Does migration promote or restrict circumpolar breeding ranges of arctic birds?
Migration has been suggested to promote large breeding ranges among birds because of the greater mobility of migratory compared with non-migratory species, but migration has also been suggested to restrict breeding ranges because of evolutionary constraints imposed by the genetically based migration control programme. We aim to investigate the association between migration and the breeding ranges of both land birds and pelagic birds breeding in the Arctic region. Location
The Arctic region. Methods
Information on breeding and wintering ranges and migratory status of bird species breeding in the arctic tundra biome was compiled from the literature. The association between breeding range, migration distance and primary winter habitat was tested using multivariate generalized linear models and pair-wise Mann–Whitney U-tests. Phylogenetic effects were tested for using Mantel’s permutation tests. Results
We found different relationships depending on the species’ major winter habitat. Among birds that are pelagic during winter, long-distance migrants have the largest breeding ranges, while among terrestrial birds, residents and short-distance migrants have the largest breeding ranges. Breeding ranges of coastal birds of all migratory distance classes are comparatively restricted. Main conclusions
As a new explanation for this pattern we suggest that the possibility of colonizing large winter ranges is a key factor for the subsequent expansion of breeding ranges in arctic bird communities and possibly also in bird communities of other regions of the world. Because of the reversal in the relative extent of continents and oceans between the hemispheres, longitudinally wide winter ranges are more likely for long-distance than short-distance migrants among pelagic birds, while the reverse holds true for birds that use terrestrial winter habitats. For coastal birds both continents and oceans form barriers restricting colonization of extensive winter quarters and consequently also of extensive breeding ranges, regardless of the distance to the winter quarters.