Marsh Wren nests are domed structures attached to several
stems of emergent marsh vegetation such as cattails or
bulrushes. Early-season nests are usually placed between
1 1/2 and 3 feet above water, and higher later in the
season. Strips of cattail leaves, grass or other stems up
to a foot long are woven into a hollow ball about 7"
tall and 5" wide with an entrance hole near the top
on one side. Males display while perched above the
females by puffing up their feathers until they look like
little balls with their tails cocked over their backs,
fluttering half-open wings, and moving their heads from
side to side. After mating, males accompany the females
on an inspection of the nests. Selecting one, the female
lines it with finer leaves and stems, cattail down and
feathers. She constructs a lip at the doorway, extending
inward, so that there is a sort of tubular entrance.
Inside she lays four to six dark brownish eggs and
incubates them for about two weeks.
Males with superior territories often have second or even
third mates, especially in western populations. Mates of
polygamous males usually tend the young hatchlings
without much help. After about 12 days in the nest, the
young fledge before their flying abilities are fully
developed. They may use some of the dummy nests for
roosting, and are fed for up to two more weeks. Marsh
Wrens are typically double-brooded.
Males sing while perched high in the marsh vegetation, or
during short song-flights. The song is loud, energetic,
bubbling, and varied, and may be heard throughout the day
and sometimes into the night. Eastern Marsh Wren songs
are slower and more musical than those of western birds,
which incorporate a wider range of harsh grating sounds.
They have a repertoire of about 50 songs, while western
birds typically have about four times as many songs. In
western Marsh Wrens especially, countersinging between
neighbors is common as the birds cycle through their
repertoires. The differences in voices and singing
behavior of eastern and western populations have led some
authorities to postulate the existence of two separate
species, although there are only slight differences in
Marsh Wrens breed across southern Canada and northern
United States, south in the West to northern Baja
California, and in the East to Florida. Northern
populations are migratory, wintering in a variety of
marshy habitats in the southern United States and Mexico.
Marsh Wrens are small (5" long) with brownish
upperparts and white or whitish throat, breast, and
belly. The cap is brownish-black over a prominent white
supercilium. The bill is thin and relatively long. On the
back are distinctive black and white longitudinal
streaks. Sexes are alike.
The Marsh Wren is usually the only wren in its habitat,
although Sedge Wrens sometimes occur nearby, in moist
meadows. The Sedge Wren is smaller and paler than the
Marsh Wren, has a proportionally shorter bill, less
prominent back streaking, and eyestripe. The wings of the
Sedge Wren are distinctly barred and the cap is streaked
unlike the solid cap of the Marsh Wren.
Male Marsh Wrens build a dozen or more "dummy
nests" during the week or so after they return to
the breeding grounds and before females arrive. It is
thought that the extra nests may serve as decoys for
predators in an environment where nest concealment is
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