bluuebunny/crossref_metadata_2025_split huggingface dataset:
Environmental Conditions Affect Offspring Sex-Ratio Variation and Adult Survival in Tawny Owls
Authors: Sasvári Lajos , Nishiumi Isao 
Published: September 2019

AbstractWe studied survival of adult Tawny Owls (Strix aluco), number of breeding pairs, breeding performance, and offspring sex ratio in relation to the number of snowy days in the preceding winter in Duna-Ipoly National Park, Hungary. A new male was more likely to be present after a winter with many snowy days, although female survival was not affected by weather. Number of breeding pairs and number of fledglings declined with increasing number of snowy days. Offspring sex ratio varied according to whether snow cover was present during the egg-laying period, with broods being male biased during adverse conditions but female biased during mild conditions. Also, female nestlings were more likely to die before fledging than male nestlings. These data suggest that female Tawny Owls are able to adjust the sex ratio of their brood according to the expected differential success of nestlings under the prevailing weather conditions. This adjustment in relation to environmental conditions has important implications for the demography of Tawny Owl breeding populations.Las Condiciones Ambientales Afectan la Variación en el Cociente de Sexos de las Crías y la Supervivencia de los Adultos en Strix alucoResumen. Estudiamos la supervivencia de los adultos de Strix aluco, el número de parejas reproductivas, el desempeño reproductivo y el cociente de sexos de las crías con relación al número de días con nieve en el invierno precedente en el Parque Nacional Duna-Ipoly, Hungría. Un macho nuevo tuvo mayor probabilidad de estar presente luego de un invierno con muchos días con nieve, aunque la supervivencia de las hembras no estuvo afectada por el clima. El número de parejas reproductivas y el número de volantones disminuyeron con un incremento en el número de días con nieve. El cociente de sexos de las crías varió de acuerdo con la presencia de cobertura de nieve durante el período de puesta de los huevos: las nidadas estuvieron sesgadas hacia los machos durante períodos de condiciones adversas y sesgadas hacia las hembras durante períodos de condiciones moderadas. Además, los pichones hembra tuvieron mayor probabilidad de morir antes de dejar el nido que los machos. Estos datos sugieren que las hembras de S. aluco son capaces de ajustar el cociente de sexos de sus nidadas de acuerdo al éxito diferencial esperado de los pichones bajo las condiciones climáticas dominantes. Este ajuste relacionado con las condiciones ambientales tiene implicancias importantes para la demografía de las poblaciones reproductivas de S. aluco.
Mandibular Bowing and Mineralization in Brown Pelicans
Authors: Meyers Ron A. , Myers René P. 
Published: September 2019

AbstractBrown Pelicans (Pelecanus occidentalis) plunge dive into water to capture fish with highly distensible pouches. During prey capture, the pouch may expand to hold 11 L of water and the mandibular rami may bow from a resting position of 5 cm to over 15 cm. We compared mineralization of two bending regions of the mandible with a nonbending region, and examined cross-sectional morphology to determine if mineral content and shape play a role in mandibular bending. A rostral bending zone, adjacent to the mandibular symphysis, possessed only about 20% mineral content, significantly less than the lateral bending zone and the rigid caudal mandible, both comprised of over 50% mineral content. Additionally, the rostral zone was solid in cross section, facilitating bending, whereas the lateral zone was made up of bones joined by connective tissue. This latter morphology permits movement between the bones even though there was relatively high mineralization. We suggest that mineral content may be an overlooked component to cranial kinesis in birds.Arqueamiento y Mineralización de la Mandíbula en Pelecanus occidentalisResumen. Los pelícanos Pelecanus occidentalis se zambullen en el agua para capturar peces utilizando bolsas bucales muy distensibles. Durante la captura de la presa, la bolsa bucal se puede expandir para contener hasta 11 litros de agua y las ramas mandibulares se pueden arquear desde una posición de descanso de 5 cm hasta más de 15 cm. En este estudio, comparamos la mineralización de dos regiones mandibulares que se arquean con una región rígida que no se arquea y examinamos la morfología transversal para determinar si el contenido mineral y la forma desempeñan una función al arquear la mandíbula. Una zona de doblado rostral adyacente a la sínfisis mandibular posee un contenido mineral de aproximadamente el 20%, lo que representa una mineralización significativamente menor que la de la zona lateral de doblado y la sección caudal rígida de la mandíbula, las cuales contienen más de un 50% de minerales. Adicionalmente, la zona rostral tiene una sección transversal sólida que facilita su arqueamiento, mientras que la zona lateral está compuesta de huesos unidos por tejido conectivo. Esta última morfología permite el movimiento entre los huesos aunque exista una alta mineralización. Sugerimos que el contenido mineral puede ser un componente de la quinesis cranial de las aves que es frecuentemente ignorado.
Lipid Reserves of Migrant Shorebirds During Spring in Playas of the Southern Great Plains
Authors: Davis Craig A. , Smith Loren M. , Conway Warren C. 
Published: September 2019

