bluuebunny/crossref_metadata_2025_split huggingface dataset:
Seasonal Decline in Leukocyte Concentrations and Reproductive Output in Female Great Tits (Parus Major)
Authors: Dubiec Anna , Witek Magdalena , Cichoń Mariusz 
Published: September 2019

AbstractWe studied the relationship between breeding parameters and leukocyte counts (number of cells in 1 mm3 of blood) in Great Tit (Parus major) females. To exclude potential effects on leukocyte concentration of high reproductive effort related to nestling provisioning, we collected blood samples from females at the end of their incubation period. Early-breeding females had greater blood counts of total leukocytes, lymphocytes, and heterophils than birds starting their clutches late in the season. Reproductive success, measured as the number of successfully fledged young, declined over the breeding season and showed no association with total leukocyte concentration. Number of leukocytes was not related to female condition measured as residuals from the regression of body weight on tarsus length. Moreover, the concentration of leukocytes did not predict the probability that a female would survive to the following breeding season.Disminución Estacional en las Concentraciones de Leucocitos y en el Rendimiento Reproductivo en Parus major
Division of Labor: Incubation and Biparental Care in House Sparrows (Passer Domesticus)
Authors: Bartlett Terri L. , Mock Douglas W. , Schwagmeyer P. L. 
Published: September 2019

AbstractIn the great majority of animal taxa, males do not participate in parental care, but substantial paternal care is common across avian species. We examined male and female incubation contributions in House Sparrows (Passer domesticus), quantifying the incubation behavior of free-living, individually color-banded parents during 47 nesting cycles. We also measured the relative warmth of male and female incubation surfaces. Females spent more time incubating than their male partners, and female time incubating served as the best single predictor for hatching success. Considered alone, male time incubating correlated negatively with hatching success, but that effect was nullified when female incubation was taken into account. Females had warmer abdomens than males, a difference that may reflect greater development of brood patch and effectiveness of incubation in that sex. Here, male badge size was not demonstrably associated with either male or female incubation patterns or hatching success.División de Labores: Incubación y Cuidado por Ambos Progenitores en Passer domesticus
Are Artificial Bird Nests Effective Surrogates for Estimating Predation on Real Bird Nests? A Test With Tropical Birds
Authors: Robinson W. Douglas , Styrsky Jennifer Nesbitt , Brawn Jeffrey D. 
Published: September 2019

AbstractArtificial bird nests are often used in studying birds whose nests are difficult to find, such as those of many tropical species. Yet the underlying assumption that predation on artificial nests accurately estimates predation on real nests may be invalid. We compared rates at which contents of real and artificial nests were lost to predators in a Panamanian rainforest. We attempted to make artificial nests as realistic as possible by moving real, undamaged nests to species-typical nest sites in a study area where the same species were actively breeding. Characteristics of new sites for the moved nests were statistically similar to nest sites chosen by birds. We baited nests with two quail eggs and monitored them for species-specific incubation periods. Predation on real and artificial nests was dissimilar in three of four species, revealing that predation on artificial nests correlated poorly with predation on real nests. In a fourth species, artificial and real nests were lost at similar rates. The latter result may have occurred by chance, because depredated real nests rarely showed any sign of damage; whereas depredated artificial nests were torn, which suggests that real and artificial nests attracted different predators. Our results indicate that artificial nests, even when built by the species themselves and placed in realistic situations, are poor predictors of real nest success and we caution against their use in the tropics.Son los Nidos Artificiales Sustitutos Efectivos para Estimar la Depredación de Nidos Verdaderos? Una Prueba con Aves Tropicales
To Double-Brood or not? Individual Variation in the Reproductive Effort in Black-Throated Blue Warblers (Dendroica Caerulescens)
Authors: Nagy Laura R. , Holmes Richard T. 
Published: September 2019

