bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reproductive Success of American Kestrels: The Role of Prey Abundance and Weather
Authors: Dawson Russell D. , Bortolotti Gary R. 
Published: September 2019

Abstract
We investigated how natural variation in abundance and availability of the main prey of American Kestrels (Falco sparverius), small mammals, influenced provisioning rates by parents, and offspring size and survival. Provisioning behavior of kestrels was not constrained by the abundance of food in the environment; however, the availability of food, mediated through variation in weather, appeared to significantly influence parental provisioning behavior. Moreover, variation in weather had clear effects on reproductive success because nestlings exposed to inclement weather were smaller and lighter at fledging, and less likely to survive to fledging, compared to nestlings raised during good weather conditions. Prey abundance was not related to offspring size or survival. Our results suggest American Kestrels are limited by the availability, as opposed to abundance, of food on territories. It is likely that during our study, prey abundance was above some minimum threshold necessary to support successful reproduction, and so variation in weather affected reproduction more than variation in prey abundance.
Nesting Habitat and Reproductive Success of Southwestern Riparian Birds
Authors: Powell Brian F. , Steidl Robert J. 
Published: September 2019

AbstractVegetation structure and floristic composition strongly influence the structure of bird communities. To assess the influence of vegetation and other environmental characteristics on songbirds, we quantified nest-site characteristics and reproductive success of a riparian songbird community in Arizona. Although we found interspecific variation in characteristics associated with nest sites, we identified two suites of species that chose sites with similar characteristics. These “nest groups” were explained largely by nest height and characteristics of nest trees. Overall, nest success was low for songbirds in this community, and averaged 23%. The most common cause of nest failure was predation (81%), although brood parasitism by Brown-headed Cowbirds (Molothrus ater) was highest at nests of Bell's Vireos (Vireo bellii) (29%). No vegetation or environmental features were associated with the likelihood of cowbird parasitism for any species; nest success for Bell's Vireos was negatively associated with the amount of netleaf hackberry (Celtis reticulata) in the understory. Arizona sycamore (Platanus wrightii) and netleaf hackberry trees contained 41% and 17% of all nests, respectively, and therefore provide critically important nesting substrates for birds in this rare yet diverse vegetation community.
Patterns of Flock Size, Diet, and Vigilance of Naturalized Monk Parakeets in Hyde Park, Chicago
Authors: South Jason M. , Pruett-Jones Stephen 
Published: September 2019

Abstract
We examined patterns of diet, foraging group size, and vigilance effort of naturalized Monk Parakeets (Myiopsitta monachus) in Hyde Park, a neighborhood of Chicago, Illinois. Parakeets exhibited a highly seasonal and varied diet consisting of fruits, seeds, and buds, and they fed almost exclusively on birdseed provided at backyard feeding stations during the winter months. Birds foraged in groups of 1 to 31 birds, but most flocks were of 10 birds or less. Foraging group size was greatest in the fall and early winter, and smallest at the beginning of the spring when breeding began. Monk Parakeets adjusted their vigilance effort with changes in flock size. Individual vigilance effort declined with increasing flock size through a decrease in time spent scanning as well as the number of times scans were initiated. The number of parakeets exhibiting vigilance in a flock at any given time also decreased with flock size. It is likely that the highly adaptable and varied diet of Monk Parakeets contributes greatly to the persistence and growth of populations in a variety of North American habitats.
Mitochondrial DNA and Morphological Variation of White-Winged Doves in Texas
Authors: Pruett Christin L. , Henke Scott E. , Tanksley Susan M. , Small Michael F. , Hogan Kelly M. , Roberson Jay 
Published: September 2019

