- Minnesota Breeding Bird Distribution
- Breeding Habitat
- Population Abundance
- Literature Cited
A regular breeding resident and migrant; the Philadelphia Vireo was rare during the Minnesota Breeding Bird Atlas (MNBBA).
The Philadelphia Vireo is primarily found distributed across a narrow band in Canada from Labrador to northwestern Alberta. Its breeding range also extends southward into northern portions of Minnesota, Wisconsin, and Michigan (Figure 1). Populations are generally low, but the highest densities have been observed in parts of Ontario and Quebec.
Assigned a Continental Concern Score of 10/20 by Partners in Flight and designated a Species in Greatest Conservation Need by the Minnesota Department of Natural Resources.
Long-distance migrant that over-winters in southern Central America.
Small arthropods gleaned from foliage.
Pensile cup nest suspended in a fork usually high in a tree.
Simply described by Roberts (1932) as “no positive breeding records for Minnesota, but it seems probable that it will be found nesting in the northern part of the state.” Even breeding observations appeared to be limited because he only lists Hibbing in St. Louis County and the city of Pembina in North Dakota as locations where individuals were collected. The latter was a citation in 1873 where he quotes Coues as saying that the species “undoubtedly breeds about Pembina, in the heavy timber of the river bottom.”
More than forty years later, Green and Janssen (1975) emphasized its primary distribution in northeastern Minnesota as far south as Duluth. They found two breeding records with young being fed in eastern Becker County (1961) and a bird banded on June 16, 1966, in Little Falls, Morrison County (1966). Besides “inferred” nesting in Becker County, they also list confirmed nesting in Lake and St. Louis Counties. A few years later, Janssen (1987) provided a more restrictive distribution primarily in the northern tier of counties from Lake of the Woods County and northern Beltrami County east to northern Cook County. Janssen (1987) and Hertzel and Janssen (1998) only included confirmed nesting in Cook County since 1970. Both Green and Janssen (1975) and Janssen (1987) emphasized that the species was scarce throughout its breeding range, but identification is complicated because of its similarity to the substantially more common Red-eyed Vireo.
The Minnesota Biological Survey (MBS) included only 19 breeding season locations; all were found in Cook, Lake, and St. Louis Counties, except for one location in central Becker County (Minnesota Department of Natural Resources 2016).
The MNBBA included a total of 32 records in 22 blocks. Similar to the observations by the MBS, most detections were in northeastern Minnesota, including Cook, Lake, and St. Louis Counties, plus one in northeastern Becker County (Figure 2). There were three confirmed nesting observations: two in St. Louis County and one in Cook County. Probable nesting was also limited to one in St. Louis County; possible nesting observations were scattered throughout Cook County, southern and central Lake County, and in northern St. Louis County (Figure 3; Table 1). Note that all MNBBA records of the Philadelphia Vireo were carefully reviewed before acceptance because of the notorious difficulty in identifying this species.
The difficulty in the identification of the Philadelphia Vireo is well known. For instance, Moskoff and Robinson (2011) emphasized that its “obscurity” is related to the overwhelming abundance of the Red-eyed Vireo. The Philadelphia Vireo is very easy to overlook even by experienced observers. The first nesting in Wisconsin was not detected until 1997 in Bayfield County during Wisconsin’s first breeding bird atlas (Cutright et al. 2006). In addition, another confirmed nesting was identified in Pierce County in 1999 near the St. Croix River, adjacent to Washington County in Minnesota. Because of these complications in detection, no information on any historical changes in its breeding distribution is available.
The Philadelphia Vireo is well represented by nesting activity in the southeastern region of Manitoba (Bird Studies Canada 2017) and by high relative abundance in the western regions of Ontario, areas that are adjacent and north of Cook and Lake Counties (Cadman et al. 2007). Observations of vireos in June and early July should be scrutinized throughout the forested areas of Minnesota and pictures of any observations are important sources of confirmation.
*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.