the Success of Natural and Simulated Nests of Grassland Songbirds
Authors: Dion Nancy , Hobson Keith A. , Larivière Serge 
Published: September 2019

AbstractWe examined the influence of vegetation and predator community on nesting success of songbirds in the grasslands of eastern North Dakota, USA. Each year, eight sites were chosen: four were subject to predator removal, and four were non-removal sites. On each site, nests of grassland songbirds were monitored, and simulated nests were used to examine how vegetation characteristics at nests affect nest success. Vegetative characteristics at simulated nests did not differ from those at natural nests, but successful natural nests had greater forb and lesser grass cover than unsuccessful nests, whereas no differences in vegetation were detected between successful and depredated simulated nests. On non-removal sites, small mammals and ground squirrels (Spermophilus sp.) depredated nests in taller and denser cover when compared to nests destroyed by medium-sized mammals and birds. On removal sites, we found no difference in vegetation characteristics of nests depredated by different predator types. However, each group of mammalian predators depredated simulated nests with different vegetation characteristics on removal versus non-removal sites. On sites where predators were removed, small mammals and ground squirrels preyed on simulated nests in shorter vegetation containing fewer forbs, ground squirrels preyed on nests with higher grass cover and lower vertical density, and medium-sized carnivores preyed on nests in taller vegetation. These results support the hypothesis that high predator diversity may reduce the chance of “safe” nest sites, and suggest that the behavior of low-level predators may change when top-level predators are removed.
Seasonal Energetics of Mountain Chickadees and Juniper Titmice
Authors: Cooper Sheldon J. 
Published: September 2019

Abstract
I used behavioral, meteorological, and laboratory metabolism data to calculate daily energy expenditure (DEE) in seasonally acclimatized Mountain Chickadees (Poecile gambeli) and Juniper Titmice (Baeolophus griseus). Analyses of laboratory metabolic data revealed that foraging energy requirements were not significantly higher than alert perching energy requirements. Respective DEE of chickadees and titmice were 48.8 kJ day−1 and 48.3 kJ day−1 in summer and 66.3 kJ day−1 and 98.7 kJ day−1 in winter. DEE as a multiple of basal metabolic rate (BMR) was 2.31 in summer chickadees and 1.91 in summer titmice. DEE was 2.70 times BMR in winter chickadees and 3.43 times BMR in winter titmice. The marked increase in calculated DEE in winter birds compared to summer is in contrast to a pattern of increased DEE in the breeding season for several avian species. These data suggest that winter may be a period of even greater stringency for small birds than previously believed.
Responses of Birds to Broken Eggs in Their Nests
Authors: Mallory Mark L. , Rendell Wallace B. , Robertson Raleigh J. 
Published: September 2019

Abstract
We tested the responses of two bird species which nest on unmovable substrates (e.g., cavities and walls) to simulated and actual egg damage in their nest. Tree Swallows (Tachycineta bicolor) and Barn Swallows (Hirundo rustica) removed broken eggs and continued to incubate the rest of their clutch, but response times took up to 8 days, and observed rejection rates were lower than reported for some other passerines. Collectively, these data and other studies suggest that broken eggs represent a continuing selection pressure to which all birds respond, although there appears to be some variability among species in the strength and speed of the response to damaged eggs.
Brain, Eye, and Skull Growth in Embryonic Geese
Authors: Gille Uwe , Zachen Frank , Salomon Franz-Viktor 
Published: September 2019

Abstract
We tested the hypothesis that bill proportions at hatching are a byproduct of overall skull proportions which are a result of constraints of brain growth. We measured brain and eye weights, eye diameter, and some skull dimensions in domestic geese (Anser anser f. domestica) varying in age between embryonic day 7.5 and 29.5 (hatching), and in five adult geese. With respect to age, weights show divergent growth patterns resulting in complex allometry for eye but simple allometry for brain weight. This differs from the situation in Galliforms and probably reflects the high cerebralization of Anseriforms. Length measurements show similar growth patterns. Cranial length realizes a larger part of overall growth during incubation when compared to facial length. Cranial width is similar to eye diameter and brain weight. Bill width exhibits a unique growth pattern. Bill proportions are similar to the whole head but differ from those of the bony brain capsule. Therefore, although all craniometric measurements strongly correlate to brain size, brain growth probably influences growth of the cranial but not of the facial part of the skull.
Cloacal Microbes in House Sparrows
Authors: Stewart Reuven , Rambo T. Birch 
Published: September 2019

AbstractWe examined the communities of bacteria and fungi associated with the cloaca of adult House Sparrows (Passer domesticus) to investigate whether microbes could be transferred during copulation and thus represent a cost to mating. The levels of microbes in the cloacae of the male and female of eight breeding pairs were significantly correlated. The levels of microbes on the rim of the cloacal protuberance, which comes into direct contact with another bird during copulation, were similar to those inside the cloaca. These findings are consistent with microbes being transferred during copulation. Females could also receive non-cloacal pathogens during copulation, given that two of five males sacrificed had microbes within their testes, which could be incorporated into the ejaculate. Undeveloped eggs were screened for the presence of microbes, although only a low proportion (18%) was contaminated. It seems unlikely that microbial contamination is a general cause of egg failure in this species.
Infectious Bursal Disease Virus Antibodies in Eider Ducks and Herring Gulls
Authors: Hollmén Tuula , Franson J. Christian , Docherty Douglas E. , Kilpi Mikael , Hario Martti , Creekmore Lynn H. , Petersen Margaret R. 
Published: September 2019