AbstractWhite-winged Doves (Zenaida asiatica) in Texas are separated into four subspecies primarily based on morphological variation. However, problems differentiating the subspecies by morphological measurements alone and a recent range expansion have led to questions about their systematic status and population structure. We evaluated both morphological characters and a 289 base-pair segment of the mitochondrial control region from 183 White-winged Doves taken from 31 locations in Texas, New Mexico, and Arizona. Twenty-seven variable base changes were observed, which resulted in 44 haplotypes. An analysis of haplotypes yielded little phylogenetic signal; however, analyses of haplotype frequencies indicated geographic heterogeneity between doves collected in the four historic subspecies ranges. Doves from the range expansion areas were intermediate in size and genetically homogenous. Morphological analyses suggested congruency between control region variation and body size. Our data support the recognition of two subspecies of White-winged Doves with a zone of intergradation in the range expansion areas. The dispersal of White-winged Doves into the expansion areas appears to be a congruent process by both subspecies.
Definitive Prebasic Molt of Gray Catbirds at two Sites in New England
Authors: Heise Colleen Dwyer , Rimmer Christopher C. 
Published: September 2019

AbstractWe studied the pattern and timing of prebasic molt in adult Gray Catbirds (Dumetella carolinensis) at two New England sites: Block Island, Rhode Island (BIRI), and the Vermont Institute of Natural Science (VINS) in Woodstock, Vermont. Catbirds at VINS initiated molt earlier and molted at a significantly slower rate than catbirds at BIRI. Mean individual molt durations spanned approximately 54 days at VINS and 44 days at BIRI. The two groups ended molt at about the same time. Catbirds at VINS were more variable in the timing of their molt. At both sites, second-year catbirds began and ended molt significantly earlier than after second-year catbirds. Males and females did not differ significantly in their rate or timing of molt at either site. Behavioral observations at BIRI indicated that catbirds spent less time foraging during the heaviest period of molt, but that increased foraging during late molt stages coincided with increases in fat stores, indicating overlap of molt and hyperphagy. We found no evidence that Gray Catbirds at either site departed for migration prior to completing remigial molt. The later molt schedule of BIRI birds likely resulted from the extended breeding season of some individuals. We believe that molt schedules at the two sites were influenced less by latitude per se than by site-specific differences in vegetation, food abundance, and temperature, resulting from differing elevations and conditions of coastal and inland environments.
Cultural Diversification in the Flight Call of the Ringneck Parrot in Western Australia
Authors: Baker Myron C. 
Published: September 2019

Abstract
I investigated geographic variation in a parrot vocalization to obtain an understanding of cultural population differentiation and exchange between hybridizing taxa. The flight calls of Ringneck Parrots (Barnardius zonarius) were tape recorded in Western Australia within and outside the zone of overlap and hybridization between the Port Lincoln (B. z. zonarius) and Twenty-eight (B. z. semitorquatus) subspecies. Measured variables distinguished the Twenty-eight call from those in the overlap populations. Although birds in typical Twenty-eight plumage were present in the overlap zone, no Twenty-eight flight calls were found, suggesting convergence by immigrants. Populations within the hybrid zone also were acoustically differentiated as dialects associated with roosting areas. Observations on the social behavior of the birds indicated that this call functions in coordination of movements of the mated pair. Roost-specific dialects might aid pairs in finding each other in the event of separation during the day's foraging activity.
Comparison of Coastal Fringe and Interior Forests as Reserves for Marbled Murrelets on Vancouver Island
Authors: Burger Alan E. , Bahn Volker , Tillmanns Angeline R. M. 
Published: September 2019

Abstract
Much of the protected habitat available to the threatened Marbled Murrelet Brachyramphus marmoratus and other old-growth associated species in the Pacific Northwest is in narrow strips along the coast (e.g., parks and scenic fringes). Using data over two years from three watersheds on southwest Vancouver Island, we show that such shoreline strip forests represent suboptimal habitat for murrelets. Murrelet detections, including circling and subcanopy behaviors, were significantly lower at 30 coastal stations (20–250 m from the shoreline edge) than at 30 interior stations (1.5–21.0 km inland). Densities of predators were significantly higher at the coastal stations. The coastal trees were of similar mean height and diameter, but they had lower structural diversity and provided fewer and less suitable (thinner epiphyte cover on large boughs) nesting platforms than trees in the interior. When possible, reserves for Marbled Murrelets should be placed in interior and not shoreline forests.
Correlates of Harlequin Duck Densities During Winter In Prince William Sound, Alaska
Authors: Esler Daniel , Bowman Timothy D. , Dean Thomas A. , O'Clair Charles E. , Jewett Stephen C. , McDonald Lyman L. 
Published: September 2019

