Station 5
House Wren


Physical Traits

Small and compact, with a flat head and fairly long, curved beak. Short-winged, often keeping its longish tail either cocked above the line of the body or slightly drooped. Subdued brown overall with darker barring on the wings and tail. The pale eyebrow that is characteristic of so many wren species is much fainter in House Wrens.

Habitat

House Wrens have a huge geographic range, and they live in many habitats, so long as they feature trees, shrubs, and tangles interspersed with clearings. Examples range from eastern deciduous forests and southern swamps to western conifer forests and aspen groves as high as 10,000 feet elevation. Because they're cavity nesters, House Wrens thrive around buildings, yards, farms, and other human habitations with their many nooks and crannies.

Diet

Eats a wide variety of insects and spiders, including beetles, caterpillars, earwigs, and daddy longlegs, as well as smaller numbers of more mobile insects such as flies, leafhoppers, and springtails. Also eats snail shells, probably for the calcium they contain and to provide grit for digestion.

Behavior

A busy forager in low tree branches and shrubs. You’ll occasionally see these birds flit across openings with steady, level flight, or investigating the ground with quick hops. Male House Wrens start building several nests at once in hopes of persuading a female to mate with him. Pairs typically break up by the end of each nesting season and choose new partners the next year. House Wrens are aggressive. Single males sometimes compete for females even after a pair has begun nesting. In about half of these contests the outsider succeeds in displacing his rival, at which point he usually discards any existing eggs or nestlings and begins a new family with the female.

Nest Building Techniques

House Wrens pile twigs into the cavities they choose to nest in, either to make a bed on which to build a soft-lined cup, or sometimes mounded up into a barrier between nest and entrance, seemingly to protect the nest from cold weather, predators, or cowbirds. The cup itself is built into a depression in the twigs and lined with just a few grams (less than 0.25 oz) of feathers, grasses and other plant material, animal hair, spider egg sacs, string, snakeskin, and discarded plastic. House Wrens nest in old woodpecker holes, natural crevices, and nest boxes (or discarded tins, shoes, etc.) provided by humans. This bird’s association with open woodland is reflected in its choice of nest sites: it rarely uses nest sites more than 100 feet from woody vegetation, but also avoids heavily wooded nest sites where it’s hard to see predators coming. Despite their small size, they can be fierce competitors for nest sites, sometimes evicting a larger species and claiming its cavity after the bird has already begun nesting.

Migration and Range

Neotropical Migrant. House Wrens migrate to the southern United States and Mexico for the winter. Males return to the same breeding territory year after year. There is no information on site fidelity in females.

Cool Facts

A House Wren weighs about as much as two quarters, but it’s a fierce competitor for nest holes. Wrens will harass and peck at much larger birds, sometimes dragging eggs and young out of a nest site they want, even occasionally killing adult birds. In some areas they are the main source of nest failure for bluebirds, Tree Swallows, Prothonotary Warblers, and chickadees.

House Wrens nest inside tree holes and nest boxes. As the season progresses their nests can become infested with mites and other parasites that feed on the wren nestlings. Perhaps to fight this problem, wrens often add spider egg sacs into the materials they build their nests from. In lab studies, once the spiders hatched, they helped the wrens by devouring the nest parasites.

Where is the Wren?

Stand looking straight past the numbered station post,
look for the thin Hickory tree,
about mid way between the two large trees,
look about 3 meters up for a branch reaching to the left,
the House Wren replica is less than a meter out on that branch.

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