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House wrens (Troglodytes aedon) are small and plain but loud birds. In fact, the Ojibwa name for this bird, anaamisagadoweshiinh, means “making a big noise for its size.” Troglodyte is from Latin, meaning “cave-dweller” or “one who creeps into holes.” This term is appropriate because house wrens like to live in cavities such as old woodpecker holes. Unlike many birds, these wrens are adaptable and will nest near people, hence the common name house wren.
Some of the humanmade cavities house wrens have nested in include birdhouses, sheds, boots, flowerpots, trailer hitches and fishing creels. Ornithologist Edward Howe Forbush noted in 1916 that at a bird sanctuary in Virginia, workers put 24 cow skulls in trees – and house wrens nested in 23 of the 24 skulls.
House wrens can be a gardener’s friend, ridding plots of plant pests. The vast majority of their diet (98 percent) is insects, including grasshoppers, caterpillars, spiders and beetles. Their beak is long, thin and pointy, helpful for spearing bugs and reaching into tight crevices. These hyperactive birds never stay still for long.
The house wren has had an up-and-down history. They were common in the 1800s. According to ornithologist William Brewster,
Up to about 1875 House Wrens were abundant in Cambridge … they bred practically everywhere, even in the most densely populated parts of Cambridgeport, nesting in wooden bird-houses and in the old-fashioned, earthen-ware olive jars which were put up for them or for the Bluebirds. Where such accommodations were not to be had they occupied holes in trees and crevices in the walls or under the eaves of out-buildings. They were, indeed, among the commonest and most familiar as well as the most attractive and interesting of our city birds; adapting themselves easily to crowded and noisy surroundings; obtaining the spiders which formed their favorite food from piles of lumber or other debris in vacant lots or from fences surrounding yards quite barren of trees or shrubbery; rearing their young successfully in localities much infested by cats; ever active, cheerful, contented; delighting every one by their animated movements, fussily self-assertive ways and bright, gushing songs …
At length the English Sparrows [house sparrows] came and at once began to drive or crowd the Wrens from these long-established haunts … The boxes and olive jars became quickly filled with Sparrows’ nests, Wrens were nearly or quite banished from our city and town centers within a period extending over but little more than five years – or from about 1875 to 1880.
Our native house wrens staged a comeback in the early 1900s as cars replaced horses. One horse produces up to 50 pounds of grain-filled manure per day, a major food source for grain-eating sparrows. With less grain, populations of the invasive house sparrow plummeted. The lack of horse manure did not affect insect-eating house wrens, however, and their populations increased as the sparrow population decreased. Today house wrens have increased their range, but within each region they are less abundant than they used to be. This is perhaps due to a decrease in insects or suitable habitat.
People seem to either love or hate house wrens. On the one hand, they eat insect pests that damage gardeners’ and farmers’ plants. On the other hand, they are very territorial. They compete with other, often larger, birds for nest holes. Occasionally they destroy other bird’s eggs if the other bird is in the wren’s territory. Males also fill up other birds’ nests or tree cavities with twigs to prevent them from settling nearby. In the early 1900s, ornithologist Althea Sherman, a pioneer in observing bird behavior, declared that the house wren is a “frightful devil that thrusts its sharp bayonet” into eggs of competing birds. She said that people who defended house wrens were acting “like the parents of vicious children, refusing to believe the evil things their darlings do.”
House wrens are not evil, though. They are just trying to survive.
They do not travel far from their nests – only about 100 feet. If another bird or nest is in their territory, they may try to disturb it. After all, there is a limited supply of insects in a given territory, and the more aggressive a bird is, the greater its chance of survival. Studies have shown that the most aggressive house wrens have the best chance of mating and siring offspring. Therefore, aggressive behavior is passed on.
House wrens arrive in our region in late April or early May. Males arrive first and begin singing to claim a territory and to attract females. A male finds suitable nesting spots and claims them by filling them with twigs. The female arrives about 10 days after the male. After pairing up, the female selects one of the sites the male has procured. Together, the two build a better nest. In late May or June, the female lays five or six eggs. The couple raise two broods of young during the summer. After the second brood has flown away (mid-August), the birds abandon their nests and disappear into the woods. They keep a low profile as they molt and grow new feathers. In September or October, at night, they migrate south for the winter. A few stragglers remain into November.
Studies peeking into house wren nests in suburban and rural areas indicate that suburban chicks weigh significantly less than their rural counterparts. Suburban and rural parents bring the same number of insects to their offspring – but rural parents bring more caterpillars, whereas suburban parents bring more spiders and beetles.
Because they migrate at night, house wrens can be disoriented by light and may crash into lighted building, bridges or cell towers. You can help migrating wrens (and other birds) by keeping curtains drawn at night and minimizing outdoor lighting.
Have you taken photos of our urban wild things? Send your images to Cambridge Day, and we may use them as part of a future feature. Include the photographer’s name and the general location where the photo was taken.
Jeanine Farley is an educational writer who has lived in the Boston area for more than 30 years. She enjoys taking photos of our urban wild things.
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