BIRDS OF THE ST. CROIX RIVER VALLEY 



159 



15-25 August. Peak fall migration through the Valley occurs 5-20 Sep- 

 tember. Departure from the Northern Highland occurs 20-25 September 

 and elsewhere by 5 October (latest— 26 October 1965, Washington County). 



Nesting Season Distribution: Fairly common (locally common) nesting 

 species in the Western Upland. Population densities apparently increase 

 northward through the Valley. Goddard (1972) reported a density of 31.2 

 pairs per 40 ha along the Kinnickinnic River Valley in Pierce County; the 

 rose-breasted grosbeak was the fifth most abundant breeding bird in that 

 valley. Breeding Bird Survey data (Table 8) suggest that rose-breasted gros- 

 beaks occur in greatest abundance in the Northern Highland. 



Habitat: The rose-breasted grosbeak is a characteristic breeding species of 

 mature deciduous forest and forest edge. In the Western Upland, this gros- 

 beak uses Southern Deciduous Forest dominated by mixed stands of white, 

 red, black, and bur oaks. Also important is mature Lowland Deciduous 

 Forest characterized by cottonwood, green ash, and American elm along the 

 major river systems. In the Central Plain and Northern Highland, primary 

 use is made of mature Northern Hardwood Forest dominated by sugar 

 maple, basswood, trembHng aspen, and white birch. Residential Habitats, 

 primarily ornamental shade trees, are also used for nesting. 



Table 8. Mean number of grosbeaks, finches, towhees, and sparrows 

 recorded on western Wisconsin Breeding Bird Survey transects, 1966-78. 



Western 



Species 



Upland 



Central Plain 



Northern Highland 



Hudson 



Dresser 



Loraine 



Union 



Minong 



Cardinal 



L5 



0.6 



0.0 



<0.1 



<0.1 



Rose-breasted grosbeak 



6.0 



12.2 



18.1 



15.0 



19.6 



Indigo bunting 



7.4 



8.7 



23.3 



18.5 ' 



18.6 



Dickcissel 



12.1 



6.4 



5.4 



0.0 



0.0 



American goldfinch 



4.7 



9.1 



20.6 



6.0 



5.9 



Purple finch 



0.0 



0.0 



0.0 



1.0 



3.3 



Pine siskin 



0.0 



0.0 



<0.1 



<0.1 



0.2 



Rufous-sided towhee 



0.2 



0.2 



0.6 



21.7 



15.8 



Savannah sparrow 



17.3 



14.1 



26.3 



0.0 



0.3 



Grasshopper sparrow 



9.6 



5.7 



6.7 



0.7 



0.0 



Henslow's sparrow 



1.2 



1.1 



0.5 



0.0 



0.0 



Vesper sparrow 



18.9 



15.3 



13.7 



6.5 



8.6 



Dark-eyed junco 



0.0 



0.0 



0.0 



0.0 



0.6 



Chipping sparrow 



1.6 



6.3 



10.9 



21.2 



24.2 



Clay-colored sparrow 



4.4 



3.0 



2.7 



7.2 



14.9 



Field sparrow 



7.0 



3.2 



2.2 



10.2 



1.9 



White-throated sparrow 



0.0 



0.0 



<0.1 



0.0 



3.5 



Lincoln's sparrow 



0.0 



0.0 



0.0 



0.0 



<0.1 



Swamp sparrow 



0.0 



0.2 



0.9 



0.2 



1.1 



Song sparrow 



12.9 



24.4 



32.6 



3.5 



24.0 



