- Minnesota Breeding Bird Distribution
- Breeding Habitat
- Population Abundance
- Literature Cited
A regular breeding resident and migrant. The Tennessee Warbler was uncommon during the Minnesota Breeding Bird Atlas (MNBBA).
Found in a narrow band across Canada from southern Newfoundland and Labrador to British Columbia, the southern Northwest Territories, and southern Yukon Territory, and in the northern portions of the upper Midwest and in the northern New England states (Figure 1). The highest densities have been recorded in eastern Quebec and from northern Manitoba to northern British Columbia.
Assigned a Continental Concern Score of 7/20 by Partners in Flight.
Long-distance migrant that spends the winter in the Caribbean, Central America, and northwestern South America.
Arthropods that are gleaned from foliage, especially spruce budworm caterpillars.
Cup nest on the ground, usually hidden near the base of a shrub or hidden in Sphagnum moss.
Historically described by Roberts (1932) as “undoubtedly breeding in the northern part of Minnesota, as it has been found in limited numbers in the nesting-season from Lake Superior west to eastern Marshall County and south to Cass Lake.” Roberts (1932) reported “no nests or very young” had been found in Minnesota during his tenure, but he includes many locations where the Tennessee Warbler was observed or heard singing during the breeding season. These locations included the counties of Cass, Cook, Lake, Marshall, and St. Louis. Roberts dismissed a nest found by Hatch (1892) at Lake Minnetonka in June 1881 as an identification error.
More than 40 years later, Green and Janssen (1975) described a similar distribution for the Tennessee Warbler as a breeding resident “in northeastern and north central regions as far south as Duluth and Itasca State Park.” They emphasized the species was scarce through most of this area except “along the Canadian border in Cook County, northern Lake County, and northern St. Louis County.” They only reported confirmed nesting from Lake County but inferred nesting from Clearwater, Cook, and St. Louis Counties.
A few years later, Eckert (1983) described the Tennessee Warbler as rare and local during the breeding season. Janssen (1987) modified the breeding distribution of Green and Janssen to exclude northern Aitkin County, most of Itasca County, and both Cass and Marshall Counties. He suggested the breeding range extended into northern Hubbard County. Janssen did not report any confirmed nests, but Hertzel and Janssen (1998) added St. Louis County to the list of counties where nesting has been confirmed since 1970.
During extensive county surveys, the Minnesota Biological Survey recorded 163 breeding season locations of the Tennessee Warbler (Minnesota Department of Natural Resources 2017). These locations included many in Cook County and northern St. Louis County and a few in western Lake County. Additional observations included one location in southern Clearwater County and two in southern Beltrami County. The breeding distributions of these locations likely coincided with where spruce budworm (Choristoneura fumiferana) outbreaks occurred at the time of the breeding counts.
The MNBBA included a total of 298 breeding season records. Nesting was confirmed in St. Louis and Lake Counties, probable nesting in Cook and Roseau Counties, and possible nesting in Aitkin, Beltrami, Cass, Kittson, Koochiching, Itasca, Lake of the Woods, and Marshall Counties (Figure 2). A total of 3.8% (179/4,735) of all blocks sampled and 3.9% (90/2,337) of priority blocks included breeding evidence (Figure 3; Table 1). The spatial pattern of the Tennessee Warbler’s breeding distribution from the MNBBA was similar to that described by Roberts in 1932 and by Green and Janssen in 1975. The bulk of the records were located as previously described, largely in the northeastern counties of Cook, Lake, and St. Louis.
The probability map based on MNBBA point counts predicted highest densities of the Tennessee Warbler in northeastern and northern Minnesota (Figure 4). This was especially true for Cook, Koochiching, Lake, and St. Louis Counties.
Rimmer and McFarland (2012) reviewed the North American distribution of the Tennessee Warbler and concluded that no significant changes had been documented for this species since 1966, when the federal Breeding Bird Survey (BBS) was initiated. They underscored that short-term fluctuations in local distributions were dictated by insect outbreaks, especially by the spruce budworm.
The Tennessee Warbler is a rare species in Wisconsin, with only one confirmed nesting record found in 1977 on Oak Island in the Apostle Islands (Cutright et al. 2006). No nests were found during Wisconsin’s breeding bird alas of 1995–2000. In Michigan this species is rare, and no differences in its abundance were found between its first atlas (1983–1988) and its second atlas (2002–2008) (Chartier et al. 2013).
*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.