BIRDS OF THE ST. CROIX RIVER VALLEY 



139 



records in Minnesota are from "northern Pine County." I have obtained no 

 summer records of this bird within the Valley in Minnesota or Wisconsin. 

 However, during 5-30 June 1971, I regularly observed three pairs of black- 

 throated blue warblers in Bayfield County about 24 km east of Solon 

 Springs. These observations suggest that breeding black-throated blue 

 warblers may also occur in suitable habitat along the northern reaches of the 

 St. Croix River. 



Habitat: During migration, this warbler is most common in wet or mesic 

 deciduous forest sites. I have only one record from xeric Southern Deciduous 

 Forest that was dominated by red oak. Observations of black-throated blue 

 warblers during the breeding season in Bayfield County, Wisconsin, were in 

 extensive stands of mature maple-basswood-aspen forest. 



Yellow-nimped Warbler (Dendroica coronata) 



Status: Regular migrant and nesting species, occasional winter resident. 



Migration: Abundant migrant throughout the Valley. The yeUow-rumped 

 warbler is the most numerous warbler in this region. Spring migrants arrive 

 in the Western Upland about 5 April (earUest— 21 March 1975, Pierce 

 County; 24 March 1963, St. Croix County). Migrants reach the Northern 

 Highland 10-15 April. Peak spring migration through the Valley extends 

 from 20 April to 10 May. Departure from nonbreeding areas occurs by 

 15 May (latest— 24 May 1971, Washington County). Fall migration begins 

 in the Northern Highland 15-20 August; however, the first fall migrants do 

 not reach the Western Upland until 10 September. Peak fall migration 

 occurs 20 September to 5 October. Departure from the Northern Highland 

 occurs by 15 October; 1 November is the usual departure date elsewhere. 

 Occasional stragglers remain in the Western Upland through November. 

 Late dates include 30 November 1975, Pierce County and 3 December 1961, 

 St. Croix County. 



Nesting Season Distribution: Rare and local breeding bird, restricted pri- 

 marily to the Northern Highland. Green and Janssen (1975) showed that the 

 breeding range of this warbler extended into northwestern Pine County. 

 Jackson (1943) did not record breeding season yellow-rumped warblers in the 

 Valley during 1919. Breeding Bird Survey data (Table 6) show that a limited 

 number of yellow-rumped warblers occur along the route of the Minong BBS 

 transect in Douglas County. 



On 24 June 1974 and 11 June 1977, I recorded singing yellow-rumped 

 warblers along the St. Croix River in Sec. 23, T. 43 N., R. 14 W., Douglas 

 County, and one singing male was recorded along the St. Croix River in Pine 

 County at the U.S. Highway 77 crossing 4.8 km west of Danbury. Singing 

 and behavioral activities suggested nesting, although nests or young were 

 not observed. 



Winter: The only record of an overwintering yellow-rumped warbler is that 

 of one bird remaining at a feeder near River FaUs, St. Croix County, during 

 the 1960-61 winter (Faanes and Goddard 1976). Two additional early winter 

 records exist from the Afton CBC: 1 January 1970 (St. Croix County) and 



