Posted by Fix (206.13.45.152) on December 19, 2001 at 08:58:18:
Joe has made a good choice in presenting these images! All respondents have brought to the discussion widely varying perspectives. In how many ways can scaup be distinguished? I can add a few points. Don Roberson and I had a disagreement once on whether Lesser Scaup can ever show such a conspicuous pale post-auricular crescent. I said I'd never seen it and Don said It Happens. Any reaction? I think a strong supporting mark for the female in the top shot is that she bears a vague resemblance to a Surf Scoter. In my experience, female Lessers cannot. A caveat on the top image is that ad. male Lesser Scaup which are constantly diving routinely remove air from the plumage at the surface by effecting what looks like an overall compression of the feathers --this is readily seen by watching the top of the head in the instant before the bird dives again. What this does to the duck's looks is that the crown profile is lowered, changing three things: the eye appears closer to the crown (mimicking the 'bullish' or stern demeanor of Greater); it reduces the apparent bill-to-crown angle (see Irons' post), again imparting a heavier-headed feel; and it erases the cowlick break in the upper hind-crown, otherwise such a good mark for alert or sleeping Lesser Scaup. Although I think the two birds in the top photo are indeed a pair (summering locally-- the months these ducks were photographed is a 'teaser') , the possibility that an actively feeding ad. male Lesser alongside a female Greater should be at least given passing consideration. A final thought. Phil mentions having seen Greater Scaup with the hind crown higher than the front. I have not seen this and wonder if anyone else can respond yea or nay.