- Minnesota Breeding Bird Distribution
- Breeding Habitat
- Population Abundance
- Literature Cited
A regular breeding resident and migrant in Minnesota; an uncommon species during the Minnesota Breeding Bird Atlas (MNBBA).
The Henslow’s Sparrow has a very restricted breeding range that spans the grasslands of Minnesota south to eastern Kansas, east across the Ohio River valley and Great Lakes to southern Ontario, western New York, and Pennsylvania. Small populations occur along the mid-Atlantic coast from Maryland south to Virginia. Even within this limited distribution, populations may be localized in occurrence. The species is sparsely distributed throughout its breeding range; the highest breeding densities occur in north-central Missouri (Figure 1).
Assigned a Continental Concern Score of 14/20 and designated a Yellow Watch List species by Partners in Flight. Officially listed as a state Endangered Species in Minnesota and designated a Species in Greatest Conservation Need by the Minnesota Department of Natural Resources.
A short-distance migrant that winters in the southeastern United States.
An omnivorous ground feeder that consumes insects, particularly grasshoppers, crickets, and beetles, and seeds.
An open-cup nest located on or near the ground; some of the surrounding ground litter may form a partial dome over the top.
Audubon (1841) described the Henslow’s Sparrow as a “mouse with wings”, a reference to the small bird’s habit of evading intruders by running like a mouse through the grasses rather than taking flight. Only a handful of records of this rare sparrow were available when Roberts published his 1932 treatise on Minnesota birds. He described it as “a generally distributed summer resident throughout the southern half of Minnesota as far north as Grant and Isanti Counties, where it breeds.” There were 2 isolated records from the northwestern region: (1) a June 1898 record from Hallock, Kittson County, and (2) a July 1879 record from Pembina, North Dakota, “just across the river from Minnesota.” The records were so rare that he detailed every report from 1880 to 1928. The records covered all corners of the state’s grassland landscape, including Goodhue, Grant, Hennepin, Isanti, Jackson, Kittson, and Pipestone Counties. Only 1 nesting record was available from Jackson County, in 1902. The most detailed observation was from June 1928, when several were found “in the meadows along the south side of the Minnesota River Valley above Fort Snelling.” Roberts concluded his account of the species by noting “the bird is probably much more common and more widely distributed than these observations indicate, as its secretive habits and weak song make it difficult to find.” When he published the second edition of his book in 1936, nesting had also been confirmed in Stearns County near St. Cloud (Roberts 1936).
Despite Roberts’s optimism about the species’ abundance, breeding season reports only trickled in during the next several decades. Through the 1960s, documented reports included a nest in Lac qui Parle County (Chambers 1947), a report of “several” birds in Mahnomen County (Janssen 1959), and 1 adult with 1 young in Clay County (Huber 1961). With one exception, 1 or more pairs would appear at a site one year only to disappear in subsequent years.
The exception was in Winona County. Several grassland sites with Henslow’s Sparrows were frequently visited by Brother Theodore Voelker in the 1950s. Voelker first reported 3 nests in 1953 (Herz 1954) and 6 nests that raised 20 young in 1955 (Guttman 1956). It is unclear if the site or sites he visited were in the same area that became O. L. Kipp State Park in 1976, and was renamed to Great River Bluffs State Park in 1997. Unfortunately most of the early accounts simply refer to the “usual Winona County areas” in reports submitted to the Minnesota Ornithologists’ Union (MOU). Summer seasonal reports compiled by MOU imply that there were several sites where the birds could be found, but once the state park was established, nearly all Henslow’s Sparrow records in Winona County make sole reference to the state park (Minnesota Ornithologists’ Union 2016). If Warner’s map of all known Henslow’s Sparrow records up until 1959 is accurate, it suggests that Brother Voelker’s original site(s) was northwest of the state park (Warner 1959).
The majority of reports in subsequent years, from the mid-1970s through the early 1990s, continued to come from the southeastern corner of the state, especially from O. L. Kipp State Park. This was the one site in the state where birders usually could be assured of spotting a Henslow’s Sparrow. Gradually, however, reports began to accumulate from other sites in southern and western Minnesota. Eckert (1974) documented the species’ presence at Blue Mounds State Park in Rock County, and Fall and Eliason (1982) found a nest in Hennepin County. Other summer reports were submitted from several east-central and southeastern counties, including Dakota, Fillmore, Houston, Ramsey, Sherburne, Steele, and Wabasha (Minnesota Ornithologists’ Union 2016). Farther west, reports came from Grant (Igl 1996), Norman (Johnson 1986), and Wilkin Counties (Millard 1995). Hanowski and Niemi (1983) even documented the presence of several birds in the peatlands north of Waskish in Beltrami County!
