Geographical origin of dabbling ducks wintering in Iberia: Sex differences and implications for pair formation

Los humedales ibéricos naturales y antropógenos del sur de Europa son bien conocidos por sustentar a un gran número de aves migratorias acuáticas del Palaearctico en cada invierno. Sin embargo, la información sobre el origen geográfico de los patos de humedal que pasan el invierno en estos espacios es escasa y se limita principalmente a datos de sonar. Aquí, hemos utilizado marcadores isotópicos para determinar el origen geográfico de machos y hembras de Pintails septentrional, Anas acuta y Anas crecca euroasiática en Extremadura, en el interior de la península Ibérica, sitio clave para invernar los patos de humedal. Además, hemos instalado seis etiquetas GPSGSM en Pintails septentrional para complementar los datos derivados del análisis de isótopos estables. La mayoría (> 70%) de los Pintails septentrional, dentro del primer año calendario, fueron asignados a regiones situadas por encima de los 55° N, volando 2600-5600 km desde sus regiones de procedencia a Extremadura. Los valores promedio de δ2Hf variaron significativamente entre macho y hembra de Pintails septentrional, sugiriendo que los sexos tienen diferentes orígenes geográficos. Los datos de los adultos etiquetados Pintails septentrional apoyan los datos isotópicos, un macho volando más de 5000 km de la costa de la mar Pechora (Rusia). La mayoría (> 70%) de los Teal euroasiáticos, dentro del primer año calendario, fueron asignados a la región situada entre 48° y 60° N y viajaron 1500-4500 km para llegar en Extremadura. Los machos y hembras de Cerceta euroasiáticos mostraron diferencias marginales en valores promedio de δ2Hf. En patos de humedal migratorios, el emparejamiento se produce normalmente en las zonas de invernada, y los patos en su primer invierno pueden reproducirse en la primavera siguiente. Para Pintails septentrional, la formación de parejas en Extremadura podría suceder entre individuos con diferentes orígenes geográficos, lo que podría contribuir a la variabilidad genética de su descendencia.Natural and anthropogenic Iberian wetlands in southern Europe are well known for supporting large numbers of migratory Palaearctic waterbirds each winter. However, information on the geographical origin of dabbling ducks overwintering in these wetlands is scarce and mostly limited to data from ringing recoveries. Here, we used intrinsic isotopic markers to determine the geographical origin of male and female Northern Pintails Anas acuta and Eurasian Teal Anas crecca in Extremadura, inland Iberia, a key site for overwintering dabbling ducks. Additionally, we fitted six Northern Pintails with GPSGSM tags to complement the data derived from stable isotope analysis. Most (> 70%) first calendar-year Northern Pintails were assigned to regions above 55°N, flying 2600–5600 km from their main natal regions to Extremadura. Mean values of δ2Hf varied significantly between male and female Northern Pintails, suggesting that the sexes had different geographical origins. Data from tagged adult Northern Pintails supported the isotopic data, one male flying more than 5000 km to the coast of the Pechora Sea (Russia). Most (> 70%) first calendar-year Eurasian Teal were assigned to the region between 48° and 60°N, travelling 1500–4500 km to arrive in Extremadura. Male and female Eurasian Teal showed marginal differences in mean values of δ2Hf. In migratory dabbling ducks, pairing typically occurs on the wintering grounds, and ducks in their first winter can breed the following spring. For Northern Pintails, pair formation in Extremadura could occur between individuals with different geographical origins, which could contribute to the genetic variability of their offspring.Trabajo patrocinado por: Junta de Extremadura. Proyecto PRI 09C128 Gobierno de Extremadura y Fondos FEDER. Ayuda GR10174 Confederación Hidrográfica del Guadiana (Ministerio de Medio Ambiente). Ayuda financierapeerReviewe

The +49A>G CTLA-4 polymorphism is associated with rheumatoid arthritis in Mexican population

Nest concealment by vegetation is considered an important factor affecting predation rates for many passerines and, therefore, is frequently measured in studies examining nest predation. However, the time when concealment measurements are made may affect the results of such studies, particularly in highly seasonal ecosystems where characteristics of the vegetation later in the breeding period may differ considerably from those at the time of nest-site selection. We used artificial nests baited with quail (Coturnix sp.) eggs in a highly seasonal tropical dry forest in Jalisco, western Mexico, to test the effects of seasonal change in concealment on nest predation. We placed 40 open-cup, artificial nests in shrubs at the end of the dry season and again at the beginning of the rainy season in 2007, and monitored the fate of the nests and the degree of concealment by vegetation during both periods. Nest concealment was significantly greater during the wet season than during the dry season. The percentage of nests predated was marginally higher during the dry (100%) than the wet (72.5%) season, and daily nest survival was lower during the dry than the wet season. Our results suggest that, in highly seasonal environments such as tropical dry forests, delayed measurement of nest concealment after nest completion rather than during nesting may constitute a significant source of error. " 2009 Association of Field Ornithologists.",,,,,,"10.1111/j.1557-9263.2009.00234.x",,,"http://hdl.handle.net/20.500.12104/45002","http://www.scopus.com/inward/record.url?eid=2-s2.0-69449105709&partnerID=40&md5=36cfd653611179f7237fce1f1817a540",,,,,,"3",,"Journal of Field Ornithology",,"30

