Northern Prairie Wildlife Research Center
Status: Regular migrant and nesting species.
Migration: Uncommon and local migrant restricted primarily to the Western Upland. Spring migrants arrive 1-5 May and are most conspicuous after 15 May. Fall migration apparently begins in late July with dispersal of family groups. This species is most common during the fall 1-15 August and departure occurs by 25 August (latest-6 September 1975, Washington County).
Nesting Season Distribution: Uncommon and local nesting species in the Western Upland. Occasional summer records at St. Croix Falls, Polk County, suggest possible nesting. The observations by Breckenridge (in Roberts 1932) and Maurer (1970) of nests at Marine-on-St. Croix are probably the northernmost documented records in the Valley. Breckenridge reported two adults, but no young, at Taylor's Falls, Chisago County, on 11 August 1938 (Erickson and Upson 1938). The area of greatest abundance is restricted to the lower St. Croix River and its major tributaries from Stillwater, Washington County, south to its confluence with the Mississippi River.
The status of this species as a nesting bird in the Valley is apparently changing. Robbins (1963) suggested that as of 1962 blue-gray gnatcatchers "may not be counted on to be present every year" at Hudson, St. Croix County. Since first observing nesting pairs along the Willow River at Hudson in 1973, the number of pairs on one site has risen from 7 in 1973 to 17 in 1978. Expansion of this species along major St. Croix River tributaries in Wisconsin is also evident. During 1976 and 1977, breeding pairs were located along the Kinnickinnic River near Roberts, St. Croix County (Sec. 11, T. 28 N., R. 18 W.), along the Willow River near Jewett, St. Croix County (Sec. 4, T. 30 N., R. 17 W.), and along the Apple River near Amery, Polk County (Sec. 8, T. 32 N., R. 17 W.). Expansion along streams that are tributary to the St. Croix River in Washington County has also been observed.
Habitat: Characteristic species of mature tracts of Lowland Deciduous Forest along the St. Croix and its tributaries. Several breeding pairs located along the Lower Kinnickinnic River, Pierce County, in 1976 were using medium-aged Southern Deciduous Forest that was dominated by white oak and Hill's oak. The territories occupied by five pairs in 1976 and seven pairs in 1977 along the Willow River were associated with sapling cottonwood and green ash in the Lowland Forest. Three nests were placed from 2.1 to 6.1 m above the ground in young green ash trees.
Status: Regular migrant and winter resident.
Migration: Fairly common migrant throughout the Valley. Spring migrants arrive in the Western Upland 15-25 March, reaching the Northern Highland 25-30 March. Peak abundance through the Valley occurs 5-25 April and departure by 15 May. Green and Janssen (1975) stated that the St Croix River Valley can be included in this species' breeding range in Minnesota, although there are no breeding records to support this. Fall migrants arrive in the Northern Highland in mid-September, reaching the Western Upland 25 September to 1 October. Peak fall abundance occurs 15 October to 1 November and most have departed by 1 December.
Winter: Uncommon to rare and local winter resident in the Western Upland, casual in the Northern Highland where several late December records have been obtained.
Habitat: During migration and winter, this species is most commonly observed in coniferous communities and occasionally in Lowland Deciduous Forest. Most important among coniferous habitats are Pine Plantations and Lowland Coniferous Forest dominated by black spruce, balsam fir, and hemlock.
Status: Regular migrant, casual summer and early winter resident.
Migration: Common spring and fall migrant throughout the Valley. Spring migrants arrive in the Western Upland 5-10 April, reaching the Northern Highland by 15 April. Peak abundance occurs 1-10 May and departure by 25 May. A female collected at St. Croix Falls, Polk County, on 22 May 1919, was considered a migrant (Jackson 1943). Fall migrants arrive in the Northern Highland 1-10 September, reaching the Western Upland about 10 September (earliest-23 August 1963, St. Croix County). Peak fall abundance occurs 25 September to 10 October and departure by 30 October.
Nesting Season Distribution: There are no documented nest records in the Valley. Green and Janssen (1975) showed that the breeding range of this species in Minnesota extended south to the northern border of Pine County. On 20 and 21 June 1976, I observed two singing male ruby-crowned kinglets along the St. Croix River in Douglas County (Sec. 24, T. 43 N., R. 14 W.). Although the behavior of these birds suggested nesting, I failed to observe nests or young.
Winter: Casual early winter resident in the Western Upland, usually observed during the CBC period. The latest observations are two birds on the Afton CBC 1 January 1976.
Habitat: During migration, this species uses a wide range of both deciduous and coniferous communities. During these periods, ruby-crowned kinglets appear to prefer brushy communities including Deciduous Clear Cuts. The singing males that I recorded in Douglas County were in an extensive Lowland Coniferous Forest dominated by black spruce, balsam fir, and yellow birch.