bluuebunny/crossref_metadata_2025 huggingface dataset:
Body Condition and Parasite Load Predict Territory Ownership in the GaláPagos Hawk
Authors: Whiteman Noah Kerness , Parker Patricia G.
Published: September 2019

We tested for associations between body condition, territory ownership, and permanent parasite load of Galápagos Hawks (Buteo galapagoensis) on Isla Marchena, Galápagos. Two louse species were collected from most of the 26 hawks sampled: the amblyceran Colpocephalum turbinatum and the ischnoceran Degeeriella regalis. Nonterritorial hawks were in significantly poorer body condition than territorial hawks. Body condition was negatively correlated with the abundance of C. turbinatum. Nonterritorial hawks had significantly higher mean abundances, mean intensities, and median intensities of both louse species than territorial hawks. The amblyceran's mean abundance and intensity were significantly higher than the ischnoceran's. Abundances of the two lice were positively related when the population size of C. turbinatum was <100 individuals, and negatively related when >100 individuals. Parasite load and body condition both predicted territory ownership well.

La Condición Corporal y la Carga Parasitaria Predicen la Posesión de Territorios en Buteo galapagoensis

Resumen. Probamos la relación entre la condición corporal, la posesión de territorios y la carga parasitaria permanente en el Gavilán de Galápagos (Buteo galapagoensis) en la Isla Marchena, Galápagos. En la mayoría de los 26 gavilanes muestreados se colectaron dos especies de piojo: el ambliceránido Colpocephalum turbinatum y el ischnoceránido Degeeriella regalis. Los gavilanes no territoriales se encontraron en condiciones corporales significativamente peores que los gavilanes territoriales. Encontramos una correlación negativa significativa entre la condición corporal y la abundancia de C. turbinatum. Los gavilanes no territoriales tuvieron significativamente mayor abundancia, intensidad media e intensidad mediana de las dos especies de piojo que los gavilanes territoriales. La abundancia promedio y la intensidad de los ambliceránidos fueron significativamente mayores que las de los ischnoceránidos. Las abundancias de las dos especies de piojo estuvieron positivamente correlacionadas cuando el tamaño poblacional de C. turbinatum fue <100 individuos y negativamente correlacionadas cuándo fue >100 individuos. Tanto la carga parasitaria como la condición corporal predijeron bien la posesión de territorios.
Estimating Survival Probabilities of Unmarked Dependent Young When Detection is Imperfect
Authors: Lukacs Paul M. , Dreitz Victoria J. , Knopf Fritz L. , Burnham Kenneth P.
Published: September 2019

We present a capture–recapture modeling approach to the estimation of survival probability of dependent chicks when only the attending adult bird is marked. The model requires that the bird's nest is found prior to hatching and that the number of eggs that hatch are counted. Subsequent data are sightings of the marked adult and a count of chicks with the adult. The model allows for imperfect detection of chicks, but the number of chicks can never exceed the number of eggs in the nest (i.e., adults cannot adopt chicks). We use data from radio-tagged adult Mountain Plovers (Charadrius montanus) and their unmarked chicks as an example. We present the model in terms of precocial bird species, but the method extends to many other taxa.

Estimación de las Probabilidades de Supervivencia de Crías Dependientes no Marcadas cuando la Detección es Imperfecta

Resumen. Presentamos un enfoque de captura y recaptura para modelar la estimación de la probabilidad de supervivencia de polluelos dependientes cuando sólo el adulto que atiende a los polluelos esta marcado. El modelo requiere que el nido sea encontrado antes de la eclosión y que se cuenten el número de huevos que eclosionan. Los datos subsecuentes necesarios son los avistamientos del adulto marcado y el conteo de los polluelos que se encuentran con el adulto. El modelo permite la detección imperfecta de los polluelos, pero el número de polluelos nunca puede exceder el número de huevos en el nido (i.e., los adultos no pueden adoptar polluelos). Como ejemplo, utilizamos datos de adultos marcados con radio transmisores de Charadrius montanus y de sus polluelos no marcados. Presentamos el modelo en términos de especies de aves precociales, pero el método también se extiende a muchas otras especies.
A New Fossil Furnariid from the Pleistocene of Uruguay, With Remarks on Nasal Type, Cranial Kinetics, and Relationships of the Extinct Genus Pseudoseisuropsis
Authors: Claramunt Santiago , Rinderknecht Andrés
Published: September 2019

