BIRDS OF THE ST. CROIX RIVER VALLEY 



129 



Records: Five records exist during 13 May to 7 September: Polk County, 

 18 May 1974; Chisago County, 7 September 1968; and St. Croix County, 

 13 May 1964, 17 June to 21 July 1977, and 3 July 1963. The 1977 St. Croix 

 County record may have been a breeding pair. One male was observed 

 almost daily on territory 5.6 km east of New Richmond. The male was heard 

 singing and appeared to be defending a breeding territory. Attempts to 

 locate a nest or a mated female failed. 



Habitat: The 1977 observation was of a bird in second-growth Lowland 

 Deciduous Forest along the Willow River. 



Yellow-throated Vireo (Vireo flavifrons) 

 Status: Regular migrant and nesting species. 



Migration: Uncommon migrant in the Western Upland and Central Plain, 

 rare and local in the Northern Highland. Spring migrants arrive in the 

 Western Upland 5-10 May and the Northern Highland 10-15 May and are 

 well distributed 15-25 May. Fall migration begins about 15 August. Peak 

 movements occur 25 August to 10 September and departure 20-25 Sep- 

 tember. 



Nesting Season Distribution: Fairly common nesting species in the Western 

 Upland and Central Plain, uncommon and local in the Northern Highland. 

 Jackson (1943) recorded this species nesting at St. Croix Falls, Polk County; 

 however, he failed to obtain records elsewhere in northwestern Wisconsin. 

 Bernard (1967) considered this vireo an "uncommon to rare summer resi- 

 dent" in Douglas County. Nesting records have been obtained from Solon 

 Springs, which is at the northern limit of their range in Wisconsin. There are 

 several nest records for Chisago and Pine counties, the farthest north at St. 

 Croix State Park, Pine County (Sparkes 1953). Breeding Bird Survey data 

 (Table 6) indicate that the breeding population is fairly uniform throughout 

 the Valley. Goddard reported a density of 2.9 pairs per 40 ha in the Kin- 

 nickinnic River Valley, Pierce County. 



Habitat: A characteristic breeding bird of mature deciduous forests. During 

 the breeding season, this species is most commonly found in Northern Hard- 

 wood Forest and Lowland Deciduous Forest. Occasional breeding pairs are 

 recorded in residential habitats and in Lowland Coniferous Forest. 



Solitary Vireo (Vireo solitarius) 



Status: Regular migrant and nesting species. 



Migration: Uncommon to fairly common migrant throughout the Valley. 

 Spring migrants arrive in the Western Upland 1-5 May, reaching the North- 

 ern Highland by 10 May. Peak spring migration occurs 10-20 May and de- 

 parture from nonbreeding areas is by 30 May. Fall migration begins in the 

 Northern Highland in mid- August. The first migrants reach other regions 

 by 25 August. Peak fall migration occurs 10-20 September and departure 

 by 30 September (latest— 27 October 1970, Pine County). 



