BIRDS OF THE ST. CROIX RIVER VALLEY 



157 



Migration: Abundant spring and uncommon fall migrant throughout the 

 Valley. Spring migrants arrive in the Western Upland 15-20 March and 

 reach the Northern Highland by 10 April. Peak spring populations occur 

 10-25 April. Fall migration begins with flock formation in late June. A grad- 

 ual movement away from breeding areas occurs throughout the fall; conse- 

 quently, no peak population dates can be given. Most migrants have de- 

 parted by 15 September and stragglers remain through October. 



Nesting Season Distribution: Common to locally abundant nesting species 

 throughout the Valley. Breeding Bird Survey data (Table 7) show a large 

 and well-distributed breeding population. Goddard (1972) reported a density 

 of 24.2 pairs per 40 ha in the Kinnickinnic River Valley, Pierce County. 



Winter: Several early winter records exist from CBC's in Washington, St. 

 Croix, and Douglas counties. These records include: 1 January 1970 (St. 

 Croix); 1 January 1975, and 3 January 1976 (Washington); and 18 December 

 1974 (Douglas). 



Habitat: Brown-headed cowbirds use virtually all habitats in this region. 

 Largest breeding populations occur in woodland edge situations. 



FAMILY THRAUPIDAE: Tanagers 



Scarlet Tanager (Piranga olivacea) 

 Status: Regular migrant and nesting species. 



Migration: Fairly common migrant throughout the Valley. Spring migrants 

 arrive in the Western Upland 1-5 May, reaching the Northern Highland 

 5-10 May. Peak spring migration through the Valley occurs 10-25 May. 

 Fall migration begins in mid- August. Peak fall migration occurs 25 August 

 to 15 September and departure by 1 October. 



Nesting Season Distribution: Fairly common nesting species throughout the 

 Valley. This species is more widespread and probably occurs in greater 

 densities in the Central Plain and Northern Highland. Bernard (1967) consid- 

 ered the scarlet tanager a common summer resident in Douglas County. 

 Jackson (1943) reported this species as common at St. Croix Falls, Polk 

 County, and mentions the observation of mated pairs at that location. God- 

 dard (1972) reported a density of 4.5 pairs per 40 ha in the Kinnickinnic 

 River Valley, Pierce County. 



Habitat: Characteristic nesting species of deciduous forest communities. 

 Habitat use by nesting scarlet tanagers varies with geomorphic province. In 

 the Western Upland, this species is most abundant in mature Lowland 

 Deciduous Forest and Southern Deciduous Forest. In the Central Plain and 

 Northern Highland, scarlet tanagers are most abundant in mature Northern 

 Hardwood Forest and in early successional stage aspen forest. Breeding 

 pairs in Jack Pine Barren habitat are normally found in the "scrub" oak sa- 

 vannahs interspersed with j ack pine. 



