Eidereenden met een afwijkend verenkleed: een oproep

Abnormal plumages in Eiders have been observed in the Dutch Wadden Sea during the last few years: a dark variety (figure 1), male-like with dark rump and wings, and a light variety (figure 2 and 3), being old female birds in male-like plumage. Further data are requested and a call for corpses to examine these abnormalities is put forward.