- Minnesota Breeding Bird Distribution
- Breeding Habitat
- Population Abundance
- Literature Cited
Regular breeding species and migrant in southern and central Minnesota; the Blue-gray Gnatcatcher was an uncommon species during the Minnesota Breeding Bird Atlas (MNBBA).
Broadly distributed across the southern and central United States, north to the Great Lakes and southern New England, the Blue-gray Gnatcatcher is largely absent from the Great Plains, though it may be found locally where suitable woodlands are present. In Canada, it is limited to southeastern Ontario and southwestern Quebec. It is also found year-round in Baja California, Florida, and Central America. The core of the species’ breeding range is in the southeastern United States (Figure 1).
Assigned a Continental Concern Score of 7/20 by Partners in Flight.
Breeding birds in the northern regions are long-distance migrants that winter primarily in Central America.
Insectivorous foliage gleaner that also sallies after flying insects and hovers above the foliage. Gnats are consumed but are not a significant component of their diet.
Tightly woven open-cup nest placed in a deciduous tree at variable heights.
Roberts (1932) gave only a brief account of the Blue-gray Gnatcatcher’s presence in Minnesota. He described it as a “southern species which reaches Minnesota in only very limited numbers.” Although a specimen had been collected as far west as Lake Shetek in Murray County in 1900, the bird was considered to be restricted to the Mississippi floodplain and its larger tributaries. “Apparently the northward extension of the Gnatcatcher’s range has followed the Mississippi River bottom-land, the Murray County bird probably veering off westward up the Des Moines River which begins in Lake Shetek.” Roberts himself had encountered the species only once, when he observed a pair near Minneapolis in 1931.
Although many accounts of the Blue-gray Gnatcatcher’s northward range expansion state that its first appearance in Minnesota occurred in the 1930s (e.g., Chartier et al. 2013; Kershner and Ellison 2012), the first documented record in Minnesota was a specimen collected in 1877 in Minneapolis (Roberts 1932). Then, in 1895, an account was published in The Auk by a local student, Walton Mitchell, describing 6 Blue-gray Gnatcatcher nests found in the general vicinity of St. Paul (5 specifically from West St. Paul in Dakota County) from 1892 to 1894! Nearly 30 years would pass until summer observations, although still rare, at least became more regular with each passing year (Roberts 1932). Other breeding evidence would come from Frontenac in Goodhue County, where a “family party” was observed for many years beginning in 1924, and from northern Washington County, where a brood of 3 young birds were being fed by an adult (1930).
The absence of Minnesota records for nearly 30 years, between the 1890s and the 1920s, is similar to the species’ pattern of range expansion in New England. The Blue-gray Gnatcatcher became a regular breeding species in eastern Pennsylvania and northern New Jersey following a major spring flight that was unprecedented in its size and scope in 1947 (Ellison 1993). That same year the species bred for the first time as far north as Connecticut (Saunders 1950). It is not unusual during such flights for some birds to overshoot their normal spring destination points. Often the birds make adjustments and return southward. But if conditions are suitable, a few may remain and breed far north of their normal range, as they did in Connecticut. Twenty years and many more major spring flights passed before the species became established as a regular breeding species in New England in the 1970s.
By 1975, Green and Janssen depicted the Blue-gray Gnatcatcher’s breeding distribution as stretching from those counties bordering the Mississippi River north to southeastern Stearns County in east-central Minnesota and along the St. Croix River in Washington County. Spring migration and summer observations beyond these counties suggested that the breeding range might extend even farther north and west. Breeding had been confirmed in 8 counties: Carver, Dakota, Hennepin, Houston, Fillmore, Sherburne, Stearns, and Winona.
