bluuebunny/crossref_metadata_2025_split huggingface dataset:
Field Metabolism and Water Flux of Carolina Chickadees During Breeding and Nonbreeding Seasons: A Test of the “Peak-Demand” and “Reallocation” Hypotheses
Authors: Doherty Paul F. , Williams Joseph B. , Grubb Thomas C. 
Published: September 2019

AbstractWe tested the “peak-demand” and “reallocation” hypotheses of seasonal energy expenditure which predict, respectively, that energy expenditure is greatest during the breeding season or varies little seasonally. We tested these predictions by utilizing the doubly labeled water technique to estimate energy expenditure and water flux of Carolina Chickadees (Poecile carolinensis) in both the breeding and nonbreeding seasons. Similar to Weathers et al. (1999), we did not find support for either of these hypotheses, finding instead that energy expenditure was greater during the nonbreeding season. The fact that our study site was at the northern edge of the species' range, where winters are severe, may have influenced this result. Comparisons with other parid studies were equivocal because body size was an important factor in explaining seasonal energetics, and only the larger species have been examined during the breeding season.
Nonrandom Mating and Productivity of Adult and Subadult Cooper's Hawks
Authors: Boal Clint W. 
Published: September 2019

Abstract
Among 90 independent pairings of Cooper's Hawks (Accipiter cooperii) in Tucson, Arizona, fewer adult-subadult pairings and more adult-adult and subadult-subadult pairings occurred than was expected. On average, hatching occurred at nests of adult pairs five days earlier than subadult male-adult female pairs, 12 days earlier than adult male-subadult female pairs, and 19 days earlier than subadult pairs. Brood sizes were largest among adult pairs, lower among mixed-age pairs, and smallest among subadult pairs. Adult female Cooper's Hawks nested earlier and had larger broods than subadult females, but brood size did not differ between subadult females paired with adult or subadult males. Adult pairs fledged significantly more young per year than mixed-age and subadult pairs. Differences in phenology between adult and subadult Cooper's Hawks may be associated with adults being preferred as mates. Differences in productivity, however, may be more closely associated with age-related constraints on reproductive physiology of females.
Sex Ratio Bias at Hatching and Fledging in the Roseate Tern
Authors: Szczys Patricia , Nisbet Ian C. T. , Hatch Jeremy J. , Kesseli Richard V. 
Published: September 2019

Abstract
Several hypotheses have been proposed to explain facultative manipulation of sex ratios in birds, but existing data are inconsistent within and among species, and do not clearly support any one of the hypotheses. The sex ratio among breeding Roseate Terns (Sterna dougallii) at Bird Island, Massachusetts is female-biased (56%). We sought to determine at what stage of the life cycle this sex ratio bias is established. We monitored 461 eggs from 252 nests and, using molecular markers, we sexed 342 chicks at hatching and followed them to a stage when survival (or non-survival) to fledging could be inferred. We found that the sex ratio at hatching (and, by inference, at fertilization) was biased toward females (55%). This bias was significant in chicks from first-laid eggs (58%) but not second-laid eggs (48%). We also found that the overall bias increased (to 56.6%) during the chick stage through differential loss of male chicks.
Vocal Mimicry in Distress Calls of Phainopeplas
Authors: Chu Miyoko 
Published: September 2019

AbstractPhainopeplas (Phainopepla nitens) utter contact calls, loud distress screams, and 37 other distinguishable vocalizations when captured, including imitations of at least 12 species. In southern California, Phainopeplas captured in the desert and coastal woodlands imitated species from both regions, suggesting that individuals occupy both habitats during the year and have an extended period of learning that spans the period of time when they move between regions. There was no significant difference in the number of calls imitated based on sex, male age, or habitat. A high percentage of Phainopeplas in both desert and coastal woodlands imitated Red-tailed Hawks (Buteo jamaicensis) and Northern Flickers (Colaptes auratus), whereas the use of other species' calls varied with habitat. Phainopeplas did not simply imitate the calls of the most abundant species or those that were most vocal.
Digestive Constraints and Nutrient Hydrolysis in Nestlings of Two Flamingo Species
Authors: Sabat Pablo , Novoa F. Fernando , Parada Mario 
Published: September 2019

