46 



NORTH AMERICAN FAUNA 73 



Croix County. 



Fall migrants occur 5 October to 20 November; most records are 20 Octo- 

 ber to 5 November. Fall migrants are usually observed intermixed with 

 large rafts of lesser scaup, whereas in spring migration, greater scaup seem 

 to be more segregated from lesser scaup. 



Habitat: Large, open permanently flooded wetlands typically support the 

 most greater scaup in this region. Cedar Lake on the Polk-St. Croix County 

 line is probably the most productive lake in the region for observing greater 

 scaup. 



Lesser Scaup (Ay thy a af finis) 



Status: Regular migrant, casual nesting species, and occasional in early 

 winter. 



Migration: Abundant migrant throughout the Valley. The lesser scaup is the 

 most numerous migrant duck in the Valley. In St. Croix County, Goddard 

 (1975) found that lesser scaup made up 24.6% of the total spring waterfowl 

 population and 54.6% of the diving duck population. Spring migrants arrive 

 in the Western Upland 10-15 March (earUest— 6 March 1976, Washington 

 County) and the Northern Highland 1-10 April. Peak spring populations 

 occur 20 April to 10 May when flocks of 700 to 1,000 individuals are typi- 

 cally observed on larger lakes. Departure occurs 20-30 May. 



Fall migrants arrive 20 September to 1 October. Fall migration is charac- 

 terized by a rather low increase in numbers until about 20 October when 

 large influxes occur. Peak fall populations at Crex Meadows Wildlife Area, 

 Burnett County, occur 25 October to 5 November and have totaled up to 

 7,000 individuals (30 October 1965). In the Western Upland, peak fall popu- 

 lations larger than 3,000 individuals are observed 25 October to 5 Novem- 

 ber. Departure from the Valley is dependent on ice conditions on larger 

 lakes; most birds depart by 1 December. 



Nesting Season Distribution: Regular summer resident on wetlands in Polk, 

 St. Croix, and central Washington counties. Usually up to 10 pairs can be 

 found on wetlands near New Richmond, St. Croix County. There are two 

 brood records for the Valley; both broods were found on 7 July 1976, on wet- 

 lands in Alden Township, Polk County. These broods were within 0.8 km of 

 each other and constituted the eighth and ninth, 20th century breeding rec- 

 ords for Wisconsin. At Crex Meadows, 10 pairs were observed during 1958. 

 Since then at least one pair has been present yearly; however, no broods 

 have been observed. Jackson (1942) reported the collection of a male lesser 

 scaup on Upper St. Croix Lake, Douglas County, on 1 August 1919. 



Winter: Occasional early winter visitor primarily on open stretches of rivers. 

 These birds are probably late fall migrants rather than wintering birds 

 because no midwinter records exist. Dates range from 22 December 1956 to 

 1 January 1973, 1975, 1976 (Afton CBC); 29 December 1973 to 3 January 

 1976 (Suburban St. Paul CBC); 12-13 January 1949, 12 January 1955, 

 9 January 1956, and 7 January 1957 (Crex Meadows); 31 January 1949, St. 

 Croix Falls (Polk County); and 23 December 1975, Solon Springs CBC 



