Fernandez-Juricic E. (2000) Forest fragmentation affects winter flock formation of an insectivorous guild. ARDEA 88 (2): 235-241

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 trees > 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 any landscape and habitat factor. Coefficients of associations in multi-species flocks were higher for the most abundant species. That the probabilities of flock formation decreased in small fragments is probably a result of the reduction of habitat quantity and quality Flock formation appears greatly affected by the abundance of individual species (Chiffchaff Phylloscopus collybita and Coal Tit Parus ater), as they, attract less abundant species and form the core of the winterflocks