bluuebunny/crossref_metadata_2025 huggingface dataset:
Lekking Behavior of the Round-Tailed Manakin
Authors: Tello Jose G.
Published: September 2019

Along the Rio Manu in southeastern Peru, Round-tailed Manakins (Pipra chloromeros) breed mainly from August to November. Male P. chloromeros have a dispersed lek breeding system, with each lek composed of two to five territorial males. Sites used by males for display had significantly higher densities of shrubs, vines, and small trees than did non-display sites. Interlek distances ranged from 220 to 1000 m. Within leks, most males occupied territories within auditory range, but not visual range. Distance to the closest neighbor's display perch varied from 8 to 87 m. Males vigorously defended territories that ranged from 20 to 50 m in diameter. Males progress in social status within the lek (from immature to non-territorial adult to territorial adult). Territorial adult males were always dominant to males of the other two categories. Territorial males engaged in daily ritualized encounters at the borders of their territories. Encounters involved slow, coordinated displays reminiscent of those performed toward females. Such interactions may help maintain dominance relationships within the lek, but an analysis of interaction outcomes failed to show clear dominance relationships among males. Female visitation was most frequent in early afternoon, during males' maximum territory attendance and display activity. Lekking P. chloromeros employ ten display elements, six vocalizations, and one mechanical noise. One display element has not been observed in any other species of Pipra. The displays and sounds in the P. erythrocephala clade are compared from the perspective of understanding the evolution of display behavior in this group.
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

We 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

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

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

Phainopeplas (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

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

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

Mayr 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

Sharp 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 Vuelo

Resumen. 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

We 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 adeliae

Resumen. 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

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

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

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

During 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 Reproductiva

Resumen. 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.
Predicting Species' Geographic Distributions Based on Ecological Niche Modeling
Authors: Peterson A. Townsend
Published: September 2019

Recent developments in geographic information systems and their application to conservation biology open doors to exciting new synthetic analyses. Exploration of these possibilities, however, is limited by the quality of information available: most biodiversity data are incomplete and characterized by biased sampling. Inferential procedures that provide robust and reliable predictions of species' geographic distributions thus become critical to biodiversity analyses. In this contribution, models of species' ecological niches are developed using an artificial-intelligence algorithm, and projected onto geography to predict species' distributions. To test the validity of this approach, I used North American Breeding Bird Survey data, with large sample sizes for many species. I omitted randomly selected states from model building, and tested models using the omitted states. For the 34 species tested, all predictions were highly statistically significant (all P < 0.001), indicating excellent predictive ability. This inferential capacity opens doors to many synthetic analyses based on primary point occurrence data.

Predicción de Áreas de Distribución de Especies con Pase en Modelaje de Nichos Ecológicos

Resumen. Avances recientes en los sistemas de información geográfica y su aplicación en la biología de conservación presentan la posibilidad de analisis nuevos y sintéticos. La exploración de estas posibilidades, de todas formas, se limita por la calidad de información disponible: la gran mayoria de datos respecto a la diversidad biológica son incompletos y sesgados. Por eso, procedimientos de inferencia que proveen predicciones robustas y confiables de distribuciones de especies se hacen importantes para los análisis de la biodiversidad. En esta contribución, se desarrollan modelos de los nichos ecológicos por medio de un algoritmo de inteligencia artificial, y los proyeccionamos en la geografía para predecir las distribuciones geográficas de especies. Para probar el método, se usan los datos del North American Breeding Bird Survey, con tamaños de muestra grande. Se construyeron modelos con base en 30 estados unidenses seleccionados al azar, y se probaron los modelos con base en los 20 estados restantes. De las 34 especies que se analizaron, todos mostraron un alto grado de significanza estadística (todos P < 0.001), lo cual indica un alto grado de predictividad. Esta capacidad de inferencia abre la puerta a varios analisis sintéticos con base en puntos conocidos de ocurrencia de especies.
Passive Interference Competition by Glaucous-Winged Gulls on Black-Legged Kittiwakes: A Cost of Feeding in Flocks
Authors: Maniscalco John M. , Ostrand William D. , Suryan Robert M. , Irons David B.
Published: September 2019

We analyzed data from two independent studies of foraging Black-legged Kittiwakes (Rissa tridactyla) in Prince William Sound, Alaska. Our purpose was to determine if Glaucous-winged Gulls (Larus glaucescens) hindered prey capture by kittiwakes. At tightly aggregated feeding flocks, gulls remained on the water directly over the prey and foraged by making brief hop-plunges or surface-seizes. Kittiwakes, in contrast, fed by diving from the air into open spots in the flock or around its periphery. Data from both studies indicated that kittiwakes made fewer feeding attempts in flocks that had greater numbers of gulls. However, kittiwake success rate per feeding attempt did not change as the number of gulls increased. Kittiwakes were more likely to avoid flocks that had a greater number of Glaucous-winged Gulls. Gulls successfully pirated less than 1% of fish captured by kittiwakes. Our findings suggest that passive interference may be costly for smaller birds that feed in multispecies feeding flocks.