We describe Pseudoseisuropsis cuelloi, a new fossil furnariid from the upper Pleistocene of Uruguay, and investigate its phylogenetic relationships. Results of a cladistic analysis using 52 osteological characters from 29 taxa, including the extinct Pseudoseisuropsis nehuen, were consistent with placing the new species in the genus Pseudoseisuropsis. We conclude that the skull of Pseudoseisuropsis was prokinetic, although the shape of the nostrils was like a typical schizorhinal and rhynchokinetic furnariid. This observation reveals the inadequacy of the traditional categories of nasal types in characterizing the diversity of morphologies found in skulls of the Furnariidae. Finally, the analysis did not support a close relationship between Pseudoseisuropsis and Pseudoseisura, as previously thought, but suggests that Pseudoseisuropsis either belongs to the Dendrocolaptinae, or represents a more basal lineage within the Furnariidae.

Un Nuevo Furnárido Fósil del Pleistoceno de Uruguay, con Observaciones sobre Tipos Nasales, Quinesis Craneal y Relaciones Filogenéticas del Género Extinto Pseudoseisuropsis

Resumen. En el presente estudio se describe a Pseudoseisuropsis cuelloi, una nueva especie fósil de Furnariidae del Pleistoceno superior de Uruguay, y se investigan sus relaciones filogenéticas. El resultado de un análisis cladístico con 52 caracteres osteológicos y 29 taxa, incluyendo el ejemplar tipo de Pseudoseisuropsis nehuen es consistente con la inclusión de la nueva especie en el género Pseudoseisuropsis. Se concluye que el movimiento craneal de Pseudoseisuropsis era proquinético, a pesar de que la forma de las aberturas nasales es similar al de un típico furnárido esquizorrino/rincoquinético. Esta aparente contradicción pone en evidencia que las categorías tradicionales de tipos nasales son poco adecuadas para caracterizar la diversidad morfológica del cráneo en los Furnariidae. Por último, el análisis filogenético revela que Pseudoseisuropsis no esta estrechamente emparentado con Pseudoseisura, como fuera propuesto originalmente, sino que sugiere su inclusión en Dendrocolaptinae o en un linaje más basal dentro de la familia Furnariidae.
Nocturnal Hypothermia in Seasonally Acclimatized Mountain Chickadees and Juniper Titmice
Authors: Cooper Sheldon J. , Gessaman James A.
Published: September 2019

We measured body temperature of Mountain Chickadees (Poecile gambeli) and Juniper Titmice (Baeolophus ridgwayi) at different times of day and under a range of ambient temperatures in order to determine the use of nocturnal hypothermia in seasonally acclimatized small passerines. Our findings show both species used nocturnal hypothermia year-round. Depth of hypothermia was inversely correlated to body mass in Juniper Titmice but not in Mountain Chickadees. In both species, depth of hypothermia did not vary seasonally but nocturnal body temperature was regulated 3–11°C lower than daytime values. Nocturnal energy savings range from 7%–50% in chickadees and from 10%–28% in titmice. These nocturnal energy savings translate into ecologically important reductions in daily energy expenditures for these two species.

Hipotermia Nocturna en Individuos de Poecile gambeli y Baeolophus ridgwayi Aclimatados Estacionalmente

Resumen. Medimos la temperatura corporal de Poecile gambeli y Baeolophus ridgwayi a diferentes horas del día y en un rango de temperaturas ambientales para determinar el uso de hipotermia nocturna en pequeñas aves paserinas aclimatadas estacionalmente. Nuestros resultados muestran que ambas especies presentaron hipotermia nocturna durante todo el año. La profundidad de la hipotermia estuvo inversamente correlacionada con la masa corporal en B. ridgwayi, pero no en P. gambeli. En ambas especies, la profundidad de la hipotermia no varió estacionalmente, pero la temperatura corporal nocturna estuvo regulada 3–11°C por debajo de los valores diurnos. El ahorro nocturno de energía varió entre 7%–50% en P. gambeli y entre 10%–28% en B. ridgwayi. Estos ahorros nocturnos de energía se tradujeron en reducciones ecológicamente importantes en los gastos diarios de energía para ambas especies.
Parental Body Condition Does not Correlate With Offspring Sex Ratio in Cory's Shearwaters
Authors: Genovart M. , Oro D. , Forero M. G. , Igual J. M. , González-Solís J. , Ruiz X.
Published: September 2019

