120 



NORTH AMERICAN FAUNA 73 



Migration: Uncommon migrant throughout the Valley. Spring migrants 

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

 10-15 May. Peak spring migration through the Valley occurs 10-25 May. 

 During late July this species becomes very secretive and is not regularly en- 

 countered. Peak fall migration apparently occurs 15-30 August and de- 

 parture 20-30 September. 



Nesting Season Distribution: Uncommon nesting species throughout the 

 Valley. Jackson (1943) found this species "fairly common" at St. Croix Falls 

 and heard it occasionally at Danbury (Burnett County) in 1919. Breeding 

 Bird Survey data (Table 5) show a fairly uniform breeding density through- 

 out the Western Upland and Central Plain. The greatest abundance appar- 

 ently occurs in the Northern Highland. In Minnesota, however. Green and 

 Janssen (1975) consider it most common south of the latitude occupied by 

 the Twin Cities. Goddard (1972) reported a density of 2.1 pairs per 40 ha in 

 the Kinnickinnic River Valley, Pierce County. 



Habitat: In the Western Upland, the wood thrush is most common in 

 mature Southern Deciduous Forest and Lowland Deciduous Forest. Breed- 

 ing pairs in the Central Plain are most commonly encountered in mesic 

 Northern Hardwood Forest. In the Northern Highland, this species uses 

 Northern Hardwood Forest and is occasionally found in Lowland Coniferous 

 Forest. In all instances, wood thrushes appear to select woodlands with a 

 closed canopy of mature trees. 



Hermit Thrush (Catharus guttatus) 

 Status: Regular migrant and nesting species. 



Migration: Common migrant throughout the Valley. The hermit thrush is 

 the first of the Catharus thrushes to arrive in spring. The first migrants 

 arrive in the Western Upland 5-10 April (earliest— 31 March 1967, Wash- 

 ington County) and reach the Northern Highland 10-15 April. Peak spring 

 migration occurs 15-25 April and departure from nonbreeding areas occurs 

 by 10 May. Fall migration begins in late August. Peak abundance occurs 

 25 September to 15 October and departure by 1 November (latest— 5 No- 

 vember 1975). 



Nesting Season Distribution: Fairly common nesting species in the North- 

 ern Highland, rare and local in the Central Plain (Table 5). Confirmed nest 

 records exist for Douglas and Pine counties, and nesting is inferred in Bur- 

 nett and Polk counties. 



Habitat: This species is characteristic of wet coniferous-deciduous forests in 

 the Northern Highland. Important among these are Lowland Coniferous 

 Forest, Black Spruce-Tamarack Bogs, and low areas of Northern Hardwood 

 Forest. Breeding pairs also use drier portions of Jack Pine Barrens through- 

 out the Northern Highland. 



Swainson's Thrush {Catharus ustulatus) 



Status: Regular migrant and probable nesting species. 



