110 



NORTH AMERICAN FAUNA 73 



Common Crow {Corvus brachyrhynchos) 



Status: Regular migrant, nesting species, and winter resident. 



Migration: Spring migration begins in the Western Upland during mid-Feb- 

 ruary with dispersal from local winter roosts. Numbers of migrants grad- 

 ually increase, reaching peak numbers 25 March to 10 April. Fall migration 

 begins in late August with flock formation. Peak movements occur 20 Sep- 

 tember to 15 October and non wintering birds have departed by 15 No- 

 vember. 



Nesting Season Distribution: Common nesting bird in all regions. Breeding 

 Bird Survey data indicate a fairly uniform breeding population throughout 

 the Valley; greatest abundance is in the Central Plain (Table 5). Documented 

 breeding records exist for all eight counties. 



Winter: The CBC data (Table 4) show the winter distribution pattern of the 

 common crow. This species is common to locally abundant in the Western 

 Upland, fairly common in the Central Plain, and rare and local in the North- 

 ern Highland. The highest winter counts include 959 (1 January 1975), 941 

 (1 January 1977), and 908 (1 January 1974), all on the Afton CBC. 



Habitat: The common crow is primarily an edge species using several wood- 

 land habitat types. Common crow breeding habitat is further characterized 

 by the association of agricultural fields or Old Field Community. Also used 

 is Lowland Deciduous Forest and Northern Hardwood Forest. The occur- 

 rence of large farming operations and the resultant abundance of waste 

 grains probably enhance the habitats of the Western Upland for wintering 

 common crows. 



FAMILY PARIDAE: Titmice 



Black-capped Chickadee (Parus atricapillus) 

 Status: Regular permanent resident. 



Distribution: Uncommon (locally common) nesting species in the Western 

 Upland, common and more widespread in the Central Plain and Northern 

 Highland. Analysis of BBS data (Table 5) suggests a rapid increase in abun- 

 dance moving northward from the southern oak forest type of the Western 

 Upland to the mixed deciduous-coniferous forest of the Northern Highland. 

 Goddard (1972) reported a breeding density of 15.1 pairs per 40 ha in mixed 

 habitats along the Kinnickinnic River, Pierce County. Jackson (1943) re- 

 ported that this species was "only moderately common at most locaUties" in 

 northwestern Wisconsin. However, he reported it "seemed to be more plenti- 

 ful .. . at Solon Springs." 



Winter: Common and well-distributed winter resident in the Western Up- 

 land and Central Plain, uncommon in the Northern Highland. Christmas 

 Bird Count data (Table 4) also suggest that the largest winter densities 

 occur in the southern regions. Mean numbers of black-capped chickadees on 

 the Afton CBC (Western Upland) are nearly three times as large as those 