We analyzed offspring sex ratio variation in Mediterranean Cory's Shearwater (Calonectris d. diomedea) during two consecutive breeding seasons in two colonies. We test for differential breeding conditions between years and colonies looking at several breeding parameters and parental condition. We then explored the relationship between offspring sex ratio and parental condition and breeding parameters. This species is sexually dimorphic with males larger and heavier than females; consequently we expected differential parental cost in rearing sexes, or a greater sensitivity of male chicks to adverse conditions, which may lead to biased sex ratios. Chicks were sexed molecularly by the amplification of the CHD genes. Offspring sex ratio did not differ from parity, either at hatching or fledging, regardless of the colony or year. However, parental body condition and breeding parameters such as egg size and breeding success were different between years and colonies. Nevertheless, neither nestling mortality nor body condition at fledging varied between years or colonies, suggesting that male and female chicks were probably not differentially affected by variability in breeding conditions.

La Condición Parental no está Correlacionada con las Proporciones de Sexos en los Pollos de Calonectris d. diomedea

Resumen. Se analizaron las proporciones de sexos en la descendencia en dos colonias mediterráneas de Calonectris d. diomedea, durante dos temporadas de cría consecutivas. Se estudió la relación entre la proporción de sexos de los pollos y la condición parental y algunos parámetros reproductivos durante la cría. La especie es dimórfica, siendo los machos mayores y más pesados que las hembras; en consecuencia, se esperarían costos parentales diferenciales en la cría de los sexos, o una sensibilidad mayor de los pollos machos a condiciones adversas, que se traduciría en un sesgo en la proporción de sexos. Se determinó el sexo de los pollos por medio de técnicas moleculares, mediante la amplificación del gen CHD. Las proporciones de sexos en los pollos no se desviaron del 50% ni en la eclosión, ni en los volantones, independientemente de la colonia o el año de estudio. Sin embargo, la condición parental y algunos parámetros reproductivos como el tamaño del huevo o el éxito reproductivo sí variaron entre años y colonias. La mortalidad o la condición física de los volantones tampoco mostraron ninguna variación en función de la colonia o del año de estudio, sugiriendo que los pollos de los dos sexos probablemente no se vieron afectados de manera diferencial por la variabilidad en las condiciones de cría.
Variation in Human Disturbance Differentially Affects Predation Risk Assessment in Western Gulls
Authors: Webb Nicolaas V. , Blumstein Daniel T.
Published: September 2019

Many studies have demonstrated that birds behave differently in areas with different levels of human disturbance. Studies frequently characterize sites as having an overall level of human disturbance, and compare how birds respond at sites with high and low levels of disturbance. Doing so assumes that disturbance has a fairly constant effect on animals throughout a site. We measured the distance at which individual Western Gulls (Larus occidentalis) moved away from an approaching observer along a stretch of beach on both sides of the Santa Monica Pier, a heavily visited tourist attraction in southern California. We found that these flight initiation distances decreased in areas where more people visited the beach, and specifically in a small area near the pier. We found that flight initiation distance changed very rapidly within a short distance from the pier. Our results indicate that anthropogenic features may leave a “behavioral footprint.” Identifying the scale of such behavioral footprints should be an important goal of studies that seek to reduce anthropogenic impacts on birds.

La Variación del Disturbio Humano Afecta Diferencialmente la Percepción del Riesgo de Depredación en Gaviotas Larus occidentalis

Resumen. Muchos estudios han demostrado que las aves se comportan de modo diferente en áreas con distintos niveles de disturbio humano. Los estudios frecuentemente caracterizan sitios con base en su nivel general de disturbio y comparan las respuestas de las aves entre lugares con niveles altos y bajos de disturbio. Al hacer esto, se supone que el disturbio tiene un efecto aproximadamente constante sobre los animales a través de un sitio dado. En este estudio medimos la distancia a la cual gaviotas de la especie Larus occidentalis se desplazaron alejándose de un observador a lo largo de un tramo de playa en ambos lados del embarcadero de Santa Monica, una atracción turística muy visitada ubicada en el sur de California. Encontramos que las distancias al observador a las que las aves iniciaron el vuelo disminuyeron en áreas donde más personas visitaron la playa, y específicamente en un área cercana al embarcadero. Las distancias a las que las gaviotas iniciaron el vuelo cambiaron muy rá pidamente en una distancia muy corta desde el puerto, hasta alcanzar una distancia constante. Nuestros resultados indican que las estructuras antropogénicas podrian dejar una “huella comportamental”. Identificar la escala de dichas huellas debería ser un objetivo importante de estudios que tengan como fin reducir el impacto antrópico sobre las aves.
Dietary Specialization on High Protein Seeds by Adult and Nestling Serins
Authors: Valera Francisco , Wagner Richard H. , Romero-Pujante Marilo , Gutiérrez Jose E. , Rey Pedro J.
Published: September 2019

