Marsh Wren    Cistothorus palustris

Migratory Status: Short-distance migrant

PIF Population Estimate: 8 000 000

Percent of western hemisphere population breeding in boreal forest: <25%

BAM Effective Detection Radius (m) : 104.47

PIF Maximum Detection Distance (m) : 125

Canadian BBS Population trend: 0.6 n.s. (-0.9 to 2.1)

Life History

Marsh Wrens are small, pugnacious birds that are more often heard than seen. They breed in shallow freshwater and saltwater marshes where they tend to skulk among dense vegetation. Only the male sings, during both day and night. The song is a sharp, gurgling chatter that usually starts with one or two introductory notes followed by a raspy trill. The song is often described as the sound of an old-fashioned sewing machine. Songs are variable with some males having a repertoire of over 200 variations.

Adults are visually similar: both have striped, cinnamon-brown upperparts and tail, dull white underparts with a buffy wash on the sides, a dark crown, and a white eyebrow stripe. Marsh Wrens are similar in appearance to Sedge Wrens (C. platensis). The two species have overlapping ranges and are distinguished by the lighter colour of the Sedge Wren, its preference for grass and sedge habitats, and different song. Marsh Wrens prefer to nest over standing water in freshwater marshes dominated by cattail, bulrush and fragmites, or coastal marshes dominated by tall grasses and rush.

Marsh Wrens have a patchy breeding range, probably due to their specific breeding requirements associated with low elevation marshlands. This species breeds along the Gulf and Atlantic coasts across the southern Great Lakes, northern Mississippi valley and southern Ontario and Quebec, up through the Canadian prairies and into the interior of British Columbia and across most of the Great Plains of the United States to the Pacific coast. Breeding pairs are generally absent from the higher mountain ranges of the west and high desert plateaus.

Marsh Wrens have a complex and confusing taxonomy in North America consisting of two separate population groups and at least 14 recognized subspecies. Populations in the east are a separate evolutionary group from populations found in the west; in the centre of the continent, the two groups overlap and mix. The two groups have noticeably different songs and males in the west have a greater variety of songs compared to those in the east. Western males are also more likely to have multiple mates than eastern males. Both populations winter in separate areas of the continent.

Reference(s)

Kroodsma, D. E., and J. Verner. 1997. Marsh Wren (Cistothorus palustris), The Birds of North America Online, . A. Poole, Ed. Ithaca: Cornell Laboratory of Ornithology; Retrieved from The Birds of North America Online database: http://bna.birds.cornell.edu/bna/species/308