Extent of recent polewards range margin shifts in Finnish birds depends on their body mass and feeding ecology

Abstract

Global warming would predict that, all else being equal, species should shift their range margins polewards, and that a failure to do so could be detrimental for a population. A polewards range margin shift has been documented previously in the Finnish avifauna. Here, I showed that the polewards range margin shift of 116 Southern Finnish bird species was larger for small-bodied species and differed according to their feeding ecology, but not to their migration ecology. Species foraging in wet habitats had experienced strong range margin shifts as compared with other feeding ecologies. For 53 species, population trends for 1983-2005 were available. I found no evidence that those feeding ecological groups that showed a relatively small shift in range margin had experienced low popula- tion growth or a population decline. Instead, I found some evidence that the long-term trend in population numbers varied across migration ecologies after correcting for changes in their Finnish breeding range. The results suggest that those processes that cause a shift in the range margin of birds are not involved in the recent changes in bird abundances.