More often heard than seen, the Marsh Wren has a distinctive song that quickly alerts you to the fact that they are nesting in the area. Sung by the male at dawn, dusk and sometimes throughout the night, the song is a rapid series of gurgling and buzzy trills. Though each note may only last for 1–2 seconds, they can sing continuously for up to 20 minutes, rarely repeating the same note. To hear their song go to https://www.allaboutbirds.org/guide/Marsh_Wren/sounds .
Even though their nests are plentiful (males build multiple nests) they are well hidden and difficult to detect in amongst the cattails and bulrushes where they are built. About 50% of males mate with two or more females and most males build at least six dummy nests for every female they mate with. (In some parts of their range males build an average of 22 nests.) Scientists aren’t sure why the males build so many dummy nests – perhaps as decoys for predators. They are built two to five feet above the ground and are about 7” tall and dome-shaped with an entrance hole in the upper half. Once the female has chosen one of the male’s nests or built her own, she lines it with strips of grass, sedge, cattail down, feathers, and rootlets.
Possibly as a result of intense competition for resources in the marsh environments in which they nest and raise young, Marsh Wrens routinely destroy the eggs of other birds, including other Marsh Wrens. (Note: Pictured active Marsh Wren nest was built in rushes, which are preferred over cattails later in the nesting season, when cattails have dried out.)