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NORTH AMERICAN FAUNA 73 



used by the preceding species. Nests in Polk County were in Alder Thicket 

 habitat where speckled alder was the predominant shrub species. Elsewhere, 

 breeding pairs have been recorded in Northern Hardwood Forest, Black 

 Spruce-Tamarack Bogs, and Deciduous Clear Cuts. 



Least Flycatcher {Empidonax minimus) 

 Status: Regular migrant and nesting species. 



Migration: Common to locally abundant migrant in all regions, reaching 

 largest numbers in the Central Plain and Northern Highland. Spring 

 migrants arrive in the Western Upland 1-5 May and the Northern Highland 

 by 10 May. Peak abundance occurs 15 May in the Western Upland to 

 20 May in the north. Fall migration begins in early August. Peak fall migra- 

 tion occurs 20 August to 1 September in the north and 25 August to 5 Sep- 

 tember elsewhere. Departure from the Northern Highland occurs 10-15 Sep- 

 tember and elsewhere by 30 September (latest— 5 October 1974, St. Croix 

 County). 



Nesting Season Distribution: Common to locally abundant nesting species 

 in all regions. Goddard (1972) reported a breeding density of 8.1 pairs per 

 40 ha in the Kinnickinnic River Valley, Pierce County. Confirmed nesting 

 records exist only for Polk County; inferred nesting has been documented in 

 all other counties. Breeding Bird Survey data (Table 3) indicate that least 

 flycatcher breeding populations apparently increase in abundance moving 

 northward through the Valley, reaching peak density in the Northern High- 

 land. Jackson (1942) reported that the least flycatcher was the most abun- 

 dant flycatcher in Polk and Burnett counties. 



Habitat: Primarily an edge species; nesting season least flycatchers are 

 usually recorded in a variety of habitat types. Western Upland breeding 

 birds are usually associated with medium-aged Southern Deciduous Forest 

 and mature Lowland Deciduous Forest. Central Plain and Northern High- 

 land birds are typically recorded in mature Northern Hardwood Forest, 

 Deciduous Clear Cut, and mixed coniferous-deciduous forest. In the Jack 

 Pine Barren regions of the Central Plain, breeding pairs are usually asso- 

 ciated with deciduous habitats along streams rather than jack pines. 



Eastern Wood Pewee [Contopus virens) 

 Status: Regular migrant and nesting species. 



Migration: Eastern wood pewees are among the latest arriving flycatchers 

 in this region, usually not observed until after 15 May (earliest— 26 April 

 1974, Burnett County), and peak migration occurs 20-30 May. Fall migra- 

 tion begins about 5 August in the Northern Highland and 15 August else- 

 where. Peak migration occurs 20 August to 1 September and departure by 

 25 September (latest— 27 September 1976, Washington County). 



Nesting Season Distribution: Fairly common nesting species in all regions of 

 the Valley. Confirmed nesting has been documented in St. Croix and 



