bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Analysis of Vocal Communication in Young Brown Noddies (Anous stolidus)
Authors: Riska Diane E. 
Published: October 2019

Abstract
Nestlings and young fledglings of the Brown Noddy (Anous stolidus) produce three structurally different vocal signals. The postures of the chicks and the contexts in which these signals are produced differ for each call. Nestlings produce all three calls within one day after hatching. One is given during pipping, when the chick is moving on or near the nest, or when it is isolated from the nest. The second is given by begging chicks. The third is given when an intruder approaches. The repertoire is composed of frequency-modulated tonal elements and broad-band bursts of sound. Although changes occur in the temporal and frequency patterns of the calls during the nestling and fledgling stages, there is little resemblance to the adult repertoire during these periods.
Survival Analysis of Eggs and Chicks of AdÉlie Penguins (Pygoscelis adeliae)
Authors: Davis Lloyd S. , McCaffrey Frances T. 
Published: October 2019

Abstract
Survival analysis was used to examine the fates of eggs in six colonies of Adélie Penguins (Pygoscelis adeliae) at Cape Bird, Antarctica. Hatching success was 56.2% and fledging success for chicks was 63.3%, giving an overall reproductive success of 35.6%. The major cause of losses of both eggs and chicks was predation by South Polar Skuas (Catharacta maccormicki). The second-most important causes of egg and chick mortality were desertion and starvation, respectively, both of which resulted from inadequate timing of nest relief. Eggs were at risk of predation by skuas throughout the incubation period, while chicks were at risk for the first 30 days after hatching. The likelihood of desertion increased after the eggs had been incubated for 16 days and reached a peak at 22-24 days. Starvation occurred during the guard stage and was most likely to occur when chicks were 6-8 days old. Timing of breeding and clutch size were factors that influenced the survival of eggs through the initial stage of incubation. Nest location had a significant effect on the survival of eggs and chicks, from laying through the end of the guard stage. Eggs laid in 2-egg clutches and in central nests were most likely to produce chicks that fledged.
Mitochondrial DNA: A Source of Genetic Markers for Studies of Similar Passerine Bird Species
Authors: Mack Andrew L. , Gill Frank B. , Colburn Robert , Spolsky Christina 
Published: October 2019

Abstract
Restriction enzyme analyses of mitochondrial DNA (mtDNA) of the Black-capped Chickadee (Parus atricapillus), Carolina Chickadee (P. carolinensis), and Tufted Titmouse (P. bicolor) indicate substantial genetic divergence (p = 0.04-0.09). Eleven of 14 enzymes produced fragment patterns that distinguish the two chickadees, revealing a bounty of markers for studies of these sibling species.
Female Choice in Middendorff's Grasshopper-Warbler (Locustella Ochotensis)
Authors: Nagata Hisashi 
Published: October 2019

Abstract
Morphological and territorial factors that influence female mate choice were examined in the monogamous Middendorff's Grasshopper-Warbler (Locustella ochotensis) on an islet near Fukuoka, Japan. I assumed that pairing date corresponded with female mate choice. Pairing date was correlated with both territory size and food abundance but was not correlated with selected morphological characteristics of males. Territorial quality was assumed to be correlated with territory size because preferable food resources and nest sites were distributed randomly. I conclude that female mate choice was influenced by territory quality rather than by the morphological characteristics of males.
Low Genic Variation between Black Ducks and Mallards
Authors: Ankney C. Davison , Dennis Darrell G. , Wishard Lisa N. , Seeb James E. 
Published: October 2019

Abstract
We used allozyme electrophoresis to estimate the degree of genetic differentiation among allopatric and sympatric populations of American Black Ducks (Anas rubripes) and Mallards (A. platyrhynchos). Mallards were collected in California, Saskatchewan, Manitoba, and Ontario, and Black Ducks were collected in Newfoundland, Nova Scotia, and Ontario. The mean genetic distances, D̄, between Black Duck populations (0.0007), between Mallard populations (0.0010), and between Mallard and Black Duck populations (0.0006) were virtually identical; there was as much genetic differentiation within the two species as there was between them. Such small genetic distances are characteristic of local populations of avian species in other orders, and are consistent with what is known about the lack of reproductive isolation between Black Ducks and Mallards. Although the two taxa are still somewhat split on an east-west basis, our genetic data do not support even subspecific status for the Black Duck.
Foraging Behavior of Gentoo and Chinstrap Penguins as Determined by New Radiotelemetry Techniques
Authors: Trivelpiece Wayne Z. , Bengtson John L. , Trivelpiece Susan G. , Volkman Nicholas J. 
Published: October 2019

