- Minnesota Breeding Bird Distribution
- Breeding Habitat
- Population Abundance
- Literature Cited
A regular breeding resident and migrant in Minnesota. Black-throated Blue Warblers were uncommon during the Minnesota Breeding Bird Atlas (MNBBA).
Found in northeastern and sparsely in upper midwestern North America from Nova Scotia to western Ontario and Minnesota and south in the Appalachian Mountains to northern Georgia (Figure 1). Patches of highest densities are found scattered in Ontario, Nova Scotia, and New York State, as well as in western North Carolina and eastern Tennessee.
Continental Concern Score of 7/20 by Partners in Flight; identified as a Species in Greatest Conservation Need in Minnesota by the Minnesota Department of Natural Resources.
Long-distance migrant, this species primarily overwinters in the Caribbean and in Central America.
Insects, spiders, and other arthropods that are gleaned primarily from deciduous shrubs and trees.
Cup nest usually low or close to the ground in deciduous or coniferous shrubs or saplings.
Described as one of the rarest breeding warblers in the state by Roberts (1932), the Black-throated Blue Warbler was primarily found as far south as Pine County and west to Itasca State Park. He suggested Minnesota was the northwestern limit of its breeding range in North America, with few observations from Manitoba. Nesting was reported from Cass Lake (nest with eggs) and Cook (adults with young and two pairs with young) County. In Roberts 1936 revision, he added three additional breeding observations including a nest with four eggs at Loon Lake in Cook County, a nest with four half-grown young at Lake Winnibigoshish in north-central Minnesota, and a “pair feeding 2 half-grown young” at Lake Vermilion in St. Louis County.
Roberts provided many personal accounts by observers from the late 1800s and early 1900s. He stated there were “early summer records, indicating nesting, for Pine, Mille Lacs, Aitkin, Itasca, northern St. Louis, Crow Wing, and Lake Counties, and Itasca Park.” He summarized that “the Black-throated Blue Warbler breeds sparingly throughout the evergreen forests of the state and may, perhaps, be fairly well-represented in the northeastern portion for some distance south of the Canadian boundary.”
More than 40 years later, Green and Janssen (1975) emphasized its breeding distribution as northeastern and north-central Minnesota but “scarce throughout most of this range except in Cook County.” They included confirmed nesting in Beltrami, Cass, and Cook Counties and inferred nesting in Clearwater and northern St. Louis Counties. Several years later, Janssen (1987) suggested a greatly restricted breeding range limited to Cook County and eastern Lake County. He stated the Black-throated Blue Warbler was “casual in the north-central region of Beltrami, Cass, and Clearwater Counties.” Both Janssen (1987) and Hertzel and Janssen (1998) only cite confirmed nesting in Cook and Lake Counties since 1970.
The Minnesota Biological Survey (MBS) recorded 288 breeding season locations for the Black-throated Blue Warbler (Minnesota Department of Natural Resources 2016). These locations were very extensive along the North Shore of Lake Superior from southeastern St. Louis to Lake and Cook Counties but were also relatively common in the northern portions of these counties. Additional potential breeding locations were from eastern Becker County, Cass County near Leech Lake, northern Mille Lacs County, and western Itasca County.
The MNBBA reported 317 records, most of which were concentrated in northern Cook, Lake, and St. Louis Counties, plus western Itasca County (Figure 2). The latter area roughly corresponds to the eastern region of the Chippewa Plains Ecological Subsection. Nesting was confirmed in Cook and Lake Counties. Probable nesting activity was recorded in southern Aitkin, northern Cass, western Itasca, and St. Louis Counties, and possible nesting in Beltrami County. Breeding observations were surprisingly sparse along the North Shore of Lake Superior compared with those from the MBS, except for southeastern Lake County and in Cook County. The species was only observed in 3.0% of the priority blocks (69/2,337) (Figure 3; Table 1).
The probability map for the Black-throated Blue Warbler predicted the species to be almost exclusively found in Cook and eastern Lake Counties (Figure 4). Some possible habitat is predicted to exist in other portions of the northeast, the north-central region, and east-central Minnesota. Overall the map is consistent with the suggestion above from Janssen that the Black-throated Blue Warbler is primarily found in Cook and Lake Counties.
Overall this species continues to be a relatively rare warbler in Minnesota, except for the extreme northeastern portion of the state and in western Itasca County. Scattered breeding observations may be expected in appropriate habitat throughout much of the Laurentian Mixed Forest Province. Observations in Wisconsin and Michigan (Cutright et al. 2006; Brewer et al. 1991) both suggested that the species’ breeding range had retracted northward with the clearing of forests and conversion to agriculture and urbanization over the past 100–150 years. The breeding bird atlas for Ontario (2001–2005) also indicated breeding populations along the northern shore of Lake Superior, with scattered observations extending to the extreme southwestern regions (Cadman et al. 2007). Manitoba’s breeding bird atlas (2010–2014) only recorded one possible nesting from the extreme southeastern portion of the state.
In their review of the Black-throated Blue Warbler in North America, Holmes et al. (2005) stated that the breeding habitat for this species shrank considerably with the clearing of mixed deciduous/coniferous forests in the northeastern United States in the seventeenth and eighteenth century. However, with the subsequent abandonment of farmland in the New England states, the species has increased again in the late nineteenth and twentieth century. The authors felt that the breeding habitat of the Black-throated Blue Warbler was more extensive now in the early twenty-first century than it was 100 to 150 years ago. There is little evidence that these changes have occurred in Minnesota because of the paucity of observations reported by Roberts from more southern locations in the state. However, its distribution may have retracted to some extent, because the MNBBA did not record it from as far west as Clearwater County, nor were there any observations from Pine County, where Roberts had reported it previously.
*Note that the definition of confirmed nesting of a species is different for Breeding Bird Atlas projects, including the definition used by the Minnesota Breeding Bird Atlas, compared with a more restrictive definition used by the Minnesota Ornithologists’ Union. For details see the Data Methods Section.