Competencia por Interferencia Pasiva de Larus glaucescens sobre Rissa tridactyla: El Costo del Forrajeo en Grupo

Resumen. Analizamos datos de dos estudios independientes sobre forrajeo de Rissa tridactyla en Prince William Sound, Alaska. El propósito de nuestro estudio fue determinar si Larus glaucescens impedía la captura de presas por parte de R. tridactyla. Las gaviotas permanecieron sobre el agua directamente sobre sus presas en bandadas de forrajeo altamente agregadas y forrajearon realizando zambullidos breves o capturas de superficie. En contraste R. tridactyla forrajeó lanzándose desde el aire a espacios abiertos entre la bandada o en su periferia. Los datos de ambos estudios indicaron que R. tridactyla realizó menos intentos de forrajeo en bandadas que tenían mayor número de gaviotas. Sin embargo, la tasa de éxito por intento de forrajeo no cambió con el aumento del número de gaviotas. R. tridactyla presentó una mayor probabilidad de evitar las bandadas con mayor número de gaviotas. Las gaviotas cleptoparasitaron exitosamente menos del 1% de los peces capturados por R. tridactyla. Nuestros resultados sugieren que la interferencia pasiva puede ser costosa para las aves más pequeñas que forrajean en bandadas multiespecíficas.
Organochlorine Concentrations and Eggshell Thickness in Failed Eggs of the California Clapper Rail from South San Francisco Bay
Authors: Schwarzbach Steven E. , Henderson John D. , Thomas Carmen M. , Albertson Joy D.
Published: September 2019

In 1992 we collected 22 failed California Clapper Rail (Rallus longirostris obsoletus) eggs from four tidal marshes of south San Francisco Bay for organochlorine analysis and determination of eggshell thickness. Mean eggshell thickness of these eggs (262 microns) was not statistically distinguishable from that of pre-1932 museum eggs (271 microns). Total PCB concentrations in eggs ranged from 0.65 to 5.01 μg g−1 on an adjusted fresh wet weight basis, with a geometric mean concentration of 1.30 μg g−1. DDE concentrations were extremely low at a geometric mean of 0.11 μg g−1. Geometric mean concentrations of all other organochlorines detected were below 0.10 μg g−1. The concentrations of all organochlorines except PCBs appear to have declined in California Clapper Rails since the mid 1980s. PCBs may still be high enough in some rail eggs to produce embryotoxic effects but additional work to quantify the more toxic PCB congeners in rail eggs is needed.

Concentraciones de Organocloros y Espesor de los Cascarones en Huevos Fallados de Rallus longirostris obsoletus de la Bahía de San Francisco del Sur

Resumen. En 1992 recolectamos 22 huevos de Rallus longirostris obsoletus que fallaron en salir del cascarón en cuatro ciénagas de marea del sur de la Bahía de San Francisco para su análisis de contenido de organocloros y la determinación del espesor de los cascarones de dichos huevos. La media proporcional del espesor de los cascarones de huevo recolectados en el campo en 1992 (262 micras) no era menor que la de aquellos huevos (en museo) anteriores a 1932 (256 micras). Las concentraciones totales de PCB en los huevos fluctuaban desde 0.65 hasta 5.01 μg g−1 en base a un ajuste del peso húmedo fresco, con una concentración media geométrica de 1.30 μg g−1. Las concentraciones de DDE eran extremadamente bajas a una media geométrica de 0.11 μg g−1. La concentración media geométrica de todos los otros organocloros descubiertos estuvo por debajo de 0.10 μg g−1. La concentración de todos los organocloros, excepto los PCBs parece haber disminuido en R. l. obsoletus desde mediados de los años ochenta. Los PCBs todavía pueden ser suficientemente altos en algunos huevos de gallinetas de California como para producir efectos tóxicos en embriones, pero es necesario realizar investigaciones adicionales para cuantificar mayores congeners de los PCBs.
Passerine Densities in Riparian Forests of Southeast Alaska: Potential Effects of Anadromous Spawning Salmon
Authors: Gende Scott M. , Willson Mary F.
Published: September 2019

Spawning salmon (Oncorhynchus spp.) greatly influence many biotic processes in both the aquatic and terrestrial components of riparian systems, possibly including the community of breeding birds. In southeastern Alaska in 1996–1997, the riparian forests bordering salmon streams supported, on average, higher densities, but not diversity, of forest passerines compared to non-salmon streams. The presence of salmon in the fall increases the abundance of terrestrial and aquatic invertebrates and possibly enhances food resources to riparian birds in the spring.