AbstractInland-migrating shorebirds rely on wetlands as stopover sites to replenish nutrient reserves. Because wetlands are spatially and temporally dynamic, shorebirds may accumulate highly variable lipid reserves. We compared lipid reserves among four shorebird species (American Avocets [Recurvirostra americana], Long-billed Dowitchers [Limnodromus scolopaceus], Least Sandpipers [Calidris minutilla], and Western Sandpipers [C. mauri]) collected from playa wetlands in the southern Great Plains during spring 1993 and 1994. Because playas are ephemeral, we had the opportunity to examine the influence of a variable environment (a wet year and a dry year) on lipid reserves. Additionally, we examined the influence of different migration distances and strategies, and body sizes on lipid reserves. Western Sandpipers had the highest lipid reserves (41%–50%) and Dowitchers had the lowest reserves (18%). Least and Western Sandpipers had 7%–9% higher lipid reserves in the wet year than dry year. Thus, small-bodied shorebirds may be more affected by variable habitat conditions than large-bodied shorebirds because of their higher mass-specific metabolic rates.Reservas Lipídicas de Aves Playeras Migrantes Durante la Primavera en Humedales del Sur de la Gran PlanicieResumen. Las aves playeras que migran tierra adentro necesitan de humedales como lugares de escala migratoria para recuperar sus reservas de nutrientes. Debido a que los humedales son espacial y temporalmente dinámicos, las aves playeras pueden acumular lípidos como reserva de forma muy variable. En este estudio comparamos las resevas lipídicas entre cuatro especies de aves playeras (Recurvirostra americana, Limnodromus scolopaceus, Calidris minutilla y C. mauri) colectadas en los humedales “playa” de la parte sur de la gran planicie durante la primavera de 1993 y 1994. Debido a que estos humedales son ambientes efímeros, tuvimos la oportunidad de examinar la influencia de un ambiente variable (un año húmedo y un año seco) sobre las reservas lipídicas de las aves. Además, examinamos la influencia de distintas distancias y estrategias de migración y del tamaño corporal sobre las reservas. La especie con las mayores reservas lipídicas fue C. mauri (41%–50%) y la especie con las menores reservas fue L. scolopaceus (18%). Las dos especies de Calidris presentaron reservas lipídicas un 7%–9% mayores en el año húmedo que en el año seco. Por tanto, las aves playeras de tamaño pequeño podrían verse más afectadas por condiciones ambientales variables que las de tamaño grande como consecuencia de sus mayores tasas metabó licas con respecto al peso.
Disparities Between Results and Conclusions: Do Golden Eagles Warrant Special Concern Based on Migration Counts in the Western United States?
Authors: McCaffery Brian J. , McIntyre Carol 
Published: September 2019

