Lesser Scaup
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| Aythya affinis (Eyton, 1838) |
The Lesser Scaup (Aythya affinis) is a small diving duck.
Adults are 38-45 cm long, with a blue bill and yellow eyes. Adult males have a dark head with a purple sheen, a black breast, a light grey back, a black tail and white underparts. Adult females have a white band at the base of the bill and a brown head and body. They are smaller than the Greater Scaup.
Their breeding habitat is marsh ponds in Alaska and western Canada. They nest in a sheltered location on the ground near water.
There can be difficulties for inexperienced birdwatchers in distinguishing the Greater and Lesser Scaup. The differently colored sheen on the head is unreliable because light conditions vary, and these birds are often far from the shoreline.
The Lesser Scaup is best identified on its much smaller size, different head shape with a peaked hind crown, and a white wing bar that is visible only on the secondaries (it extends onto the primaries in Greater). The drake also shows vermiculations on the back. In North America, a large scaup flock will often have both species present.
Lesser Scaup migrate in flocks and winter in lakes, rivers and sheltered coastal waters along the west coast of North America, the southern United States and northern South America. They are more likely to be found on freshwater than Greater Scaup. These birds move south late in the fall and return in early spring.
They are a rare but apparently increasing vagrant to western Europe, where the identification also needs to exclude similar looking hybrids.
These birds dive and swim underwater, occasionally dabbling. They mainly eat mollusks and aquatic plants. It has been reported that both the Lesser and the Greater Scaup have shifted their traditional migration routes to take advantage of the presence of zebra mussels in Lake Erie. This may pose a risk to these birds because zebra mussels are efficient filter feeders and so accumulate environmental contaminants rapidly.
[edit] References
- BirdLife International (2004). Aythya affinis. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 11 May 2006. Database entry includes justification for why this species is of least concern
- Madge and Burn, Wildfowl ISBN 0-7470-2201-1
- Mullarney, Svensson, Zetterstrom and Grant, Collins Bird Guide ISBN 0-00-219728-6
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