- Minnesota Breeding Bird Distribution
- Breeding Habitat
- Population Abundance
- Literature Cited
A regular breeding resident and migrant. The Northern Parula was a common species during the Minnesota Breeding Bird Atlas (MNBBA).
Found exclusively in the forests of eastern North America with two broad populations, one in the northeastern and upper midwestern United States and Canada and the other in the southeastern United States (Figure 1). The highest densities occur in Nova Scotia and in northwestern Florida.
Assigned a Continental Concern Score of 8/20 by Partners in Flight.
Short to long-distance migrant that winters in southern Florida, the Caribbean, Mexico, and northern Central America.
Insects gleaned from foliage.
Nests at variable heights in trees, where it hollows out its nest within the epiphytic hanging moss.
Roberts (1932) stated the Northern Parula was “a summer resident throughout the northern coniferous forests, where it breeds as far south as northern Isanti County and as far west as Itasca Park and eastern Polk County.” He noted nesting activity in Becker (nest with eggs), Itasca (feeding young in nest), and Pine (“young of the year with parents”) Counties, as well as at Cass Lake (feeding young) and Itasca Park (feeding young). Descriptions within these areas indicate it was a common species. For instance, Roberts described it as “by no means uncommon” at Lake Itasca in the summer of 1902,” “the commonest warbler around Gull Lake, Crow Wing County, nesting in tamarack and spruce swamps,” “at Cass Lake, in June and July, 1916, a field party from the University Museum found it fairly common and feeding young out of the nest,” “fairly common in northern Itasca County in June 1923,” and summarizes “it may be detected in almost every suitable locality by the sharp-eyed and quick-eared observer.” The latter suggested the species was easily overlooked because it can be difficult to find foraging or singing in the trees and because observers are potentially unaware of its song.
Green and Janssen (1975) described the breeding distribution of the Northern Parula as primarily in the northeastern and north-central regions of the state. They emphasized that it was sparse in the northern portions of the north-central region and concur with Roberts that its western distribution is limited to central Polk County. Confirmed or inferred nesting beyond those reported by Roberts included Aitkin, Cook, Crow Wing, Hubbard, Lake, and St. Louis Counties. Several years later, Janssen (1987) documented confirmed nests in 5 counties since 1970: Cass, Clearwater, Cook, Hubbard, and Lake. He also emphasized that the species’ distribution in the northwestern portion of the state was not well known. In 1998, Hertzel and Janssen added no additional nesting records for this species confirmed since 1970.
The Minnesota Biological Survey included 524 breeding season locations and largely confirmed the breeding distribution previously described (Minnesota Department of Natural Resources 2017). They also confirmed the sparseness of the species in the northwestern region and included no locations from that region. They recorded many locations from Becker and Mahnomen Counties in western Minnesota, plus two more “southerly” locations in Carlton County and one location in Pine County near the Wisconsin border.
The MNBBA included 1,388 breeding records and confirmed the difficulty in finding nests of this species. Only 16 blocks were identified with confirmed nesting; a meager 2.4% (16 of 676) of all the blocks where breeding evidence was detected (Figures 2 and 3; Table 1). This is partly due to the patchy nature of the Northern Parula’s breeding habitat and the difficulty of definitively observing the species in a nest placed high in a tree covered in moss. The Northern Parula was recorded in 14.3% (676 of 4,735) of all blocks and in 16.9% (396 of 2,337) of the priority blocks. The MNBBA confirmed nesting of the Northern Parula in five counties: Aitkin, Cook, Lake, Itasca, and St. Louis Counties. Its distribution was very limited in the northwest and western regions, confirming Janssen’s suspicions. No observations were made in Polk County, where Roberts had reported its presence, but probable nesting was recorded in Becker County as well as several possible records in the “northwest angle” in Lake of the Woods County. In addition, possible nesting was identified in northeastern Morrison County, and two possible nesting detections were recorded in Pine County.
The predicted probability map based on MNBBA point counts indicates the primary distribution of the Northern Parula is in the extreme northeastern regions of Minnesota, especially in Cook County (Figure 4). Smaller, isolated populations are also predicted across much of northern and north-central Minnesota as far west as Becker and Otter Tail Counties and northwest to eastern Roseau County.
Roberts described the breeding distribution as far south as Isanti County and as far west as Polk County, so it appears the breeding range of this species has retracted since the early 1900s. This is likely due to reductions in forested habitat, especially riparian floodplain forests with suitable hanging moss for nesting. Breeding bird atlas results in Wisconsin (Cutright et al. 2006) indicated a similar pattern of range contraction due to apparent habitat loss. However, Chartier et al. (2013) in Michigan indicated the species had increased and expanded its range from its first atlas of 1983–1988 to its second atlas of 2002–2008. Results between the first and second atlases in Ontario also suggest an increase in Northern Parula populations, but Cadman et al. (2007) was cautious about the validity of the increase because of the lack of confirmation from the Ontario Breeding Bird Survey roadside counts.
Moldenhauer and Regelski (2012), in their review of the Northern Parula in North America, stated this species had largely been extirpated or reduced in numbers as a nesting species in several northeastern states. These range contractions were purportedly due to air pollution and limited growth of epiphytes that the species uses for nesting. They also point out that habitat loss in southern Michigan and Wisconsin primarily due to agricultural and urbanization expansion had severely reduced available habitat in those states. Range expansions, however, were reported in Tennessee and North Carolina, plus recolonization of New York State was reported from 1985 to 2005.
Overall, it is difficult to draw firm conclusions regarding changes in the distribution of the Northern Parula in Minnesota. Roberts (1932) only reported the species as a migrant in southern Minnesota and suggested its breeding range was limited south to Isanti County. Therefore, its breeding distribution is likely similar to the past, but the ability of early explorers to identify the species and its patchy nesting requirements in epiphytic moss may have rendered it easily overlooked. Cadman et al. (1987) also suggested the species is very easily overlooked because of its quiet song, especially when heard among a chorus of other actively singing birds.
*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.