bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dispersal Pattern of Black-Billed Magpies (Pica Hudsonia) Measured by Molecular Genetic (Rapd) Analysis
Authors: Wang Xiao-hong , Trost Charles H. 
Published: September 2019

AbstractBlack-billed Magpies (Pica hudsonia) are a relatively sedentary corvid, with greater dispersal of females than males. To genetically confirm that dispersal pattern, 29 reproductively active adults were captured over two years and were scored for primer-specific random amplified polymorphic DNA (RAPD) bands (53 polymorphic bands in 1996 and 104 in 1997). In both years, we captured more previously banded males than females, and individuals recaptured were more often the heaviest nestling in their brood from the previous years. Genetic distances between all possible adult pairs were calculated and degree of genetic similarity between pair-wise comparisons was assessed using the Mantel test. In the pair-wise comparison of genetic distances, data for both years showed that genetic distances between males were significantly less (P < 0.05) than those for other adult combinations (male–female and female–female). Using the same analytical approach, we found that females were no more genetically similar to one another (P > 0.05) than were random pairs of adults. Group-distance analysis using the computer package RAPD also showed higher genetic similarity among males than among females. We suggest that a plausible hypothesis to account for the relatively high genetic homogeneity of the breeding male population compared to the female population is that a long-lasting intraclutch dominance hierarchy exists among siblings. That hierarchy is sufficiently long-lasting to influence the breeding population, resulting in alpha males remaining in the natal area, whereas lower ranking birds, including females, are forced to disperse.
Sexual Selection and Tail-Length Dimorphism in Scissor-Tailed Flycatchers
Authors: Regosin Jonathan V. , Pruett-Jones Stephen 
Published: September 2019

AbstractScissor-tailed Flycatchers (Tyrannus forficatus) exhibit elongated tails in both sexes, and sexual dimorphism in tail length. At Fort Sill, Oklahoma, during 1991 and 1992, Scissor-tailed Flycatchers exhibited sexual dimorphism (male–female) in tail length (1.48), with more moderate sexual dimorphism in wing length (1.09) and beak length (1.04). Based on an analysis of museum specimens, immature birds (<1 year of age) of both sexes in their first calendar year exhibited significantly shorter tails than adults (measured in the field). Furthermore, tail length was highly variable among both sexes relative to other morphological traits. Male tail length was correlated with early clutch initiation by the male's mate and, in 1991, with larger clutch size. Similarly, female tail length was correlated with early clutch initiation, and, in one year, larger clutches. Longer-tailed females also tended to arrive earlier on the breeding grounds in 1992, the only year for which such data were available. Assortative mating by tail length was observed. Those findings support the hypothesis that tail length is a sexually selected trait in this socially monogamous species, and that female tail length may be correlated with measures of female quality (e.g. early arrival and breeding, large clutches). However, confounding effects of age on tail length make it difficult to distinguish among various hypotheses for evolution of elongated tails in this species.
Variation in Growth of Nestling Tree Swallows Across Multiple Temporal and Spatial Scales
Authors: McCarty John P. 
Published: September 2019

AbstractDifferences within a species in rates of growth of nestlings can be used as indicators of the quality of parental care, environmental conditions, and future success of offspring, whereas comparisons among different species may reflect a history of different ecological conditions or life-history strategies. The presesnt study examines the patterns of variation in growth in nestling Tree Swallows (Tachycineta bicolor) from across the species' range and compares Tree Swallows to other species. Growth of Tree Swallows was typical of other species in the family Hirundinidae. As a family, the Hirundinidae have slower growth than typical for passerines. Growth rate of species of Hirundinidae was not correlated with adult body mass or average brood size. Contrary to predictions, species that are double-brooded did not have higher growth rates, but swallow species living at higher latitudes did have higher growth rates than tropical species. Substantial variation in growth rates was observed among populations of Tree Swallows, yet the amount of variation observed between breeding colonies only a few kilometers apart, or from the same colony in different years, was as great as that seen in populations separated by hundreds of kilometers. Within a population, differences in growth among years were correlated with temperature and food supply when nestlings were being raised. No correlation between climate and growth was seen when comparing different populations. Differences between populations were not explained by local habitat, nor were large-scale geographic patterns evident. I used both experimental and observational evidence to evaluate the implications of short-term reduction in growth for subsequent growth and survival. Nestlings were slow to recover from even very short periods of delayed growth that occur early in the nestling phase. Return of nestlings with experimentally or naturally induced delayed growth was reduced, which suggests that short interruptions in growth may have long term effects on postfledging survival, even though mass at fledging is not affected.
Patterns of Corticosterone Secretion in Migrating Semipalmated Sandpipers at a Major Spring Stopover Site
Authors: Mizrahi David S. , Holberton Rebecca L. , Gauthreaux, Jr Sidney A. 
Published: September 2019

