EFFECT OF HABITAT AND LATITUDE ON NESTLING DIET OF PIED FLYCATCHERS FICEDULA-HYPOLEUCA

Composition and diversity of the nestling diet of Pied Flycatchers Fic edulo hypoleuca was compared among 17 European study areas that differ ed in habitat type (deciduous or coniferous forest). The most abundant foods were butterflies and moths (Lepidoptera), with a high proportio n of caterpillars. The proportions of beetles (Coleoptera) and Lepidop tera in the nest ling diet differed significantly between deciduous an d coniferous forests. The contribution of caterpillars to the total nu mber of Lepidoptera was significantly higher in deciduous than in coni ferous forests, but did not show any relationship with latitude. Thus, Slagsvold's (1975b) hypothesis that in northern regions passerines br eed early in respect to the seasonal development of arthropod food res ources (as indicated by relative amount of caterpillars), was not supp orted. Diversity of nestling diet did not differ between forest types, and neither did it show any relationship with latitude. The probabili ty of two items taken at random being different (another measure of di et diversity, and of the difficulty in obtaining food), did not show r elationships with latitude of, or average clutch size in, study areas. The hypothesis, put forward by Von Haartman (1973) and Owen (1979), t hat geographical variation in prey diversity explains geographical var iation in clutch size, was therefore rejected as well.