AbstractWe evaluated relationships of Harlequin Duck (Histrionicus histrionicus) densities to habitat attributes, history of habitat contamination by the 1989 Exxon Valdez oil spill, and prey biomass density and abundance during winters 1995–1997 in Prince William Sound, Alaska. Habitat features that explained variation in duck densities included distance to streams and reefs, degree of exposure to wind and wave action, and dominant substrate type. After accounting for these effects, densities were lower in oiled than unoiled areas, suggesting that population recovery from the oil spill was not complete, due either to lack of recovery from initial oil spill effects or continuing deleterious effects. Prey biomass density and abundance were not strongly related to duck densities after accounting for habitat and area effects. Traits of Harlequin Ducks that reflect their affiliation with naturally predictable winter habitats, such as strong site fidelity and intolerance of increased energy costs, may make their populations particularly vulnerable to chronic oil spill effects and slow to recover from population reductions, which may explain lower densities than expected on oiled areas nearly a decade following the oil spill.
Influence of Female Age and Body Mass on Brood and Duckling Survival, Number of Surviving Ducklings, and Brood Movements in Redheads
Authors: Yerkes Tina 
Published: September 2019

AbstractI documented brood and duckling survival, the number of surviving ducklings, and brood movements of Redheads, and examined the association between these variables and female age and body mass. Redhead brood success was 55% and duckling daily survival rates averaged 0.868. Female body mass, but not age, was related to brood and duckling survival and the number of surviving ducklings. Successful females were heavier and produced more ducklings. All brood-movement measures differed between successful and unsuccessful females, however, the distance of the first move between wetlands accounted for the most variability in brood success. Increased body mass, but not age, was associated with longer first brood movements.
Effects of Hatching Date and Egg Size on Growth, Recruitment, and Adult Size of Lesser Scaup
Authors: Dawson Russell D. , Clark Robert G. 
Published: September 2019

AbstractEvidence suggests that birds breeding early in the season or laying larger eggs are at a selective advantage because quality and survival of their offspring are higher. We tested whether wild Lesser Scaup (Aythya affinis) hatching early in the season or from larger eggs had enhanced growth as ducklings and larger size or higher probability of recruiting to the local breeding population in years after hatching. After correcting for age at capture, body mass, head length, and culmen of ducklings were inversely related to hatching date, but were unrelated to egg volume. As adults, late-hatched birds had shorter wing lengths (second-year birds only) and tended to have smaller head lengths (all after-hatch year birds) than early hatching birds. We suggest that later-hatching birds are smaller due to increased competition for food during brood rearing. Recruitment probability increased as natal egg volume increased and decreased among birds with later natal hatching dates. We speculate these results are due to higher mortality of ducklings hatched from small eggs, and because early-hatched birds have more time to acquire nutrient reserves that would reduce vulnerability to costs of migration.
Effects of Water Conditions on Clutch Size, Egg Volume, and Hatchling Mass of Mallards and Gadwalls in the Prairie Pothole Region
Authors: Pietz Pamela J. , Krapu Gary L. , Buhl Deborah A. , Brandt David A. 
Published: September 2019

AbstractWe examined the relationship between local water conditions (measured as the percent of total area of basins covered by water) and clutch size, egg volume, and hatchling mass of Mallards (Anas platyrhynchos) and Gadwalls (A. strepera) on four study sites in the Prairie Pothole Region of North Dakota and Minnesota, 1988–1994. We also examined the relationship between pond density and clutch size of Mallards and Gadwalls, using data collected at another North Dakota site, 1966–1981. For Mallards, we found no relationships to be significant. For Gadwalls, clutch size increased with percent basin area wet and pond density; hatchling mass marginally increased with percent basin area wet. These species differences may reflect, in part, that Mallards acquire lipid reserves used to produce early clutches before they reach the breeding grounds, whereas Gadwalls acquire lipid reserves locally; thus Gadwall clutches are more likely to be influenced by local food resources.
Reproductive Success and Survival in Relation to Experience During the First Two Years in Canada Geese
Authors: Raveling Dennis G. , Sedinger James S. , Johnson Devin S. 
Published: September 2019

