- Minnesota Breeding Bird Distribution
- Breeding Habitat
- Population Abundance
- Literature Cited
A regular breeding resident and migrant that occurs in open forests throughout much of the state. The Warbling Vireo was a common species during the Minnesota Breeding Bird Atlas.
The breeding distribution of the Warbling Vireo ranges from southeastern Alaska, south across the southern regions of the Canadian Prairie Provinces and across much of the northern and central regions of the United States. It is absent across broad stretches of the southern United States. Farther west, the population extends south into western Mexico. Within North America, populations reach their highest breeding densities in British Columbia and in scattered regions of the western United States (Figure 1).
Assigned a Continental Concern Score of 8/20 by Partners in Flight.
A medium- to long-distance migrant that spends winters in western Mexico and northern Central America.
A foliage-gleaning insectivore.
A compact open-cup nest usually placed high within a deciduous tree or shrub and some distance from the tree trunk.
Roberts (1932) considered the Warbling Vireo to be a common species throughout much of Minnesota in the late 1800s and early 1900s. It was “most abundant in open woodlands, preferring small groves of poplars and elms, in orchards or on tree-bordered country roads, and is one of the common birds of city parks and shaded streets.” In the grasslands of southern and western Minnesota, “every grove and tree-claim has its quota of Warbling Vireos.” Roberts wrote at length about the species’ history in Minnesota’s northern forest region, documenting a long list of early explorers and naturalists, including himself, who failed to find the species in the region in the late 1800s. The earliest report was in 1902, when a single bird was encountered in the town of Walker, on the west side of Leech Lake. In the years that followed, reports began to document the species’ gradual appearance in small settlements and cleared areas as far north as Crow Wing, Itasca, Lake of the Woods, and Pine Counties. Roberts predicted that it would be only a matter of years before the Warbling Vireo would likely become a more common inhabitant of the north country. At the time of his publication, however, confirmed nesting reports (nests with eggs or young) were limited to just 6 counties south and west of the boreal forest region: Goodhue, Hennepin, Polk, Sherburne, Traverse, and Wright.
Indeed, more than 40 years later, Green and Janssen (1975) documented summer records for the Warbling Vireo from nearly every county in the state. Nevertheless, it remained rare in the far north-central and northeastern counties, where breeding records were virtually absent. A few years later, Janssen (1987) included a distribution map in his updated account that depicted the species as a breeding resident everywhere except the Arrowhead region north and east of Duluth and in much of Koochiching and eastern Itasca Counties. He identified 22 counties where nesting had been confirmed since 1970. Records indicated the species was most abundant in east-central and southeastern Minnesota. By 1998, Hertzel and Janssen had identified a total of 26 counties where nesting had been confirmed since 1970.
Beginning in the late 1980s, the Minnesota Biological Survey (MBS) documented 744 breeding season locations for the Warbling Vireo. Included were several records in St. Louis County and 1 along the North Shore of Lake Superior in Cook County. Elsewhere the species was relatively common in all but the most intensively cultivated regions of the Red River valley and the upper Minnesota River valley (Minnesota Department of Natural Resources 2016).
During the MNBBA, participants reported a total of 2,409 Warbling Vireo records in 34.2% (1,624/4,754) of the surveyed atlas blocks and in 47.1% (1,101/2,337) of the priority blocks. Breeding evidence was documented in 42 blocks (Figures 2 and 3; Table 1). The birds were reported from all but 2 of Minnesota’s 87 counties: Lake and Cook. Breeding was confirmed in 28 counties. Eighteen of the counties were additions to the list published by Hertzel and Janssen (1998), and most were located in western and southern Minnesota. Although the species was least common in the northeastern forests and north-central peatlands, it was reported throughout much of the remainder of the state, including the intensively cultivated regions of western and southern Minnesota.
The predicted distribution map for the Warbling Vireo suggests that the core of the species’ breeding range lies within west-central and northwestern Minnesota, from Lac qui Parle and Yellow Medicine Counties north to Kittson and Roseau Counties (Figure 4). Small pockets of relatively high breeding densities are found scattered throughout the Tallgrass Aspen Parklands Province. The open, park-like landscape of this region provides ideal habitat for this obscure little vireo. Outside of this core area, moderate densities can be found along the Mississippi River valley south of the Twin Cities and throughout central Minnesota. Relatively low breeding densities are predicted throughout much of the Laurentian Mixed Forest Province.
Roberts’s (1932) prediction that the Warbling Vireo would become a more common inhabitant of the north country was correct. This is especially true in the recreational communities near the cities of Brainerd, Grand Rapids, and Bemidji (Figure 2). It remains a rare species, however, in the densely forested landscape of Lake and Cook Counties and in the north-central landscapes dominated by extensive peatlands.
Elsewhere in its breeding range there have been few large-scale changes in the vireo’s distribution. This is attributed in part to the paucity of historic information on the species (Gardali and Ballard 2000). The vireo has expanded along the northern periphery of its’ breeding range in Quebec and Ontario, facilitated largely by forest clearing in the late 1800s and 1900s. Other Great Lakes states, including Wisconsin, Michigan, and Ohio, have seen little change in the species’ historic distribution (Gardali and Ballard 2000; Cutright et al. 2006; Chartier et al. 2013; Rodewald et al. 2016; Cadman et al. 2007). In Wisconsin, Robbins (1991) predicted the species would be negatively impacted by the loss of American elms to Dutch elm disease, but the species’ acceptance of a wide variety of habitats has enabled it to adapt to many regional landscape changes.
*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.