Lesser Scaup, Aythya affinis
Lesser Scaup, male,  2/18/07, Guadalupe River, San Jose
Lesser Scaup, female, 2/18/07, Guadalupe River, San Jose
Lesser Scaup, female, 4/13/07, Palo Alto Baylands
Lesser Scaup, male, 3/16/08, Palo Alto Baylands
Lesser Scaup, male, 3/2/07, Palo Alto Baylands
Lesser Scaup, female, 2/11/06, Palo Alto Baylands duck pond
Lesser Scaup, male, 5/25/06, Moss Landing, Monterey Co
Lesser Scaup, adult male winter, 12/26/03, Palo Alto Baylands Park
How do you tell the Scaup species apart? One mark that isn't reliable is the iridiscent sheen of the male's head -- usually green on the Greater (remember G) and purple on the Lesser. Notice that this Lesser looks green on the lower part of his cheek, and purple on his crown. A diagnostic mark, if you get a close look, is the width of the nail on the bill. The Lesser's, visible here, is about half the width of what it would be in a Greater. A more difficult mark is the shape of the head -- the highest point of the crown is behind the eye in the Lesser, ahead of it in the Greater. This is good for both sexes and can work at a distance. But apparent head shape is highly dependent on angle of view, and how the bird is holding its feathers -- as these pictures show. There's also a bill shape difference; see the good discussion in Kenn Kaufman, Advanced Birding.
Lesser Scaup, adult female, 7/17/04, Palo Alto Baylands Park
A female in eclipse.
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