AbstractWe studied the relationship between family associations of immature Canada Geese (Branta canadensis) and their reproductive success as 2-year-olds and survival to three years. A higher proportion of immature Canada Geese associated with family members survived to breeding age and were more successful in reproducing in their first potential year of sexual maturity (age 2) than were geese that were not in family associations. These results illustrate the benefits of prolonged parental care outweighing costs to parents and the probable influence of family association on future successful breeding. Many reproductive failures of vertebrates with complex social organization may be related to experience during maturation.
Impact of Brood Parasitism on Nest Survival Parameters and Seasonal Fecundity of Six Songbird Species in Southeastern Old-Field Habitat
Authors: Whitehead Maria A. , Schweitzer Sara H. , Post William 
Published: September 2019

Abstract
We monitored 259 nests of six Brown-headed Cowbird (Molothrus ater) hosts within old-field habitat on James Island, South Carolina during the 1997 and 1998 breeding seasons to determine the effect of parasitism on three nest-survival parameters (clutch size, hatching rate, and number of fledglings). We determined daily predation and parasitism rates, and probability of nest abandonment after parasitism to derive an estimate of seasonal fecundity. Clutch size of parasitized nests was reduced in four host species. Brood parasitism did not affect hatching rate in any species, and reduced the number of fledglings from only Blue Grosbeak (Guiraca caerulea) nests. Despite brood reduction during the nesting cycle, cowbird parasitism had little impact on seasonal fecundity of these host species because of low parasitism intensity, double-brooding behavior, and hosts' ability to raise their own young with cowbird young.
Sociality and Foraging Behavior of the Cerulean Warbler in Venezuelan Shade-Coffee Plantations
Authors: Jones Jason , Perazzi Paolo Ramoni , Carruthers Erin H. , Robertson Raleigh J. 
Published: September 2019

Abstract
We examined the use of Venezuelan shade-coffee plantations by the Cerulean Warbler (Dendroica cerulea) and other Neotropical migrants. Cerulean Warblers were commonly observed as pairs in mixed-species flocks. Average (± SE) flock size was 13 ± 2 species with 22 ± 3 individuals. Average flock territory size was 2.5 ± 0.2 ha. No differences were detected in foraging behavior (maneuvers, location, or success) among adult males, adult females, and immature birds. Adult males were often observed visiting flowers of canopy trees. The results of this study indicate that shade coffee plantations may provide suitable wintering habitat for Cerulean Warblers although comparisons with other habitats are needed.
Comparative Phylogeography of Some Aridland Bird Species
Authors: Zink Robert M. , Kessen Ann E. , Line Theresa V. , Blackwell-Rago Rachelle C. 
Published: September 2019

AbstractWe compared mitochondrial DNA sequences for six species distributed across the aridlands of North America to document phylogeographic patterns and assess levels of congruence. The Curve-billed Thrasher (Toxostoma curvirostre) and Canyon Towhee (Pipilo fuscus) show genetic divisions between the Sonoran and Chihuahuan Deserts, whereas the Cactus Wren (Campylorhynchus brunneicapillus), Black-tailed Gnatcatcher (Polioptila melanura), and Verdin (Auriparus flaviceps) do not. Most likely, species without phylogeographic structure only recently colonized their entire current range. Therefore, although these species are today part of a widespread avifauna, species' distributions were historically different from today. In Baja California, the Cactus Wren and the Verdin show phylogeographic breaks at 28°–30°N, consistent with a division previously described in the LeConte's Thrasher (Toxostoma lecontei) and in some members of the herpetofauna. These genetic divisions were likely caused by isolation resulting from a mid-peninsular seaway that existed one million years ago. Hence, these species appear to have been broadly sympatric for at least one million years. In contrast, the California Gnatcatcher (Polioptila californica) lacks such a phylogeographic division, and apparently only recently expanded into the northern part of its current range. Thus, not all species in Baja California have had similar histories, although further sampling might reveal a general pattern. Comparative phylogeography therefore provides an indirect method of evaluating the long-term stability of faunas via assessment of levels of phylogeographic congruence, and can show whether particular species are likely to have had a long period of co-association.
Using Hydrogen Isotope Geochemistry to Estimate the Natal Latitudes of Immature Cooper's Hawks Migrating Through the Florida Keys
Authors: Meehan Timothy D. , Lott Casey A. , Sharp Zachary D. , Smith Ruth B. , Rosenfield Robert N. , Stewart Andrew C. , Murphy Robert K. 
Published: September 2019