Abstract
A recent summary of raptor migration count data concluded that the status of Golden Eagles (Aquila chrysaetos) in western North America warranted concern (Hoffman and Smith 2003). Our analysis of these data did not lead us to the same conclusion. We have three specific concerns. First, the regional characterizations of eagle migration in Hoffman and Smith (2003) are based on a very small sample of sites. Therefore, we recommend that these characterizations be considered as hypothetical in nature. Second, we suggest that the population cycles and patterns of age-specific population change described by Hoffman and Smith (2003) are neither as general nor as clear-cut as they indicated. Finally, although the authors expressed concern about the status of Golden Eagles based upon both their findings and data from other sources, we did not find compelling evidence for population declines in our inspection of those same data.
Disparidad entre Resultados y Conclusiones: ¿Es el Estatus de Aquila chrysaetos Especialmente Preocupante de Acuerdo a los Conteos Migratorios del Oeste de los Estados Unidos?
Resumen. Un resumen de los datos de conteos de migración de rapaces realizado recientemente concluyó que el estatus de Aquila chrysaetos en el oeste de Norte América es preocupante (Hoffman y Smith 2003). Nuestro análisis de los mismos datos no nos llevó a la misma conclusión, y tenemos tres inquietudes específicas. Primero, las caracterizaciones regionales de la migración de las águilas en Hoffman y Smith (2003) están basadas en una muestra de sitios muy pequeña. Por tanto, recomendamos que dichas caracterizaciones se consideren hipotéticas. Segundo, sugerimos que los ciclos poblacionales y los patrones de cambio poblacional edad-específicos descritos por Hoffman y Smith (2003) no son tan generales ni tan claros como ellos lo indicaron. Finalente, aunque los autores se manifestaron preocupados por el estatus de A. chrysaetos basándose en sus hallazgos y en datos de otras fuentes, al inspeccionar los mismos datos nosotros no encontramos evidencia contundente de que existan tales disminuciones poblacionales.
Nocturnal Foraging Behavior of Wintering Surf Scoters and White-Winged Scoters
Authors: Lewis Tyler L. , Esler Daniel , Boyd W. Sean , Žydelis Ramūnas 
Published: September 2019

AbstractWe studied the nocturnal foraging behavior of Surf Scoters (Melanitta perspicillata) and White-winged Scoters (Melanitta fusca) during winter in coastal British Columbia, Canada. Using radio telemetry, we collected nocturnal and diurnal data documenting the frequency of foraging dives and the location of scoters in relation to their intertidal foraging grounds. We found that dive foraging rarely occurred during nocturnal periods for either species. Only 2% of nocturnal observation blocks for both scoter species contained diving, compared with 98% of diurnal observation blocks. This corresponded to an average of only 0.1 min spent underwater per half-hour observation block during the night and over 7 min during the day. Both species of scoters were located farther offshore and in deeper waters during nocturnal hours, indicating that they were not using intertidal foraging areas at night. Our results suggest that Surf Scoters and White-winged Scoters face daylight-imposed limits on the amount of available foraging time. These potential day-length restrictions should be considered when reviewing human activities that potentially alter the amount of available foraging time or food supplies in winter habitats.Comportamiento de Forrajeo Nocturno de Melanitta perspicillata y M. fuscaResumen. Se estudió el comportamiento de forrajeo nocturno de Melanitta perspicillata y M. fusca durante el invierno en la costa de British Columbia. Utilizando radio-telemetría, se colectaron datos nocturnos y diurnos sobre la frecuencia de buceos para alimentarse y la ubicación de las aves con relación a la zona intermareal. Se encontró que los buceos nocturnos son infrecuentes para ambas especies. Sólo en el 2% de las observaciones nocturnas de ambas especies se presentaron instancias de buceo, en comparación con el 98% de las observaciones diurnas. Esto corresponde a un promedio de 0.11 minutos bajo el agua por cada 30 minutos de observación durante la noche y más de 7 minutos durante el día. Ambas especies se ubicaron más alejadas de la costa y en aguas más profundas durante la noche, indicando que los individuos no utilizaron zonas intermareales durante este periodo. Estos resultados sugieren que M. perspicillata y M. fusca enfrentan restricciones en el número de horas disponibles para alimentarse en función de la cantidad de luz. El efecto de la duración del día debe ser considerado cuando se estudia el impacto de actividades humanas que pueden alterar el tiempo disponible para forrajeo o la cantidad de alimento durante el invierno.
Mate and Territory Retention in Yellow-Eyed Penguins
Authors: Setiawan Alvin N. , Massaro Melanie , Darby John T. , Davis Lloyd S. 
Published: September 2019