AbstractIndividuals within a population vary in important fitness components, such as reproductive success. In general, females can maximize the number of young they produce by altering either the number of young per breeding attempt or the number of breeding attempts per season. In short-lived species, and especially in small passerine birds, number of breeding attempts per season varies markedly among individuals. Here, we evaluated factors influencing whether female Blackthroated Blue Warblers (Dendroica caerulescens) initiated additional nests after a successful breeding attempt (i.e. double-brooded). The percentage of females that laid a second clutch after successfully fledging a first brood ranged from 0 to 87% and averaged 53% (n = 7 years). Multiple logistic regression and AICc model selection indicated that double-brooded females bred in territories with greater food availability and produced heavier nestlings than single-brooded females. Female age, male age, date of first breeding attempt, and number of young in the first clutch were not included in the best-fit model. Older females, however, produced heavier fledglings, and females mated to older males occurred on territories with greater food availability, indicating that age contributed to individual variation in reproductive output. Because the proportion of females that produce multiple broods within a season can have a substantial effect on the annual fecundity of a population, variation among females and among the territories they occupy (i.e. habitat quality) are key factors influencing population dynamics in this and other multibrooded, shortlived species.Poner Nidadas Dobles o No? Variación Individual en el Esfuerzo Reproductivo en Dendroica caerulescens
A Tiny Barbet-Like Bird From the Lower Oligocene of Germany: The Smallest Species and Earliest Substantial Fossil Record of The Pici (Woodpeckers and Allies)
Authors: Mayr Gerald 
Published: September 2019

Abstract
Rupelramphastoides knopfi, a new genus and species of the Pici (barbets, woodpeckers, and allies), is described from Frauenweiler, a Lower Oligocene (30–34 mya) fossil site in Germany. The disarticulated skeleton of the new species constitutes the first associated remains of a fossil member of the Pici and is the smallest known species and earliest substantial fossil record of this taxon. Despite an overall resemblance to modern Ramphastidae, R. knopfi appears to be distinguished from crown group Pici by several plesiomorphic characteristics. It is classified “family incertae sedis,” pending discovery of additional, better-preserved specimens. The fossil record and geographic occurrence of the basal lineages within the crown group are in concordance with an Old World origin of the Pici. The reasons that led to extinction of tiny Pici in Europe remain uncertain, but food competition with passeriform birds during periods of limited food availability may have played a major role.
Ein winziger bartvogelähnlicher Vogel aus dem Unter-Oligozän Deutschlands: die kleinste Art und der älteste substantielle Fossilnachweis der Pici (Spechte und Verwandte)
Extrapair Fertilization in the Black-Browed Reed Warbler (Acrocephalus Bistrigiceps): Effects on Mating Status and Nesting Cycle of Cuckolded and Cuckolder Males
Authors: Hamao Shoji , Saito Daichi S. 
Published: September 2019

Abstract
We studied the relationship between the occurrence of extrapair fertilizations (EPFs) and mating status and nesting cycle of mates, respectively, in a population of Black-browed Reed Warblers (Acrocephalus bistrigiceps). Overall, 6.4% (9 of 140) of the chicks were sired by extrapair males, and 13.5% (5 of 37) of the broods contained at least one extrapair chick. Socially polygynous males were cuckolded more frequently than socially monogamous males (40.0% and 3.7%, respectively). In three of four cases where cuckolded males were polygynous, the fertile periods of their mates overlapped. Except for two floating males that obtained EPFs, five out of seven cuckolder males were paired. Males succeeded in EPFs when the fertile period of the extrapair females largely overlapped the incubation period of their own mates. These findings are consistent with the hypothesis that there are trade-offs between extrapair copulation activity and both mate guarding and rearing of nestlings.
Fertilisation Extraconjugale chez Acrocephalus bistrigiceps: Effets des Mâles Infidèles et Cocus sur le Statut de Couple et le Cycle de Nidification
Food Allocation in Collared Flycatcher (Ficedula Albicollis) Broods: Do Rules Change With The Age of Nestlings?
Authors: Rosivall Balázs , Török János , Szöllősi Eszter 
Published: September 2019

