Breeding Habitat:Grassland
Nest Type:N/A
Migration Status:Short distance migrant
Nest Location:Ground-low nesting
Sedge Wrens inhabit the damp margins of wetlands dominated by grasses and sedges, wet meadows, wet pastures, and other damp grassland habitats. Along the Atlantic Coast, they also frequent coastal marshes, but prefer grassy habitats in freshwater or in brackish situations where salinity levels are low. Unlike Marsh Wrens, which prefer wetlands with standing water, Sedge Wrens prefer habitats that are intermittently flooded or have damp soils.
This species is notorious for its erratic migratory movements and flexible breeding schedules. In some portions of its range, these wrens appear during May and remain for the entire summer, although they may move locally in response to changing habitat conditions. In other portions of its range, Sedge Wrens may not appear until July with nesting occurring during August. These population movements are poorly understood, and obfuscate population trends. This species has experienced a noticeable decline in the northeastern United States during recent decades, where only a small number of breeding pairs remain (Gibbs and Melvin 1992). Similar declines have been reported from the Great Lakes area, especially Michigan and Ohio (Brewer et al. 1991, Peterjohn and Rice 1991).
Based on BBS data, Sedge Wrens are most numerous from Manitoba south through Minnesota to Wisconsin (Relative Abundance Map). They are generally recorded in small numbers elsewhere in their range. These data indicate the early summer distribution pattern for this species. Its distribution later in summer may be very different as a result of its mid-summer population movements.
As a result of its erratic movements, the BBS trend estimates for Sedge Wrens should be viewed with some caution. The 1966-1994 trends are generally positive, including increases in Minnesota, the Great Lakes Transition (S20) stratum, Eastern BBS Region, United States, and survey-wide (Trend List). The only decline occurs in Michigan. These long-term trends are a result of increases during the 1980-1994 interval, when all significant trends are in a positive direction and the regional trends are generally non-significant increases. The trend estimates are considerably more negative during 1966-1979, when the only increase occurs in Iowa while declines are evident in two states/provinces, two strata, Eastern and Central BBS regions, United States, and survey-wide. The trend map shows generally increasing trends from the Dakotas into Manitoba and Minnesota (Trend Map). Declining populations predominate elsewhere.
The survey-wide indices show a very slight increasing tendency during the entire survey period (Survey-wide Annual Indices). Trends for the Eastern BBS Region are similar, while those in the Central BBS Region are more variable with several years of peak abundance followed by noticeable declines (Central BBS Region Annual Indices). Population increases during the 1980s are most evident in Manitoba, Wisconsin, and the Great Lakes Transition and Aspen Parklands (S30) strata (Manitoba Annual Indices) (Wisconsin Annual Indices) (Great Lakes Transition Annual Indices) (Aspen Parklands Annual Indices). The North Dakota population is variable with no consistent temporal patterns other than periodic peak years followed by declines (North Dakota Annual Indices). A slight but consistent decline is evident in the Black Prairie (S40) stratum (Black Prairie Annual Indices).
During winter months, Sedge Wrens are relatively inconspicuous occupants of grassy wetlands, wet meadows, and occasionally weedy fields. They are likely to be found in both freshwater and brackish habitats at this time. Since they tend to skulk within dense grassy habitats, these wrens are generally recorded in small numbers on CBCs, predominantly within the southeastern United States. Trend estimates based on CBC data indicate a decrease in the Florida population, but increases in Texas.
Factors responsible for these generally positive BBS trend estimates are poorly understood. These population increases may be real, but the trend estimates may also be influenced by the erratic movements by this species. Where regional breeding populations have declined, habitat loss is believed to be the most important factor in their negative trends (Gibbs and Melvin 1992). As occupants of wet grassland habitats, Sedge Wrens have probably experienced an overall reduction in the availability of suitable habitats across the United States during recent decades as a result of the continued drainage of wetlands (Tiner 1984).
Brewer, R., G.A. McPeek, and R.J. Adams, Jr. 1991. The atlas of
breeding birds of Michigan. Michigan State Univ. Press, East
Lansing, MI. 594 pp.
Gibbs, J.P., and S.M. Melvin. 1992. Sedge Wren. Pp. 191-209 in
K.J. Schneider and D.M. Pence, eds. Migratory nongame birds
of management concern in the Northeast. U.S. Fish and Wildl.
Serv., Newton Corner, MA.
Peterjohn, B.G., and D.L. Rice. 1991. The Ohio breeding bird
atlas. Ohio Dept. Natur. Resour., Columbus, OH. 416 pp.
Tiner, R.W., Jr. 1984. Wetlands of the United States: current
status and recent trends. National Wetlands Inventory,
Washington, D.C. 59 pp.