AbstractUsing nest and banding data collected from 1991 to 2002, we investigated mate and territory retention rates of Yellow-eyed Penguins (Megadyptes antipodes), and the effects of reproductive success. Annual mate retention rate was 63%, and territory retention for males and females were 52% and 46% respectively. The majority of pair dissolutions were due to death of a partner, with only 6% of bonds ending in separation. Previous reproductive success was a good predictor of mate or territory retention as pairs that failed to fledge a single chick were significantly more likely to separate or move their territories than those that were successful at fledging chicks. Reproductive success of birds that changed their mates or moved territories was not higher than those that retained their mates or territories. However, birds that moved territories were less likely to have reduced fledging success relative to their previous breeding attempt. Birds that did not retain their mates, particularly males, were significantly more likely to skip breeding for at least one year. This suggests that the costs of mate or territory changes are not accrued at the end of the breeding attempt (as reflected by the number of fledged chicks), but are associated with the costs of pair formation and establishment of territories at the beginning of the breeding season.Retención de Parejas y Territorios en Pingüinos Megadyptes antipodesResumen. Investigamos las tasas de retención de parejas y de territorios por parte de pingüinos Megadyptes antipodes y el efecto del éxito reproductivo sobre estas tasas con base en datos de nidificación y anillamiento recolectados entre 1991 y 2002. La tasa anual de retención de parejas fue del 63% y las de retención de territorios del 52% y 46% para machos y hembras, respectivamente. La mayoría de las disoluciones de parejas se debieron a la muerte de una de las aves y sólo el 6% de las parejas terminaron separándose. El éxito reproductivo previo predijo acertadamente la retención de compañeros y de territorios, ya que las parejas que no lograron emplumar ningún pichón tuvieron una probablilidad de disolverse o de cambiar de territorio significativamente mayor que las que criaron exitosamente. El éxito reproductivo de las aves que cambiaron de pareja o de territorio no fue mayor que el de aquellas que no lo hicieron. Sin embargo, los individuos que cambiaron de territorio fueron más propensos a presentar un éxito de emplumamiento reducido con respecto a su intento reproductivo previo. Las aves que no retuvieron sus parejas, particularmente los machos, presentaron una probabilidad mayor de no reproducirse durante al menos un año. Esto sugiere que los costos que implica cambiar de pareja o de territorio no se hacen evidentes al final del intento reproductivo (como lo indica el número de volantones producidos), sino que están asociados con los costos de la formación de parejas y el establecimiento de territorios al comienzo de la época reproductiva.
Cattle Grazing in a National Forest Greatly Reduces Nesting Success in a Ground-Nesting Sparrow
Authors: Walsberg Glenn E. 
Published: September 2019

Abstract
Grazing of domestic livestock on public lands in the western United States is a major source of habitat destruction. I quantified nest success of ground-nesting Dark-eyed Juncos (Junco hyemalis) breeding in ponderosa pine forests and pine savanna in the Kaibab National Forest of northern Arizona. Comparison of results for areas grazed by cattle to results for immediately adjacent areas protected from grazing revealed that cattle grazing was associated with a dramatic (75%) reduction in nest success. Cattle grazing reduced vegetation cover over nests by an average of 41%, exposing the nest to more extreme climatic conditions as well as possibly making them more conspicuous to predators.
El Pastoreo por Ganado Reduce Fuertemente el Éxito de Nidificación de Junco hyemalis en un Parque Forestal Nacional
Resumen. El pastoreo por parte de ganado doméstico en tierras públicas del oeste de los Estados Unidos es una de las principales fuentes de destrucción de hábitat. Cuantifiqué el éxito de nidificación de Junco hyemalis, una especie que nidifica en el suelo, en los bosques de pino Ponderosa y las sabanas de pinos en el Bosque Nacional Kaibab, norte de Arizona. La comparación entre los resultados de las áreas pastoreadas por ganado y de las áreas inmediatamente adyacentes que se encuentran protegidas del pastoreo mostró que el pastoreo por ganado se asoció con una reducción dramática (75%) del éxito de nidificación. En promedio el pastoreo por ganado redujo la cobertura vegetal sobre los nidos en un 41%, exponiendo a los nidos a condiciones climáticas más extremas y posiblemente haciéndolos más conspicuos ante los depredadores.
Increase in Avian Malaria at Upper Elevation in Hawai‘i
Authors: Freed Leonard A. , Cann Rebecca L. , Goff M. Lee , Kuntz Wendy A. , Bodner Gustav R. 
Published: September 2019

