Small scale geographical variation in plumage colour of Pied Flycatcher males

The plumage colour of Pied Flycatcher Ficedula hypoleuca males varies geographically, with darker-coloured populations occurring in Fennoscandia and lighter-coloured populations in central Europe and Russia. Our data show that males, regardless of age, were darker in northern than in southern Finland. There are two potential explanations for this. First, higher predation pressure in the south compared to the north may favour more cryptic individuals. Second, there may be more extensive gene flow to southern than to northern Finland from adjacent Pied Flycatcher populations living in sympatry with the Collared Flycatcher F. albicollis on Gotland (Sweden) and in central Europe. The later assumption agrees with the idea that gene flow from areas of sympatry might maintain high colour variation of males in nearby areas of allopatry.