Abstract
In vertebrates, enzymatic activity levels in the small intestine are correlated with dietary composition. We examined enzymatic activity levels in juvenile specimens of two flamingo species, Phoenicoparrus andinus and Phoenicoparrus jamesi. Both species feed their chicks with esophageal secretions. Based on the chemical composition of these secretions in flamingoes, we predicted low activity levels of disaccharidases and higher activities of aminopeptidase-N and esterase. As predicted, sucrase was absent in P. andinus, and its activity was low in P. jamesi. Esterase and aminopeptidase-N activities were relatively high. Low maltase activity suggested the presence of carbohydrates in esophageal secretions. Digestive features can have consequences on the growth and survival of chicks. Hence the data presented here may be relevant to the maintenance and reproduction of wild and captive endangered flamingoes.
The Social Organization and Mating System of the Striated Grasswren
Authors: Karubian Jordan 
Published: September 2019

Abstract
This paper summarizes the breeding biology, social organization, and mating system of the Striated Grasswren (Amytornis striatus), a member of one of the least-known genera of Australian passerines, the grasswrens. I studied 18 color-banded groups and 14 nests in South Australia for one breeding season in 1996. Mean territory size was 3.0 ha, and territories consisted of sandy dunes dominated by spinifex (Triodea irritans). This apparent dependency on mature spinifex, coupled with poor dispersal ability, suggests that the Striated Grasswren is particularly susceptible to habitat destruction. Most groups consisted of socially monogamous pairs, mean group size was 2.1 adults, and the adult sex ratio was 0.95 (males:females). The average clutch size was 2.2 ± 0.4 eggs and an average of 1.1 ± 1.1 young fledged per nesting effort. A male and a female provided similar amounts of parental care at a single nest. Cloacal protuberance size and amount of sperm collected did not suggest intense sperm competition among males.
The Taxonomic Rank of Spizella Taverneri: A Response to Mayr and Johnson
Authors: Klicka John , Zink Robert M. , Barlow Jon C. , McGillivray W. Bruce , Doyle Terry J. 
Published: September 2019

AbstractMayr and Johnson suggest that Spizella taverneri should be a subspecies of the biological species S. breweri, because it is possibly not reproductively isolated. We originally concluded that evidence from mitochondrial DNA sequences, habitat preferences, timing of breeding, vocalizations, and morphology supported the recognition of S. taverneri as a phylogenetic and biological species. Nothing in the commentary by Mayr and Johnson causes us to change that conclusion. We believe that it is probable that these two allopatric taxa are isolated. Contrary to Mayr and Johnson, we believe that more information is given by ranking S. taverneri as a species, because it reveals the fact that they are independently evolving taxa. The classification of Spizella should convey the sister-species status of S. taverneri and S. breweri, without regard for balancing the degree of sequence divergence among species, as suggested by Mayr and Johnson.
Attenuated Outer Primaries in Pigeons and Doves: A Comparative Test Fails to Support the Flight Performance Hypothesis
Authors: Mahler Bettina , Tubaro Pablo Luis 
Published: September 2019

AbstractSharp reduction of the inner web of the outer primary feather, hereafter referred to as the attenuated primary, is present in 54 of about 300 species belonging to the family Columbidae. The flight performance hypothesis (Goodwin 1983) suggests that attenuated primaries improve flight performance in cluttered habitats, presumably by enhancing maneuverability. This hypothesis predicts that the evolution of attenuated primaries should be associated with the use of closed habitats. A comparative analysis, using the contingent states test (Sillén-Tullberg 1993), was made to test this hypothesis. We found that 15 out of 17 independent instances of evolution of attenuated primaries occurred in clades using closed habitat, but because most species live in closed habitats, chance alone could explain this result.Atenuación de las Primarias Externas en Palomas: Un Análisis Comparativo No Apoya la Hipótesis de la Performance de VueloResumen. En 54 de las aproximadamente 300 especies pertenecientes a la familia Columbidae se observa una abrupta reducción de la lámina interna de la pluma primaria distal, denominada primaria atenuada de aquí en adelante. La hipótesis de la performance de vuelo (Goodwin 1983) sugiere que las primarias atenuadas mejoran el desempeño de vuelo en ambientes cerrados, probablemente por conferir una mayor maniobrabilidad. Esta hipótesis predice que la evolución de primarias atenuadas debería estar asociada al uso de ambientes cerrados. Para evaluar esta hipótesis, se realizó un análisis comparativo usando el método de estados contingentes (Sillén-Tullberg 1993). Se encontró que 15 de 17 instancias independientes de evolución de primarias atenuadas ocurrieron en clados de ambientes cerrados, pero dado que la mayoría de las especies del grupo habitan estos ambientes, este resultado puede ser explicado simplemente por azar.
Effect of Instrument Attachment and Other Factors on Foraging Trip Duration and Nesting Success of Adélie Penguins
Authors: Ballard Grant , Ainley David G. , Ribic Christine A. , Barton Kerry R. 
Published: September 2019