Duetting in space: a radio-telemetry study of the black-bellied wren

In many birds, individuals ‘answer’ the songs of their pair-mates to produce vocal ‘duets’. One hypothesized function of song answering is that it prevents extra-pair birds from intruding into the duetting pair's territory to obtain copulations or usurp one of the pair-mates. In this capacity, answering may signal that the pair-mates are close together, and so are prepared to defend against such an intrusion. Another functional hypothesis states that answering helps pair-mates maintain contact, and so predicts that a bird is more likely to approach its mate after a duet than after a solo song. I used radio-telemetry to monitor the distance between mated black-bellied wrens (Pheugopedius fasciatoventris). I found that birds of both sexes were more likely to answer their mate's song when the mate was close, and that maximum duet length was negatively related to the distance between pair-mates. Furthermore, song answering positively affected the likelihood of one pair-mate approaching the other after a song. In a significant majority of the approaches after duet songs, the answering bird approached the initiator. I conclude that in the black-bellied wren, (i) the occurrence and duration of vocal duets covary with physical closeness and (ii) contact maintenance is a secondary function of duet participation

Nocturnal life of young songbirds well before migration

In songbirds, nocturnal activity is believed to be a characteristic feature of migration. However, unlike experimental conditions where the onset of nocturnal restlessness is defined as a shift of activity leading up to the dark period, this behaviour has, until now, not been observed in natural conditions. Here we studied the nocturnal behaviour of radio-tagged juvenile Eurasian reed warblers (Acrocephalus scirpaceus) during the pre-migratory period. The birds started nocturnal flights at the age of 38 days, whereas migration did not commence until they were at least 50 days old. The birds left their natal site by nocturnal flights and repeatedly returned to it. Such shuttle movements suggest the existence of a previously unknown period of nocturnal activity. Motivation to perform such night flights gradually increases with age. We relate the function of these nocturnal pre-migratory flights to the development of a stellar compass, necessary for detecting the compass direction towards winter quarters and for the formation of a navigational target, which will be used during return (spring) migration

Brain size, innovative propensity and migratory behaviour in temperate Palaearctic birds

The evolution of migration in birds remains an outstanding, unresolved question in evolutionary ecology. A particularly intriguing question is why individuals in some species have been selected to migrate, whereas in other species they have been selected to be sedentary. In this paper, we suggest that this diverging selection might partially result from differences among species in the behavioural flexibility of their responses to seasonal changes in the environment. This hypothesis is supported in a comparative analysis of Palaearctic passerines. First, resident species tend to rely more on innovative feeding behaviours in winter, when food is harder to find, than in other seasons. Second, species with larger brains, relative to their body size, and a higher propensity for innovative behaviours tend to be resident, while less flexible species tend to be migratory. Residence also appears to be less likely in species that occur in more northerly regions, exploit temporally available food sources, inhabit non-buffered habitats and have smaller bodies. Yet, the role of behavioural flexibility as a response to seasonal environments is largely independent of these other factors. Therefore, species with greater foraging flexibility seem to be able to cope with seasonal environments better, while less flexible species are forced to become migratory

It takes two to tango: reproductive skew and social correlates of male mating success in a lek-breeding bird

Variance in reproductive success among individuals is a defining characteristic of many social vertebrates. Yet, our understanding of which male attributes contribute to reproductive success is still fragmentary in most cases. Male–male reproductive coalitions, where males jointly display to attract females, are of particular interest to evolutionary biologists because one male appears to forego reproduction to assist the social partner. By examining the relationship between social behaviour and reproductive success, we can elucidate the proximate function of coalitions in the context of mate choice. Here, we use data from a 4-year study of wire-tailed manakins (Pipra filicauda) to provide molecular estimates of reproductive skew and to test the hypothesis that male–male social interactions, in the context of coordinated displays, positively influence a male's reproductive success. More specifically, we quantify male–male social interactions using network metrics and predict that greater connectivity will result in higher relative reproductive success. Our data show that four out of six leks studied had significant reproductive skew, with success apportioned to very few individuals in each lek. Metrics of male social affiliations derived from our network analysis, especially male connectivity, measured as the number of males with whom the focal male has extended interactions, were strong predictors of the number of offspring sired. Thus, network connectivity is associated with male fitness in wire-tailed manakins. This pattern may be the result of shared cues used by both sexes to assess male quality, or the result of strict female choice for coordinated display behaviour