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Many animals make behavioural changes to cope with winter conditions, being gregariousness a common strategy. Several factors have been invoked to explain why gregariousness may evolve during winter, with individuals coming together and separating as they trade off the different costs and benefits of living in groups. These trade-offs may, however, change over space and time as a response to varying environmental conditions. Despite its importance, little is known about the factors triggering gregarious behaviour during winter and its change in response to variation in weather conditions is poorly documented. Here, we aimed at quantifying largescale patterns in wintering associations over 23 years of the white-winged snowfinch Montifringilla nivalis nivalis. We found that individuals gather in larger groups at sites with harsh wintering conditions. Individuals at colder sites reunite later and separate earlier in the season than at warmer sites. However, the magnitude and phenology of wintering associations are ruled by changes in weather conditions. When the temperature increased or the levels of precipitation decreased, group size substantially decreased, and individuals stayed united in groups for a shorter time. These results shed light on factors driving gregariousness and points to shifting winter climate as an important factor influencing this behaviour. [ABSTRACT FROM AUTHOR]

The article discusses research which investigated the foraging behaviour and prey preference of the great tit Parus major. Topics explored include the evaluation of the birds' physical condition prior to food choice experimentation, the use of a common Mediterranean lycosid spider and a moth larva as possible prey items, and the observed interaction between the birds and their prey.

Carotenoid-based coloration of nestling plumage is generally considered a reliable signal of quality and has consistently been related to habitat structure. The main hypothesis proposed to explain this correlation is that high quality habitats contain high quality food, which in return affects the expression of carotenoid-based plumage. It therefore assumes that, at the population level, the link between habitat structure and food composition is consistent and more relevant than inter-individual differences in foraging ability or parental investment. In addition, it is assumed by default that food and habitat produce concordant effects on nestling coloration. In this work we evaluated habitat structure and prey composition in addition to several measures of parental investment. We investigated their relative effect on carotenoid-based plumage coloration (lightness, chroma and hue) of great tit Parus major nestlings. We found a low correlation between carotenoid-based coloration of nestlings and that of their parents. Nestling coloration, especially lightness and chroma, increased with the intake of more spiders. The time of breeding was positively correlated with lightness and chroma and negatively correlated with hue. Finally, the maturity of oak trees surrounding nest-boxes correlated negatively with lightness, and the size of all tree species surrounding nest-boxes correlated positively with hue of chick plumage. Our findings support the view that habitat structure and prey composition may produce divergent effects on feather pigmentation, and that prey proportions and variables related to parental investment should be assessed when considering carotenoid-based coloration of chicks. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113, 547-555. [ABSTRACT FROM AUTHOR]

CapsuleThe pattern of moult of juvenile Common ChiffchaffsPhylloscopus collybitawintering in two distant localities of the Iberian Peninsula, Málaga (south) and Barcelona (north) differed. Individuals wintering in the northern locality moulted more contour than flight feathers, and vice versa, while sexes did not differ; individuals moulting more contour feathers arrived later and individuals moulting more flight feathers arrived earlier. Taken together, our results suggest that the pattern of moult of juvenile Common Chiffchaffs may depend on the location to which they migrate, in addition to the geographic origin and the time of breeding. [ABSTRACT FROM AUTHOR]