BIRDS OF THE ST. CROIX RIVER VALLEY 



149 



Wilson's Warbler (Wilsonia pusilla) 

 Status: Regular migrant. 



Migration: Fairly common (locally common) migrant throughout the Valley. 

 Spring migrants arrive in the Western Upland about 10 May (earliest— 

 4 May 1966, Washington County) and reach the Northern Highland from 

 10-15 May. Peak spring migration occurs 15-25 May and departure is by 

 1 June. Fall migrants arrive in the Northern Highland 10-15 August and 

 the Western Upland about 20 August. Peak fall migration occurs 25 August 

 to 10 September and departure is by 25 September (latest— 27 September 

 1967, Washington County). 



Habitat: Wilson's warbler uses a variety of deciduous and coniferous habi- 

 tats during migration. Although no single habitat is of major importance, 

 this species is most frequently observed in brushy fencerows. Deciduous 

 Clear Cuts, and young to medium-aged Northern Hardwood Forest domi- 

 nated by trembling aspen and white birch. 



Canada Warbler {Wilsonia canadensis) 

 Status: Regular migrant and summer resident. 



Migration: Uncommon migrant throughout the Valley. The Canada warbler 

 is among the latest arriving warblers during spring migration. The first 

 birds reach the Western Upland 12-15 May and the Northern Highland 

 15-20 May. Peak spring migration occurs 20-30 May and departure from 

 nonbreeding areas by 30 May (latest— 2 June 1970, Washington County). 

 The first fall migrants arrive in the Western Upland 5-10 August. Peak fall 

 migration occurs 15 August to 5 September and departure by 15 September 

 (latest— 29 September 1967, Washington County). 



Nesting Season Distribution: Rare and local during the breeding season, 

 apparently restricted to the Northern Highland. Breeding Bird Survey data 

 (Table 6) also suggest restriction to the Northern Highland. The breeding 

 range of this warbler in the Minnesota counties is known to include only 

 northern Pine County (Green and Janssen 1975). 



Habitat: Primarily encountered along the edge of Northern Hardwood 

 Forest and in Lowland Coniferous Forest during the nesting season. My ob- 

 servations of this bird's breeding habitat suggests that brushy understory 

 associated with Northern Hardwood Forest is probably most regularly used. 

 Deciduous Clear Cuts in the Northern Highland receive moderate use as 

 does the brushy edge between aspen forest and adjacent open areas. 



American Redstart {Setophaga ruticilla) 

 Status: Regular migrant and nesting species. 



Migration: Common (locally abundant) migrant throughout the Valley. 

 Spring migrants arrive in the Western Upland 1-5 May and reach the 

 Northern Highland 5-10 May. Peak spring migration occurs 10-25 May. 



