Marsh Wrens are ubiquitous in marshes along most of the coastline of the United States and southern Canada as well as many inland marshes. The behaviors of these wrens have fascinated ornithologists, the males build multiple nests for prospective mates to choose among and, they destroy the eggs and nests of other species and other Marsh Wrens. Males of this species are also notable for their vocal abilities. Some of them have as many as 200 songs in their repertoire.(Kroodsma and Verner 1997).
Vocal differences are apparent between populations in the east and west with the populations dividing in Saskatchewan and central Nebraska and no obvious interbreeding in the area of overlap. Analysis of this vocal behavior suggests the presence of two distinct species within the Marsh Wren complex (Kroodsma and Verner 1997, Kroodsma 2005). Marsh Wrens breeding in the Trans Pecos region may be members of the western population.
DISTRIBUTION. During the 1987-1992 field work of the TBBA project, atlasers found breeding records at 5 sites near the coast. Three probable and 3 possible records in latilong 29094, 1 probable in 29093, 1 possible each in 28096 and 28095, and 1 probable and 1 possible in 26097. Lockwood and Freeman (2004) report most breeding occurs along the Gulf coast south to Aransas County with other reports from the Red River east of the Panhandle and along the Rio Grande River in the Trans Pecos region. A probable record in 30103 is in this region. Two North American Breeding Bird Survey (BBS) routes along the upper Gulf coast detected an average of <1 wren per year (Sauer et al. 2005)
Within the United States and Canada, migrant populations breed in northeast and Great Lakes states, the eastern Great Plains and Canadian prairie provinces. Migratory populations also breed in British Columbia, eastern Washington, Idaho, Montana, Wyoming, Colorado, Utah and Nevada. Year-round populations occur along the Pacific, Atlantic and Gulf coasts, the lower elevations of the Great Basin, parts of Arizona, New Mexico and Colorado and an area in south-central Mexico.
Migratory individuals winter at low and mid-elevations in Arizona, New Mexico, Colorado, Texas, Florida, Baja California and mainland Mexico south almost to the Isthmus of Tehuantepec (Howell and Webb 1995, Kroodsma and Verner 1997).
SEASONAL OCCURRENCE. Breeding populations of Marsh Wrens along the Texas coast are year-round residents. Migrants and winter residents are present from mid-September to early May (Kroodsma and Verner 1997, Lockwood and Freeman 2004). In Arizona this wren breeds from March to May (Corman 2005).
BREEDING HABITAT. In North America Marsh Wrens usually nest in cattails or bulrushes, often above water. The territorial male builds as many as 24 nests from cattails, sedges and grasses for prospective mates to inspect. The female chooses one to finish and line, or builds a new nest. In nest construction a cup is formed from leaves and stems attached to supporting stems, then walls are added and joined to form a domed structure about 18 cm (7 in) high and 13 cm (5 in) in diameter, lined with soft materials. (Kroodsma and Verner 1997).
A female usually lays 4-6 (range 3-10) dark brown eggs (see Harrison  for photo of markings) which she incubates for 12-14 days (east), 15-16 days (west). Young birds usually leave the nest 13-15 days after hatching. In some populations, males may have 2 or more mates and females may raise 2 broods in a season (Kroodsma and Verner 1997).
STATUS. Lockwood and Freeman (2004) describe Marsh Wrens as common to uncommon in summer in th marshes of the upper and central Texas coast. BBS data from 2 routes (40 km [25 mi] each) is not adequate to produce a meaningful trend . North Dakota, which may be a major source of wintering March Wrens in Texas has an encouraging statistically significant +9.5% yearly population trend for the period 1986-2005 (Sauer et al. 2005), suggesting the migrant and wintering populations in Texas might increase.
Text by Robert C. Tweit (2006)
Corman, T. E. 2005. Marsh Wren (Cistothorus palustris). In Arizona breeding bird atlas. pp. 414-415 (T. E. Corman and C. Wise-Gervais, eds.). University of New Mexico Press, Albuquerque.
Harrison, H. H. 1979. A field guide to western birds’ nests. Houghton Mifflin, Boston, MA.
Howell, S. N. G. and S. Webb. 1995. A guide to the birds of Mexico and northern Central America. Oxford University Press, New York.
Kroodsma, D. E. 2005. The singing life of birds. Houghton Mifflin, Boston, MA.,
Kroodsma, D. E. and J. Verner. 1997. Marsh Wren (Cistothorus palustris). In The birds of North America, No. 308 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.
Lockwood, M. W. and B. Freeman. 2004. The TOS handbook of Texas birds. Texas A&M University Press, College Station.
Sauer, J. R., J. E. Hines, and J. Fallon. 2005. The North American Breeding Bird Survey, results and analysis 1966-2005. Version 6.2 2006. USGS Patuxent Wildlife Research Center, Laurel MD < http://www.mbr-pwrc.usgs.gov/bbs>