Factors controlling the migration phenology of Siberian Phylloscopus species

Abstract

The timing of annual events in migratory species is determined by the position of breeding and wintering grounds, length of the breeding season, the occurrence of their preferred diet or the timing of moult in birds. Previous studies found significant differences in the migration phenology of Asian Phylloscopus warbler species, a group of long-distance migratory passerines. However, the factors that influence the observed differences in migration phenology have not been studied yet. Here, we analyze the effect of the above-mentioned factors on the migration timing of seven Phylloscopus species at a stopover site in the Russian Far East. We found that spring migration phenology was best explained by moult strategy and the preferred prey size, while autumn migration phenology was linked to the southernmost wintering latitude of the species. Interspecific differences in migration timing were much higher in autumn than in spring. The duration of the species-specific migration periods was also longer in autumn than in spring, most likely caused by higher competition during spring to arrive early at the breeding grounds. Our results contribute to the understanding of migration ecology in songbirds moving along the little-studied East Asian flyway.