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We aimed to describe the morphologic and isotopic differences of European Goldfinches Carduelis carduelis according to their migratory behaviour or geographic origin. We compared morphologic and isotopic variables between birds caught in two different obligatory migratory pathways (eastern and western border of the Pyrenees) and throughout the post-breeding period (from late summer to winter). The isotopic and morphological traits varied across seasons (from autumn to winter), indicating that birds captured later in the season had traits typical of longer-distance migrants that come from regions situated further north. Moreover, our results suggest that Goldfinches caught in the eastern and western borders of the Pyrenees slightly differ in body size and in one of the two colour patch-associated traits, but not in their flight apparatus or isotopic values, these last being more strongly related to their areas of origin. Such observed regional differences, therefore, may be more strongly related to other selection pressures. [ABSTRACT FROM AUTHOR]

In the past 70 years radar technology has been increasingly applied in ornithological research in various geographical areas worldwide and has contributed greatly to a better understanding of bird migration. Many different radar types have been used, such as tracking, ship or weather radars. However, radar wind profilers (RWPs) have been largely neglected in avian research. RWPs continuously measure three‐dimensional winds and, despite the low frequency range at which these systems operate, available literature provides evidence that birds are recorded at many sites. So far the potential of RWPs in ornithological research has not been fully explored and studies deal predominantly with birds in the context of clutter removal. However, based on their broad implementation in networks (e.g. E‐PROFILE in Europe) situated in areas that are strategically important for bird migration, they could offer a valuable complement to already established or planned large‐scale bird monitoring schemes by radar. The objective of this paper is to serve as a reference for those who wish to consider RWP data in a biological context. To that end, we provide an overview of the evolution and establishment of operational RWPs as well as of their mode of operation, in order to depict their role in meteorology and to evaluate their potential in ornithology. The assessment is based on available literature on RWPs and radar ornithology outlining the past, present and potential future role of wind profilers. In the past, birds were discarded as contamination and eliminated as far as possible from the meteorological data. Only recently have the echo signatures of biological targets been scrutinized thoroughly in raw data and used successfully for ornithological investigation. On this basis it is possible to consider the potential future utility of this promising data source as a complement to other remote‐sensing instruments and other sampling techniques used in avian research. Weather independence of ornithological information was found to be a particular benefit. However, as the development of the bird‐specific method is only in an early stage, more detailed studies are necessary in the future to fully assess the potential of this type of radar. [ABSTRACT FROM AUTHOR]

The migratory behaviour of European Song Thrush (Turdus philomelos) populations ranges from resident in the south and west to partly or totally migratory in northern, central and eastern Europe. This varied migratory behaviour could be reflected in morphological adaptations, with migrants having a proportionally longer wing, lower tail:wing ratio, and, if foraging more on fruits, deeper and wider bills. We used data from Song Thrushes captured during the breeding season and in winter in northern Iberia to test for morphological variations between these two periods. In three consecutive years (2014-16), Song Thrushes were captured with mist nests in a region of southern Navarra (Spain) during the breeding season (from May to July) or in the winter period (October to February), during a period of four hours starting at dawn per sampling day. We consider the winter population to be composed of a high proportion of visitors. Breeding Song Thrushes showed proportionally longer tails for given wing lengths, even though wing length did not vary between the two periods. Moreover, winter visitors showed narrower and less deep bills than breeding Song Thrushes. Potential explanations for these results are discussed. [ABSTRACT FROM AUTHOR]

Radars of various types have been used in ornithological research for about 70 years. However, the potential of radar wind profiler ( RWP) as a tool for biological purposes remains poorly understood. The aim of this study is to assess the suitability of RWP for ornithological research questions., A 1290 MHz RWP at the south-eastern coast of the Bay of Biscay has been known to exhibit seasonally occurring nocturnal signals attributed to migrating birds. As a first step to verify the origin of these seasonal patterns, historical radar data from 2010 to 2012 were analysed, and both bird patterns and temporal occurrence were identified in RWP data at different levels of the signal processing. A thermal-imaging ( TI) camera in conjunction with moon watching was used as verification systems at the radar site to confirm the ornithological origin of the radar echoes. The simultaneous data on spring migration served as a basis for the identification of biological signatures (qualitative parameters) on time-series level (raw data) and to derive quantitative migration parameters (flight altitude, migration traffic rates) thereof. Finally, the quantitative measurements of the TI camera and the radar were compared considering meteorological conditions., The approach allowed identifying reproducible criteria based on time series to calculate migration traffic rates and altitudinal flight distribution. General flight directions were only available in the final wind data. In clear weather conditions, the calibration methods coincided well with the wind profiler data., Findings show that wind profiler raw data offer reliable information on migration intensity, flight altitudes and flight directions in a variety of meteorological conditions. The method presented can be applied as a complement to present efforts to use weather radars for large-scale bird monitoring. Furthermore, it is also interesting for the meteorological community to refine signal-processing methods. [ABSTRACT FROM AUTHOR]

