Marsh Wren

The reedy, gurgling sounds of the Marsh Wren can be heard throughout much of North America’s cattail and bulrush marshes. It is more often heard than seen. It has a year round range in the western U.S. and southern B.C. and a breeding range in the northern United States and southern Canadian provinces. It winters in the southern U.S. and Mexico.

Adult Male (spring/summer)

The Marsh Wren has a dark brown crown and white superciliary stripe. Upper back has a black triangular area striped with white. The rump and scapulars are reddish, flanks buffy and chest whitish. Undertail coverts are buffy and the tail is rusty with black bars and is usually held upright. Males are considerably larger than females. Sexes are similar.

Adult Female (spring/summer)

Sexes are similar.

Juvenile

Similar to adult, but lacks bold streaking on the back and the superciliary stripe is indistinct.

General:

A small and stocky wren with a long down-curved bill. Length: 12-13cm. Wing: 15-16cm. Weight: 9.0-14.0 g.

Behaviour:

In the marsh, this wren’s flight is short with quick wing beats giving the appearance of fluttering rapidly into the reeds. At times they cling to cattails moving up and down or straddling the reeds while vocalizing. Marsh Wrens feed on invertebrates especially insects, including aquatic insects as well as spiders. They glean prey from plants and just below water. This wren also has a large repertoire and complex singing behaviours.

Habitat:

Is restricted to freshwater and saltwater marshes in its North American range that can be unpredictable both geographically and annually.

Information:

The Marsh Wren is polygynous where the male may mate with more than one female. The male can build multiple nests and has a habit of destroying eggs and nests of its own and other species. The nests are a domed structure within which 4-6 eggs are laid. The eggs are dull brown and marked with darker brown spots.

Similar species:

Bewick’s Wren, Pacific Wren, House Wren

Conservation Status:

Currently listed as Least Concern, the Marsh Wren is decreasing in the eastern portion of its range, however is increasing in the west.

Capture Rates:

Although Marsh Wren can be a year-round resident, capture rates reflect increased activity in late summer and fall corresponding to juvenile dispersal away from the adjacent wetland where they breed.

Molt Summary:

PF: HY incomplete; PB: AHY complete; PA partial-incomplete
Preformative is variable, often being eccentric, with the outermost 5 – 7 pp, the innermost 3 – 6 ss, and the outermost 0 – 4 pp covs replaced. Others replace 5 – 10 gr covs and 1 – 3 terts, but no pp.
All rects appear to be replaced in most or all birds.
The 1st PA includes 4 – 10 inner gr covs, usually 1 – 3 terts and 0 – all 12 rects.
The adult PA includes 5 – 10 inner gr covs, 1 – 3 terts (occasionally s6, as well), and 0 to all 12 rects

Beware of pseudolimits between s6-s8 that cause terts to appear newer in AHY/ASYs. Molt limit’s among the gr covs, terts, and rects are found in both SY and ASY in Mar-Jul and should not be used for ageing during this period; use the pp and pp-cov criteria at this time.
Caution esp. in Apr-Jul when feathers become extremely worn – most birds should not be aged.

Molt limits are difficult to detect.

This HY in August is showing worn and abraded juvenal rectrices prior to replacement in the preformative molt.