AbstractSeasonal changes in corticosterone metabolism may be in part responsible for mediating the changes in nutrient reserves before and during migration. To investigate the role of glucocorticoids in the migratory physiology of Semipalmated Sandpipers (Calidris pusilla), we compared plasma levels of corticosterone in response to capture and handling stress during prolonged stopovers in Delaware Bay during spring 1996 and 1997. Although Semipalmated Sandpipers showed significant stress responses to handling in both years, the magnitude of the response was significantly lower in 1997. We found no correlation between energetic condition and initial corticosterone concentration in either year, or between energetic condition and corticosterone concentration in samples collected 30 min after capture in 1996. However, energetic condition was positively correlated with corticosterone concentration in 30 min sample collected in 1997. Between-year differences in regression functions of energetic condition by Julian date suggested that birds were accumulating fat mass more rapidly, or arriving in better energetic condition during 1996 compared to 1997. Those differences were especially evident during the “early” stages (before 26 May) of stopover periods. In 1997, we found that birds sampled early in the season did not show a significant increase in corticosterone 30 min after capture, while birds sampled in early 1996 did. In both years, birds sampled during the “late” stages of stopover periods (after and including 26 May) showed significant stress response. Birds in relatively poor energetic condition, or with low rates of fat-mass gain, were less likely to secrete additional corticosterone in response to acute stress, possibly to protect skeletal muscle needed for migratory flight. Those results suggest that patterns of corticosterone secretion in sandpipers can be modified in response to changes in energy demand during the migratory period.
Bird Assemblages in Second-Growth and Old-Growth Forests, Costa Rica: Perspectives From Mist Nets and Point Counts
Authors: Blake John G. , Loiselle Bette A. 
Published: September 2019

AbstractSecond growth has replaced lowland forest in many parts of the Neotropics, providing valuable habitat for many resident and migrant bird species. Given the prevalence of such habitats and the potential benefit for conservation of biodiversity, it is important to understand patterns of diversity in second growth and old growth. Descriptions of species-distribution patterns may depend, however, on method(s) used to sample birds. We used data from mist nets and point counts to (1) describe species diversity and community composition in second-growth (young and old) and old-growth forests at La Selva Biological Station, Costa Rica; and (2) to evaluate perspectives on community composition provided by the two methods. We recorded 249 species from 39 families, including 196 species captured in mist nets (10,019 captures) and 215 recorded during point counts (15,577 observations), which represents ∼78% of the terrestrial avifauna known from La Selva (excluding accidentals and birds characteristic of aquatic or aerial habitats). There were 32 threatened species, 22 elevational migrants, and 40 latitudinal migrants. Species richness (based on rarefaction analyses of capture and count data) was greatest in the youngest site. Latitudinal migrants were particularly common in second growth; elevational migrants were present in both young and old forest, but were more important in old-growth forest. Several threatened species common in second growth were not found in old-growth forests. Trophic composition varied less among sites than did species composition. Mist nets and point counts differed in numbers and types of species detected. Counts detected more species than nets in old-growth forest, but not in young second growth. Mist nets detected 62% of the terrestrial avifauna, and point counts detected 68%. Fifty-three species were observed but not captured, and 34 species were captured but not observed. Six families were not represented by mist-net captures. Data from mist nets and point counts both support the conclusion that second-growth vegetation provides habitat for many species.
Long-Term Study of Apparent Survival in Pacific Golden-Plovers at a Wintering Ground on Oahu, Hawaiian Islands
Authors: Johnson Oscar W. , Bruner Phillip L. , Rotella Jay J. , Johnson Patricia M. , Bruner Andrea E. 
Published: September 2019