AbstractWe constructed a regression model for the relationship between stable-hydrogen isotope ratios in immature Cooper's Hawk (Accipiter cooperii) feathers (δDf) and precipitation in areas where feathers were grown (δDp) across much of the latitudinal and longitudinal extent of the species' breeding range. We used our model to estimate δDp values from δDf values of immature Cooper's Hawks captured during migration in the Florida Keys. We compared these estimated δDp values to a published map of δDp values of North American precipitation to learn the latitudinal origins of migrants. We reviewed previous migration banding studies to estimate the longitudinal range of migrants. Our analysis suggested that most of the immature Cooper's Hawks migrating through the Keys originated in natal areas in the Mid-Atlantic and Southeast regions of the continent. We found no difference in the passage date of northern and southern birds or in the latitudinal origins of males and females. This new information will aid in the interpretation of population trends generated from the ongoing migration count in the Keys.
Repertoire, Structure, and Individual Distinctiveness of Thick-Billed Murre Calls
Authors: Lefevre Kara , Gaston Anthony J. , Montgomerie Robert 
Published: September 2019

Abstract
We describe the vocal repertoires of Thick-billed Murre (Uria lomvia) adults and chicks during the breeding season. Using recordings from throughout the chick-rearing period, we identified four distinct calls of chicks and six of adults. We present sonograms and quantitative descriptions of each call and summarize the behavioral context in which they were used. Chick calls are mostly flute-like sounds at approximately the same pitch that tend to develop from a simple peep during hatching through a rapidly frequency-modulated departure call, given shortly before, during, and after they leave the colony at fledging. Departure calls appear to facilitate interactions between the chick and the attending male parent during this risky period for the chick. Adult calls are lower pitched and sound more gruff, with different call types having significantly different pitch, duration, and number of syllables. Among-individual variation in the crow calls of adults accounts for 44% of the measured variation in this call and indicates the potential for individual recognition, such as the recognition of parents' calls by their chicks, which we have previously documented. Temporal features may form the basis of recognition of adult calls in this species, given that they accounted for twice as much variation as frequency features among individual adults.
Do Woodpecker Drums Encode Information for Species Recognition?
Authors: Dodenhoff Danielle J. , Stark Robert D. , Johnson Eric V. 
Published: September 2019

Abstract
We investigated whether woodpecker drums are exchanged interspecifically and attempted to ascertain the drum variables responsible for species recognition. Playback experiments were conducted on four woodpecker species (Nuttall's Picoides nuttallii, White-headed P. albolarvatus, Hairy P. villosus, and Downy P. pubescens Woodpeckers) comparing behavioral responses to sympatric hetero- and conspecific drums. There was a significant difference in behavioral responses to sympatric hetero- versus conspecific drums; individuals responded less intensely to drums of heterospecifics when drum cadences were dissimilar. Allopatric species drums with similar cadences were used to examine whether cadence was a variable that encodes species identity. There was no significant difference between responses to allopatric hetero- versus conspecific drums with a similar cadence, indicating that the drum's cadence encodes information for species recognition. Further playbacks eliminated drum duration and spectral properties as important variables for species recognition. Results suggest that if an individual drums at a similar cadence to a sympatric heterospecific, then their signal may elicit a conspecific response.