122 



NORTH AMERICAN FAUNA 73 



Upland. Jackson (1943) reported that the veery was common throughout 

 northwestern Wisconsin. The southern Kmit of the breeding range is closely 

 associated with the southern limit of maple-basswood forest. This range 

 limit occurs about at the latitude occupied by Marine-on-St. Croix, Wash- 

 ington County. Breeding Bird Survey data (Table 5) suggest a rapid increase 

 in relative abundance moving northward across the Valley. 



Habitat: Primarily a species occupying various age classes of moist decid- 

 uous forest. In the Northern Highland and Central Plain, this species uses 

 mature stands of Northern Hardwood Forest dominated by sugar maple, 

 basswood, trembUng aspen, and white birch. Alder Thicket, Lowland Conif- 

 erous Forest, and Black Spruce-Tamarack Bogs are also used in these 

 regions. In the Western Upland, habitat use is almost entirely restricted to 

 mixed maple-oak Forest. Occasional use is made of Shrub Carr wetlands 

 that support an abundant growth of silver willow. 



Eastern Bluebird (Sialia sialis) 



Status: Regular migrant and nesting species, casual in winter. 



Migration: Fairly common spring and fall migrant in the Western Upland 

 and Central Plain, more localized in the Northern Highland. Spring mi- 

 grants arrive in the Western Upland 20-30 March (earliest— 12 March 1966, 

 Washington County and 12 March 1977, Pierce County) and the Northern 

 Highland about 1 April. Peak abundance through the Valley occurs 

 15-30 April. Fall migration begins with the formation of loose family groups 

 in mid-August. Peak fall abundance occurs 15 September to 10 October and 

 departure by 1 November (latest— 30 November 1967, Washington County). 

 On 17 October 1964, W. E. Scott observed an estimated 200 eastern 

 bluebirds near St. Croix Falls, Polk County (Kemper 1965). 



Nesting Season Distribution: Fairly common nesting species throughout the 

 Valley. Jackson (1943) found this species common in northwestern Wis- 

 consin, especially in recently burned areas. Breeding Bird Survey data 

 (Table 5) suggest that a fairly uniform abundance exists throughout the 

 Western Upland and Central Plain, except in the Jack Pine Barren region 

 along the Union transect, Burnett County. 



Concern has been expressed about the status of the eastern bluebird in 

 North America (cf. Arbib 1978) and in Wisconsin (R. L. Hine, personal com- 

 munication). Some authorities believe that population declines are related to 

 mortality on the wintering grounds, whereas others believe these declines 

 are related to competition for nest sites with other hole-nesting species (e.g., 

 house sparrow). Careful monitoring of the Valley population should be 

 undertaken to determine if declines are occurring. 



Winter: One bird was observed at St. Croix Falls, Polk County, on 7 and 

 8 February 1948. Two birds were observed in Washington County on 20 De- 

 cember 1969. Roberts (1932) mentioned, without details, winter records 

 from Washington County. 



Habitat: The eastern bluebird is a characteristic species of edge and open 

 habitats including fencerows, early successional stage deciduous forest, 



