bluuebunny/crossref_metadata_2025_split huggingface dataset:
Testosterone Does not Increase in Response to Conspecific Challenges in the White-Bellied Antbird (Myrmeciza Longipes), A Resident Tropical Passerine
Authors: Fedy Bradley C. , Stutchbury Bridget J. M. 
Published: September 2019

Abstract
Resident tropical passerines that exhibit year-round territorial aggression do not fit well into the temperate-zone model, because testosterone does not increase substantially during the breeding season. We studied patterns of testosterone secretion in the White-bellied Antbird (Myrmeciza longipes), a resident tropical species in Panama that maintains territories year-round and is capable of aggression throughout the year, regardless of its stage of reproduction. Levels of plasma testosterone were low (mean = 0.30 ng mL−1) throughout the breeding and nonbreeding seasons and did not differ between them. Testosterone also did not increase in response to simulated conspecific intrusions. When we used temporary removal experiments to induce natural, extended conflict between males, testosterone levels did not increase in response to the extended social instability that resulted. White-bellied Antbirds demonstrate an apparent uncoupling of testosterone and territorial aggression throughout the year.
La Testosterona no Aumenta como Respuesta a Desafíos de Individuos Coespecíficos en Myrmeciza longipes, un Paserino Residente de la Zona Tropical
Fat Dynamics of Arctic-Nesting Sandpipers During Spring in Mid-Continental North America
Authors: Krapu Gary L. , Eldridge Jan L. , Gratto-Trevor Cheri L. , Buhl Deborah A. 
Published: September 2019

Abstract
We measured fresh body mass, total body fat, and fat-free dry mass (FFDM) of three species of Arctic-nesting calidrid sandpipers (Baird's Sandpiper [Calidris bairdii], hereafter “BASA”; Semipalmated Sandpiper [C. pusilla], hereafter “SESA”; and White-rumped Sandpiper [C. fuscicollis], hereafter “WRSA”) during spring stopovers in the Prairie Pothole Region (PPR) of North Dakota, and evaluated the contribution of stored fat to (1) energy requirements for migration to their Arctic-breeding grounds and (2) nutrient needs for reproduction. All spring migrant WRSA (n = 124) and BASA (n = 111), and all but 2 of 99 SESA we collected were ≥2 years old. Male and female BASA migrated through North Dakota concurrently, male SESA averaged earlier than females, and WRSA males preceded females. Fat indices (ratio of fat to FFDM) of male and female SESA and WRSA averaged approximately twice those of male and female BASA. Total body fat of male and female BASA increased with date in spring 1980, but not in 1981; slopes were similar for both sexes each year. Male and female SESA arrived lean in 1980 and 1981, and total body fat increased with date in both years, with similar slopes for all combinations of sex and year. Male and female WRSA arrived lean in 1980–1981 and 1981, respectively, and total body fat increased with date, whereas females arrived with fat reserves already acquired in 1980. Interspecific and sex differences in migration schedules probably contributed to variation in fat storage patterns by affecting maintenance energy costs and food availability. Estimated flight ranges of BASA suggest that few could have met their energy needs for migration to the breeding grounds exclusively from fat stored by the time of departure from North Dakota. Estimated flight ranges of SESA and WRSA, along with fresh body masses of both species when live-trapped on or near their breeding grounds in northern Canada, suggest that major parts of both populations stored adequate fat by departure from temperate mid-continental North America to meet their energy requirements for migration and part of their nutrient needs for reproduction.
Dinámica de la Grasa en Chorlos que Nidifican en el Ártico durante la Primavera en el Área Continental Central de América del Norte
A New Species of Hawaiian Finch (Drepanidini: Loxioides) From Makauwahi Cave, Kaua‘i
Authors: James Helen F. , Olson Storrs L. 
Published: September 2019