AbstractWe compared foraging-trip duration of Adélie Penguins (Pygoscelis adeliae) carrying various combinations of radio-telemetry transmitters, implanted, passively interrogated transponder (PIT) tags, and time-depth recorders at two widely separated colonies of different size on Ross Island, Antarctica, during three austral summers. Trip duration was measured by electronic devices rather than human observation. Instrumentation had no significant effect on foraging trip duration. Most of the variation in foraging trip duration was attributed to individual and year. Males' trips were significantly shorter than females' in a subset of known-sex birds. No effect was evident in nesting success even for birds that wore instruments for >20 days. We recommend use of small, hydrodynamically designed and placed instruments to researchers who wish to collect data unaffected by instrument attachment.Efectos de la Sujeción de Instrumentos y Otros Factores en la Duración de las Salidas de Forrajeo y el Éxito Reproductivo en Pygoscelis adeliaeResumen. Se comparó la duración de las salidas de búsqueda de alimento de Pygoscelis adeliae a los que se les colocaron distintas combinaciones de radiotransmisores, emisores implantados de interrogación pasiva y medidores de tiempo y profundidad de buceo. El estudio fue realizado durante tres veranos australes en dos colonias ampliamente separadas de diferente tamaño en Ross Island, Antártica. La duración de las salidas fue medida por instrumentos electrónicos en lugar de observaciones humanas. Los instrumentos no tuvieron un efecto significativo en la duración de las salidas de búsqueda de alimento. La mayor parte de la variación en la duración de las salidas fue atribuida a individuos y años. Las salidas de los machos fueron significativamente más cortas que las de las hembras en una sub-muestra de aves previamente sexadas. No se detectaron efectos evidentes en éxito de nidificación incluso en individuos que llevaron instrumentos por más de 20 días. Recomendamos el uso de instrumentos pequeños diseñados y colocados hidrodinámicamente a fin de no influenciar los datos colectados.
Reproductive Success of Water Pipits in an Alpine Environment
Authors: Bollmann Kurt , Reyer Heinz-Ulrich 
Published: September 2019

Abstract
To understand the evolution of avian reproductive strategies it is important to assess how differences in reproductive success are related to timing of the breeding season, quality of nesting territories or breeders, or to a combination of these factors. Over three years, we studied the reproductive performance of female Water Pipits (Anthus spinoletta) in a temporally and spatially variable alpine environment. The study area covered two valley slopes that differed in the probability of nest predation, food availability, and climate. Nest predation and harsh weather were the main proximate causes of differences in female reproductive success. Because these two environmental factors were locally unpredictable, individual females could best optimize their seasonal reproductive success by choosing the “right” breeding time. The average number of young fledged per season was inversely related to the date of initial breeding and increased from females with only first attempts, through females with replacement clutches, to females that raised two broods. Hence, the main advantage of early breeding lies in the chance of rearing a second brood after the first has fledged, or of producing a replacement clutch if the first fails due to predation or harsh weather.
Éxito Reproductivo de Anthus spinoletta en un Ambiente Alpino
Resumen. Para entender la evolución de las estrategias reproductivas de las aves es importante determinar cómo las diferencias en el éxito reproductivo se relacionan con el comienzo de la época reproductiva, la calidad de los territorios de nidificación o los reproductores o con una combinación de estos factores. Durante un período de tres años, estudiamos el desempeño reproductivo de hembras de Anthus spinoletta en un ambiente alpino temporal y espacialmente variable. El sitio de estudio comprendió dos laderas que diferían en la probabilidad de depredación de nidos, disponibilidad de alimento y clima. La depredación de nidos y el clima severo fueron las principales causas proximales de la diferencia del éxito reproductivo de las hembras. Debido a que ambos factores ambientales fueron localmente inpredecibles, cada individuo hembra podía optimizar el éxito de su período reproductivo eligiendo el tiempo “correcto” para reproducirse en la temporada. El número promedio de juveniles por temporada se relacionó inversamente con la fecha del inicio de la reproducción y aumentó desde hembras con sólo un intento de cría, pasando por hembras que reemplazaron sus nidadas, hasta hembras que criaron dos nidadas. Por tanto, la ventaja principal de reproducirse tempranamente en la temporada está dada por la posibilidad de criar una segunda nidada luego de la partida de los primeros juveniles o de producir una nueva nidada si la primera falla debido a depredación o clima severo.
Does Habitat Fragmentation Influence Nest Predation in the Shortgrass Prairie?
Authors: Howard Melissa N. , Skagen Susan K. , Kennedy Patricia L. 
Published: September 2019

