Niche Differentiation during Winter in Woodland Birds in Southern Sweden and the Island of Gotland

Niches of a group of ecologically related woodland birds during winter were compared between the South Swedish mainland and the island of Gotland in the Baltic. Proportions of species, flock sizes, habitat distribution, relative densities, and location of feeding stations were examined. The group consisted of 10 species on the mainland, but 3 of these were absent from Gotland. Only the coal tit Parus ater L. showed differences in niche parameters between the mainland and Gotland. This represents a case of ecological release due to relaxed competition on the island. Although the bird species constellation differed between the mainland and Gotland, certain feeding stations were equally visited by birds in both areas. All bird species absent on Gotland are highly sedentary.