Troglodytes aedon
house wren

House wrens are native to the Nearctic region. During the breeding season they live from southern Canada to southern Argentina, Chile and the Falkland Islands. They spend the winter in a narrower range; the southern limits of the United States, southwestern California east to Florida and south throughout the Gulf Coast and Mexico. (Johnson, 1998)

In the wild, house wrens live in open, shrubby woodlands. However, they were named for their preference for small town and suburban backyards and human-made bird houses. Small wood-lots and forest edges are also common habitats for these birds. Human farming and towns have created more good breeding habitat for the wren by breaking forests up into small chunks. This explains why house wrens have expanded their range and their population in North America has grown. During the winter, wrens live in thickets, shrubby and brushy areas, riparian forests, and savannas in the southern United States. In Mexico, they prefer tropical evergreen and semideciduous forests. (Johnson, 1998)

House wrens are small, squat birds without bold or characteristic markings. They have long, curved bills and, like other wrens, perch in a characteristic posture with their tail held erect. Their heads, napes, and backs are almost uniformly brown with very fine darker brown stripes. Their throats and chests are light grey, and they may have some black, dark brown, or pinkish spots on their flanks, tails, and wings. There is a faint, white eyebrow-like stripe above their eyes.

House wrens are usually 11 to 13 cm long and weigh 10 to 12 g. Males and females are identical in coloration, but males are slightly larger in some traits.

There are about 30 recognized subspecies of Troglodytes aedon. These subspecies are differentiated by plumage shading, amount of barring on flanks, variation in wing-to-tail proportions, and vocalizations. (Johnson, 1998; McGillivray and Semenchuk, 1998)

House wrens are socially monogamous, meaning that one male and one female mate together and share parental responsibilities. However, some studies have shown that males that have surplus nest sites in their territory advertise for secondary mates. About 10% of the males in one study were polygynous. Adults often switch breeding partners between the first and second brood of a season. Breeding pairs do not last for any more than one season. (Johnson, 1998)

House wrens breed between late April and early September, with the majority of clutches started in mid-late May. The males are the first to return from migration and establish territory for nesting within a few hours/days of arrival. The females return in time to complete the nest after choosing a male. Females that nest at low latitudes (including most of the U.S.) and/or low altitudes generally raise two broods per season.

House wrens nest in tree cavities, such as old woodpecker holes. They prefer cavities closer to the ground with small entrances. The male begins building the nest by placing sticks in the bottom of the cavity. When the female arrives, she finishes building the nest. The female lays a clutch of 4 to 8 (usually 6) eggs, which she incubates for about 12 days. The chicks are altricial when they hatch, and are brooded by the female. Both parents feed the chicks, which fledge after 15 to 17 days. The chicks all leave the nest within a few hours of each other. After the chicks leave the nest, both parents continue to feed them for about 13 days.

House wrens are able to breed (have reached sexual maturity) when they are 1 year old, but some first time breeders skip the regular breeding time and choose instead to breed alongside the older birds who are attempting a second clutch in a season. (Johnson, 1998)

House wren chicks are completely helpless and dependant on their parents, who both care for the young. They fledge after about 15 to 17 days and all leave the nest within a few hours of each other. The parents continue to feed them for about 13 days after they leave the nest. (Johnson, 1998)

The oldest known house wren lived to be at least 7 years old. It is difficult to estimate the lifespan of these birds because they do not return to the same area every year. (Johnson, 1998)

House wrens mostly hop while on the ground and have a direct, steady flight only about 1 meter above the ground in open areas. They are diurnal and migratory. House wrens are very territorial and are usually found alone, in pairs, or in small family groups. Males take primary responsibility for defending the territory and will chase away intruders. When the male confronts a territorial intruder he will crouch, droop his wings, erect his back feathers, and lower his fanned out tail. Females repel intruders that try to enter the nest. (Johnson, 1998; McGillivray and Semenchuk, 1998)

During the breeding season, the home range of house wrens is roughly the same as their territory. We have no information on the winter home range of this species. (Johnson, 1998)

House wrens are widely known for their songs. While both sexes produce calls and songs, the males' songs are more complex. Altogether, 130 different song types are known from house wrens. Unmated males can sing for up to 10 minutes. Males with a mate often sing a "whispering song", which is very quiet, and is only sung around the time of copulation. The purpose of the quiet song may be to avoid revealing the location of his fertile mate to other males. The female sings during the first days of pairing when she responds to her mate's song.

House wrens also communicate using body language. If a predator approaches, males crouch and drop their wings, raise their back feathers, and lower their fanned-out tail. (Johnson, 1998; McGillivray and Semenchuk, 1998)

House wrens feed primarily on small, terrestrial insects. The independent young and adults consume mostly spiders, beetles, and bugs while the nestlings are fed mostly grasshoppers, crickets, and caterpillars. Adults feed their young and supplement their own diet with sources of calcium such as mollusk shells. House wrens forage primarily in the woodland subcanopy, in shrubs and among herbaceous ground cover. (Johnson, 1998)

Predators of house wrens include cats, rats, opossums, woodpeckers, foxes, owls, raccoons, squirrels, and various snakes. Adult house wrens respond to predators by chasing and striking at the predator while giving a loud, harsh alarm call. (Johnson, 1998)

House wrens help to control insect populations. They also supply food for many different animals. (Johnson, 1998)

House wrens eat insects that may be considered to be pests by humans.

There are no known adverse affects of house wrens on humans.

House wrens are a very successful species because they have benefited from forest fragmentation and other human-induced habitat changes. They are quite tolerant of pesticides, habitat alteration and nest disturbance, allowing them to live and reproduce successfully even in human populated areas. This species is protected under the U.S. Migratory Bird Act. (Johnson, 1998)