Abstract
A new species of Hawaiian finch is described from two fossil maxillae recovered from Holocene lacustrine sediments in Makauwahi Cave, island of Kaua‘i. The new species is assigned to Loxioides on the basis of characters defined in a previous study of drepanidine phylogeny. The maxilla of the new species resembles that of L. bailleui (the only other member of the genus) in its distinctly foreshortened shape, but differs in size and several qualitative characters. The species was sympatric with Loxioides cf. bailleui during the Holocene on Kaua‘i. Like L. bailleui, it may have been a resource specialist feeding mainly on leguminous pods. The radio-carbon chronology of the Makauwahi site indicates that the species became extinct in the late Holocene and, more tentatively, that it may have survived well beyond the time when humans first discovered and colonized Kaua‘i.
Una Nueva Especie de Pinzón de Hawaii (Drepanidini: Loxioides) de la Cueva Makauwahi, Kaua‘i
Point-Transect Surveys for Songbirds: Robust Methodologies
Authors: Buckland Stephen T. 
Published: September 2019

AbstractPoint-transect sampling is widely used for monitoring trends in abundance of songbirds. It is conceptualized as a “snapshot” method in which birds are “frozen” at a single location. With conventional methods, an observer records birds detected from a point for several minutes, during which birds may move around. This generates upward bias in the density estimate. I compared this conventional approach with two other approaches: in one, the observer records locations of detected birds at a snapshot moment; in the other, distances to detected cues (songbursts), rather than birds, are recorded. I implemented all three approaches, together with line-transect sampling and territory mapping in a survey of four bird species. The conventional method gave a biased estimate of density for one species. The snapshot method was found to be the most efficient of the point-sampling methods. Line-transect sampling proved more efficient than the point-sampling methods for all four species. This is likely to be generally true, provided that terrain and habitat allow easy use of a design with random transect lines. I concluded that the snapshot method is more appropriate than the conventional timed-count method for surveying songbirds. Although precision was rather poor with the cue-based method (partly because too few resources were devoted to cue rate estimation), it may be particularly useful for some single-species surveys. In addition, it is the only valid method for estimating abundance from surveys in which acoustic equipment is used to detect birds.Muestreos en Transectos Puntuales para Aves Canoras: Metodologías Robustas
Salinity and Population Parameters of Bald Eagles (Haliaeetus Leucocephalus) in the Lower Chesapeake Bay
Authors: Watts Bryan D. , Markham A. Catherine , Byrd Mitchell A. 
Published: September 2019

Abstract
We evaluated the relationship between salinity and Bald Eagle (Haliaeetus leucocephalus) population parameters using 26 years of survey data for the lower Chesapeake Bay. Tidal tributaries within the study area were stratified according to the Chesapeake Bay Program's segmentation scheme, and segments with the same salinity classification were considered spatial replicates. Salinity categories included tidal fresh, oligohaline, mesohaline, and polyhaline. Four parameters— colonization rate, nesting density, projected carrying capacity, and productivity— were derived from nesting data within each shoreline segment and compared across the salinity gradient. The study-wide Bald Eagle population is exhibiting exponential growth, with an average doubling time of 7.9 years. All population parameters showed significant directional variation with salinity. Average population doubling time for tidal fresh reaches was <6 years, compared with >16 years for polyhaline areas. Current Bald Eagle nesting density is negatively related to salinity and varies by a factor of 4 across the gradient. Comparison of current densities with projected carrying capacity suggests that these differences will be stable or increasing as the geographic areas approach equilibrium densities. We suggest that fisheries within lower saline reaches, including spring spawning runs of anadromous Clupeidae (shad and herring), are the most likely explanation for salinity effects. Observed distribution patterns suggest that lands along low-salinity waters are the core of the Bald Eagle nesting population within the lower Chesapeake Bay and should be the focus of long-term programs designed to benefit nesting eagles.
Salinidad y Parámetros Poblacionales de Haliaeetus leucocephalus en la Bahia de Chesapeake
Egg Rejection in Marsh Warblers (Acrocephalus Palustris) Heavily Parasitized by Common Cuckoos (Cuculus Canorus)
Authors: Antonov Anton , Stokke Bård G. , Moksnes Arne , Røskaft Eivin 
Published: September 2019

