(1976) estimates (a) suggest that about 358,000 of these scaup were Greater 

 Scaup; his earlier calculations indicated a total of about 317,000 birds. Prob- 

 ably somewhat more than 12% of the Greater Scaup seen in 1975 wintered in the 

 southeast, a substantial majority of them in waters off Florida and Louisiana. 



The difficulty in identifying the Greater Scaup in the field has been fre- 

 quently noted above. The very similar Lesser Scaup is more abundant in the 

 southeast, and there is a tendency either to apply the name of the more common 

 species or to hedge by not Identifying scaup to species. Thus, reliance on ob- 

 server's reports is likely to convey an erroneous concept of the relative abun- 

 dance of the two species. Population estimates given by Bellrose (1976) are 

 based on the total number of scaup detected on aerial surveys, allotted in pro- 

 portion to the percentage of Greater and Lesser Scaup found in spot checks of 

 hunters' bags, a method that has obvious shortcomings. 



Migration The principal migration routes of Greater Scaup from their 

 breeding grounds in northwestern North America extend east- southeast to the 

 principal wintering grounds on the northern Atlantic coast. Some, perhaps most, 

 of the birds wintering along the Pacific coast move south well offshore but 

 others apparently follow a more interior pathway through western Canada. Great- 

 er Scaup wintering along the Gulf coast apparently diverge from east-southeast 

 routes to fly south along the Mississippi drainage and through Iowa and Georgia 

 to western Florida (Bellrose 1976). 



HABITAT 



Nesting Preferred nest sites of the Greater Scaup in open boreal forest 

 (taiga) of North America are islands in large lakes. In the Yukon Delta, how- 

 ever, these birds nest on marshy, lowland tundra on slightly elevated areas near 

 ponds (Bellrose 1976). Some nests have been found as much as a thousand meters 

 from water (Palmer 1976b), but most are close to ponds or other bodies of water 

 (Bellrose 1976, Palmer 1976b). Similar breeding habitats have been reported in 

 the Old World; in Scandinavia they frequent upland birch communities (Cramp et 

 al. 1977). 



Nests are usually concealed in tall grass (Bellrose 1976). Preferred cover 

 is usually grass-sedge, mostly Glyceria (R. Kirkpatrick in Palmer 1976b), but 

 nests have also been found in rock crevices, under shrubs, and on floating veg- 

 etation (Bellrose 1976, Palmer 1976b). 



Feeding Greater Scaup have a pronounced tendency to feed in open water 

 and are the most marine of the genus Aythya (Cramp et al. 1977). They prefer 

 to feed in water about 1-4 m (3-13 ft) deep (Palmer 1976b). Non-breeding 



(a) We assumed that the estimates Bellrose (1976) made for the proportion of 



Greater Scaup among scaup seen in Louisiana (6.6%) applies also for Missis- 

 sippi and Alabama. For the flyway as a whole we used his estimate that 

 13.7% of scaup seen were Greater Scaup. We also used his proportions of 

 1.4% for Texas, 2.3% for the Central Flyway, and his overall proportion 

 of 37.7% for the Pacific Flyway. 



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