Abstract
Analysis of radio signals from transmitters affixed to 7 Gentoo (Pygoscelis papua) and 6 Chinstrap (P. antarctica) penguins allowed us to track penguins at sea. Signal characteristics allowed us to distinguish among 5 foraging behaviors: porpoising, underwater swimming, horizontal diving, vertical diving, and resting or bathing. Gentoo Penguins spent a significantly greater portion of their foraging trips engaged in feeding behaviors than Chinstraps, which spent significantly more time traveling. Gentoos had significantly longer feeding dives than Chinstraps (128 s vs. 91 s) and significantly higher dive-pause ratios (3.4 vs. 2.6). These differences in foraging behavior suggest Gentoo and Chinstrap penguins may have different diving abilities and may forage at different depths.
Divergent Prey Selection in Two Species of Waterthrushes (Seiurus)
Authors: Craig Robert J. 
Published: October 2019

Abstract
I studied Louisiana (Seiurus motacilla) and Northern (S. noveboracensis) waterthrushes during an exceptionally dry spring to determine if environmental stress elicited interspecific competition. Previously, I had found little evidence for competition between these species despite wide overlap in foraging methods, use of foraging microhabitats, and characteristics of breeding habitat. I observed breeding adults forage by placing them in a portable flight cage located in natural habitat, and concurrently gathered data on the influence of waterthrush foraging on aquatic invertebrate prey and prey abundance. The species selected different prey. Louisiana Waterthrushes fed predominantly on Trichoptera larvae and on larger average prey than did Northern Waterthrushes, which fed predominantly on Diptera larvae. The species had similar foraging methods and attack rates, indicating that, unlike many Parulinae, their principal foraging differences were in prey selection rather than in means of locating prey. Experiments with foraging exclosures gave no clear evidence that waterthrushes affected prey biomass or composition. There was no significant relation between territory size vs. prey biomass and water cover. No interspecific aggression was observed, and territories overlapped widely, indicating that interference competition did not occur. Divergence in prey selection implies exploitive competition, but invertebrate and habitat data indicate that prey were not limiting, thus making competition for prey unnecessary. Therefore, from these data I cannot eliminate the alternative hypothesis that observed differences between the species may only reflect independent specialization.
Revision of “Falco” Ramenta Wetmore and the Neogene Evolution of the Falconidae
Authors: Becker Jonathan J. 
Published: October 2019

Abstract
"Falco" ramenta Wetmore 1936 is redescribed and moved to a new genus as Pediohierax ramenta (Wetmore). In addition to the holotypical distal end of the tarsometatarsus, this species is now known from a complete tarsometatarsus, humerus, and coracoid from mid-Miocene (Late Hemingfordian and Early Barstovian) fossil localities in the Sheep Creek and Olcott formations, northwestern Nebraska. Pediohierax n. gen. is the primitive sister group of the Falconinae. The earliest fossil records now known of the Falconinae are a species of? Falco from the late Miocene of Idaho and Falco medius from the late Miocene of the Ukrainian S.S.R.
Chlorostilbon bracei Lawrence, an Extinct Species of Hummingbird from New Providence Island, Bahamas
Authors: Graves Gary R. , Olson Storrs L. 
Published: October 2019

Abstract
Chlorostilbon bracei Lawrence, known from the unique holotype taken on New Providence Island, Bahamas, in 1877, is shown to be a valid species that is evidently now extinct. Compared with C. ricordii of Cuba and the Bahamas, C. bracei is smaller, has a longer bill, and has distinctly different plumage. Fossil evidence demonstrates that a small Chlorostilbon, tentatively referred to C. bracei, was present on New Providence in the Pleistocene. Populations of C. ricordii from Andros, Abaco, and Grand Bahama are indistinguishable from Cuban birds, and C. ricordii is therefore regarded as monotypic.
Suppression of Autumnal Migratory Unrest in Dark-Eyed Juncos Held During Summer on, Near, or Far From their Previous Wintering Sites
Authors: Ketterson Ellen D. , Nolan Val 
Published: October 2019

