Posted by Phil Pickering (184.108.40.206) on December 15, 2001 at 22:03:38:
I hate scaup photos, since I'm typically lazy and don't pay much attention to scaup in the field. But anyway -
Lower - female Greater by combination of:
- rounded hind-crown, without any hint of a peak. Lessers seem to typically maintain at least a hint of a peak or squared-off angle to the hind-crown, even as their head shape flattens or compresses.
- pale yellow iris. Even mature female Lessers seem to average noticeably darker-eyed than is apparent here.
- dark on bill tip (nail) seems somewhat extensive for Lesser here, even though bill tip is partially cropped in the photo.
- proportionately sort of long and chunky body, overall jizz seems like Greater to me (whatever that's worth to anyone else).
Upper pair - Lessers based on combination of:
- squared-off hind-crowns
- block-headed look. Even with changes to head shape, my impression is that Greaters typically don't show quite such a blocky look to the head, while Lessers often do.
- minimal or no black on bill tips.
- somewhat short, thin bodies - jizz of Lessers.
No expertise claimed. Hopefully aythya-ists can illuminate which differences are most consistent and important to look at, or at least which ones typically show up best in photos.
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