This North American species is found breeding west from the Atlantic coast to Nebraska and north from southern Illinois to southern Canada. In the western United States this species is a year round resident and there are also breeding and resident populations along the coasts of the southern Atlantic and Gulf states. The wintering range extends south from the southwestern states of New Mexico, Arizona and Texas and into Mexico. Florida is also a wintering ground for the marsh wren.
The marsh wren is 10-14 cm long and weighs 9-14 g.
Marsh wrens use a variety of wetland habitats, showing some preference for cattail and bulbrush dominated vegetation. They occurs in salt and brackish marshes in addition to freshwater sites. The winter habitat is similar to that of the breeding range.
These birds eat various invertebrates, especially insects like bees, ants, wasps, beetles, and moths, as well as spiders and aquatic invertebrates in freshwater marshes.
Marsh wrens are polygynous, with males mating with several females. The male builds several domed nests using grasses and sedges, before the females arrive in his territory. Each female uses one nest, laying 3-10 brown eggs with dark spots, which she incubates alone for 12-14 days. The chicks are brooded by the female alone, but males will sometimes feed older young. The young fledge 13-15 days after hatching.
IUCN status – LC (Least Concern)
This species has a very large breeding range and a global population of 8 million individuals. Degradation and destruction of marshes and other wetland habitats is the main threat affecting this species, both during the breeding season and in winter. This population is slowly declining in the eastern portion of their range, but increasing in the western parts due an increase in the extent of favourable habitat.