Sunday, March 30, 2014

Greater Scaup

Greater and Lesser scaup can be tricky to identify. These ducks are Greater Scaup that Erika and I photographed at Black Dog Lake on the south edge of Minneapolis/St. Paul on 29 March 2014. Field guides used to imply that the two species are separable by the color of the iridescence of the males’ heads—green in Lesser Scaup and purple in Greater. You can clearly see in the first photo that this field mark is not reliable.

A better key is the shape of the head. The Greater Scaup has a rounded head, while the Lesser’s head is almost crested—at least the back of the head has more of a corner than does the Greater’s. I have always felt that the Greater Scaup’s back is brighter than that of a Lesser. The brightness is the result of finer bars on the Greater’s back. I think that the white spot behind the female’s bill is bigger on a Greater Scaup.

One of the best ways to distinguish the two species is shown in the lower photo by a bird that obligingly stretched its wings. The white stripe on the Greater Scaup’s wing clearly continues across its primary feathers. Compare this photo to one I took of a Lesser Scaup. The white is restricted to the secondaries on the Lesser Scaup. Note also the darker back stripes on the Lesser in the linked photos.

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