Abstract
In previous experiments, Dark-eyed Juncos (Junco hyemalis) were captured on a winter home range to which they had shown year-to-year site fidelity and held there until just before the autumn. They failed to show normal autumn migratory restlessness and fattening, which suggested that previous experience at the migratory destination suppressed readiness to migrate. We asked what the suppressing cues might be. Possibilities included very local features peculiar to the individual's winter home range (e.g. its trees) and cues common to the general region (e.g. geophysical or celestial information); features of the latter sort might give information about latitude. To test these possibilities we monitored autumn restlessness and fattening of new groups of juncos that were held before migration where some could perceive landmarks of their familiar winter home range and others only more general information about their location. In autumn those held at, near, and far south of their winter home ranges again failed to become restless or fat. A small group held far north of their winter home ranges became somewhat restless, significantly more so than the others. These may have perceived that they had not reached their usual winter latitude, but alternative explanations are possible.
Multiple Paternity in a Wild Population of Mallards
Authors: Evarts Susan , Williams Christopher J. 
Published: October 2019

Abstract
Blood, heart, liver, and breast muscle samples from wild Mallard (Anas platyrhynchos) hens and their ducklings were analyzed using starch-gel electrophoresis. We found that 17.4% of the total broods sampled (n = 46) involved observable multiple mating events, that 25.8% of the sample broods involved multiple mating events when broods that were unlikely to yield information on multiple paternity were excluded (n = 31), and that a pooled maximum-likelihood estimate indicated a 60% chance that a particular duckling came from a brood that was multiply fathered, or at least 48% of broods involved multiple mating events.
Morphometric Correlates of Age and Breeding Status in American Coots
Authors: Alisauskas Ray T. 
Published: October 2019

Abstract
I studied morphometric variation in 13 linear measurements from 228 American Coots (Fulica americana) collected in southern Manitoba. Univariate and multivariate techniques revealed differences in size and shape among adult coots that were 1, 2, and =2 yr old. In addition to the obvious differences in size between males and females, the morphometry of older birds differed from that of younger birds in two ways. First, older coots were of larger body size than younger coots of the same sex. Second, older coots had proportionately larger feet and claws relative to the size of their tarsi, and proportionately wider bills and heads relative to other head measurements, than did younger birds. Multivariate dispersion matrices within age/sex cohorts were less variable for older coots. In an analysis of 1-yr-old males, breeders did not differ from nonbreeders in overall body size, but breeders had relatively longer claws and wings than nonbreeders. Age-related differences in morphology may have relevance to the social structure of nesting coots, which involves highly aggressive territorial behavior. Part of the age-related variation in nesting phenology that has been documented elsewhere for coots may be a consequence of covariation in body size and shape.
Feeding-Time Minimization and the Territorial Behavior of the Willow Flycatcher (Empidonax traillii)
Authors: Prescott David R. C. , Middleton Alex L. A. 
Published: October 2019

Abstract
We studied breeding male Willow Flycatchers (Empidonax traillii) to test a model of optimal territorial behavior for feeding-time minimizers proposed by Hixon (1980). Specific predictions were that feeding time, defense time, and territory size should decrease with increasing food availability and increase with increased pressure from both conspecific and heterospecific competitors.
The constant reproductive output of 4 and 3 eggs for first and second clutches, respectively, and the large component of uncommitted (sitting) time (62.6 ± 3.2%) over the breeding season confirmed that the Willow Flycatcher conformed to a time-minimization strategy. Data analyzed over three stages of the breeding cycle, and over all stages, however, showed that only 5 of the 36 possible relationships were significant as predicted by the model. In general, food availability and competitor pressure were not important influences on the territorial behavior of these birds. Variations in territory size could not be attributed to constraints on feeding time, but correlated closely with the energetic requirements of all birds occupying the territory.
We believe that breeding insectivorous passerines, including Willow Flycatchers, maintain a large component of uncommitted time, as well as a larger than necessary territory, to minimize the impact of short-term variations in competitor pressure and food supply. Such birds need not conform to the predictions of models that optimize foraging time.
Evolutionary Genetics of Flycatchers. II. Differentiation in the Empidonax difficilis Complex
Authors: Johnson Ned K. , Marten Jill A. 
Published: October 2019

