Resource Partitioning among a Flycatcher Guild in Finland

Multidimensional overlaps of foraging sites between three species (two flycatchers, Muscicapidae and the redstart Phoenicurus phoenicurus (L.)) varied from 0.357 to 0.591, when the following resource axes were taken into account: habitat, macrosubstrate (air, trees, ground), tree species, tree part, height in air. Most of the differences between the species can be explained in terms of the use of the three macrosubstrate categories, but the overlap between the pied flycatcher Ficedula hypoleuca (Pallas) and the redstart was clearly lowered by further axes. The pied flycatcher in particular had a clear shift in foraging site during the summer months. The sexes of the redstart and the pied flycatcher differed in foraging sites, males having the wider niches. These differences may be related to sexual behaviour, as males preferred foraging sites near the singing posts. In low temperatures the spotted flycatcher Muscicapa striata (Pallas) shifted from air-hunting to ground and tree attacks, which resulted in increased overlap with the other two species. Perch sites of the spotted flycatcher overlapped with the other species more than the foraging sites. The role of competition in the use of resources is discussed.