Densidades de Aves Paserinas en Bosques Riparios del Sureste de Alaska: Efectos Potenciales del Desove de Salmones Anádromos

Resumen. El desove de salmones anádromos (Oncorhynchus spp.) ejerce una importante influencia sobre muchos procesos bióticos en los componentes acuáticos y terrestres de los sistemas ribereños, incluyendo posiblemente las comunidades de aves. Entre 1996 y 1997, los bosques riparios del sureste de Alaska ubicados alrededor de arroyos con salmones tuvieron en promedio mayores densidades (pero no mayor diversidad) de aves paserinas de bosque que bosques situados alrededor de arroyos sin salmones. La presencia de los salmones en el otoño incrementa la abundancia de invertebrados terrestres y acuáticos y posiblemente causa aumentos en la cantidad de recursos alimenticios disponibles para las aves ribereñas en la primavera.
Movements and Survival of Lark Bunting Fledglings
Authors: Adams Amy A. Yackel , Skagen Susan K. , Adams Rod D.
Published: September 2019

We quantified post-fledging pre-independence behavior and survival in Lark Buntings (Calamospiza melanocorys) using radio-telemetry. Brood division was recorded in six broods and was maintained throughout the observed fledgling care period. Chicks were capable of short flights (up to 25 m) by fledgling day 6 and longer flights (to 100 m) by fledgling day 13. During the first three weeks after fledging, juveniles moved as far as 800 m from nests. Nine of 23 (39%) monitored fledglings died within 15 days of fledging, primarily due to predation by raptors. Daily survival rates were 0.953 ± 0.019 for fledgling days 0–9, 0.955 ± 0.038 for fledgling days 10–20, and 0.953 ± 0.015 for fledgling days 0–20. The probability of surviving fledgling days 0–20 was 0.367. More quantification of juvenile survival is clearly needed to understand the role of post-fledging mortality in source-sink dynamics.

Los Movimientos y Supervivencia de los Volantones de Calamospiza melanocorys

Resumen. Cuantificamos la conducta y la supervivencia de volantones de Calamospiza melanocorys antes de independizarse de sus padres usando telemetría de radio. La división de la nidada se registró en seis nidadas y se mantuvo a través del período del cuidado de los volantones. Tras seis días de haber abandonado el nido, los polluelos eran capaces de realizar vuelos cortos (de hasta 25 m) y para el día trece ya realizaban vuelos más largos (a 100 m). Durante las primeras tres semanas después de salir del nido, los juveniles se movieron hasta 800 m de los nidos. Nueve de 23 (39%) volantones se murieron en los primeros 15 días fuera del nido, principalmente debido a depredación por aves rapaces. Las tasas diarias de supervivencia fueron de 0.953 ± 0.019 para los días 0 a 9, 0.955 ± 0.038 para los días 10 a 20, y 0.954 ± 0.015 para días 0 a 20. La probabilidad de sobrevivir entre los días 0 y 20 fue de 0.367. Se necesita más cuantificacion de la sobrevivencia en la etapa juvenil para entender el papel de la mortalidad tras la salida del nido en la dinámica de fuente-sumideros.
The Function of Displays of Male Rufous Hummingbirds
Authors: Hurly T. Andrew , Scott Renée D. , Healy Susan D.
Published: September 2019

We observed 26 male Rufous Hummingbirds (Selasphorus rufus) on their breeding territories to quantify display behaviors and to interpret their functions. Territory holders responded to intruding conspecific males with aggressive chases until the intruder left the territory. Female intruders received dive displays and shuttle-flights, which we interpret as courtship behavior. Dive displays were J-shaped (concave upward) in both ascent and descent, contrary to other reports of oval-shaped displays. We present a representative sonogram of the sounds produced during these dive displays.