AbstractFood allocation among nestlings has a strong influence on parental fitness. Maximizing fledging success in a favorable environment requires food distribution based on offspring need signals. However, food limitation, differences among individual nestlings in their quality, or variation in the costs of rearing different young may result in preferential allocation of food by parents. If signals of nestling quality or need change in meaning with age, parents are expected to adjust their feeding rules to those changes. We examined food allocation in broods of Collared Flycatchers (Ficedula albicollis), a sexually size-monomorphic passerine. In a multivariate analysis, we investigated the role of sex, size, condition, position, and begging intensity in two nestling ages. Size, condition, and sex of nestlings did not affect parental decisions. Begging intensity and nestling position, however, had a role in food allocation in both age categories. Both parents preferred the more intensely begging nestlings. Males did not show clear position preference in the “young” age category, but had preferred positions with older nestlings. Female position preference was observed in both age categories. Preferred positions of male and female parents differed; still, we observed overall position preference.Asignación de Alimentos en Nidadas de Ficedula albicollis: ¿Cambian las Reglas con la Edad de los Pichones?
Long-Term Trends in Spring Arrival Dates of Migrant Birds at Delta Marsh, Manitoba, in Relation to Climate Change
Authors: Murphy-Klassen Heather M. , Underwood Todd J. , Sealy Spencer G. , Czyrnyj Ashleigh A. 
Published: September 2019

AbstractWe examined a 63-year data set of dates of first spring sightings for 96 species of migrant birds at Delta Marsh, Manitoba, and considered the influence of local climate change on those arrival dates. Mean monthly spring temperatures increased (0.6–3.8°C) for all four months considered; however, trends for February and March were stronger than those for April and May. Over the 63-year period, 27 species significantly altered their arrival dates. Most of those species arrived significantly earlier; whereas only two species, Greater Yellowlegs (Tringa melanoleuca) and Lesser Yellowlegs (T. flavipes), arrived significantly later over time. About half of the migrants showed significant relationships between arrival dates and mean temperature for their month of arrival. Fifteen species showed significantly earlier arrivals over time and a significant relationship between arrival date and temperature. We also characterized migrants by taxon, breeding status, and wintering location to determine whether there were any trends for altered arrivals within certain groups. Waterfowl, species that breed at Delta Marsh, and short-distance migrants showed slightly higher incidences of advancing arrival dates compared with other groups. Our results provide evidence that climate warming has influenced spring migration arrival dates of several species in Manitoba.Tendances à Long-terme des Dates d'Arrivée Printanières des Oiseaux Migrateurs dans le Delta Marsh, Manitoba, en Relation avec les Changements Climatiques
Nest Building is an Indicator of Parental Quality in the Monogamous Neotropical Buff-Breasted Wren (Thryothorus Leucotis)
Authors: Gill Sharon A. , Stutchbury Bridget J. M. 
Published: September 2019

AbstractIn species with long-term partnerships, optimal mate preferences may differ from actual mate choice, and pair displays that advertise individual quality may be expected. We examined the relationship between nest-building and nestling-provisioning effort in Neotropical Buff-breasted Wrens (Thryothorus leucotis) to determine whether male or female expenditure during nest construction was used as an indicator of subsequent parental ability. Buff-breasted Wrens build two nest types: breeding nests used for raising offspring, and “dormitory“ nests built year-round and used by pairs for roosting overnight. The building effort of males was greater than that of their mates for dormitory nests, whereas male and female effort were similar during breeding-nest construction and nestling provisioning. Despite large within-sex variation in building and provisioning efforts, male and female effort within pairs were significantly positively correlated for construction of both nest types and for nestling feeding. Effort expended by males during dormitory-nest construction was positively correlated with nestling-provisioning effort, whereas female building effort was not. No relationship existed between effort in breeding-nest construction and nestling provisioning in either sex. These results suggest that effort in dormitory-nest construction was an indicator of male Buff- breasted Wren parental ability. Females that survived to the year following observation built dormitory nests at a lower rate than those that disappeared, which suggests that nest building may be costly and that by building more than females, males may increase the survival prospects of their partners. Dormitory-nest building by males may play dual roles throughout the year, indicating parental ability and investment in the partnership.La Construcción de Nidos es un Indicador de la Calidad de los Padres en la Especie Neotropical Monógama Thryothorus leucotis
Effects of Food Abundance, Weather, and Female Condition on Reproduction in Tree Swallows (Tachycineta Bicolor)
Authors: Nooker Jacqueline K. , Dunn Peter O. , Whittingham Linda A. 
Published: September 2019

