Effect of habitat and latitude on nestling diet of Pied Flycatchers Ficedula hypoleuca.

Composition and diversity of the nestling diet of Pied Flycatchers Ficedula hypoleuca was compared among 17 European study areas that differed in habitat type (deciduous or coniferous forest). The most abundant foods were butterflies and moths (Lepidoptera), with a high proportion of caterpillars. The proportions of beetles (Coleoptera) and Lepidoptera in the nestling diet differed significantly between deciduous and coniferous forests. The contribution of caterpillars to the total number of Lepidoptera was significantly higher in deciduous than in coniferous forests, but did not show any relationship with latitude. Thus, Slagsvold’s (1975b) hypothesis that in northern regions passerines breed early in respect to the seasonal development of arthropod food resources (as indicated by relative amount of caterpillars), was not supported. Diversity of nestling diet did not differ between forest types, and neither did it show any relationship with latitude. The probability of two items taken at random being different (another measure of diet diversity, and of the difficulty in obtaining food), did not show relationships with latitude of, or average clutch size in, study areas. The hypothesis, put forward by Von Haartman (1973) and Owen (1979), that geographical variation in prey diversity explains geographical variation in clutch size, was therefore rejected as well

Sanz J.J., ARDEA 86 (1): 81-88.