Forest fragmentation affects winter flock formation of an insectivorous guild

The purpose of this paper was to assess the effects of forest fragmentation on winter nock formation in a guild of insectivorous birds in 23 parks (0. 23-118 ha) in the Madrid area, Spain. Flock size was positively affected by fragment size, the amount of coniferous cover, and the mean number of tree s > 50 cm diameter at breast height; and negatively by the distance to the nearest large forest track (1722 ha). Flock richness was not affected by an y landscape and habitat factor. Coefficients of associations in multi-speci es flocks were higher for the most abundant species. That the probabilities of flock formation decreased in small fragments is probably a result of th e reduction of habitat quantity and quality Flock formation appears greatly affected by the abundance of individual species (Chiffchaff Phylloscopus c ollybita and Coal Tit Parus ater), as they, attract less abundant species a nd form the core of the winterflocks.