AbstractFood abundance, weather, and female body condition are believed to influence the timing of breeding and reproductive performance of birds. We simultaneously studied the effects of weather and food abundance on reproduction in Tree Swallows (Tachycineta bicolor) while experimentally reducing female condition and foraging efficiency by clipping some flight feathers prior to egg laying. Control females laid larger clutches earlier in the season, had longer incubation periods, and raised heavier nestlings than experimental females. Fledging success did not differ after controlling for laying date and brood size. Greater insect abundance was associated with laying earlier in the season, heavier eggs, and shorter incubation periods. Most likely, feather-clipping affected clutch size through reduced foraging efficiency, which delayed the date of laying, rather than through loss of body condition. This outcome is consistent with the idea that Tree Swallows are “income” breeders that base their timing of reproduction on short-term rates of food intake near the time of breeding. Contrary to studies of other species, Tree Swallows do not appear to time their laying so that hatching will coincide with seasonal peaks in food supply. Rather, they appear to breed when temperature and food abundance are sufficient to allow females of a given body condition to initiate egg laying.Efectos de la Abundancia de Alimento, del Clima y de la Condición de las Hembras sobre la Reproducción en Tachycineta bicolor
Diurnal Studies do not Predict Nocturnal Habitat Choice and Site Selection of European Golden-Plovers (Pluvialis Apricaria and Northern Lapwings (Vanellus Vanellus)
Authors: Gillings Simon , Fuller Robert J. , Sutherland William J. 
Published: September 2019

AbstractMany species, including shorebirds, feed during both day and night, yet little is known about how this affects behavior and habitat preferences. European Golden-Plovers (Pluvialis apricaria) and Northern Lapwings (Vanellus vanellus) feeding on arable farmland were more widely dispersed at night: nocturnal flocks were smaller, typically monospecific, and occurred in many more fields than diurnal mixed-species flocks. Diurnal numbers of European Golden-Plovers could not be used to predict nocturnal numbers; this indicates that ranging behavior differed between day and night. For both species, nocturnal feeding was recorded on almost all nights, irrespective of moon phase. Northern Lapwing nocturnal feeding activity decreased with increasing cloud cover and decreasing ground temperature, but no clear relationships were detected between European Golden-Plovers’ nocturnal feeding activity and environmental variables. Habitat selection differed between day and night, and between species at night. Diurnal studies of habitat choice and site selection may misrepresent the full requirements of such species.Los Estudios Diurnos no Predicen la Preferencia Nocturna de Hábitat ni la Selección Nocturna de Sitio en Pluvialis apricaria y Vanellus vanellus
Habitat and Sex Differences in Physiological Condition of Breeding Southwestern Willow Flycatchers (Empidonax Trailliiextimus)
Authors: Owen Jennifer C. , Sogge Mark K. , Kern Michael D. 
Published: September 2019

Abstract
The Southwestern Willow Flycatcher (Empidonax traillii extimus; here- after “flycatcher”) is a federally listed endangered species that breeds in densely vegetated riparian habitats dominated by native and exotic plants, including introduced monotypic saltcedar (Tamarix ramosissima). Some workers have theorized that saltcedar is unsuitable habitat for the flycatcher, primarily because it generally supports a smaller and less diverse invertebrate community (the flycatcher's food base) than native habitats (e.g. Salix spp.). However, differences in insect communities between native and saltcedar habitats are not proof that saltcedar habitats are inferior. The only way to evaluate whether the habitats differ in dietary or energetic quality is to document actual food limitation or its manifestations. Measurements of an individual's body condition and metabolic state can serve as indicators of environmental stressors, such as food limitation and environmental extremes. We captured 130 flycatchers breeding in native and saltcedar habitats in Arizona and New Mexico and measured 12 variables of physiological condition. These variables included body mass, fat level, body condition index, hematocrit, plasma triglycerides, plasma free fatty acids and glycerol, plasma glucose and beta-hydroxybutyrate, plasma uric acid, total leukocyte count, and heterophil-to-lymphocyte ratio. We found substantial sex-based differences in the condition of male and female flycatchers. Ten of the 12 measures of physiological condition differed significantly between the sexes. In all cases where male and female condition differed (except mass), the differences suggest that males were in poorer condition than females. We found few habitat-based differences in flycatcher condition. Only 3 of the 12 physiological condition indices differed significantly between habitats. Our data show that, at least in some parts of the flycatcher's range, there is no evidence that flycatchers breeding in saltcedar habitats exhibit poorer nutritional condition or are suffering negative physiological affects.
Diferencias entre Hábitats y Sexos en la Condición Fisiológica de Individuos Reproductivos en Empidonax traillii extimus
Elevational Zonation and the Phylogenetic Relationships of the Henicorhina Wood-Wrens
Authors: Dingle Caroline , Lovette Irby J. , Canaday Chris , Smith Thomas B. 
Published: September 2019