AbstractIn the coevolutionary “arms race” between Common Cuckoos (Cuculus canorus) and their hosts, several adaptations and counter-adaptations have evolved. Here, we investigated natural parasitism and host sensitivity to egg rejection in Marsh Warblers (Acrocephalus palustris) in Bulgaria. The level of Common Cuckoo parasitism was high (28%), and average mimicry of Common Cuckoo eggs was good. Experimental parasitism with four egg-types that showed various degrees of mimicry of the host eggs revealed a generally high rejection rate of foreign eggs (37.5–100%). In addition, naturally laid Common Cuckoo eggs were rejected at a moderate rate (50%). The Marsh Warbler's ability to reject foreign eggs was strongly dependent on the degree of mimicry of the parasite egg but apparently not on differences in size between host and foreign eggs. Furthermore, intraclutch variation in host egg appearance was not related to the probability of egg rejection. The Marsh Warbler's highly developed egg-recognition ability and the good mimicry of Common Cuckoo eggs suggests that this poorly known host-parasite arms race has reached an advanced stage. The present study provides new insight into variables that are important for egg rejection in a heavily parasitized host population.Rechazo de Huevos en Nidos de Acrocephalus palustris Fuertemente Parasitados por Cuculus canorus
Stable Isotope Evidence Links Breeding Geography and Migration Timing in Wood Warblers (Parulidae)
Authors: Kelly Jeffrey F. 
Published: September 2019

AbstractTracking seasonal movements of songbirds is a key step in understanding the annual cycle of migrants. To better understand autumn migration of wood warblers, I analyzed stable-hydrogen isotope ratios of feathers collected from three species captured during stopover at the Bosque del Apache National Wildlife Refuge, New Mexico. To assess the form and strength of the relationship between timing of migration and breeding origins, I regressed stable-hydrogen isotope ratios of feathers against date of capture. These analyses indicated that Orange-crowned Warblers (Vermivora celata) and Common Yellowthroats (Geothlypis trichas) breeding in the southern portion of these species' ranges precede their northern conspecifics in autumn migration. By contrast, Yellow Warblers (Dendroica petechia) from northern breeding sites arrived before more southerly breeding conspecifics. This pattern is similar to that reported previously in Wilson's Warbler (Wilsonia pusilla). These findings suggest that, among wood warblers, (1) timing of autumn migration is often strongly related to breeding location and (2) interspecific variation in the direction of this relationship is large. The direction and strength of these patterns have implications for our understanding of inter- and intraspecific geographic variation in the life histories of migrants.Evidencia de Isótopos Estables Conecta la Geografía de Nidificación con el Momento de la Migración en Especies de Parulidae
Are Point Counts of Boreal Songbirds Reliable Proxies for More Intensive Abundance Estimators?
Authors: Toms Judith D. , Schmiegelow Fiona K. A. , Hannon Susan J. , Villard Marc-André 
Published: September 2019

AbstractPoint counts are often used to provide information on abundance of songbirds. If data from point counts are to be compared in space or time, however, any bias in the estimate should be consistent and linearly related to the true abundance. Several studies have suggested that this assumption may be violated for songbirds. Here, we used double sampling to test whether point counts are linearly related to true abundance, as estimated from spot mapping, for 12 songbird species in the boreal mixed-wood forest of northern Alberta, Canada. We found that total abundance of birds across several point-count stations was positively correlated with the number of territories and confirmed that point counts were linearly related to spot-mapping abundance for the species tested. However, large sampling errors masked this relationship at the scale of a single point-count station (100-m fixed-radius plot). Double-sampling models that accounted for differences in abundance between spot-mapping grids using random effects improved prediction for most species. We found no year effect on detectability. Maximum abundance over point-count rounds was a more sensitive index of abundance than mean abundance and tended to produce better-fitting models. Point-count abundance was more closely related to true abundance in species with relatively small territories, or those with large spatial or temporal variation in density. Our results further suggest that point-count abundance may be proportional to the total length of territorial boundaries in the plot rather than the total fraction of territories in the plot. Our analysis suggests that point counts provide a reasonable index of abundance, even though individual point-count stations are not consistently effective in estimating the density of territorial individuals.Est-ce que les Points D'Écoute de Passereaux Boréaux Constituent une Méthode Fiable pour L'Obtention D'Estimateurs D'Abondance Plus Avancés?
Phylogenetic Tests of Hypotheses for the Evolution of Avian Migration: A Case Study Using the Motacillidae
Authors: Outlaw Diana C. , Voelker Gary 
Published: September 2019

