Habitat Distribution in the Great Tit Parus major in Relation to Reproductive Success, Dominance, and Biometry

Abstract

This study compares reproductive success, dominance, and biometrical variables for Great Tit populations in deciduous and coniferous forest in an attempt to establish whether the birds are distributed between habitats of different quality in a despotic or ideal free manner. No critical differences could be found in reproductive output, and male birds breeding in different habitats did not differ in resource holding potential (RHP). Therefore the distribution of Great Tits over habitats of different quality seems to be in accordance with Fretwell's Ideal Free Distribution model. No relationship was found between body size and social behaviour but the oldest individual had the greatest chance of winning conflicts. Some differences in biometric measurements between habitats were observed. Similar observations have been interpreted in earlier papers as evidence that large individuals possess high RHP. Since no relationship was found between body-size and RHP, it is concluded that such differences do not necessarily imply that Great tits are distributed in a despotic way. Generally birds were smaller in the coniferous habitat. A variant of the Ideal Free Distribution model where individuals choose the habitat to which they are morphologically adapted, may be a possible explanation.