AbstractHawaiian honeycreepers (Aves: Drepanidinae) evolved in the absence of mosquito-borne diseases such as avian malaria (Plasmodium spp.). Malaria has been largely responsible for the recent wave of extinctions and endangerment among Hawaiian forest birds, which began by the 1920s. Most honeycreepers, especially endangered species, now persist only in forests above 1500 m elevation, where cool temperatures prevent effective malaria development in mosquitoes. We report here that prevalence of malaria in Hawaiian forest birds at 1900 m on the island of Hawai‘i has more than doubled over a decade. This increase was associated with breeding of mosquitoes and warmer summertime air temperatures. We also report direct evidence of tolerance to malaria, and a possible cost of tolerance, in wild native birds. Tolerance is adding to a reservoir of malaria at upper elevations even while vectors are rare and air temperatures are too low for complete development of the parasite in the vector. The data provide a glimpse of how malaria is becoming an emergent infectious disease at upper elevations.
Melanin-Based Black Plumage Coloration is Related to Reproductive Investment in Cardueline Finches
Authors: Bókony Veronika , Liker András 
Published: September 2019

AbstractAvian color ornaments produced by different mechanisms (i.e., melanin, carotenoid, and structural colors) can communicate different sets of information due to differences in their condition or developmental constraints. Although this suggests that different color signals should be analyzed separately, few comparative studies have focused on specific types of coloration. In cardueline finches, interspecific variation in overall plumage brightness (which integrates all types of coloration) was previously shown to be affected by sexual selection and to covary with fecundity and parental care. Using a phylogenetic comparative approach, we extended this line of research and tested whether a specific component of plumage ornamentation, the melanin-based black frontal coloration of finches, showed a similar association with reproductive effort. We found that the extent of male melanization and melanin dichromatism increased in species with reduced clutch sizes, whereas female melanization was negatively correlated with incubation length. These results remained significant when we controlled for the effects of several ecological variables, and were also consistent between two alternative multivariate model-selection approaches. Our results are consistent with the hypothesis that interspecific variation in melanization may be related to fecundity and parental care through trade-offs between investment in sexual signals and parental efforts.
Seasonal Body Weight Variation in Five Species of Woodpeckers
Authors: Koenig Walter D. , Walters Eric L. , Walters Jeffrey R. , Kellam James S. , Michalek Klaus G. , Schrader Matthew S. 
Published: September 2019

AbstractWe investigated patterns of seasonal variation in body weight in six populations of five resident species of temperate-zone woodpeckers: Acorn Woodpecker (Melanerpes formicivorus), Red-bellied Woodpecker (M. carolinus), Red-cockaded Woodpecker (Picoides borealis), Downy Woodpecker (P. pubescens), and Great Spotted Woodpecker (Dendrocopos major). After controlling for time of day and overall body size, annual variation in body weight was small and generally not statistically significant. However, analysis revealed evidence of significant “winter fattening,” comparable in magnitude to other temperate-zone resident species, in three of the species. The degree of winter fattening did not correlate with either the size of the acorn crop (for the Acorn Woodpecker) or latitude, two variables potentially related to predictability of food resources. However, the smaller species exhibited significantly greater winter fattening than the larger species, as predicted by the hypothesis that energy storage should be more important for small-bodied species. Furthermore, the food-storing Acorn Woodpecker exhibited considerably less winter fattening than the nonfood-storing species, supporting the hypothesis that food storage provides an ecological alternative to winter fattening.
Remigial Molt Patterns in North American Falconiformes as Related to Age, Sex, Breeding Status, and Life-History Strategies
Authors: Pyle Peter 
Published: September 2019

Abstract
Examination of 1622 specimens indicates that North American Falconiformes show a wide variety of remigial (primary and secondary) replacement strategies, detectable throughout the year by evaluation of replacement patterns in the wings. Most Falconidae undergo complete prebasic molts whereas most Accipitridae display retained secondaries or show stepwise molt replacement patterns (“Staffelmäuser”). Among individuals exhibiting Staffelmäuser, minimum age can be inferred up to 5 years (fifth-basic plumage) by the number of “replacement waves” present among the primaries. It may also be able to infer breeding status during the previous summer by “suspension limits,” resulting from the interruption of molt during breeding. Among Accipitridae, Staffelmäuser occurred in species with greater mass, higher wing loading, longer migration distance, and more open rather than wooded foraging habitats: species that experience time constraints on molting and incur greater costs from large gaps in the wing. Thus, this study supports both the “time-constraints hypothesis,” suggesting that Staffelmäuser is a consequence of insufficient time for a complete annual molt, and the “aerodynamic hypothesis,” suggesting that Staffelmäuser reflects an adaptive need to replace as many feathers as possible without inhibiting flight efficiency. Time constraints may have been a proximate cause of Staffelmäuser among Falconiformes, with improvements to flying efficiency being an ultimate adaptive benefit.