Abstract
We used starch-gel electrophoresis to assess variability at 41 genetic loci in 208 individuals from 11 breeding populations of the Western Flycatcher (Empidonax difficilis) complex. Genic variability was substantial in most populations and equivalent to levels found in other avian taxa. A sample of E. d. insulicola from Santa Catalina Island, however, showed reduced heterozygosity and an unusually low percentage of polymorphic loci. We attribute this to a bottleneck at the time of the original colonization. Nei's genetic distances among populations of one taxon ranged from D̄ = 0.0003 (in E. d. difficilis) to D̄ = 0.0033 (in E. d. hellmayri). Intertaxon Nei's D̄ ranged from 0.009 (E. d. insulicola vs. E. d. difficilis) and 0.0149 (E. d. difficilis vs. E. d. hellmayri) to 0.0228 (E. d. insulicola vs. E. d. hellmayri). to 0.0228 (E. d. insulicola vs. E. d. hellmayri). F statistics revealed significant population subdivision within the complex. With Slatkin's rare-allele method we estimated the gene-flow parameter, Nm. Mainland populations experience moderately high gene flow (9.62 immigrants/generation). In contrast, Santa Catalina Island receives an estimated 0.093 immigrants/generation, pointing to very low gene flow and essential genetic isolation.
Genetic distances yielded phenograms and distance Wagner trees that provide hypotheses for the relationships and phylogenesis of populations in western North America. The lineage leading to modern E. d. difficilis split from that leading to E. flavescens in the mid-Pleistocene at 866,800 yr BP; the ancestors of modern E. d. difficilis diverged from those of present-day E. d. hellmayri at 248,700 yr BP; and the stock leading to modern E. d. insulicola budded from the lineage that became E. d. difficilis in the late Pleistocene, approximately 187,000 yr BP.
Empidonax d. difficilis and E. d. hellmayri nest sympatrically and mate assortatively in the Siskiyou region of northern California. Interbreeding has not been demonstrated conclusively, and we regard these taxa as biologic species. In the absence of a test of sympatry, the well-differentiated form E. d. insulicola of the California Channel Islands cannot be proved to be a biologic species. It is clearly a phylogenetic species, however, in the sense of Cracraft.
Asynchronous Hatching and Food Limitation: A Test of Lack's Hypothesis
Authors: Skagen Susan Knight 
Published: October 2019

Abstract
Lack's (1954, 1968) hypothesis that asynchronous hatching of altricial birds is an adaptive response to unpredictable food shortages during the breeding season was examined in the highly granivorous Zebra Finch (Poephila guttata). I compared growth and survival of nestlings in asynchronous and artificially created synchronous broods reared under food-limited and food-abundant conditions in an aviary. I also examined the role of parental experience on survival and growth of nestlings.
There was no differential mortality of Zebra Finch nestlings due to either asynchrony or food abundance. Young in abundant food treatments grew more rapidly, however, than those in food-restricted treatments. Heaviest Zebra Finch nestlings in a brood grew more quickly than their lightest siblings when food was limited, supporting Lack's hypothesis. Further, differential survival of light and heavy siblings occurred when food was abundant, suggesting that asynchronous hatching can be maladaptive under some ecological conditions. Nestlings reared by inexperienced parents suffered greater mortality and slower growth when food was abundant than nestlings raised by experienced parents. Prefledging mass was correlated with size at adulthood.
Status Signaling Is Absent within Age-and-Sex Classes of Harris' Sparrows
Authors: Jackson Wendy M. , Rohwer Sievert , Winnegrad Robin L. 
Published: October 2019

Abstract
We tested the status-signaling hypothesis in two groups of same-age and same-sex Harris' Sparrows (Zonotrichia querula). Unlike flocks of mixed age and sex composition, badge size did not correlate with social status in these groups; thus, status signaling does not appear to occur within age-and-sex classes of Harris' Sparrows. Other predictions of the status-signaling hypothesis we tested were that (1) fighting ability and social status should be correlated, and (2) fighting ability and badge size should be correlated. We used a multivariate assessment of body size as an indicator of fighting ability and found no support for either prediction in the flock of adult females. In the flock of adult males, large birds were more dominant (Prediction 1) but fighting ability and badge size were not correlated (contra Prediction 2).
A Partial Classification of Waterfowl (Anatidae) Based on Single-Copy DNA
Authors: Madsen Cort S. , McHugh Kevin P. , de Kloet Siwo R. 
Published: October 2019