Abstract
The Henicorhina wood-wren complex consists of three taxonomic species. Two of these, the Gray-breasted Wood-Wren (Henicorhina leucophrys) and the White-breasted Wood-Wren (H. leucosticta), are widespread throughout Central America and northern South America, with leucophrys occurring at higher elevations in regions where both occur. A third, recently described, species—the Bar-winged Wood-Wren (H. leucoptera)—occurs only in several isolated cordilleras in southeastern Ecuador and northeastern Peru, where it replaces the Gray-breasted Wood-Wren at the highest elevations. We used mitochondrial DNA sequences to explore the phylo-genetic relationships among populations of these taxa and to draw inferences about the evolutionary origins of elevational zonation. We found substantial mitochondrial diversity within both leucophrys and leucosticta. Differentiation across the Andes in leucophrys was negligible, but populations from Central America and from northwestern Ecuador showed substantial differentiation. Three highly differentiated haplotype groups were also present in leucosticta, corresponding to populations in the eastern Andean lowlands, Central America, and the Chocó region of northwestern Ecuador; these populations may each warrant taxonomic species status. Bar-winged haplo-types nested within the mitochondrially diverse leucosticta group, where they were most closely allied to the geographically distant Chocó haplotypes. This leucoptera-leucosticta affinity is not consistent with previous inferences, based on plumage and behavioral similarities, that grouped leucoptera and leucophrys as sister species. These reconstructions refute the hypothesis that elevational zonation in this clade originated from in situ speciation along an elevational gradient, and instead highlight the role of complex changes in geographic distributions in fostering phylogenetic and ecological diversification.
Reemplazos Altitudinales y Relaciones Filogenéticas en el Género Henicorhina (Troglodytidae)
Foraging Behavior and Predation Risk in Male and Female Eurasian Blackbirds (Turdus Merula) During the Breeding Season
Authors: Post Peter , Götmark Frank 
Published: September 2019

AbstractIn many birds, breeding males display bright colors, sing, and engage in active territory defense; whereas females are less conspicuous. Therefore, it is sometimes assumed that in the breeding season males suffer higher predation than females. Several studies have reported, however, higher female predation rates, which suggests that traits other than coloration and mate-acquisition behaviors are important in determining predation rates for the sexes. Theoretical and empirical work suggests that foraging behavior and foraging rate are major determinants of predation risk. Here, we examine this possibility in a study of breeding Eurasian Blackbirds (Turdus merula) and predation on them by Eurasian Sparrowhawks (Accipiter nisus). Female Eurasian Blackbirds foraged more than males and foraged closer to the ground, both early and late in the breeding season. On the basis of this observation, we predicted that females should suffer higher predation than males. Of 98 Eurasian Blackbirds taken in 33 Eurasian Sparrowhawk territories during four years, 56 were females and 42 males. On the basis of the male-biased sex ratio in the population, female Eurasian Blackbirds suffered higher predation risk than males. For breeding birds, these results indicate a trade-off between foraging effort and predation rate, which is of importance for sexual dichromatism (selection for female crypsis), population sex ratio, and behaviors of the sexes.Le Comportement de Quête Alimentaire et les Risques de Prédation chez Turdus merula au Cours de la Saison de Reproduction