We examined the possible contributions of food availability and the energetic and nutritional contents of seeds on the diets of adult and juvenile Serins (Serinus serinus). We found that Serins are specialized granivores during the breeding season, with a single plant species (Diplotaxis virgata) comprising the majority of the diets' of adults and offspring. Food availability did not account for this diet specialization. Rather, the high protein and energy content of this plant appears to account for this strong preference and may explain why Serins, unlike almost all other granivorous bird species, do not provision their nestlings with insects. Because Serins and many other species often breed in modern agrosystems, knowledge of feeding adaptations may be invaluable for habitat management.

Especialización Dietética en Semillas con alto Contenido Proteico por parte de Adultos y Pollos de Serinus serinus

Resumen. Este trabajo examina la posible contribución de la disponibilidad de alimento y del contenido energético y nutricional de las semillas en la dieta de individuos adultos y jóvenes de la especie Serinus serinus. Encontramos que durante la temporada de cría S. serinus se comporta como un granívoro especializado puesto que una sola planta (Diplotaxis virgata) constituye la mayor parte de la dieta de adultos y pollos. La disponibilidad de alimento no explica esta especialización trófica. Más bien, el alto contenido proteico y energético de las semillas es lo que parece explicar la fuerte preferencia de S. serinus por esta planta y por qué este ave, a diferencia de casi todas las especies de aves granívoras, no alimenta a sus pollos con insectos. Puesto que S. serinus y muchas otras especies animales a menudo se reproducen en modernos agrosistemas, el conocimiento de las adaptaciones alimenticias puede ser muy valioso en cuanto a manejo del hábitat se refiere.
Impacts of Housing Developments on Wood Thrush Nesting Success in Hardwood Forest Fragments
Authors: Phillips Judith , Nol Erica , Burke Dawn , Dunford Wendy
Published: September 2019

We studied the impacts of low density, exurban housing developments on Wood Thrushes (Hylocichla mustelina) breeding in small forest fragments in two regions of rural southern Ontario. In both regions, Wood Thrushes breeding in woodlots with embedded houses (housing penetrating the forest border) experienced significantly higher rates of parasitism by Brown-headed Cowbirds (Molothrus ater) than Wood Thrushes breeding in woodlots with adjacent houses (houses within 100 m of the forest edge), or undeveloped woodlots (no houses within 100 m of the forest edge). Wood Thrushes breeding in Peterborough area woodlots with embedded or adjacent houses experienced significantly increased rates of nest predation compared to Wood Thrushes breeding in undeveloped woodlots. This increased nest predation resulted in significant reductions in seasonal productivity in developed woodlots. No increase in nest predation was experienced by Wood Thrushes nesting in developed woodlots in the Ottawa region. The effects of housing developments appear to be region-specific and may depend on other factors influencing the overall abundance of cowbirds.

Impactos de la Construcción de Viviendas en el Éxito de Nidificación de Hylocichla mustelina en Fragmentos de Bosque

Resumen. Estudiamos los impactos de la construcción en baja densidad de viviendas peri-urbanas sobre individuos de Hylocichla mustelina que se encontraron criando en fragmentos pequeños de bosque en dos regiones rurales del sur de Ontario. En ambas regiones, los individuos de H. mustelina que se reprodujeron en bosques donde había casas inmersas (que penetraban el borde del bosque) experimentaron tasas de parasitismo por Molothrus ater significativamente mayores que los individuos criando en bosques con casas adyacentes (dispuestas a menos de 100 m del borde del bosque), o en bosques no alterados por la presencia de casas (a más de 100 m del borde del bosque). Los individuos de H. mustelina que se encontraron criando en áreas boscosas de Peterborough, donde las casas estaban adentro o adyacentes al bosque, experimentaron incrementos significativos en las tasas de depredación de nidos comparados con individuos que criaron en bosques no alterados. Este incremento en la depredación de nidos llevó a reducciones significativas en la productividad estacional en los bosques con viviendas. No registramos un incremento en la depredación de nidos de H. mustelina en bosques con viviendas en la región de Ottawa. Los efectos de la construcción de viviendas parecen estar relacionados de modo específico con la región y podrían depender de otros factores que influencian la abundancia de M. ater.
Environmental Conditions Affect Offspring Sex-Ratio Variation and Adult Survival in Tawny Owls
Authors: Sasvári Lajos , Nishiumi Isao
Published: September 2019