AbstractThe evolution of avian migration continues to be an intriguing research subject, even though relationships between migration and factors such as seasonality clearly exist. The question remains whether these relationships are evident within phylogenies containing both sedentary and migratory taxa. We explore the evolution of migration in the family Motacillidae by evaluating existing hypotheses for the evolution of migration in a comparative, phylogenetic framework at the interspecific level. Many hypotheses to explain the evolution of avian migration—such as the “evolutionary precursor” hypothesis (Levey and Stiles 1992, Chesser and Levey 1998) and the “stepping-stone” hypothesis (Cox 1968, 1985)—are based on New World migratory systems. The central components of these hypotheses should apply across biogeographic realms (i.e. the Old World), given that seasonality and habitat regimes are similar in the New and Old worlds. Using a molecular phylogeny containing most species in the Motacillidae, we investigated the potential interactions of seasonality and ecology with migratory and sedentary behavior. Our results suggest that habitat and migration are not correlated in the manner predicted by the evolutionary precursor hypothesis, but they also suggest the importance of increasing seasonality in explaining the patterns of the evolution of migration, an expected but previously unexamined evolutionary relationship. While understanding the limitations of applying generalizations to a complex evolutionary system such as migration, we have delineated here a broad methodology for testing hypotheses about the evolution of migration within a phylogenetic context.Pruebas Filogenéticas de Hipótesis sobre la Evolución de la Migración: Un Estudio de Caso en la Familia Motacillidae
Home-Range Characteristics, Age, Body Size, and Breeding Performance of Female Mallards (Anas Platyrhynchos)
Authors: Mack Glenn G. , Clark Robert G. 
Published: September 2019

Abstract
Understanding reproductive and survival consequences of space use is of general interest to ecologists and vital to successful conservation planning. Hypothesized effects of home-range habitat composition and female attributes on these vital rates have not been adequately evaluated in breeding female Mallards (Anas platyrhynchos). Thus, we investigated reproductive and survival consequences of home-range variability and individual characteristics for 126 female Mallards studied on 12 study areas in the Canadian prairie parklands, 1995–1998. We used nine variables to discriminate between three reproductive categories (females that did not nest, nested but failed, or nested successfully) and two survival categories (killed by predator and survived the nesting season). Discriminant function analysis separated females that nested successfully from those that did not, with successful females having higher percentages of wood-shrub and planted grass habitat within their home ranges, a lower percentage of seasonal and semipermanent wetlands, smaller home-range sizes, and a higher percentage of wetlands at the study-area scale. We also distinguished females that did not nest from failed nesters; females that did not nest were younger and smaller and had larger home-range sizes, with a higher percentage of seasonal and semipermanent wetlands. Females that were killed did not differ from nesting-season survivors of either individual or home-range characteristics.
Características del Rango de Hogar, Edad, Tamaño Corporal y Desempeño Reproductivo de las Hembras en Anas platyrhynchos
Seasonal Fecundity of Sagebrush Brewer's Sparrow (Spizella Breweri Breweri) at The Northern Edge of its Breeding Range
Authors: Mahony Nancy A. , Krannitz Pamela G. , Martin Kathy 
Published: September 2019

