House Wrens are loud!

Nature Notes for June 30, 2017

What is the small bird that is singing so much in my garden? It seems to be nesting in the nest box. Its song is pleasant, but it is really loud.

On several occasions recently, I have had conversations along this theme.

Since the birds were using nest boxes in suburban gardens, it was quite easy to identify as a House Wren. This species always nests in cavities and will readily nest in a nest box. They are not particularly fussy about the cavity. An old woodpecker hole, a hole in a rail fence, a tin can, a flower pot, or an old shoe will all provide a suitable place in which to nest. A few years ago, I found a House Wren singing vigorously from a bison skull that had been nailed to a sign at the farm gate of a bison farm near Roseneath. I assumed that the bird’s nest was in the skull, although I didn’t clamber through the ditch to check.

House Wrens are brown or grayish-brown in colour, with next to no pattern. The male and female have the same plumage. Sometimes they hold their tail erect, but they are just as likely to hold it straight out.

The song of a male House Wren has been disturbing my neighbour's sleep.

photo © Rob Lonsberry Photography

This species has quite a broad distribution in the New World. It breeds from southern Canada through the West Indies and Central America, almost to the tip of South America. The birds that breed here winter mostly in the southern U.S. and Mexico. They usually arrive back in southern Ontario in early May.

During the breeding season, House Wren males sing a loud burbling song, and they sing and sing and sing. They do this to attract a mate and to mark their territory. The male will also choose a suitable hole and proceed to fill it with small twigs. It is quite a chore to find suitable twigs and then poke them into a nest box until the box is almost full. The male may do this with several nest boxes, but only one will be used for the nest.

The chosen nest will have a deep cavity lined with finer grasses. The nest often also contains other plant material, animal hair, spider egg sacs, string, snakeskin, and discarded plastic. In the lined cavity, the female will lay her eggs. Clutch size is usually six to eight eggs. The eggs are pinkish with blotches of reddish brown. Incubation lasts from 12 to 16 days.

When the chicks hatch, they are naked and helpless. The young will stay in the nest from 15 to 19 days. By this time, they are fully feathered and can fly. After the nestlings fledge, they are still fed by the adults for about two weeks.

Usually, House Wrens will raise two broods in a breeding season. When the second nest is initiated, the male will begin to sing again.

House Wrens eat 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. It could prove very beneficial to your garden to have birds that eat the pests of your vegetables and flowers. They also eat snail shells, probably for the calcium they contain and to provide grit for digestion.

House Wrens are very aggressive birds that defend their territories vigorously. They will chase much larger birds away, scolding loudly. They have been known to attack nests of other House Wrens, removing or puncturing eggs. They will also remove or puncture eggs and attack young of other species such as Tree Swallows or Eastern Bluebirds. Since House Wrens prefer shrubby deciduous habitat and the other two species named prefer open habitats, careful placement of nest boxes can reduce depredation by wrens.

As I write this, I can hear a House Wren singing. My neighbor will have to put up with a bit more loud song as the wrens in his garden prepare for the second nesting of the season.