Success of migration in birds in part depends on habitat selection. Overall, it is still poorly known whether there is habitat selection amongst landbird migrants moving across landscapes. Europe is chiefly covered by agro-forestry mosaic landscapes, so migratory species associated to either agricultural landscapes or woodland habitats should theoretically find suitable stopover sites along migration. During migration from wintering to breeding quarters, woodcocks (Scolopax rusticola) tagged with PTT satellite-tracking transmitters were used to test for the hypothesis that migrants associated to agro-forest habitats have no habitat selection during migration, at a meso-scale level. Using a GIS platform we extracted at a meso-scale range habitat cover at stopover localities. Results obtained from comparisons of soil covers between points randomly selected and true stopover localities sites revealed, as expected, the species may not select for particular habitats at a meso-scale range, because the habitat (or habitats) required by the species can be found virtually everywhere on their migration route. However, those birds stopping over in places richer in cropland or mosaic habitats including both cropland and forest and with proportionally less closed forest stayed for longer than in areas with lower surfaces of cropland and mosaic and more closed forest. This suggests that areas rich in cropland or mosaic habitat were optimal. [ABSTRACT FROM AUTHOR]

In birds, spatial segregation between age or sex categories during the non-breeding period is a common phenomenon. The main single-factor hypotheses that have been stated to explain this are: (1) body-size variations (that result in more or less cold tolerance) interact with local climate, which promotes age- or sex-associated distributional optima; (2) the dominant age or sex monopolizes high-quality areas; and (3) the age or sex overwintering closer to breeding quarters does so due to the benefits of earlier arrival at the breeding quarters. Southern European countries host millions of birds from northern Europe during the winter period each year. In this work, we aimed to determine the ultimate causes (geographic location and distance to obligate migratory pathways, temperature and land use as a surrogate for food availability) explaining spatial segregation of Reed Buntings ( Emberiza schoeniclus) by age and sex in winter. We used data from 38 sampling points across Iberia during the winter of 2011-2012. Reed Bunting abundance did not fit any of our possible models better than the null model, so we were unable to predict bird numbers across Iberia. Moreover, males were found to be predominant at sites close to presumably obligate migratory pathways (western/eastern Pyrenees). Body mass was higher in first-year birds and males, and tended to increase with distance to obligate migratory pathways, land use (in particular with a decreasing proportion of open habitats and urban areas), increasing minimum temperature, and decreasing mean temperature. Our data suggest that the increase in the proportion of males close to obligate migratory pathways is associated with the advantage to males in wintering as close as possible to breeding quarters. [ABSTRACT FROM AUTHOR]

Spatial behaviour and habitat selection at stopover sites have a strong influence on the foraging and fuelling performance of migrating birds and hence are important aspects of stopover ecology. The aim of this study was to analyse the spatial behaviour and habitat use of reed warblers Acrocephalus scirpaceus during the autumn migration. We used radio tracking data from reed warblers surveyed at a stopover site in northern Iberia and assigned to three different groups: ( I ) local adult birds which were still at their breeding site, (2) migrating first-year birds (originating from beyond Iberian peninsula) and (3) migrating adult birds. Overall, migrating first-year birds tended to have larger home ranges than both local and migrating adults and to move more widely in the study area. They also showed lower fat deposition rates than adults. The proportion of habitats in home ranges (reed-beds and tidal flats being the most abundant habitats) was similar amongst groups. The spatial distribution and habitat use of organisms have been theorised to follow an ideal-free or ideal-despotic distribution. However, according to our results, other complex underlying mechanisms may play an important role in shaping the spatial behaviour of birds at stopover sites. [ABSTRACT FROM AUTHOR]

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Meteorological conditions, fuel load and date in the season can affect the departure decisions among migratory birds. However, it is poorly understood to what extent the departure decisions are more influenced by some parameters in relation to others, and how they interact with each other. We explored here how fuel load, date, rain and wind (measured on the ground and at high altitude, codified as a tailwind component) influenced the departure decisions of migratory Blackcaps ( Sylvia atricapilla) from a stopover site. We used mark-recapture data of 947 Blackcaps collected during the autumn migration period 2005 at a stopover site in northern Iberia, estimating the emigration likelihood with Cormack-Jolly-Seber models, in which we tested for the effect of these four study variables. Best models fitting data showed an additive and positive effect of tailwind and fuel load on the emigration likelihood. [ABSTRACT FROM AUTHOR]

The article discusses a study on the movements of first-year Yellow-legged Gulls or Larus michahellis lusitanius from the southeastern Bay of Biscay. It cites the use of darvic rings which allow researchers to conduct a more detailed analyses on movements of large gulls with consideration on the maximum distance where each individual was sighted. It suggests that a precise data on distribution of food availability can lead to a better understanding of the seasonal geographic distribution patterns of Yellow-legged Gulls in the southeastern Bay of Biscay.

The article discusses a study on the patterns of migration and wintering of European Robins Erithacus rubecula in northern Iberia, Spain focusing on seasonal patterns of captures and the relationship among migrating and wintering Robins, age and sex ratios and biometrics, fuel load and body condition. Robins were mist-netted weekly from July 2004 to May 2005 and data from robins trapped between September and April were considered. It suggests that the Robins are either birds moving at short distances or at migrating in short steps at longer distances.