Abstract
We measured antibodies to infectious bursal disease virus (IBDV) in blood of nesting Common Eider (Somateria mollissima) females and immature Herring Gulls (Larus argentatus) in the Baltic Sea, and in blood of Spectacled Eider (Somateria fischeri) females nesting in a remote area of western Alaska. Positive (≥ 1:16) IBDV titers occurred in 75% of the eiders and 45% of the Herring Gull chicks. In eiders, the prevalence of positive titers differed among locations. We found no evidence that IBDV exposure impaired the immune function of Herring Gull chicks, based on their response to inoculation of sheep red blood cells. We suggest that eider ducks and Herring Gulls have been exposed to IBDV, even in locations where contact with poultry is unlikely. The presence of this virus in wild bird populations is of concern because it causes mortality of up to 30% in susceptible poultry.
Satellite Tracking of Cory's Shearwater Migration
Authors: Ristow Dietrich , Berthold Peter , Hashmi Dean , Querner Ulrich 
Published: September 2019

Abstract
Transmitters were attached to four adult male Cory's Shearwaters (Calonectris diomedea) caught at their breeding sites off Crete, Greece, in autumn 1998. The birds had left the Mediterranean by the beginning of December. Two were last recorded in the eastern tropical Atlantic in January/February. The other two wintered east of the Mid-Atlantic Ridge, one at about 10°N, the other one in equatorial waters, and could be tracked until return migration in March/April. The seasonal variation in travel speed is in accordance with a conventional pattern of migration with phases of migration and wintering, rather than continuous movement throughout the nonbreeding cycle. The birds left the Mediterranean later and wintered farther north than expected. We suggest that the known longitudinal cline in body size, morphology, and vocalizations of Cory's Shearwater may also be found in migration behavior.
Effects of Sampling Design on Age Ratios of Migrants Captured at Stopover Sites
Authors: Kelly Jeffrey F. , Finch Deborah M. 
Published: September 2019

Abstract
Age classes of migrant songbirds often differ in migration timing. This difference creates the potential for age-ratios recorded at stopover sites to vary with the amount and distribution of sampling effort used. To test for these biases, we sub-sampled migrant capture data from the Middle Rio Grande Valley of New Mexico. We created data sets that reflected the age ratios of migrants that would have been captured with stratified and concentrated designs at four levels of mist-netting effort. Analysis of these data indicate that age-ratios of Neotropical migrants varied significantly with sampling design, but not with sampling effort. More after-hatch-year Neotropical migrants were captured with stratified than with concentrated sampling designs. Age-ratio of temperate migrants did not vary with either amount of sampling effort or sampling design. Sampling design is an important consideration in the interpretation of age ratios among stopover sites, and standardization of sampling among sites could improve our understanding of differential migration of age classes.
Time-Activity Budgets of Harlequin Ducks Molting in the Gannet Islands, Labrador
Authors: Adams Peter A. , Robertson Gregory J. , Jones Ian L. 
Published: September 2019

AbstractWe studied the time-activity budgets of Harlequin Ducks (Histrionicus histrionicus) molting at the Gannet Islands, Labrador in the summer of 1998. For the entire population, a large proportion of time was spent hauled out of the water (61.4%), and resting (53.5%). Only a small proportion of time was spent foraging (11.6%). Male Harlequin Ducks undergoing the pre-basic molt were hauled out of the water significantly more (92.2%) than males in basic plumage (8.1%). Males undergoing the pre-basic body feather molt foraged significantly less (1.7%) than males in basic plumage (17.7%). Harlequin Ducks do not appear to increase their food intake to meet the nutritional requirements of molt. Instead they may try to reduce thermoregulatory and maintenance costs by engaging in activities that do not consume much energy, and by staying out of cold water while their plumage is not intact. Furthermore, they may deliberately lose body mass while molting to regain the ability to fly at an earlier stage of wing molt.
A New Hybrid Warbler (Dendroica Nigrescens × D. Occidentalis) and Diagnosis of Similar D. Townsendi × D. Occidentalis Recombinants
Authors: Rohwer Sievert , Wood Christopher , Bermingham Eldredge 
Published: September 2019

Abstract
We use 13 color characters to describe the first known Dendroica nigrescens × D. occidentalis hybrid. Because this specimen was collected in the southeastern Cascade Mountains of Washington during the breeding season, D. townsendi, D. occidentalis, and D. nigrescens are the only plausible parents for a hybrid male falling within the black-throated clade of Dendroica warblers. Multiple character states in the hybrid refute the alternative parental combinations, townsendi × occidentalis and townsendi × nigrescens. Two characteristics of this hybrid suggested further tests of the parentage of 38 problematic hybrids that were treated previously as townsendi × occidentalis recombinants by assumption only. These hybrids lack yellow on their breast, the only character that refutes a nigrescens × occidentalis parentage. The new hybrid is intermediate between nigrescens and occidentalis in the color of its posterior face and its anterior crown; thus, we scored these new characters in the 38 problematic hybrids. None of these 38 specimens was intermediate or white in either of these regions, and there was no correlation between having tinges of white in these regions and the extent of flank streaking. These results fail to support nigrescens in the parentage of these 38 specimens; furthermore, none of the problematic hybrids carried a nigrescens mitochondrial DNA haplotype. Thus, we conclude that all are unusual recombinants of townsendi × occidentalis hybridization, rather than nigrescens × occidentalis hybrids.