During this period, an intensive study of the species was conducted by graduate student Lynelle Hanson, who studied the breeding population at O. L. Kipp State Park from 1987 through 1989 (Hanson 1994). Included was an assessment of 23 sites throughout the state where the birds had been reported since 1968. In all three years of the study, the overwhelming majority of birds reported in the state were located at O. L. Kipp State Park, where she documented 23 adults in 1987, 19 in 1988, and 22 in 1989.
Considered rather ephemeral in nature, Henslow’s Sparrow populations often fluctuate considerably from year to year (Herkert et al. 2002). Their abundance at the state park in the late 1980s was followed by four consecutive years (1992–995) when they were entirely absent from the site despite intensive field searches (Minnesota Ornithologists’ Union 2016; Svingen 1998). These lean years were followed by an abundance of reports throughout the state beginning in 1996 when a total of 21 birds were reported from 5 separate locations (Svingen 1998). In 2000 they were reported from 10 counties across the southern two-thirds of the state, and in 2005 they were reported from 32 counties, including 28 singing males at renamed Great River Bluffs State Park! The only regions lacking reports were north-central and northeastern Minnesota (Minnesota Ornithologists’ Union 2016). Faber speculated that the unprecedented number of birds in Minnesota could be due to increased grassland management efforts and/or to the influx of birds from areas farther south that were experiencing a significant drought (Faber 2006).
Field biologists surveying grasslands throughout Minnesota as part of the Minnesota Biological Survey documented 80 Henslow’s Sparrow breeding season locations, all south of a line from southern Otter Tail County in the west to southern Crow Wing County in the east (Minnesota Department of Natural Resources 2016). Henslow’s Sparrows are exceedingly difficult to find, and the number of confirmed nesting records in the state remains low. Since 1970, Hertzel and Janssen (1998) documented a total of only 2 counties with nesting records: Hennepin and Winona. Indeed these remained the only 2 counties where nesting had been documented for nearly 40 years, until the MNBBA began in 2009.
During the MNBBA, participants reported 185 Henslow’s Sparrow records in just 2.1% (99/4,740) of the surveyed atlas blocks and in 1.6% (37/2,337) of the priority blocks. Breeding evidence was confirmed in only 3 atlas blocks (Figures 2 and 3; Table 1). The birds were observed in 46 counties, which covered the southern half of the state and extended north through the Red River valley and the Tallgrass Aspen Parklands Province (3 blocks straddled 2 counties each). Breeding was confirmed in 3 counties: Carver, Murray, and in a block in the Murphy-Hanrehan Park Reserve that straddled Scott and Dakota Counties. Detailed notes that accompanied the latter record confirmed that the record was in the Scott County portion of the block. The Interactive Map, however, displays the location of the block and therefore highlights both counties. Submitted by Bruce Fall, the notes for this 2012 record provide further details on the presence of the birds: “There are 7-8 Henslow’s Sparrow territories within the block in unburned restored prairie . . plus another 16 territories in the adjacent block to the west.” Similar to the situation Hanson (1994) found at Great River Bluffs State Park, the density of breeding pairs suggests the species is “loosely colonial” (Herkert et al. 2002). The breeding records from Murphy-Hanrehan and from Carver County were observations of adults feeding young; the record from Murray County was of a juvenile sited in a block where an adult male was singing earlier in the season.
Despite the large number of counties where the Henslow’s Sparrow was reported, it remains a sparsely distributed and uncommon species. Nevertheless, Roberts (1932) prediction that the birds might be more common in southern Minnesota than the few records in the early 1900s suggested has finally proven true!
In their comprehensive review of the species, Herkert et al. (2002) provided a detailed description of the historical changes in the Henslow’s Sparrow’s distribution. In the 1800s, the species was represented by two disjunct populations: one in the central grasslands of Nebraska and Kansas, and one in the coastal marshes of New England. As the eastern forests were cleared, local populations increased and expanded north in the Great Plains and east throughout New England and the northern Ohio River valley. However, by the mid-1900s populations were declining, especially in New England. An extensive survey of more than 1,000 grassland sites in 1997 found no birds in New England. Populations in New York were limited to just 2 counties. Apart from a few remnant populations, the species has largely disappeared from the Atlantic Coast and is now confined primarily to the eastern tallgrass prairie biome of the north-central United States.
*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.