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Migration is a significant event in the annual cycle of many avian species. During migration birds face many challenges, including unfamiliar foraging and refuge habitats, resulting in a much higher rate of mortality during migration than during other seasons of the year. Weather may significantly affect a bird's decision to initiate migration, the course and pace of migration, and its survival during...
We studied a newly established breeding population of the range‐expanding Mediterranean Gull Larus melanocephalus in eastern Spain, situated in close proximity to the species' main wintering area. By investigating the origin, population composition and wintering area of the new breeders, we found that recruitment from locally wintering birds was unlikely and that the emerging colonies were probably...
Tracking devices have contributed enormously to our knowledge of avian migration, although their effects on birds are controversial. Here, we study the short‐ and long‐term effects of deploying geolocators on European Rollers Coracias garrulus and assess the optimal weight of tracking devices to use. In nests in which both parents had geolocators, brood mass was lighter than in nests where only one...
Slow life histories are characterized by high adult survival and few offspring, which are thought to allow increased investment per offspring to increase juvenile survival. Consistent with this pattern, south temperate zone birds are commonly longer‐lived and have fewer young than north temperate zone species. However, comparative analyses of juvenile survival, including during the first few weeks...
For migratory birds, it is necessary to estimate annual and overwinter survival rates, identify factors that influence survival, and assess whether survival varies with age and sex if we are to understand population dynamics and thus inform conservation. This study is one of the first to document overwinter and annual survival from the wintering grounds of a declining Afro‐Palaearctic migrant bird,...
Sensory mechanisms controlling avian clutch size have diversified into distinct types, according to the nature of the input that is used to disrupt the growth of ovarian follicles and hence halt egg‐laying. In an article on brood parasitism, Lyon (2003) claimed that female American Coots Fulica americana can reduce their clutch size on the basis of visual cues in response to eggs laid in their nests...
Birds show considerable variation in sperm morphology. Closely related species and subspecies can show diagnostic differences in sperm size. There is also variation in sperm size among males within a population, and recent evidence from passerine birds suggests that the coefficient of inter‐male variation in sperm length is negatively associated with the level of sperm competition. Here we examined...
Published information relating to changes in the chemical element content of avian eggs caused by embryonic development is extremely scarce, although it may be crucial for understanding both the presence of anthropogenic pollutants as well as physiological levels of micronutrients. We assessed the variation in concentrations of calcium (Ca) and magnesium (Mg) and nine trace elements: seven essential...
The heavily traded Grey Parrot Psittacus erithacus is believed to have undergone rapid population decline, yet there are almost no quantitative data on abundance changes over time from anywhere within its huge range. We reviewed the species’ historical abundance across Ghana, undertook targeted searches during 3‐ to 5‐day visits to 42 100‐km2 cells across the country's forest zone, repeated counts...
Critical information for evaluating the effectiveness of management strategies for species of concern include distinguishing seldom occupied (or low‐quality) habitat from habitat that is frequently occupied and thus contributes substantially to population trends. Using multi‐season models that account for imperfect detection and a long‐term (1981–2002) dataset on migratory Arctic Peregrine Falcons...
Interspecific aggression is predicted to be common in diverse tropical avifaunas but is seldom tested experimentally. I conducted two playback experiments to measure interspecific aggression between two sympatric Australo‐Papuan robin species that inhabit the understorey of montane New Guinean forests: Slaty Robin Peneothello cyanus and Ashy Robin Heteromyias albispecularis. The first experiment,...
Migration is costly in terms of time, energy and safety. Optimal migration theory suggests that individual migratory birds will choose between these three costs depending on their motivation and available resources. To test hypotheses about use of migratory strategies by large soaring birds, we used GPS telemetry to track 18 adult, 13 sub‐adult and 15 juvenile Golden Eagles Aquila chrysaetos in eastern...
Radar systems have been increasingly used to monitor birds. To take full advantage of the large datasets provided by radars, researchers have implemented machine learning (ML) techniques that automatically read and attempt to classify targets. Here we used data collected from two locations in Portugal with two marine radar antennas (VSR and HSR) to apply and compare the performance of six ML algorithms...
Avian carcasses can provide important information on the trophic ecology of birds. Usually, the number of carcasses available for examination is limited and therefore it is important to gain as much dietary information per specimen as possible. In piscivorous birds and raptors, the stomach has been the primary source of dietary information, whereas the gut (intestine) has so far been neglected as...
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