Abstract
Single-copy DNA-DNA hybridization was used to establish phylogenetic relationships among 13 species of waterfowl (Anatidae) chosen from 10 tribes. On the basis of UPGMA clustering of Delta Tm distances, we suggest that the tribes Anatini, Aythyini, Tadornini, Mergini, and Cairinini diverged more recently than the Anserini, Stictonettini, Oxyurini, Dendrocygnini, and Anseranatini. The Freckled Duck (Stictonetta naevosa, tribe Stictonettini) is only distantly related to the other Anatidae. Presumably the lineage diverged very early. The sheldgeese (tribe Tadornini) and the true geese (Anserini) are only remotely related. The Oxyurini, considered to be in the subfamily Anatinae, is remotely related to the other Anatidae. The Dendrocygnini form an isolated tribe with no close relationship to the swans and geese (subfamily Anserinae). We found that the screamers (Anhimidae) are distantly related to the Anatidae.
A method to estimate missing cells in a data matrix of pairwise distances is presented.
Molecular Genetic Divergence between Avian Sibling Species: King and Clapper Rails, Long-Billed and Short-Billed Dowitchers, Boat-Tailed and Great-Tailed Grackles, and Tufted and Black-Crested Titmice
Authors: Avise John C. , Zink Robert M. 
Published: October 2019

Abstract
Surveys of electrophoretic variation in proteins, and restriction site variation in mitochondrial DNA (mtDNA), were conducted to assess the resolving power of these molecular genetic techniques to distinguish four pairs of avian sibling taxa. Samples of rails (Rallus elegans and R. longirostris), dowitchers (Limnodromus scolopaceus and L. griseus), grackles (Quiscalus major and Q. mexicanus), and titmice (Parus bicolor bicolor and P. b. atricristatus) were assayed for allozymes encoded by 34-37 nuclear loci, and for an average of 77 mtDNA restriction sites per individual by 19 endonucleases. MtDNA's of the two rail species showed large-scale size polymorphism and individual heteroplasmy, the first such findings of these molecular features in an avian species. Genetic distances based on allozyme comparisons were small for all assayed taxa (Nei's D ≤ 0.063). The mtDNA assays offered consistently greater resolving power, providing at least five fixed restriction site differences for samples of any taxon pair. The Long-billed and Short-billed dowitchers were especially divergent, differing by at least 24 assayed mtDNA restriction sites and an estimated nucleotide sequence divergence of p = 0.082. We compared these results to previous reports of genetic distances within and among closely related bird species. The mtDNA divergence among dowitchers is near the high end of the scale of such estimates for avian congeners. The mtDNA distances between the pairs of rails (p = 0.006), titmice (p = 0.004), and grackles (p = 0.016) were typical for extremely closely related species, and overlap maximum values reported for some avian conspecifics.
Body-Size Variation and Fitness Components in Lesser Snow Geese (Chen caerulescens caerulescens)
Authors: Davies J. Chris , Rockwell R. F. , Cooke Fred 
Published: October 2019

Abstract
We examined the potential action of selection on body size in a population of Lesser Snow Geese (Chen caerulescens caerulescens) breeding in the Canadian subarctic. We evaluated the genetic basis of phenotypic variation in body size and examined the association of body size and components of fitness related to fecundity and viability. There was a heritable component to body size in this population derived in part from the action of additive genes. There was no relation between adult body size and the number of eggs laid, the number of eggs surviving predation, the number of goslings that left the nest, or the number of goslings fledged. Small birds entered the breeding population at a younger age. They did so with no reduction in viability and may actually live longer than large birds. The heritable variation in body size combined with the directional selection gradient should lead to a gradual reduction in adult body size in this population. We found no evidence for such a change over 5 generations. We discuss this in terms of additional fitness components, the retarding effects of age structure on the response to selection, and the interaction of selection and gene flow.