Wren Housing & Nesting
Nesting Behavior
Nest Building: Carolina Wrens begin breeding as early as mid-March in some
regions, in early April in others. Males build multiple nests within the
territory, but females select the final nest site. Nests are usually built
in enclosed areas: natural cavities, vine tangles, upturned roots, tree
stumps, or abandoned woodpecker holes. They also nest in nest boxes and
other, less-natural nooks and crannies such as mailboxes, glove
compartments, tin cans, and old shoes.
Both sexes construct the nest. It can take a pair from four days to over a
week to complete a nest. Nests, dome-shaped with a side entrance, are made
from bark strips, dried grasses, dead leaves, sticks, pine needles, mosses,
feathers, straw, shed snakeskin, paper, and string. Nests are lined with
hair or fur. They are rarely more than 12 feet above the ground.
Egg Laying: The eggs are creamy white to pinkish white, heavily spotted with
purplish brown to rusty brown flecks. Flecking can form a wreath around the
large end of the egg. Eggs are laid in the morning, one egg per day. A
complete clutch usually contains four to five eggs but may contain as many
as eight. Carolina Wrens are sometimes parasitized by Brown-headed Cowbirds.
Incubation: Only the female incubates; she begins the day the last egg is
laid. Females are tight sitters, not readily flushing from the nest. The
incubation period lasts 12 to 14 days. During this time, the male often
brings food to the nest for the female. Compared to other passerines,
Carolina Wrens spend unusually long periods on the nest, taking few breaks.
For example, during incubation House Wrens leave the nest 27 to 43 times a
day, whereas Carolina Wrens leave only six to seven times a day.
Nestling Care: The eggs hatch synchronously, within 24 hours of each other.
For the first four days after hatching, the female broods the young.
Nestlings are fed immediately after hatching, and the male brings food to
feed the family. As the young grow, the female broods only at night and
helps the male collect food and feed the young during the day.
After 12 to 14 days, the parents coax the young out of the nest. The
nestlings usually leave the nest in the morning, hopping and flying short
distances. The fledglings stay together and are fed by both parents. If the
female begins another nesting attempt, however, the male alone cares for the
fledglings. Four weeks after fledging, the young are independent.
Carolina Wrens in northern regions usually raise two broods, whereas birds
living in southern areas can raise three.
More About Wrens
Physical Description
The size of a small sparrow, the Carolina Wren is a relatively large member
of the wren family. Male and females look alike, but males are slightly
heavier and have longer bills, wings, and tails. The back is dark rusty
brown, but the rump is bright rust. The breast and belly are buffy and
unmarked; the flanks are cinnamon. The throat and chin are white, and the
prominent eye stripe is white to buffy white. The bill is dark above and
yellowish below. Juvenile plumage resembles adult plumage but is paler.
Distribution and Breeding Habitat
Carolina Wrens are commonly found in the southeastern United States. They
range as far north as southeastern Ontario, Canada, and as far west as
eastern Oklahoma, Nebraska, and Texas, USA. Their southern range extends to
the northeastern corner of Mexico and parts of Central America. Isolated
populations exist outside of the range boundaries, as the species is slowly
expanding its range north and westward.
These shy wrens require dense shrub and brushy habitats for concealment. As
a result, they are more often heard than seen. They are common in forests,
clear cuts, and wooded suburban areas with thick underbrush. They prefer
moist bottomland forests and swamps over dry upland woods.
Diet
Carolina Wrens are ground foragers, hopping and flitting on the ground
turning over leaf litter and investigating upturned tree roots to find a
variety of food items. The diet mainly consists of insects, including
beetles, caterpillars, moths, crickets, bees, and ants. These birds are also
seen hitching up tree trunks in the manner of creepers and nuthatches,
probing the bark for prey items such as snails and spiders. The diet rarely
includes seeds, acorns, or other vegetable matter.
Harsh winters with much snow can be hard on these ground foragers. During
these times, individuals may visit feeding stations located near brush piles
and other brushy cover.
Pair Formation and Territoriality
Carolina Wrens are monogamous and maintain pair bonds and territories
year-round. Both sexes use songs and calls to defend territory boundaries.
All nesting, foraging, and feeding of nestlings occurs within the territory.
Pairs may bond any time of the year, sometimes as early as the fall of a
bird's hatch year. Males court females intensively, hopping stiffly around
them, puffing their feathers, and erecting their tails like a turkey. Males
may offer food to the female during courtship and the early stages of nest
building. Once formed, pair bonds are lifelong, but a bird may find a new
mate to replace one that has died.
Winter Movement and Dispersal
Carolina Wrens are non-migratory. Pairs remain together on territories year
round, but in periods of harsh weather birds move off territories in search
of food. Nest boxes containing straw can provide roosting sites for
individuals during harsh winters.
After reaching independence, young Carolina Wrens move off the natal
territory. They stay nearby, setting up territories near their natal area.
Source: Cornell Lab of Ornithology