Seasonal variation of foraging niches in a guild of passerine birds in a cork-oak woodland

Spatial foraging niches of a pariform guild in a cork-oak woodland were exa mined during winter and spring. Niche structure was described in terms of t he niche dimensions foraging substrate, foraging height and part of tree, a nd seasonal changes in niche breadth and overlap were examined. Considering the difficulties of dealing with the multidimensionality of Hutchinson's n iche concept, we adopted a multivariate approach and identified the most im portant factors for spatial segregation. Significant differences between wi nter and spring utilisation of the foraging dimensions were found for the g uild as a whole. At the species level, however, no major seasonal differenc es in the utilisation of foraging dimensions were found. No consistent seas onal trend occurred in terms of niche size or niche overlap. Multivariate a nalysis showed that the guild structure is basically the same in winter or spring, with Little influence of species that are present in only one of th e two seasons. These results suggest that there is no food shortage in wint er for the pariform guild in this woodland. The niche dimensions related wi th tree structure and foraging substrate appeared to be the most important ones in species segregation.