They almost always return to a territory where they have previously nested successfully. Like bluebirds, male house wrens arrive before the females - usually in late March or April. Upon return, males will establish their territory by singing and by building stick nest foundations. Often you will find a nest box filled to the top with 4 inch long sticks. Other times, only 3 or 4 sticks will be found.
Males are relentless nest builders, often stealing twigs from a neighbor's nest.
When the female arrives, the male leads her to each nest to inspect them. 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.