Abstract
We examined the effects of habitat fragmentation and vegetation structure of shortgrass prairie and Conservation Reserve Program (CRP) lands on predation rates of artificial and natural nests in northeastern Colorado. The CRP provides federal payments to landowners to take highly erodible cropland out of agricultural production. In our study area, CRP lands have been reseeded primarily with non-native grasses, and this vegetation is taller than native shortgrass prairie. We measured three indices of habitat fragmentation (patch size, degree of matrix fragmentation, and distance from edge), none of which influenced mortality rates of artificial or natural nests. Vegetation structure did influence predation rates of artificial nests; daily mortality decreased significantly with increasing vegetation height. Vegetation structure did not influence predation rates of natural nests. CRP lands and shortgrass sites did not differ with respect to mortality rates of artificial nests. Our study area is only moderately fragmented; 62% of the study area is occupied by native grassland. We conclude that the extent of habitat fragmentation in our study area does not result in increased predation in remaining patches of shortgrass prairie habitat.
¿La Fragmentación de Hábitat Influencia la Depredación de Nidos en Praderas de Pasto Corto?
Resumen. Examinamos los efectos de fragmentación de hábitat y estructura de la vegetación sobre la tasa de depredación de nidos artificiales y naturales en praderas de pasto corto y tierras del Programa de Reserva de Conservación (CRP) en el noreste de Colorado. El CRP proporciona pagos federales para que los dueños de las tierras retiren sus cultivos de áreas agrícolas altamente erosionables. En nuestra área de estudio, las tierras de CRP han sido vueltas a sembrar principalmente con céspedes no nativos que son más altos que la vegetación nativa de las praderas de pasto corto. Medimos tres índices de fragmentación de hábitat (tamaño del parche, grado de fragmentación de la matriz, y distancia al borde), ninguno de los cuales influyó sobre la tasa de mortalidad de nidos artificiales o naturales. La estructura de la vegetación influenció la tasa de depredación de nidos artificiales: la mortalidad diaria disminuyó significativamente con incrementos en la altura de la vegetación. La estructura de la vegetación no influenció la tasa de depredación de nidos naturales. Los sitios de CRP y de pastos cortos no difirieron con respecto a la tasa de mortalidad de nidos artificiales. Nuestra área de estudio es sólo moderadamente fragmentada pues el 62% del área es ocupada por prado nativo. Concluimos que el grado de fragmentación de hábitat en nuestra área del estudio no causa aumentos en la depredación en los parches de hábitat remanentes.
Life History Implications of Complete and Incomplete Primary Molts in Pelagic Cormorants
Authors: Filardi Christopher E. , Rohwer Sievert 
Published: September 2019

