Sex-specific migration of Phylloscopus warblers at a stopover site in Far Eastern Russia

摘要

In the majority of the Phylloscopus warblers there is no sexual plumage dimorphism and this makes it almost impossible to determine the sex of birds trapped during migration. We analysed a data set of 6287 individuals of seven warbler species ringed at a stopover site at Muraviovka Park in Far Eastern Russia. The wing length showed a bimodal distribution in four species, and decreased during spring migration but increased during autumn migration. We argue that this pattern is caused by sex-specific migration: the larger males face the pressure to reach the breeding grounds earlier, while they stay longer in their territories in autumn.