- Minnesota Breeding Bird Distribution
- Breeding Habitat
- Population Abundance
- Literature Cited
A regular breeding resident and migrant. The Magnolia Warbler was common during the Minnesota Breeding Bird Atlas (MNBBA).
Found throughout the upper midwestern and northeastern United States and Canada and south in the Appalachian Mountains to Virginia. Also patchily distributed in the central and western provinces of Canada to British Columbia (Figure 1). High densities are observed in northeastern Minnesota, Ontario, Quebec, Labrador, and British Columbia.
Assigned a Continental Concern Score of 7/20 by Partners in Flight.
Long-distance migrant, overwinters from the southern United States, to Mexico and south in Central America to Panama, also throughout the Caribbean.
Arthropods gleaned from foliage.
Low to mid-canopy in coniferous trees near trunk, especially balsam fir and spruce.
Historically described as a common summer resident in the northern evergreen forests as far south as northern Mille Lacs County and west to Itasca State Park and eastern Marshall County (Roberts 1932). Roberts included nesting observations at Cass Lake (nest with one cowbird egg), Itasca Park (male feeding young out of the nest), Itasca County (nest with four young), and St. Louis County (feeding young out of the nest). The paucity of nesting observations was likely a consequence of limited coverage in the late 1800s and early 1900s in the northern coniferous forests. Roberts stated the Magnolia Warbler was “nowhere really abundant in Minnesota during the summer months,” though he found it “common about Island Lake, in northwestern Itasca County, in June 1923.” He considered it strictly a species of the “Canadian Zone.”
More than 40 years later, Green and Janssen (1975) expanded inferred or confirmed nesting to Aitkin, Cook, Hubbard, and Lake Counties, plus they emphasized the Magnolia Warbler was most numerous in the eastern parts of its range. A few years later, Janssen (1987) included confirmed nesting from 6 counties since 1970: Aitkin, Beltrami, Clearwater, Cook, Hubbard, and Lake Counties. He also defined the breeding range as south to central Carlton, southern Crow Wing, and Hubbard Counties and west to central Roseau County. Hertzel and Janssen in 1998 added no new confirmed nesting records to Janssen’s list since 1970.
Observations by the Minnesota Biological Survey (MBS) included 619 records of breeding season locations for the Magnolia Warbler (Minnesota Department of Natural Resources 2017). The MBS included locations from southeastern Roseau County, eastern Becker County, and northern Aitkin and Carlton Counties. However, as emphasized by Green and Janssen (1975) and Janssen (1987), the bulk of breeding observations are found in northern St. Louis and Lake Counties and throughout Cook County.
The MNBBA reported 1,683 records and clearly emphasized the major distribution of the Magnolia Warbler was found in the Laurentian Mixed Forest Ecological Province. Magnolias were especially common to abundant in eastern and northern St. Louis County, northern Lake County, and Cook County (Figure 2). The observations were comprised of probable nesting in western Roseau County and northern Lake of the Woods County, as well as possible nesting in northern Marshall, eastern Mahnomen, central Becker, and northern Pine Counties. Collectively, these records slightly expand the breeding range of this species to the northwest and western portions of Minnesota from that presented by Janssen (1987).
The MNBBA added no new confirmed nesting activity for the Magnolia Warbler in counties not previously reported. Confirmed nesting blocks only represented 3.4% (23 of 676) of all blocks where the species was detected (Figure 3; Table 1). Nests or observations of young are very difficult to find among the dense, young coniferous trees. Few observers have the patience or stealthy skills necessary to discover its nest.
The predicted probability map (Figure 4) also emphasizes the highest densities occur in the northeastern region of the state, especially northern Lake and Cook Counties, plus scattered high-density areas in St. Louis County. Low densities were predicted farther south, west, and to the northwest beyond where observations currently exist in Minnesota. However, MBS and MNBBA included breeding evidence as far west as Becker, Clearwater, and Roseau Counties and the Wisconsin Breeding Bird Atlas (Cutright et al. 2006) had probable breeding evidence for the Magnolia Warbler as far south as the extreme southwestern part of the state in Grant County. The Magnolia Warbler should be looked for in areas of dense, young conifers during the breeding season in many areas on the periphery of its current range.
In their review of the Magnolia Warbler in North America, Dunn and Hall (2010) identified range extensions southward in Ontario from 1985 to 2005. They also reported on range expansions in several New England states as forests regenerated following clearing in the 1800s and early 1900s. Some range contractions may have occurred in the western fringes of the species’ range in Minnesota because balsam fir and spruce have become less common in these areas.
Although the Wisconsin breeding bird atlas primarily found this species in coniferous forests in the northern tier of counties, it confirmed nesting in Pierce and Grant Counties (Cutright et al. 2006); these counties are far south of any breeding observations found in Minnesota. Whether this is due to more intense coverage in the latest atlas or to more appropriate habitat for the species on the Wisconsin side is unclear. More focused efforts in eastern and even southeastern forests of Minnesota may be warranted where suitable patches of young conifers exist.
*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.