- Minnesota Breeding Bird Distribution
- Breeding Habitat
- Population Abundance
- Literature Cited
A regular breeding resident and migrant; the Canada Warbler was common during the Minnesota Breeding Bird Atlas (MNBBA).
Restricted to the Canadian boreal forest, from British Columbia east to the Maritime Provinces, and to the northern forests of the Great Lakes, New England, and the Appalachian Mountains. The core of the species’ breeding range is in northeastern Minnesota and southwestern Ontario (Figure 1).
Assigned a Continental Concern Score of 14/20 and designated a Yellow Watch List species by Partners in Flight.
A long-distance migrant; winters are spent in northern South America.
Insects captured by fly-catching, foliage gleaning, hover gleaning, and ground gleaning.
An open-cup nest located on or near the ground in dense undergrowth.
The Canada Warbler is an inhabitant of Minnesota’s northern forests. Roberts (1932) described the species’ summer distribution as stretching as far south as northeastern Pine and southern Mille Lacs Counties and as far west as Itasca State Park and Lake of the Woods County. Roberts and other contributors described the species as relatively common in a number of localities, including the North Shore of Lake Superior, at Lake Vermilion, along the Iron Range in northern St. Louis County, and at Leech Lake and Cass Lake. It was described as regular but not common north of Deer River in Itasca County. It was, Roberts wrote, “most numerous in the far-northern part of the state.” One report noted that the Canada Warbler was second only to the Mourning Warbler in abundance in Cook County. The species’ abundance declined, however, as one moved farther west. Although Roberts himself spent several summers working at Itasca State Park, he found only 1 male, in June 1917. The warbler was abundant in some localities, but breeding was confirmed only in Cass County (nest with eggs), Lake of the Woods County (feeding young), and at Mille Lacs Lake (feeding young) and Cass Lake (feeding young).
Roberts devoted much of the Canada Warbler account to his personal lament regarding the species’ name:
This charming little bird, with its beautiful necklace of black pendants, is surely deserving of a less prosaic name than that with which it has been inflicted. Canada Warbler, it is true, indicates plainly enough that the summer home of this bird is chiefly to the north of the United States, but this applies with no more force to this species than to many others of its kind. . . . Let us hope there may be evolved appropriate common names, descriptive enough to really mean something distinctive.
He gave as an example a name others had proposed for the species, “Necklaced Warbler.” Needless to say, the name Canada Warbler has remained.
In 1975 Green and Janssen added confirmed nesting reports from Beltrami, Cook, Lake, and St. Louis Counties and an inferred nesting report in Clearwater County. A few years later Janssen (1987) noted 2 summer reports of Canada Warblers at the Cedar Creek Ecosystem Science Reserve in Anoka County from June 1978 and June 1980. Although the species is one of the latest spring migrants, arriving from early May to mid-June (Janssen 1987), each of these observations was in late June: June 23 and 30, 1978, and June 20, 1980 (Bardon 1998). The species’ status in the county, however, would remain unclear for nearly 20 years. Janssen (1987) also included a state distribution map that identified 4 counties where nesting had been confirmed since 1970: Clearwater, Cook, Hubbard, and Lake. Hertzel and Janssen’s updated map published in 1998 still identified only 4 counties with confirmed nesting.
In the interim, the Minnesota Biological Survey reported 447 breeding season locations documented during the course of fieldwork. The overwhelming majority of records were from eastern St. Louis County east through Cook County. To the south, survey staff also observed the species in east-central Pine County and in northern Mille Lacs County; to the west they observed it in southern Clearwater, western Mahnomen, and western Becker Counties (Minnesota Department of Natural Resources 2016).
Then, in June 1997 and 1998, further evidence of the species’ status in east-central Minnesota was gathered. In both years, Karl Bardon documented 2 males on territory at the Boot Lake Scientific and Natural Area in Anoka County. Although he repeatedly saw 1 male carrying food in 1997, he could not locate a female or a nest. In 1998, however, he was successful in locating a pair of Canada Warblers and a nest with 5 young on the Falls Creek Scientific and Natural Area in northeastern Washington County. Both of these sites, he noted, as well as the Cedar Creek Ecosystem Science Reserve, represent outposts of the northern boreal forest ecosystem and support a suite of other northern forest species, including Winter Wren, Nashville Warbler, and Common Raven (Bardon 1998). Several Canada Warblers continued to be found on territory in Anoka and Washington Counties during the 1999, 2000, and 2003 summer breeding seasons (Minnesota Ornithologists’ Union 2017).
The MNBBA further confirmed the species’ known breeding range in the state, with a few new reports outside of the traditional northern forest region. Participants reported 1,059 Canada Warbler detections in 10.3% (486/4,736) of the surveyed atlas blocks and in 11.5% (268/2,337) of the priority blocks. Breeding was confirmed in 33 blocks (Figures 2 and 3; Table 1). Once again, the majority of reports were located from eastern St. Louis County and farther east through Cook County. The MNBBA documented possible records outside of the species’ traditional breeding range, in Marshall, Pennington, and Roseau Counties, and an observed record in Murphy-Hanrehan Park Reserve in Scott and Dakota Counties. The latter record, submitted by Bruce Fall, was a singing male observed on June 14, 2009; the bird repeatedly sung for more than 30 minutes. Unfortunately, there were no reports during the atlas from either Anoka or Washington Counties. Canada Warblers were reported from 18 of Minnesota’s 87 counties (1 record straddled 2 counties: Scott and Dakota) and were confirmed breeding in 6 counties: Beltrami, Cass, Cook, Itasca, Lake, and St. Louis. All but Cook and Lake were additions to the list published by Hertzel and Janssen (1998).
The MNBBA predicted distribution map predicts the highest breeding densities are primarily limited to a narrow band that stretches across northern St. Louis, Lake, and Cook Counties; moderate breeding densities occur as far south as Pine and northwestern Morrison Counties and as far west as eastern Becker, southeastern Mahnomen, and southern Clearwater Counties. Breeding densities decline rapidly beyond the boundaries of the Laurentian Mixed Forest Province (Figure 4).
Overall, the Canada Warbler’s breeding distribution has changed very little in the past 100 years. Reports outside of the Laurentian Mixed Forest Province indicated that birds occasionally find appropriate habitat in sites farther south and in the far northwest, but such occurrences are not common. The core of the species’ range is in the extensive forest landscape of northeastern Minnesota.
Elsewhere there have been few wide-scale changes in the Canada Warbler’s breeding range in the past 100 years. Forest clearing and development have resulted in some range retractions, such as in southern Michigan and eastern Pennsylvania. Meanwhile, in areas of New England, where forest cover is increasing, populations appear to be more widely distributed (Reitsma et al. 2009).
*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.