Función de los Despliegues de los Selasphorus rufus Machos

Resumen. Observamos 26 Selasphorus rufus machos en sus territorios de reproducción para cuantificar sus comportamientos de despliegue e interpretar las funciones de éstos. Los dueños de los territorios respondieron a intrusiones de machos coespecíficos con persecuciones agresivas hasta que los intrusos abandonaron el territorio. Por su parte, las hembras intrusas recibieron despliegues en picada y patrones de vuelo repetidos, los cuales interpretamos como comportamientos de cortejo. Los despliegues en picada tuvieron forma de J (cóncava hacia arriba) tanto en ascenso como en descenso a diferencia de reportes previos sobre despliegues en forma de óvalo. Adicionalmente presentamos un sonograma representativo de los sonidos producidos durante los despliegues en picada.
Some Considerations on the Use of Ecological Models to Predict Species' Geographic Distributions
Authors: Peterjohn Bruce G.
Published: September 2019

Peterson (2001) used Genetic Algorithm for Rule-set Prediction (GARP) models to predict distribution patterns from Breeding Bird Survey (BBS) data. Evaluations of these models should consider inherent limitations of BBS data: (1) BBS methods may not sample species and habitats equally; (2) using BBS data for both model development and testing may overlook poor fit of some models; and (3) BBS data may not provide the desired spatial resolution or capture temporal changes in species distributions. The predictive value of GARP models requires additional study, especially comparisons with distribution patterns from independent data sets. When employed at appropriate temporal and geographic scales, GARP models show considerable promise for conservation biology applications but provide limited inferences concerning processes responsible for the observed patterns.

Algunas Consideraciones del Uso de Modelos Ecológicos para Predecir la Distribución Geográfica de las Especies

Resumen. Peterson (2001) usó Modelos de Algoritmos Genéticos para la Predicción de Reglas (GARP) para predecir los patrones de distribución de los datos del Censo de Aves Nidificantes (BBS). Las evaluaciones de estos modelos deberían considerar las limitaciones propias de los datos del BBS: (1) los métodos del BBS pueden meustrear especies y hábitats de modo diferente; (2) usar los datos del BBS tanto para desarrollar los modelos como para probarlos puede evadir el pobre desempe;tzno de algunos modelos; y (3) los datos del BBS pueden no proveer la resolución espacial deseada y capturar los cambios temporales en la distribución de especies. El valor predictivo de los modelos GARP requiere estudios adicionales, especialmente comparaciones con patrones de distribución obtenidos de bases de datos independientes. Cuando los modelos GARP son empleados a las escalas temporales y geográficas apropiadas muestran aplicaciones promisorias para biología de la conservación, pero proveen inferencias limiadas sobre los procesos responsables de los patrones obervados.
Annual Patterns of Molt and Reproductive Activity of Passerines in South-Central Brazil
Authors: Marini Miguel Â , Durães Renata
Published: September 2019

We analyzed the occurrence of molt and brood patches in resident passerines from four localities in south-central Brazil. The annual patterns of molt and reproductive activity were very similar among the sites. Brood patches first appeared in August, but were most common between October and January, with a peak in November, early in the rainy season. Molt started in October but was most widespread from the middle to the end of the rainy season, between December and April with a peak in February. Timing of the appearance of brood patches was not related to trophic guild (insectivores, frugivores, omnivores). Molt of flight feathers started at the end of the reproductive period, which varied slightly among trophic guilds. Molt and brood patch overlap occurred in little more than 4% of individual birds, or in less than 2% considering just those molting flight feathers. This overlap occurred mostly between November and February. Regional environmental factors, instead of local factors, seem to be responsible for the annual breeding and molt patterns of the considered species.

Padrões Anuais de Muda e Atividade Reprodutiva de Passeriformes na Região Centro-Sul do Brasil

Resumo. Este estudo analisa a ocorrência de muda de penas e reprodução em Passeriformes residentes em quatro localidades na região centro-sul do Brasil. A atividade reprodutiva foi inferida a partir da presença de placas de incubação ativas. Os padrões anuais de muda e reprodução apresentaram-se bastante similares entre as regiões estudadas. Placas de incubação começaram a ser detectadas em agosto, sendo mais comuns entre outubro e janeiro, com um pico em novembro, no início da estação chuvosa. O principal período de mudas começou em outubro, sendo mais intensas nos dois terços finais da estação chuvosa, entre dezembro e abril, com um pico em fevereiro. Os padrões de ocorrência de reprodução e mudas apresentaram pequenas diferenças entre diferentes guildas alimentares, e, de modo geral, o início do período de mudas esteve relacionado ao fim do período reprodutivo. Sobreposição entre mudas e placas de incubação foi detectada em pouco mais de 4% do total de indivíduos analisados, ou em menos de 2%, quando apenas indivíduos mudando penas de vôo foram considerados. Esta sobreposição ocorreu principalmente entre novembro e fevereiro. Os padrões ambientais regionais, mais que os locais, parecem influenciar os ciclos anuais das espécies analisadas.
Annual Variation in Great Skua Diets: The Importance of Commercial Fisheries and Predation on Seabirds Revealed by Combining Dietary Analyses
Authors: Bearhop Stuart , Thompson David R. , Phillips Richard A. , Waldron Susan , Hamer Keith C. , Gray Catherine M. , Votier Stephen C. , Ross Ben P. , Furness Robert W.
Published: September 2019

