Male defends territory by singing. Courtship involves male singing, showing the female potential nest sites. Adults often puncture the eggs of other birds nesting nearby (including other House Wrens). Male may have more than one mate; female may leave male to care for young from first brood while she moves to another male's territory and nests again. Nest site is in any kind of cavity, including natural hollows in trees and stumps, old woodpecker holes, crevices in buildings, often in nest boxes. May nest in almost any kind of enclosed space (flowerpots, parked cars, shoes, drainpipes, etc.). Site is usually low, may be high in trees, especially in western mountains. Male builds incomplete "dummy" nests in several cavities; female chooses one and finishes nest by adding lining. Nest has a foundation of twigs, topped with softer cup of plant fibers, grass, weeds, animal hair, feathers. Eggs: 6-7, sometimes 5-8, occasionally more. White, heavily dotted with reddish brown. Incubation is probably mostly or entirely by female, about 12-15 days. Young: Probably both parents feed nestlings. Young leave the nest about 12-18 days after hatching. 2 broods per year, rarely 3.