- Minnesota Breeding Bird Distribution
- Breeding Habitat
- Population Abundance
- Literature Cited
A regular breeding resident, migrant, and winter vagrant; the Marsh Wren was common during the Minnesota Breeding Bird Atlas (MNBBA).
The Marsh Wren has a widespread distribution, from the northern portions of the Atlantic Coast to the Pacific Coast, throughout the southern Great Lakes region and the northern prairies, and patches throughout the western United States and Canada. Its highest densities are in North Dakota (Figure 1).
Assigned a Continental Concern Score of 7/20 by Partners in Flight; formerly a Species in Greatest Conservation Need in Minnesota but removed in 2015.
Short- to medium-distance migrant that winters along the Atlantic and Pacific Coasts, the southern United States, and Mexico.
Invertebrates, primarily insects and spiders.
Globular, dome nest in cattails or bulrushes; many (5 to 22) are usually built in a territory.
Aptly described by Roberts (1932) as a “summer resident throughout the state; common in the southern part and on the prairies to the Manitoba line, but more sparingly represented in the marshes of the northern forested area.” Hatch (1892) also emphasized the ubiquity of this species, when he wrote, “[That] it is generally distributed over the entire State there can be no doubt.” Along the Red River valley in northwest Minnesota, he also stated that his collector, Mr. F.L. Washburn, found the species “breeding in large colonies.” Roberts reported confirmed nests with eggs from 1879 to 1929 in Cass, Grant, Jackson, Kittson, Otter Tail, and Polk Counties and in Minneapolis. Nest building, but not yet finished, was reported from Anoka County.
Green and Janssen (1975) also described the Marsh Wren’s breeding distribution throughout the state as scarce in the northeastern and adjacent north-central counties, where cattail marshes are uncommon. Janssen (1987) echoed this description and identified confirmed nesting in 13 counties since 1970. These counties were all widely scattered from the extreme northwest to the extreme southwest and northeast to southern St. Louis County. Hertzel and Janssen (1998) would later add 6 more counties with confirmed nesting records since 1970 but excluded Clearwater County.
The Minnesota Biological Survey (MBS) provided a broader perspective on the breeding distribution of the species in the state, though accounts were supportive of the general descriptions previously noted (Minnesota Department of Natural Resources 2017). The MBS included 893 records of the Marsh Wren, with higher concentrations west of Mower County in the south, west of Itasca County in the north-central region, and northwest to Roseau County. Scattered breeding observation locations were found northeast to southern St. Louis County; one location each in Carlton, Chisago, Cook, and Pine Counties; and one in Houston County in extreme southeastern Minnesota.
The MNBBA substantially adds to the breeding observations in the state but generally confirms previous accounts: the Marsh Wren was widely distributed throughout the state but scarce in the northeastern and northern forested regions (Figure 2). MNBBA participants reported 1,663 records in 21.4% (1016/4,757) of the surveyed blocks and 25.3% (592/2,337) of the priority blocks (Figure 3; Table 1). A majority of records were of possible nesting. Confirmed nesting was reported from 48 blocks within 33 counties; one confirmed nest straddled the boundary between Redwood and Renville Counties.
The species was recorded during the breeding season from every county in the state except Cook County, but as noted above, the MBS had previously found the Marsh Wren in that county. It was found at only one location in Carlton, Fillmore, and Koochiching Counties and at only two locations in Houston, Martin, Olmstead, Washington, and Winona Counties. Marsh Wren records were particularly numerous in Big Stone, Lac qui Parle, and Kandiyohi Counties.
The predicted distribution map accentuated the scarcity of the species’ habitat throughout Minnesota with small pockets in the southern and western portions of its range (Figure 4). High densities were predicted at the Agassiz National Wildlife Refuge in Marshall County, at Swan Lake in Nicollet County, and in many scattered areas in west-central, southwestern, and northwestern Minnesota. The distribution of the Marsh Wren predicted by the MNBBA data was also very similar to the distribution map from the federal Breeding Bird Survey (BBS) (Figure 1), but provided greater resolution within the species’ range.
The general distribution of this species in Minnesota appears to be largely intact, but the substantial loss of wetland habitat due to agricultural, industrial, and residential development has clearly reduced breeding populations in the state. This is especially true in the southern and western portions of Minnesota. This is supported by previous atlas observations throughout many other parts of the species’ range, including Michigan (Brewer et al. 1991; Chartier et al. 2013) and Ontario (Cadman et al. 2007). Additional evidence was noted by Kroodsma and Verner (2013) in the northeastern and western United States, as well as breeding range retractions in southern Florida. Fortunately, the Marsh Wren’s breeding population is still widely distributed in Minnesota despite extensive habitat loss.
*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.