House wrens breed in Temperate areas of North America and throughout most of South America. During the colder months, they head for warmer climes and most of the house wrens that breed in North America spend the winter in the Southern States or in Mexico.
By mid spring, the males reappear on the nesting grounds and begin to construct several nests in tree cavities, nest boxes or other protected sites. When the females arrive, the males escort them to their rudimentary nests, hoping to gain favor (and mating privileges). House wrens prefer open woodlands with shrubs and thickets and are thus often found in suburban areas, on farms or in urban parks. They feed on a wide variety of insects and spiders and are known to place spider eggs in their nests; it is thought that the spider hatchlings feed on mites and other parasites that threaten the welfare of the nestlings.
Despite their small size and beautiful song, house wrens are very aggressive and highly territorial, easily out-competing chickadees, bluebirds, tree swallows and prothonotary warblers for available nest cavities. Though they have not yet returned to our Littleton farm, I did encounter several at South Platte Park this morning, just the latest confirmation that winter has made its final retreat (upslope snowstorms notwithstanding).