Separating Female Wigeon: A Little-known Field Mark

In recent decades Eurasian Wigeon have become increasingly prevalent across much of North America, particularly in the West. Along the Pacific Flyway, where wigeon winter by the hundreds of thousands, almost any flock of 100 or more American Wigeon might include a Eurasian or two. Males of these two species are readily separable (see images below), thus nearly all reports of Eurasians pertain to drakes. Despite the regular detections of male Eurasians, their mates, often swimming side-by-side with the male, go mostly unnoticed.

Unlike their female counterparts, male Eurasian (left) and American Wigeon (right) are rather easy to tell apart even from a distance.

With practice, the females of these two species are not overly difficult to separate. Since waterfowl typically remain paired throughout the year, one the best ways to pick out a female Eurasian Wigeon is to look for the females that appear to be associating with the male Eurasians. Female Eurasians look uniform reddish brown overall, showing no obvious contrast between the head, breast, and flank coloration. Their heads usually look solid brown and somewhat less spotted than the heads of female Americans (although at close range the spotting is about the same). It should be noted that there two color morphs of female Eurasian Wigeon. Some birds are warm cinnamon brown all over (like those shown below), while others are a duller earthy brown. In both color forms, there is no discernible contrast between the head and the rest of the bird. Conversely, female Americans present a similar overall pattern to males in the sense that they are brown on the flanks and breast and they have a somewhat grayish head with fine black spotting. In most cases, the contrast between the gray head and rusty brown body is obvious. Female Americans do not show the whitish cream-colored crown or the green head stripe seen on males.

This female Eurasian Wigeon, photographed at Westmoreland Park in Portland, Oregon 1 February 2009 shows fairly uniform warm reddish brown tones on the head, breast, and flanks, with no apparent contrast between the head and breast/flank coloration.

Notice the much grayer head of this American Wigeon, also photographed at Portland's Westmoreland Park 1 February 2009, and how it contrasts with the mostly reddish brown breast and flanks.

If you are not absolutely positive about which species you are seeing even after applying the field marks described above, there is one more excellent field mark for separating female wigeon. I was unaware of this mark until about a year ago when I noticed it illustrated in The Sibley Guide to the Birds (2000).  American Wigeon (both sexes) show a narrow strip of black at the base of their mostly pale gray-blue upper mandible (top half of the bill). Sometimes this black can be obscured a bit by feathering, but if you look closely it is always evident. Eurasian Wigeon do not have this narrow margin of black and the area where the base of the upper mandible meets the head feathering is pale gray-blue like most of the rest of the bill.  The close-up head shots below show this difference.

This extreme close-up of the head of a female Eurasian Wigeon shows the lack of black at the base of the upper mandible. Also notice that edge of the feathering around the base of the bill looks somewhat curved particularly around the gape.

Looking closely at this female American Wigeon's bill, notice the narrow black margin right at the base where the feathers meet the bill. As seen on this bird, this creates the illusion of a very straight vertical line where the feathers end and the bill begins.

Clearly, the latter field mark (black on the base of the bill) is not going to useful when sorting through a mass of wigeon hundreds of yards away. However, sizeable wigeon flocks often gather in urban parks and on golf courses where they quickly acclimate to the presence of humans. Once one develops a strong search image by experiencing these birds at close range, picking out a female Eurasian in a more distant flock becomes a lot less challenging. It stands to reason that there are just as many female as male Eurasian Wigeon wintering in North America, but the reporting of this species hardly reflects this presumed gender balance.

All photos taken by David Irons using a Canon EOS XSI 450D camera and an EF 100-400mm f/4.5-5.6 lens