Common Eiders. S. m. dresseri and S. m. borealis (right). Provincetown, MA. December 28th, 2006.Common Eider. (Presumed) S. m. borealis. Provincetown, MA. December 28th, 2006. Captioned image describing distinguishing features in direct comparison to S. m. dresseri. Dave Pullan has kindly reminded me that the lack of a green band between the white cheek and black cap of the presumed borealis is an additional feature separating it from the resident dresseri. The green band can be seen fairly clearly on the male dresseri below.
Photo-comparisons of adult male borealis and dresseri Common Eiders from Provincetown Harbor, Massachusetts, December 2006 with reference to a recent discussion on the Surfbirds identification forum. This bird showing characteristics of S. m. borealis could represent the first state record since 1946, with at least two others being reported and photographed in MA since.
Common Eiders. S. m. dresseri and S. m. borealis (front). Provincetown, MA. December 28th, 2006. Note differences in head shape and especially the shape of the frontal bill lobes.