AbstractWe examined the effects of environmental and ecological factors associated with seasonal fecundity on spatial and temporal patterns of productivity in Sagebrush Brewer's Sparrow (Spizella breweri breweri) in British Columbia, the northwestern edge of its breeding range. This study is the first examination of seasonal fecundity in this species. Seasonal fecundity of females varied from 1998 to 2000. It was highest in 2000, when nest predation was lowest and number of clutches per female was intermediate, and lowest in 1998, when nest predation and number of clutches per female were the highest and warm El Niño conditions led to early breeding. Potential fecundity gains from early breeding were diminished by the interaction of shifting predation rates and variable effects of weather at different elevations. Early breeding in 1998 proved an advantage only at the low-elevation site, because an early spring storm destroyed 43% and 20% of first nests at two high-elevation sites. High seasonal fecundity varied between the sites, such that the best site in 1998 became the least productive in 1999 and vice versa. The overriding factor driving spatiotemporal variation was shifting rates of nest predation, though the elevation-related storm effects and variation in number of clutches were partly responsible. To maintain high productivity for Sagebrush Brewer's Sparrow at the northern edge of its range, where conditions are unpredictable and where there is no consistently best or worst site in terms of productivity, managers must protect sites from habitat loss or alteration across a range of elevations and conditions.Fécondité Saisonnière de Spizella Breweri Breweri à la Limite Nord de Son Aire de Reproduction
Mate Opportunity Hypothesis and Extrapair Paternity in Waved Albatrosses (Phoebastria Irrorata)
Authors: Huyvaert Kathryn P. , Anderson David J. , Parker Patricia G. 
Published: September 2019

Abstract
Early arrival at breeding sites can influence reproductive success through enhanced access to critical resources such as nest sites or mates. One hypothesis explaining protandry, or male-first arrival at breeding sites, proposes that males arrive earlier to increase their extrapair copulation (EPC) opportunities, which may, in turn, enhance males' reproductive success through extrapair fertilizations (EPFs) (“mate opportunity hypothesis”). Extrapair behavior is unexpected in long-lived birds, in which the male is expected to abandon a brood of uncertain paternity, because his probability of future reproduction is high. A previous study of the Waved Albatross (Phoebastria irrorata), a long-lived, socially monogamous seabird, showed evidence of EPFs in 4 of 16 (25%) families. Here, we combined behavioral observations of copulations with additional molecular genetic evidence of EPFs in Waved Albatross families to investigate the fitness consequences of protandry under the mate opportunity hypothesis. During three breeding seasons, we documented 3,661 attempted copulations between birds of known identity; >60% of copulations that involved at least one breeding bird were classified as EPCs. Protandry was pronounced in all three study years: 76.3–96.6% of males arrived before (typically, 6–10 days before) their social mates. Early arrival was associated with increased opportunities for copulations: individual EPC frequencies were higher for breeding males than for breeding females, and males that arrived earlier than their social mates engaged in the most EPCs. Extrapair fertilizations were also regular in our study population; social fathers were excluded as the genetic sire in 14–21% of families. Egg laying dates of EPFs tended to be earlier in the season than those of within-pair fertilizations (WPFs). However, earlier arrival by a male did not translate into a higher probability of siring either within-pair or extrapair offspring, nor did cuckolding males have enhanced reproductive success. Although the fitness consequences of early arrival remain unclear, these findings suggest alternative advantages of early arrival for male Waved Albatrosses.
La Hipótesis de Oportunidad de Apareamiento y Paternidad Extra-pareja en Phoebastria irrorata
Song Sparrow (Melospiza Melodia) Song Varies with Urban Noise
Authors: Wood William E. , Yezerinac Stephen M. 
Published: September 2019

AbstractIn urban environments, anthropogenic noise may mask bird song, especially the notes occurring at lower frequencies (1–2 kHz). Birds living in urban environments may modify their songs, particularly the low-frequency portions, to minimize masking by anthropogenic noise. Such modifications have been observed in Great Tits (Parus major) in The Netherlands, as well as in some mammals. We studied Song Sparrows (Melospiza melodia), which are common in both urban and rural environments in much of North America, and recorded the songs of 28 free- living males in Portland, Oregon. We also measured the amplitude and spectrum of ambient noise at singing locations. Song Sparrows singing at noisier locations exhibited higher-frequency low notes and had relatively less energy (amplitude) in the low-frequency range of their songs (1–4 kHz), where most anthropogenic noise also occurred. Although the mechanism(s) producing the correlation are as yet undetermined, the observed match between song and noise may result from behavioral plasticity. We discuss explanations for these patterns and how to test them.Le Chant de Melospiza melodia Varie avec le Bruit Urbain