AbstractWe monitored the apparent survival of territorial and nonterritorial Pacific Golden-Plovers (Pluvialis fulva) for 20 consecutive nonbreeding seasons at a wintering ground within Bellows Air Force Station (BAFS) on the eastern shore of Oahu, Hawaii. Territorial birds were especially site-faithful from season to season, and each surviving individual reoccupied the same territory held in previous seasons. On average, territorial birds were resighted for about twice as many postbanding seasons (4.2) as nonterritorial birds (1.8). Open-population modeling indicated that apparent survival varied by age and territorial status. Our most parsimonious model estimated apparent annual survival rates in territorial plovers as 0.90 for young birds (age determined from retained juvenal primaries) from their first through their second wintering season, and 0.80 for adults over numerous seasons. For nonterritorial plovers, the corresponding values were 0.82 and 0.67, respectively. Despite lower apparent survival in nonterritorial plovers, it remains uncertain whether nonterritoriality actually results in shorter life spans. Some surviving nonterritorial birds may have gone undetected (detection probability of 0.70) because of permanent emigration from the study area. Given strong site-fidelity of territorial birds and the relative certainty of detecting them (probability = 1.0), we regarded the disappearance of a plover from its territory as an indicator of mortality. From last-recorded sightings, we concluded that territorial birds died with about equal frequency during the nonbreeding and breeding seasons. Because the latter is of much shorter duration, time-relative hazards were greatest while birds were away from the wintering grounds. Winter mortality was caused by accidents (collisions with overhead wires and other obstructions), and probable predation by owls. We estimated mean additional life expectancy among territorial plovers at 5.1 years for first-year birds, and 4.5 years for unknown-age adults. The oldest known-age individual was a male that lived 13 years 10 months; in adults of uncertain ages, one male survived to a minimum age of 18 years 10 months, and two females to at least 17 years 10 months. Pacific Golden-Plovers wintering at BAFS, especially territorial birds, demonstrated relatively high rates of apparent survival combined with adaptability for coexistence with humans in an urban environment.
Geographic Variation in the Song of Willow Flycatchers: Differentiation Between Empidonax Traillii Adastus and E. T. Extimus
Authors: Sedgwick James A. 
Published: September 2019

AbstractThe vocal signatures of the primary song form (“fitz-bew”) of the endangered Southwestern Willow Flycatcher (Empidonax traillii extimus) and its northern counterpart, E. t. adastus, are distinctive. Songs of the extimus subspecies are longer (total song, note, internote) and frequencies at maximum amplitude are lower than those of adastus. I used vocal evidence to clarify the distributional limits of the Southwestern Willow Flycatcher and that of the geographically adjacent subspecies, E. t. adastus. Unweighted pair-group method using averaging (UPGMA) cluster analysis and canonical discriminant analysis revealed that (1) low elevation, southerly desert populations (Arizona, New Mexico, and southern Utah) have a unique vocal identity corresponding to populations in the range of E. t. extimus; (2) northerly song groups (Oregon, Colorado, and northern Utah) share a different song type corresponding to populations in the range of E. t. adastus; and (3) a departure from vocal and morphological congruence occurs for a population of high-elevation Arizona birds that, although in the currently accepted range of E. t. extimus, sings songs acoustically similar to more northern populations (E. t. adastus). Multiple regression of song distance on latitude and elevation, and a comparison of a matrix of song distances with a matrix of latitude and elevation dissimilarities, demonstrated that song populations sort out by both latitude and elevation: birds with the vocal identity of extimus occur as far north as 37°N if at low elevation, and those acoustically similar to adastus occur as far south as 33.7°N if at high elevation. The vocal background of northern New Mexico birds appears to be intermediate between that of extimus and adastus, suggesting that northern New Mexico is a zone of intermixing and intergradation between the subspecies. Pure forms of E. t. extimus apparently do not occur in Colorado because even the southernmost populations are acoustically similar to more northerly populations of adastus. A low-elevation population in western Colorado, however, stands apart from other adastus populations, suggesting moderate introgression of extimus genes into the adastus gene pool.
Reclaimed Coal Mine Grasslands and Their Significance for Henslow's Sparrows in the American Midwest
Authors: Bajema Robb A. , DeVault Travis L. , Scott Peter E. , Lima Steven L. 
Published: September 2019