Janssen (1987) described the species’ continued range expansion west along the Minnesota River valley and northwest along the Mississippi River valley. The species was now “well represented in Nicollet County and as far west as Lyon County (Garvin Park).” Confirmed nesting records were even reported from Rock County in extreme southwestern Minnesota (1981) and from Otter Tail County in west-central Minnesota (1979). In addition to these 2 counties, nesting had been confirmed in 15 other counties since 1970: Anoka, Brown, Dakota, Goodhue, Hennepin, Houston, Morrison, Nicollet, Olmsted, Ramsey, Renville, Scott, Sherburne, Wabasha, and Washington. Hertzel and Janssen (1998) later added 7 more counties to the list: Blue Earth, Clay, Hubbard, Kandiyohi, Mower, Stevens, and Winona.
Beginning in the late 1980s through 2014, the Minnesota Biological Survey (MBS) documented 362 Blue-gray Gnatcatcher breeding season locations, further expanding the species’ statewide distribution. Records were most abundant in southeastern Minnesota and along the Minnesota River valley as far as the upper reaches of the river in Lac qui Parle and Swift Counties. Records were common also north through Otter Tail County in the west and southern Aitkin County in the east. Scattered records from Mahnomen, Marshall, and the border of Pennington and Red Lake Counties documented the species’ occasional presence in northwestern Minnesota (Minnesota Department of Natural Resources 2017).
MNBBA participants reported 432 Blue-gray Gnatcatcher records from 6.3% (297/4,737) of the surveyed blocks and from 8.6% (200/2,337) of the priority blocks. Breeding was confirmed in 57 blocks (Figures 2 and 3; Table 1). The birds were reported in 54 of Minnesota’s 87 counties and were confirmed breeding in 28 counties. Twelve of the counties were additions to the list published by Hertzel and Janssen (1998): Benton, Carver, Cass, Crow Wing, Fillmore, Isanti, Jackson, Kanabec, McLeod, Pope, Rice, and Stearns. Gnatcatchers were firmly established from southern Cass and Crow Wing Counties south through east-central and southeastern Minnesota. They also occurred throughout the Minnesota River valley as far west as Yellow Medicine and Renville Counties. Scattered records were reported in south-central, southwestern, and west-central Minnesota, where they were particularly common along the prairie-forest border. The most northern record was a pair of birds sighted in East Grand Forks in western Polk County in late May 2013.
The MNBBA predicted distribution map (Figure 4) predicts the highest abundance of Blue-gray Gnatcatchers along the river valleys of southeastern Minnesota with scattered pockets of moderate abundance in counties just north of the Twin Cities and along the Minnesota River valley. Elsewhere very low densities are predicted to occur throughout the Eastern Broadleaf Forest Province as far north as Mahnomen County. Forest lands along floodplains in south-central Minnesota also provide suitable habitat, including the floodplains of the Blue Earth and Des Moines Rivers.
As noted earlier, the Blue-gray Gnatcatcher has been gradually expanding its range northward throughout the 20th century but most notably since the 1930s. Kershner and Ellison (2012) noted that even since the mid-1980s, its range has expanded nearly 314 km to the north. They attribute the change to a warming climate.
Wisconsin’s first breeding bird atlas, conducted from 1995 to 2000, documented a northward range extension of at least 50 km since the early 1990s. A few confirmed breeding records were found in scattered locations even farther north of its primary range including one in Douglas County which borders Lake Superior (Cutright et al. 2006). Michigan also documented a gradual expansion north into the northern Lower Peninsula (LP) and into the southern Upper Peninsula (UP). They noted that in the LP some of the range extension appears to follow the shorelines of Lake Michigan and Lake Huron, while farther inland it follows lakefront and riparian habitats. Expansion in the UP, however, appears to originate from populations in northeastern Wisconsin (Chartier et al. 2013). In South Dakota, Blue-gray Gnatcatchers were first reported breeding in 2004 in the southeastern corner of the state. The state’s second atlas (2009-2012) documented breeding populations in all corners of the state, including numerous records in the Black Hills (Drilling et al. 2016). Nearby in Canada, Blue-gray Gnatcatchers have not yet expanded north into Manitoba (Bird Studies Canada 2017), but they are well established in Ontario’s southern shield and are continuing to expand northward in that province (Cadman et al. 2007).
*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.