Abstract
We describe the rules of primary flight-feather replacement for Pelagic Cormorants (Phalacrocorax pelagicus), and contrast the completeness of primary replacement in individuals from Asia and North America. In adult Pelagic Cormorants primary replacement is stepwise, with multiple waves of molt, each initiated at the innermost primary (P1), proceeding simultaneously toward the tip of the wing. Shugart and Rohwer's (1996) ontogenetic model for generating and maintaining stepwise primary replacement depended upon incomplete molts. In each new episode of molt, waves of primary replacement were thought to be initiated at P1 and at each arrested wave that had failed to replace all old feathers in the preceding molt. Because most adult Pelagic Cormorants from North America completely replace their primaries but maintain stepwise primary molts, the latter assumption must be relaxed. In contrast to the present-day situation in North America, Pelagic Cormorants from northeastern Asia have incomplete molts of their primaries, and may be forced to skip breeding in some years to clear their wings of overworn primaries. Young birds from Asia start the replacement of their juvenile primaries later than North American birds and replace more feathers simultaneously.
Implicancias de la Muda Primaria Completa e Incompleta en la Historia de Vida de Phalacrocorax pelagicus
Resumen. Describimos las reglas de reemplazo de plumas primarias para Phalacrocorax pelagicus y contrastamos la totalización del reemplazo de primarias entre individuos de Asia y América del Norte. En individuos adultos, el reemplazo de primarias ocurre en varias etapas, con múltiples secuencias de muda cada una iniciada en la primaria más interna (P1), procediendo simultáneamente hacia la punta del ala. El modelo ontogenético de Shugart y Rohwer (1996) para la generación y mantenimiento del reemplazo en etapas de las plumas primarias depende de mudas incompletas. Se pensaba que en cada nuevo episodio de muda las secuencias de reemplazo de primarias eran iniciadas en P1 y en cada punto de interrupción de la muda precedente que hubiera impedido el reemplazo de todas las plumas viejas. Debido a que la mayoría de los individuos adultos de P. pelagicus de Norteamérica reeemplazan completamente sus primarias pero aún lo hacen en etapas, la última suposición debe ser re-evaluada. En contraste con la situación actual en Norteamérica, individuos del noreste de Asia tienen mudas incompletas de sus primarias y pueden verse forzados a no reproducirse en algunos años para despojarse de la presencia de primarias desgastadas. Las aves juveniles de Asia comienzan el reemplazo de sus primarias más tarde y reemplazan más plumas simultáneamente que las aves de Norteamérica.
Variations in Calcium Use by Birds During the Breeding Season
Authors: Dhondt André A. , Hochachka Wesley M. 
Published: September 2019

AbstractDuring the breeding season birds need increased amounts of dietary calcium during egg laying and nestling rearing. Passerines acquire calcium shortly before and during laying and do not store calcium for egg formation. Many passerines need to eat extraneous calcium in the form of snail shells or calcareous grit to acquire the element. However, very little is known about variation in the dependency of birds on extraneous calcium, and where this calcium is acquired. Using reports from volunteers who provided extraneous calcium sources at feeder sites across North America we documented that (1) the use of extraneous calcium varied during the breeding season; (2) the location in which species preferentially took the calcium varied with typical feeding location, aside from swallows which, somewhat surprisingly, favored calcium offered on the ground; (3) Brown-headed Cowbirds (Molothrus ater) did not visit calcium sites more often than other blackbirds; (4) calcium use varied among species with thrushes, wrens, and woodpeckers taking calcium only rarely, and swallows, pigeons, and corvids taking calcium frequently. The most surprising result perhaps was the very high frequency of calcium use in jays; Blue Jays (Cyanocitta cristata) may hoard calcium in the fall.Variaciones en el Uso de Calcio por Aves durante la Época ReproductivaResumen. En la época reproductiva, las aves necesitan incrementar la cantidad de calcio en la dieta durante el período de postura de huevos y cría de los pichones. Las aves paserinas adquieren calcio poco antes y durante la postura y no lo almacenan para la formación de los huevos. Muchas aves paserinas necesitan ingerir calcio de fuentes externas como conchas de caracoles o cascajo calcáreo para adquirir este elemento. Sin embargo, se sabe muy poco sobre la variación en el grado de dependencia de las aves de calcio externo y sobre dónde adquieren este calcio. Con base en reportes de voluntarios que suministraron fuentes externas de calcio en comederos a través de Norteamérica, documentamos que (1) el uso de calcio externo varió durante la época reproductiva; (2) el sitio en donde las especies tomaron el calcio preferencialmente varió de acuerdo al sitio típico de alimentación, con excepción de las golondrinas, que de manera algo sorprendente, prefirieron el calcio ofrecido en el suelo; (3) Molothrus ater no visitó sitios con calcio con más frecuencia que otros ictéridos; (4) el uso de calcio varió entre especies: los túrdidos, troglodítidos y carpinteros muy rara vez tomaron calcio, mientras que las golondrinas, palomas y córvidos lo hicieron frecuentemente. Quizás el resultado más sorprendente fue la muy alta frecuencia de uso de calcio en Cyanocitta; C. cristata podría acumular calcio durante el otoño para uso futuro.