Niche Shifts of Coal Tits Parus ater in Denmark

Foraging behaviour of Parus guilds in Denmark was studied at two study sites on the mainland and on two islands on which Crested Parus cristatus and Marsh Tits P. palustris were absent. In the absence of Crested Tits, island Coal Tits P. ater foraged among twigs and branches, which, on the mainland, were the domain of the Crested Tit. Comparing observations with and without Crested and Great Tits P. major present, I found significant differences in choice of foraging substrate and foraging height of Coal Tits. Generally, Coal Tits foraged higher in the presence of Great and Crested Tits. Consistently, there were no differences between mainland sites, nor between islands with respect to the foraging niches of the Coal Tit. These results are consistent with the hypothesis that interspecific competition has shaped the foraging niches of the Parus guild.