Foraging niche differences between species are correlated with body-size differences in mixed-species flocks near Seoul, Korea

In December 1996/January 1997, we studied the distribution of foraging site s of a guild of 5 species of birds (from larger to smaller: Sitta europaea, Parus varius, P. major P. palustris, P, ater, Aegithalos caudatus) winteri ng in Korea. Correlations between body size and the use of foraging sites i n trees are well described for European tits. Our results indicate that sim ilar correlations exist in this Korean guild. There were significant differ ences among species in frequency of use of five foraging site categories in trees: trunks, branches, twigs, leaves, needles. The larger the species, t he more often it used trunks and branches for foraging. There was a positiv e correlation between body-size difference and the difference in the foragi ng sites between species, indicating that species of similar body sizes for aged in similar sites in trees. For four species not specialized in using c onifers (Parus varius, P. major, P. palustris, Aegithalos caudatus), there was a negative correlation between body size difference between species and the difference in the frequency of foraging in conifers, suggesting that b irds of similar body sizes foraged in different tree species. We suggest a possible role of dominance in creating this relationship. This is one of th e few reports of foraging niche differences among tits in temperate forests in Asia. This report is important in that it shows, for the first time, fo raging niche differences in a previously unstudied guild of tits, and that the differences are correlated with size differences, just as in the well s tudied guild of tits in Europe.