Marsh Wrens are lively and distinctive inhabitants of Oregon's wetlands, particularly in marshes dominated by cattails, bulrushes, and other emergent vegetation. They are known for their loud, gurgling, and buzzy songs, especially from the males.

When it comes to distinguishing between male and female Marsh Wrens in Oregon, they have very similar plumage, making visual identification difficult in the field based on appearance alone.

Shared Plumage (Both Male and Female):
Overall Coloration: They are a small, plump wren with rich rusty-brown upperparts.
Back Pattern: A key field mark for Marsh Wrens (and very helpful in separating them from other wrens) is the black and white streaking on their upper back/mantle, forming a somewhat triangular pattern.
Head: They have a bold white eyebrow (supercilium) contrasting with a darker, often blackish-brown, crown.
Underparts: Their throat and belly are whitish, often with buffy or brownish flanks and breast.
Bill: They have a relatively long, thin, and slightly decurved bill.
Tail: Their short tail is often held cocked upward and shows dark barring.

Subtle Physical Difference (Difficult to Use in the Field):
Size: Males are on average slightly larger than females, but this difference is often too subtle and overlaps too much to be a reliable field mark for individual birds.
Song: This is the most definitive clue. Only the male Marsh Wren sings its distinctive, loud, gurgling, and often buzzy song. Males sing incessantly from prominent perches in the marsh (like the tops of cattails) to defend their territory and attract mates. Western populations (which includes Oregon) are known for particularly complex songs and larger repertoires. Females produce various calls but do not sing.
Nest Building: The male Marsh Wren is a prolific nest builder, constructing numerous "dummy" or incomplete nests within his territory before a female even arrives. These are typically dome-shaped, woven structures anchored to marsh vegetation. The female then inspects these nests and chooses one (or occasionally builds a new one), adding the final soft lining (such as plant down, feathers, and fine grasses) to create the actual nest cup for eggs.
Polygyny: Marsh Wrens are often polygynous, meaning one male may mate with multiple females. A male's continuous singing, even after he has one mate, is often an attempt to attract a second or third female.
Incubation: The female alone incubates the eggs. The male will continue to defend the territory and may or may not help feed the young, depending on the population and whether he has multiple mates.