When she chooses one, the female accepts the male and will begin to line the stick nest with fine grasses. She will often make up to 150 trips to the nest each day for several days to complete the inner nest. Other than grass, the nest can be lined with feathers, hair, wool, spider eggs and catkins. If she does leave the nest, the male will stay nearby, but will not enter the box until after the young have hatched. The young remain in the nest for about 14 days and are fed by both parents.
House wrens can have a second brood.
The male will also take on all feeding activities for the first brood while the female starts on the second nesting. They will compete with house sparrows, bluebirds, tree swallows, red squirrels, chipmunks, deer mice, and even paper wasps. When populations of these animals are high, and few nest sites are available, male house wrens may puncture eggs and kill young of both other wrens and other songbirds. For optimum success for both bluebirds and wrens, make sure you have adequate numbers of nest boxes. For bluebirds, make sure boxes are placed far out in the open, away from the woods.