While making my usual circuit around Eaglewatch Lake this morning (at South Platte Park), the distinctive song and chatter of a marsh wren rose from a dense cluster of reeds near the shore. Summer residents of wetlands across Canada and the Northern U.S., these reclusive birds also breed along the Pacific coast and in marshes of the Intermountain West. While most winter in the Southern States or Mexico, some are permanent residents of relatively mild weather locations throughout the West. Here along the Colorado Front Range, they are uncommon summer residents but are also occasionally observed in winter.
During the breeding season, the male marsh wren constructs a number of dome-shaped nests in cat-tails, cordgrass or other low wetland vegetation and may mate with more than one female if they find his handiwork acceptable. While the females care for the eggs and hatchlings, he defends the territory, chasing away intruders and often destroying the eggs or killing the nestlings of other marsh birds. Throughout the year, marsh wrens feed on insects or their larvae which they glean from wetland plants or directly from the water.
Despite this aggressive behavior, marsh wrens are seldom seen, preferring to remain secluded in the dense vegetation. On the other hand, the males are frequently heard (especially during the breeding season) and may briefly survey their territory from the tip of a reed or cat-tail. Most of the time, however, birders must settle for fleeting glances of this wetland resident, perhaps noting its white eye-stripe, streaked back, long, narrow bill or cocked tail.