Resource Partitioning in an Island Community of Insectivorous Birds During Winter

Abstract

Resource partitioning within an assemblage of seven species of insectivorous birds inhabiting remnant Melaleuca woodland on Rottnest Island off the coast of Western Australia was studied during May-July 1993. Foraging behaviour, foraging height, foraging substrate and foraging plant associations of all species (and of both sexes in two species) were recorded for each month. These data were used to calculate overlaps in each foraging dimension and for all foraging dimensions combined. The significance of total foraging overlap between species and sexes (defined as overlap > 0.6) was low in May (only 14% of all total foraging overlaps) but increased slightly in June and July (25 and 29% of all total foraging overlaps respectively). Foraging habits were associated significantly both with bird species and month of observation, indicating that foraging partitioning occurred and that its pattern varied temporally. The diversity of foraging habits displayed by each bird species in each foraging dimension (determined by the Shannon-Wiener function) varied widely, although a species which was a generalist in one foraging dimension also tended to be a generalist in other foraging dimensions.