We 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 aluco

Resumen. 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

Brown 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 occidentalis

Resumen. 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

Inland-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 Planicie

Resumen. 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

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

We 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. fusca

Resumen. 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

Using 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 antipodes

Resumen. 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

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

Hawaiian 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

Avian 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

We 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

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.
The Relationship Between Habitat Characteristics and Demographic Performance of Northern Spotted Owls in Southern Oregon
Authors: Dugger Katie M. , Wagner Frank , Anthony Robert G. , Olson Gail S.
Published: September 2019

We used data from Northern Spotted Owl (Strix occidentalis caurina) territories to model the effects of habitat (particularly intermediate-aged forest stand types), climate, and nonhabitat covariates (i.e., age, sex) on owl reproductive rate and apparent survival in southwestern Oregon. Our best model for reproductive rate included an interaction between a cyclic, annual time trend and male breeding experience, with higher reproductive rates in even years compared to odd, particularly for males with previous breeding experience. Reproductive rate was also negatively related to the amount of winter precipitation and positively related to the proportion of old-growth forest near the owl territory center. Apparent survival was not associated with age, sex, climate or any of the intermediate-aged forest types, but was positively associated with the proportion of older forest near the territory center in a pseudothreshold pattern. The quadratic structure of the proportion of nonhabitat farther from the nest or primary roost site was also part of our best survival model. Survival decreased dramatically when the amount of nonhabitat exceeded ∼50%. Habitat fitness potential estimates (λ̂h) for 97 owl territories ranged from 0.29–1.09, with a mean of 0.86 ± 0.02. Owl territories with habitat fitness potentials <1.0 were generally characterized by <40%–50% old forest habitat near the territory center. Our results indicate that both apparent survival and reproductive rate are positively associated with older forest types close to the nest or primary roost site. We found no support for either a positive or negative direct effect of intermediate-aged forests on either survival or reproductive rate.
Effects of Savanna Restoration on the Foraging Ecology of Insectivorous Songbirds
Authors: Hartung Sarah C. , Brawn Jeffrey D.
Published: September 2019

We studied the foraging behavior of insectivorous songbirds during the breeding season at four sites in Illinois, each with restored open-canopy savanna habitat (65% mean canopy closure) and closed-canopy forests (89% mean canopy closure). We sampled and compared apparent tree species preference, foliage layer preference, and proportional use of different prey-attack maneuvers in the two habitats. In closed-canopy forests, three of nine songbird species foraged in black oak (Quercus velutina) and white oak (Q. alba) more than expected based on availability, and foraged less than expected in shade-tolerant trees such as sugar maple (Acer saccharum) and red elm (Ulmus rubra). Four species also displayed apparent preferences for black locust (Robinia pseudoacacia) and hackberry (Celtis occidentalis). In contrast, songbirds used tree species according to availability in open-canopy habitat. We observed apparent preferences for the shrub and subcanopy vegetation layers (0–5 m and 6–10 m) in open-canopy habitat and apparent preferences for the subcanopy and lower canopy vegetation layers (6–10 m and 11–15 m) in closed-canopy forests. Relative use of prey-attack maneuvers in open versus closed-canopy habitat was significantly different for the Eastern Wood-Pewee (Contopus virens) and the Great Crested Flycatcher (Myiarchus crinitus), but not for foliage-gleaning species. These results suggest that restoration of oak savannas has important effects on the habitat use and foraging ecology of selected insectivorous birds.
Mallard Duckling Survival in the Great Lakes Region
Authors: Simpson John W. , Yerkes Tina J. , Smith Barry D. , Nudds Thomas D.
Published: September 2019

Survival of young in waterfowl is poorly understood, particularly in regions outside of the traditional prairie breeding areas. Further, traditional methods of survival estimation lack the ability to statistically characterize between the extremes of random and catastrophic mortality events. We estimated Mallard (Anas platyrhynchos) duckling survival rates for 121 broods at nine study sites across the Great Lakes region from 2001–2003, using a novel statistical method that allows for the partitioning of random and correlated mortality processes. Results indicated that survival increased rapidly with age, did not change with hatching dates, did not differ among years, but varied across site-by-year replicates. Rates of random mortality were found to vary among site-years, while rates of correlated mortality varied little across site-years. In contrast to most studies of Mallard duckling survival, seasonal increases in duckling survival were not detected. We speculate that the observed patterns in survival rates with hatching date are related to productivity in Great Lakes brood-rearing wetlands and temperate regional climate.