150 



NORTH AMERICAN FAUNA 73 



During 1919, Jackson (1943) reported that American redstarts were "the 

 commonest of the warblers" at St. Croix Falls, Polk County, and he found 

 them "abundant" in timber along the St. Croix River. Fall migration begins 

 5-10 August in the Northern Highland and 20-25 August elsewhere. Peak 

 fall migration occurs 25 August to 15 September and departure is by 5 Octo- 

 ber (latest— 13 October 1966, Washington County). 



Nesting Season Distribution: Common nesting species throughout the 

 Valley. Locally abundant in the Western Upland and Central Plain, in areas 

 associated with the mouths of major streams. Goddard (1972) reported a 

 density of 3.9 pairs per 40 ha in the lower Kinnickinnic River Valley, Pierce 

 County. However, his study area was primarily upland deciduous forest, 

 which is not preferred habitat of breeding American redstarts. Breeding 

 Bird Survey data (Table 6) suggest that highest breeding densities occur in 

 the Central Plain and Northern Highland. Unfortunately, this route of 

 survey does not traverse important American redstart habitat directly adja- 

 cent to the St. Croix River and its tributaries in the Western Upland. 



Habitat: Characteristic breeding bird of Lowland Deciduous Forest in the 

 Western Upland and Central Plain. Vegetation of these areas includes 

 American elm, box elder, green ash, and basswood. Important upland 

 habitat in the Northern Highland includes medium-aged to mature Northern 

 Hardwood Forest that is dominated by basswood, maple, big-toothed aspen, 

 and white birch. Use of coniferous habitats by nesting American redstarts is 

 very hght. 



FAMILY PLOCEIDAE: W^eaver Finches 



House Sparrow {Passer domesticus) 

 Status: Introduced permanent resident. 



Distribution: Common to locally abundant resident throughout the Valley. 

 The largest concentrations of house sparrows occur in residential areas and 

 other sites of human habitation, including rural residential developments 

 and farms. This species is less numerous and more locaUzed in heavily for- 

 ested habitats away from the influence of humans. 



Habitat: Closely related to areas of human settlement including houses, 

 office buildings, feedmills, railroad tracks, farmyards, feedlots, and 

 pastures. 



FAMILY ICTERIDAE: Meadowlarks, Blackbirds, and Orioles 



Bobolink {Dolichonyx oryzivorus) 

 Status: Regular migrant and nesting species. 



Migration: Common to locally abundant migrant in Western Upland and 

 Central Plain, uncommon and local in the Northern Highland. Spring mi- 