Abstract
Present methods of surface coal-mine reclamation in the Midwest produce large grasslands, some of which exceed 2,000 ha in extent. Total “mine grassland” production in southwestern Indiana alone is well in excess of 70 square miles (180 km2). Our work in 19 reclaimed coal mines in southwestern Indiana indicates that mine grasslands harbor many Henslow's Sparrows (Ammodramus henslowii). We base that conclusion on point-count and line-transect surveys that yielded between 200–300 singing male Henslow's Sparrows during the 1997 and 1998 breeding seasons. Those survey results imply an uncorrected population density of ∼0.10 males per hectare, and a corrected density of ∼0.16 males per hectare (correcting for undetected males). Extrapolating this corrected density to total habitat coverage suggests an overall population of a few thousand Henslow's Sparrows in the mine grasslands of southwestern Indiana. Small-scale vegetational surveys suggest that much of the within-mine variation in Henslow's Sparrow abundance reflects local vegetative structure, with males preferring sites typically associated with that species of bird: tall, dense grass-dominated vegetation with a substantial litter layer. Management for this kind of vegetative structure could greatly increase the number of Henslow's Sparrows inhabiting reclaimed mines. Midwestern mine grasslands could play a significant role in stabilizing the populations of Henslow's Sparrows and other grassland birds.
Avian Responses to Restoration: Nest-Site Selection and Reproductive Success in Song Sparrows
Authors: Larison Brenda , Laymon Stephen A. , Williams Pamela L. , Smith Thomas B. 
Published: September 2019

AbstractRiparian habitats typically support high diversity and density of both plants and animals. With the dramatic loss of riparian habitats, restoring them has become a priority among conservation practitioners. Diversity and density of avian species tend to increase following riparian restoration, but little is known about how restored habitats function to meet particular species' needs. Habitat structure is an important factor affecting species diversity and density and can influence nest-site selection and reproductive success. To evaluate habitat restoration, we examined interactions between habitat structure, nest-site selection, and nesting success in Song Sparrows (Melospiza melodia) nesting in restored, mature, and young naturally regenerating stands of riparian forest. We found that stand types differed markedly in structure, and that habitat structure influenced both nest-site selection and rates of nest loss to predation. Comparison of habitat structure among the three stand types indicated that restored stands offered fewer acceptable nest sites and poorer protection from nest predation. Concordant with those differences in habitat structure, Song Sparrows showed trends toward less density in restored stands than in mature forest, and had poorer nesting success as a result of predation.
Bird Diversity Components in Australian Eucalyptus and North-Temperate Quercus Woodlands
Authors: Cody Martin L. 
Published: September 2019

