BIRDS OF THE ST. CROIX RIVER VALLEY 



43 



terns and arrival in the Northern Highland occurs 1-10 April. Peak spring 

 migration occurs 15-25 April in the Western Upland and 25 April to 5 May 

 in the Northern Highland. Goddard (1975) reported that wood ducks consti- 

 tuted 0.4% of the total spring waterfowl population and 1.2% of the dab- 

 bhng duck population on prairie wetlands in St. Croix County. This low per- 

 centage is undoubtedly related to their preference for riverine habitats. 



Fall migration begins during mid- August with the formation of feeding 

 groups. A gradual buildup in numbers occurs throughout September. Peak 

 populations at Crex Meadows, Burnett County, usually occur 20 September 

 to 5 October; the largest groups were noted on 4 October 1967 (1,500) and 

 14 September 1968 (1,000). Elsewhere, peak populations occur 1-20 Octo- 

 ber. Especially important riverine staging areas occur along the Kettle 

 River (Pine County), Apple River (Polk and St. Croix counties), and Willow 

 River (St. Croix County). Departure from the Valley occurs rapidly after 

 mid-October; the latest dates were 20 November 1976 and 20 December 

 1956 (both Washington County). 



Nesting Season Distribution: Uncommon to fairly common nesting species 

 in all regions. Nesting records exist for all counties and nesting birds are 

 numerous along the larger tributaries of the St. Croix River. In St. Croix 

 County, the wood duck ranks third in abundance behind mallard and blue- 

 winged teal as a breeding duck (B. A. Moss, personal communication). 



Winter: Winter records include 1 January 1972 and 1973 (Afton CBC, Wash- 

 ington County); 27 December 1970 (Solon Springs CBC, Douglas County); 

 and 20 January 1975 (McKenzie Creek, Polk County). 



Habitat: Primary habitat use by nesting wood ducks includes wooded 

 streams, rivers, backwater sloughs, and wooded lakes. In the Northern 

 Highland, breeding pairs also use tamarack bogs and spruce-lined lakes. In 

 the Western Upland, use of prairie wetlands has been enhanced by the place- 

 ment of artificial nest boxes. 



Redhead {Ay thy a americana) 



Status: Regular migrant and casual nesting species. 



Migration: Fairly common migrant in the Western Upland, particularly in 

 western St. Croix and eastern Washington counties. Uncommon to rare else- 

 where, especially in the Northern Highland. Spring migrants arrive in the 

 Western Upland 5-10 April (earliest— 23 March, St. Croix County). Peak 

 abundance occurs 25 April to 5 May and most have departed by 25 May. 

 Goddard (1975) found that redheads made up 2% of the total spring water- 

 fowl population and 4.5% of the spring diving duck population in St. Croix 

 County. At the Crex Meadows Wildlife Area, Burnett County, the average 

 date of spring arrival is 15 April; peak populations occur 1-10 May, and 

 departure by 1 June. 



Fall migrants begin to arrive 10-20 September. Populations build slowly 

 through October, reaching largest numbers 20 October to 1 November. The 

 principal fall migration route used by redheads is south of the Valley. 

 Because of this, concentrations larger than 50 birds are rarely encountered 



