Marsh Wren

The Marsh Wren can be an extremely frustrating bird to see. Its song is loud and unmistakable, but even when it’s singing from a few feet away the bird is typically hidden deep in the cattails where it nests. If you’re lucky, you’ll catch a glimpse as it flits across an opening in the dense vegetation. It seems appropriate that this song is usually one’s first experience with this species, since this is also the area of its biology that has received the most research. Marsh Wrens have extensive repertoires, and while their songs may sound similar to the human ear they can have as many as 50 different variations (up to 200 in the West, which might be a different species). They use these songs in seemingly unending vocal battles for mates, and in a good marsh it can be hard to avoid hearing them during the peak of the breeding season.

Like most wrens, this species has a habit of building multiple nests, these being constructed entirely by the male. Over a dozen are sometimes built, and one hypothesis for all this work is that more prolific males are more likely to attract mates. Another is that they serve as decoys for predators, and when a nest is destroyed during egg-laying the female will sometimes shift to a different one in her male’s territory. Wrens are also notorious for destroying the eggs of other birds, and the Marsh Wren is no exception. This may serve to reduce competition for resources in dense populations, but more study is needed.

Marsh Wrens are sparsely distributed in New Hampshire but can be common in the marshes where they occur. There is even some indication that occupied sites vary among years, with birds using a location for a few years in a row before disappearing, even though the habitat does not appear to have changed. This may be an adaptation to an evolutionary history of needing to deal with ephemeral wetlands created by beavers or lost to extended droughts. Thus, although these wrens can be reliable in the areas indicated on the map, there’s always the possibility that they’ll appear in an unexpected location every now and then.