AbstractDiversity patterns of breeding bird assemblages (exclusive of raptors and nocturnal species) of western North American oak and Australian eucalypt woodlands are derived from data recorded at 113 census sites distributed over four regions, two on each continent. Regional species richness varies by a factor of 2 among regions. The contribution to regional species totals by various diversity components is examined: α-diversity (species richness within sites), β-diversity (species turnover between sites related to differences in vegetation structure), and γ-diversity (turnover related to distance between sites, independent of habitat change). Mean α-diversity is relatively constant among regions (mean 25.5 to 29.7 species). Variation in α-diversity within regions is related to variation in vegetation structure, and bird-density variation is best predicted by a measure of vegetation density. The relationships between bird diversity and density and vegetation structure are similar in the four regions. With the influence of vegetation structure removed, there is no (Australia) or at best a modest (North America) latitudinal gradient in α-diversity. Within regions, regression analysis shows that species turnover is significantly related to both vegetation structural differences (β-diversity) and distance between sites (γ-diversity), with the latter accounting for a larger proportion of, and correlating strongly with, regional species totals. Identification of factors promoting species turnover between sites, beyond distance and vegetation effects, remains a major challenge to ecologists.
Geographic Variation, Hybridization, and the Leapfrog Pattern of Evolution in the Suiriri Flycatcher (Suiriri Suiriri) Complex
Authors: Hayes Floyd E. 
Published: September 2019

AbstractThe Suiriri Flycatcher (Suiriri suiriri) of South America is represented by three distinct forms occurring in parapatry: (1) S. s. suiriri to the southwest in the Chaco/Pampas; (2) S. s. affinis located centrally in the Cerrado/southern Amazonia; and (3) S. s. bahiae to the northeast in the Caatinga. On the basis of an analysis of 366 specimens of S. suiriri, I found meager evidence for long-distance migration, little support for Bergmann's rule, and more support for Gloger's rule. I postulate that an ancestral population of S. suiriri split into three isolated populations, with the central population differentiating most rapidly into affinis, thus explaining the leapfrog pattern of greater similarity between peripheral suiriri and bahiae. After secondary contact, affinis freely hybridized with nominate suiriri in a hybrid zone to the southwest, where specimens demonstrate morphometric intermediacy and increased plumage variability; the rarity of parental phenotypes within the hybrid zone suggests that the two forms are conspecific according to the biological species concept. In the northeast, affinis may have hybridized with a remnant population of suiriri, possibly represented by poorly known bahiae. The intermediate size and increased plumage variability of bahiae resemble that of suiriri × affinis hybrids, supporting a hypothesis of hybrid origin for bahiae, but alternative hypotheses cannot be ruled out. This hypothesis of differentiation is supported by the concordant patterns of disjunction among several pairs of sister taxa of bird species that occur in the Chaco and Caatinga, with no intervening populations in the Cerrado, implying a shared historical process of vicariance. Genetic and behavioral studies are needed to elucidate further the status and history of differentiation within S. suiriri.
Avifauna of a Lowland Forest Site on Isabel, Solomon Islands
Authors: Kratter Andrew W. , Steadman David W. , Smith Catherine E. , Filardi Christopher E. , Webb Horace P. 
Published: September 2019

AbstractWe provide the first comprehensive description of a bird community from a lowland rainforest site on a major island in the Solomon Islands. During two dry season visits (July 1997, June 1998) to the lower Garanga River valley on the island of Isabel, we recorded 65 resident and 6 migrant species of birds. We document relative abundances, habitat preferences, and foraging guilds for the members of the bird community. The Garanga River site sustains all but 11 of the 76 species of landbirds known from Isabel. Of those 11 species, four are small-island or beach specialists, three are montane, and four are of unknown status. Habitat heterogeneity, maintained largely by river dynamics, is a major contributor to avian diversity at the site. The avifauna is dominated by nonpasserines, especially parrots, pigeons, kingfishers, and hawks. The flightless rail Nesoclopeus woodfordi, previously regarded as rare and threatened with extinction, was common. We recorded Ixobrychus flavicollis, Falco severus, and Eudynamys scolopacea for the first time on Isabel. We also documented occurrence in the lowlands of Micropsitta finschii, Collocalia spodiopygia, Coracina caledonica, and Pachycephala pectoralis, four species previously thought to be confined to upper elevations on Isabel. The depauperate understory avifauna of the Garanga River site may be anthropogenic and could belie what otherwise seems to be an intact avifauna.