- Minnesota Breeding Bird Distribution
- Breeding Habitat
- Population Abundance
- Literature Cited
A regular breeding resident and migrant in southern Minnesota; the Bell’s Vireo was a rare species during the Minnesota Breeding Bird Atlas (MNBBA).
The species’ breeding range stretches from northern Mexico, across southern Texas, Arizona, and New Mexico, and north through the lower Mississippi River valley and its tributaries. In the United States, the Bell’s Vireo reaches its highest breeding densities in southern Texas and southern Arizona (Figure 1).
Assigned a Continental Concern Score of 11/20 by Partners in Flight; officially classified as a Special Concern Species in Minnesota and designated a Species in Greatest Conservation Need by the Minnesota Department of Natural Resources. One subspecies, which occurs in southern California and northern Baja California, the Least Bell’s Vireo (Vireo bellii pusillus), is federally endangered.
A medium-distance Neotropical migrant that winters in Central America.
A foliage-gleaning insectivore that feeds on a variety of arthropods, especially spiders and caterpillars.
A hanging cup whose rim is secured into the fork of a horizontal branch of a small tree or shrub.
In Minnesota’s first comprehensive account of the state’s avifauna, Hatch (1892) described Bell’s Vireo as a “relatively common” summer resident, its favorite haunts being “our beautiful, sylvan lakes.” Forty years later, Roberts (1932) challenged that assertion:
The author’s long acquaintance with Dr. Hatch leads him to believe that this is one of several misconceptions that found their way into his writings, for no capable observer in the years that preceded the publication of the book or in the many years that have elapsed since has found anything to substantiate the statement. Extensive and careful search has several times been made through the southern part of the state without results.
Roberts could account for only 2 positive records of the species. The first was a nesting pair that he and his colleague Mr. Kilgore found in May 1927 “in a dense poplar thicket on the west side of the Fort Snelling Reservation.” The second was a well-documented sighting in Winona in August 1930 by a keen observer, Mrs. Bailey.
More than 20 years passed before a rather remarkable account of 6 nesting pairs in Winona County was documented by Brother Theodore in 1952 (Theodore 1952). All nesting pairs were found in the general vicinity of St. Mary’s College and the city of Winona. In the following years, records continued to accumulate, including another nesting record in Houston County in 1961 (Huber 1961). When Green and Janssen summarized the status of the species in 1975, they described its distribution as restricted to the Mississippi River corridor, from the Twin Cities south to the Iowa border. Their account also included an interesting summer record of a singing male in Rock County.
Several years later, when Janssen (1987) provided an update on the species, nesting had been confirmed in 2 additional counties, Ramsey and Olmsted. There also were new summer reports from the southwest corner of the state (Pipestone County) as well as from several southeastern counties.
When the Minnesota Biological Survey (MBS) was working in southern Minnesota in the 1990s, field staff reported 12 breeding season locations. These records further expanded the species’ range westward to Blue Earth, Dodge, Lyon, and Mower Counties (Minnesota Department of Natural Resources 2016). About the same time, other observers documented nesting in Blue Earth County at Minneopa State Park in 1990 and 1996 (Minnesota Ornithologists’ Union 2016).
In 1998, Hertzel and Janssen published an updated map delineating 6 counties where nesting had been confirmed since 1970: Blue Earth, Dakota, Olmsted, Ramsey, Wabasha, and Winona.
During the MNBBA, participants reported 32 Bell’s Vireo records from 0.5% (25/4,734) of the surveyed atlas blocks and from 0.5% (11/2,337) of the priority blocks. Breeding was confirmed in only 4 blocks (Figures 2 and 3; Table 1). The birds were observed in 15 of Minnesota’s 87 counties and were confirmed breeding in 3 counties: Dakota, Hennepin, and Rice (1 block straddled Hennepin and Dakota Counties). Most observations were within the greater Twin Cities metropolitan area, in Hennepin, Ramsey, Washington, and Dakota Counties. Records were also documented as far west as Kandiyohi and Watonwan Counties, and as far north as Sherburne and Chisago Counties (Figure 2).
The vireo’s range expansion in Minnesota is represented by a series of maps that depict the cumulative number of counties where they were reported during the summer seasons during three time periods: (1) in the 1960s, (2) from the 1960s through the 1980s, and (3) finally from the 1960s through the last year of the MNBBA, in 2013. As Figure 4 illustrates, over a period of 50 years Bell’s Vireo expanded its range to the north (as far as Chisago County) and to the west.
The species’ northward expansion appears to have occurred along two fronts. The primary one was along the Mississippi River valley into southeastern and east-central Minnesota. From there, the species expanded west to south-central Minnesota, including along the lower Minnesota River valley. The second front appears to have been northward from northwestern Iowa or southeastern South Dakota, likely along some of the smaller river valleys of the Prairie Coteau region.
Elsewhere, Bell’s Vireo also appears to have followed river corridors to expand along the northern periphery of its breeding range. The shrubby vegetation that dominates many floodplains provides ideal habitat for the species. Wisconsin documented its first Bell’s Vireo record in 1914 in south-central Wisconsin; today the species occurs as far north as the town of Prescott in Pierce County at the mouth of the St. Croix River as well as at sites along the floodplains of the Mississippi and Wisconsin rivers (Cutright et al. 2006). The first nesting in southern Ohio occurred in 1968; the state’s second atlas, conducted from 2006 to 2011, documented 20 records spread across the western half of the state (Rodewald et al. 2016). Farther west, the birds expanded more than 200 km along the Colorado River in Arizona in the latter half of the 20th century (Kus et al. 2010).
Factors responsible for the range expansion of this small, rather inconspicuous little vireo are not entirely clear. Improved coverage by skilled observers may be contributing to the changes, as well as habitat changes along river corridors that increase the growth of riparian shrubs (Kus et al. 2010).
*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.