A small (4 ½ -5 inches) wren, the House Wren is most easily identified by its plain tan-brown back, tan breast, short tail (often held up at an angle), curved bill, and faint white eye-stripes. This species may be distinguished from the similar Carolina Wren (Thryothorus ludovicianus) by that species’ larger size and redder plumage and from Bewick’s Wren (Thryothorus ludovicianus) by that species’ larger size and brighter eye-stripes. Male and female House Wrens are similar to one another in all seasons. The House Wren breeds in southern Canada and the northern half of the United States, with other breeding populations occurring from southern Mexico and the West Indies to southern South America. In winter, populations breeding in North America winter in the southern half of the United States and northern Mexico. By contrast, tropical and South American House Wren populations are non-migratory. House Wrens inhabit a variety of semi-open habitats, including bushy fields, woodland edges, and scrub. This species has also adapted to life in well-vegetated urban and suburban areas, and its habit of nesting in artificial nest-boxes, also known as “bird houses,” has become part of this species’ English-language common name. House Wrens exclusively eat small insects. In appropriate habitat, House Wrens may be seen foraging for food on the ground or in the branches of bushes and shrubs. Birdwatchers may also listen for this species’ song, a rapid series of warbled notes. House Wrens are most active during the day.

Threat Status: Least concern

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.

Biogeographic Regions: nearctic (Native ); neotropical (Native )

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Breeding

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: Breeding range extends from southern British Columbia across southern Canada to New Brunswick, and south to northern Baja California, Texas, and northern Georgia; also Mexico, West Indies, and Central and South America (to Tierra del Fuego). During the northern winter, this species ranges from the southern United States southward.

The southern limit of the wintering range of North American populations is about at the northern limit of resident populations in Central America, so migratory and resident populations rarely co-occur (AOU 1983).

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.

Range mass: 10 to 12 g.

Range length: 11 to 13 cm.

Other Physical Features: endothermic ; bilateral symmetry ; polymorphic

Sexual Dimorphism: sexes alike; male larger

Length: 12 cm

Weight: 11 grams

• Terrestrial

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.

Habitat Regions: temperate ; tropical ; terrestrial

Terrestrial Biomes: forest

Other Habitat Features: urban ; suburban ; agricultural

Comments: House wrens inhabit thickets, shrubbery, and brushy areas in partly open situations, open woodland, farmlands, chaparral, and areas around human habitations; also (south of the United States) humid montane forest, forest edge, clearings, pine-oak associations, and mangroves. This species occurs most often in human-disturbed habitats. It sleeps in all seasons in crannies in buildings, holes in trees, niches in banks, or in similar sites. Nests usually are in cavities (natural, abandoned woodpecker holes, bird boxes, and within various human artifacts).

House wrens commonly reuse nesting cavities in successive years. Prior to reuse, the male usually removes the old nest-lining and sometimes the old sticks as well. Removal of old nest material can significantly reduce the abundance of parasitic mites that may attack the wrens.

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

North- and south-temperate populations are migratory; tropical populations are resident. Breeding populations north of the southern United States migrate south for winter, south to southern Mexico. Spring migrants arrive in northern breeding areas March-May.

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.

Animal Foods: insects

Primary Diet: carnivore (Insectivore )

Comments: Eats almost entirely insects; also other small invertebrates (Terres 1980).

House wrens help to control insect populations. They also supply food for many different animals.

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.

Known Predators:

• domestic cats (Felis silvestris)
• brown rats (Rattus norvegicus)
• Virginia opossums (Didelphis virginiana)
• woodpeckers (Piciformes)
• red foxes (Vulpes vulpes)
• owls (Strigiformes)
• raccoons (Procyon lotor)
• squirrels (Sciuridae)
• various snakes (Serpentes)
• Mississippi kites (Ictinia mississippiensis)

See Drilling and Thompson (1988) for intensive study, using 910 nest boxes over several years, of natal and breeding dispersal in Illinois.

Density was 10-18 pairs per 40 ha in northern Arizona pine forest (Brawn and Balda 1988).

Sometimes destroys the clutches of other birds, including conspecifics.

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.

Communication Channels: visual ; acoustic

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.

Range lifespan

Status: wild: 7 (high) years.

Average lifespan

Status: wild: 108 months.

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.

Mating System: monogamous

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.

Breeding interval: House wrens may raise up to two broods each breeding season.

Breeding season: House wrens breed between late April and early September.

Range eggs per season: 4 to 8.

Average time to hatching: 12 days.

Range fledging age: 15 to 17 days.

Average time to independence: 13 days.

Average age at sexual or reproductive maturity (female): 1 years.

Average age at sexual or reproductive maturity (male): 1 years.

Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate)

Average time to hatching: 14 days.

Average eggs per season: 7.

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.

Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Protecting: Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female)

Breeding season is relatively short and strongly seasonal in the north, protracted and variable in the tropics (e.g., see Young, 1994, Condor 96:341-353). Egg laying in the United States begins as early as April in some areas, in May in most regions. Nesting may extend into July or August in some areas. Clutch size averages about 3-4 at low latitudes, about 5-7 at high latitudes (Young, 1994, Auk 111:545-555). Individual females in the north produce 2, sometimes 3, broods per year (3-4 in Costa Rica). Incubation, by the female, lasts 12-15 days. Young are tended by both parents, leave nest at 12-18 days; male may feed fledged young while the female renests. Breeding is most commonly monogamous; males sometimes polygynous.

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.

US Migratory Bird Act: protected

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

Canada

Rounded National Status Rank: N5B - Secure

United States

Rounded National Status Rank: N5B,N5N : N5B: Secure - Breeding, N5N: Secure - Nonbreeding

Rounded Global Status Rank: G5 - Secure

Management Requirements: See Mitchell (1988) for specifications for the construction and placement of nest boxes.

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

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

Positive Impacts: controls pest population

Comments: Complex of five groups; species limits within complex are not well understood (AOU 1983). Groups are: aedon (Northern House-Wren), brunneicollis (Brown-throated Wren), musculus (Southern House-Wren), martinicensis Antillean House-Wren), and beani (Cozumel Wren) (AOU 1998). Phillips (1986) used the specific name domesticus for this species, from which he separated the Cozumel Island beani. Banks and Browning (1995) acknowledged that based on priority alone, the correct name is T. domesticus, but they argued for retention of the name T. aedon because that would best serve nomenclatural stability.