174 



NORTH AMERICAN FAUNA 73 



land, rare and local in the Central Plain. Christmas Bird Count data (Table 4) 

 suggest that highest winter populations occur in areas directly adjacent to 

 the lower St. Croix River. Populations decrease rapidly in areas northward 

 from the Central Plain. The tree sparrow has not been recorded on the Solon 

 Springs CBC, Douglas County. 



Habitat: During migration, the tree sparrow uses a variety of open habitats 

 including agricultural fields, retired cropland, and wetland edges. During 

 midwinter, extensive use is made of retired croplands that support dense 

 weedy patches. Grassy openings in Southern Deciduous Forest and occa- 

 sional remnant prairie patches occurring along the river bluffs are also im- 

 portant. 



Chipping Sparrow [Spizella passerina) 

 Status: Regular migrant and nesting species. 



Migration: Common migrant throughout the Valley. Spring migrants arrive 

 in the Western Upland 10-15 April (earhest— 3 April 1971, Washington 

 County) and reach the Northern Highland about 15-20 April. Peak spring 

 migration through the Valley occurs 1-15 May. Peak fall migration occurs 

 10 September to 1 October and departure by 15 October (latest— 3 No- 

 vember 1963, St. Croix County). 



Nesting Season Distribution: Common nesting species throughout the 

 Valley. Breeding Bird Survey data (Table 8) suggest that the largest breed- 

 ing population occurs in the northern regions of the Central Plain and 

 throughout the Northern Highland. Jackson (1943) reported that chipping 

 sparrows were common nesting birds throughout northwestern Wisconsin. 

 Goddard (1972) reported a density of 11.1 pairs per 40 ha in the Kinnickinnic 

 River Valley, Pierce County. 



Habitat: Primarily a nesting species of various coniferous habitats including 

 Lowland Coniferous Forest, Black Spruce-Tamarack Bogs, and Jack Pine 

 Barrens. In residential areas, this sparrow is common in ornamental shrubs. 

 Breeding pairs are occasionally encountered in brushy margins between 

 Lowland Deciduous Forest and open fields. Jackson (1943) described a chip- 

 ping sparrow nest at St. Croix Falls that was 6.4 m above ground in a large 

 white pine. 



Clay-colored Sparrow (Spizella pallida) 

 Status: Regular migrant and nesting species. 



Migration: Fairly common migrant throughout the VaUey. Spring migrants 

 arrive in the Western Upland 25 April to 1 May and the Northern Highland 

 5-10 May (earliest— 29 April 1961, Burnett County). Peak spring migration 

 through the Valley occurs 10-20 May. Peak fall migration occurs 20 August 

 to 5 September in the Northern Highland and 10-25 September elsewhere. 

 Departure from the Northern Highland occurs about 20 September (latest— 

 16 October 1963, Burnett County) and the Western Upland 1-15 October. 



