ISLAND SIZE, ISOLATION, OR INTERSPECIFIC - COMPETITION - THE BREEDINGDISTRIBUTION OF THE PARUS GUILD IN THE DANISH ARCHIPELAGO

The Parus guild (Parus spp., Sitta, Certhia, and Regulus) is distribut ed as a complex mosaic within the Danish archipelago, with from one to eight species on different islands. We assessed the roles of island i solation, island size, and interspecific competition in determining th e breeding species compositions of this guild on 53 Danish islands. Sm all, isolated islands supported fewer species than larger, nearshore i slands. These effects, however, were largely restricted to a few seden tary species (P. cristatus, P. palustris, S. europaea) that are known to be poor dispersers/colonizers. In some cases, these three species w ere also absent from large, nearshore islands with suitable habitat, s uggesting that habitat availability was not always responsible for the absence of a species. Monte Carlo simulations suggested that the patt ern of species presence/absence was not a result of interspecific inte ractions. Thus, although a number of previous studies have documented interspecific competition among members of the Parus guild, our result s suggest that such competition is not responsible for the unusual pat tern of species distribution within the Danish archipelago.