This study combines conventional dietary assessment with stable isotope techniques to describe Great Skua (Stercorarius skua) diet. Stable carbon and nitrogen isotope ratios in feathers of Great Skua chicks collected over three years were analyzed in conjunction with pellet and regurgitate collections. A significant drop in trophic status was detected in 1997, which likely resulted from an increase in herring and mackerel in the diet. These items were almost certainly obtained from a commercial trawler, as evidenced by a significant drop in territorial attendance during the ship's absence. Feathers yielded significantly different δ13C values among years, and part of this may have been related to a period of enhanced phytoplankton growth during 1996. A combined approach, such as the one described here, is likely to become increasingly useful in elucidating the diets of polyphagous birds.

Variación Anual en la Dieta de Stercorarius skua: La Importancia de Pesqueros Comerciales y Predación de Aves Marinas Revelada por la Combinación de Análisis de Dieta

Resumen. Este estudio combina evaluaciones de dieta convencionales con técnicas de isótopos estables para describir la dieta de Stercorarius skua. Analizamos la proporción de isótopos estables de carbono y nitrógeno en las plumas de pichones de S. skua colectadas durante más de tres años, en conjunto con colecciones de pellets y regurjitados. Un descenso significativo en la posición trófica fue detectado en 1997 probablemente como consecuencia del incremento de arenque y caballa en la dieta. Estos ítems fueron casi con seguridad obtenidos de un pesquero de arrastre comercial, como lo sugiere la caída significativa de la presencia en el territorio durante la ausencia del barco. Las plumas generaron valores significativamente diferentes de δ13C entre años, parte de lo cual puede haber estado relacionado con un período de gran crecimiento del fitoplancton durante 1996. Un enfoque combinado como el descripto aquí será probablemente cada vez más útil para elucidar la dieta de aves polífagas.
The Influence of Kinship on Nutritional Condition and Aggression Levels in Winter Social Groups of Tufted Titmice
Authors: Pravosudova Elena V. , Grubb Thomas C. , Parker Patricia G.
Published: September 2019

During winter, adult Tufted Titmice (Baeolophus bicolor) share their territories with both offspring and immigrant young. For such situations in social permanent-resident birds, the prolonged brood care hypothesis (Ekman and Rosander 1992) states that adults should be more tolerant of their own young than of unrelated immature birds, allowing their offspring better access to limited resources. We tested two predictions from this hypothesis using the Tufted Titmouse: (1) offspring should be in better nutritional condition than immigrants; (2) territorial adults should be more aggressive toward immigrant immature birds than toward their own offspring. We estimated relatedness using DNA fingerprinting. To assess nutritional condition, we used a fatness index and ptilochronology. We found no difference between the condition of retained and immigrant young. We tested the second prediction by recording aggressiveness among the individually marked members of social groups. Supporting the second prediction, territorial adults were significantly more aggressive toward unrelated than related immature birds.

Influencia del Parentezco en la Condición Nutricional y Niveles de Agresividad en Grupos Sociales de Invernada de Baeolophus bicolor

Resumen. Durante el invierno, los individuos adultos de Baeolophus bicolor comparten sus territorios con su descendencia y con jóvenes inmigrantes. Dada esta situación en aves sociales que son residentes permanentes, la hipótesis de cuidado prolongado de la nidada (Ekman y Rosander 1992) establece que los adultos deberían ser más tolerantes con sus propios hijos que con aves inmaduras no relacionadas, permitiéndole a su descendencia mejor acceso a recursos limitados. Evaluamos dos predicciones de esta hipótesis usando a B. bicolor: (1) los hijos deberían presentar una mejor condición nutricional que los inmigrantes; (2) los adultos territoriales deberían ser más agresivos con las aves inmaduras inmigrantes que con su propia descendencia. Estimamos el grado de parentezco utilizando huellas dactilares genéticas. Empleamos un índice de grasitud y ptilocronología para establecer la condición nutricional. No encontramos diferencias entre las condiciones de los jóvenes retenidos e inmigrantes. Evaluamos la segunda predicción registrando la agresividad entre miembros individualmente marcados de los grupos sociales. Los adultos territoriales fueron significativamente más agresivos con aves no relacionadas que con inmaduros relacionados, apoyando la segunda predicción.