The whimsical Carolina wren (Thryothorus ludovicianus) is found across the eastern half of North America and parts of Central America, ranging from Ontario and Quebec west to Kansas and Nebraska and south to Texas, Florida, Mexico’s Yucatan region, and parts of Belize and Nicaragua.
The name might be a giveaway, but this bird has special importance to Carolina, where it's the state’s national bird. This is a guide to Carolina wren nesting.
Carolina wrens nest early in spring, and some eggs are laid as early as early March. Nests are built in low-lying shrubs, hedges, bushes, and on the ground or in the lower levels of trees. Artificial nests are common, too - Carolina wrens have been found nesting in old buckets, mailboxes, tin cans, coat pockets, and even old shoes.
These diminutive birds move fast during the breeding season and may raise three broods. Their average breeding season spans around 190 days in some states!
Of course, there is much more to learn about these intriguing birds - read on to find out!
Carolina Wren chicks in the nest
Carolina wrens typically nest in cavities around 3 to 6ft above the ground, but they also build nests in hollows on or under the ground. Interestingly, the first nests of the season are more likely to be built on the ground. Later nests are usually built above the ground.
Nests are built in weedy foliage, shrubs, the lower branches of dense trees, upturned roots, stumps, and artificial objects. Artificial nesting sites include everything from abandoned cars, garages, mailboxes, and tin cans to old shoes, coat pockets, and anything with a usable hollow.
Carolina wrens are known for being incredibly flexible regarding nesting sites and seem to pick unusual synthetic cavities, such as old boots or parts of abandoned cars. Researchers speculate that because Carolina wrens forage in and around human settlements and buildings, they’ve gained familiarity with items humans leave lying around.
Carolina wrens are non-migratory and remain in and around their breeding grounds all year.
Carolina Wrens don’t reuse nests from year to year, however. Instead, the male builds ‘draft’ or ‘dummy’ nests as early as March before the male and female choose one together and finish it off.
Then, subsequent nests are built from scratch. If a nest survives the next season, then the male may choose the same site and modify or refine the same nest, but this hasn’t been formally observed.
Carolina Wren perched above its nest in palm tree
Carolina wren nests are cupped or domed with a top or side entrance. They’re fairly bulky and well-packed with bark, soft twigs, leaves, straw, and human objects like plastic, paper, and string.
The outside of the nest is often covered in mosses and green foliage, perhaps to help camouflage the structure. When built in synthetic cavities, Carolina wren nests look small and packed with foliage with a circular or cylindrical-looking entrance.
Carolina wren nests are small, measuring around 8 to 23cm long by 8 to 15cm wide.
They’re packed into the cavity they’re made in, and there’s very little room to maneuver once the eggs hatch!
The nest of a Carolina Wren inside a nest box, with newly hatched chicks inside
Carolina wrens nest from as early as March to as late as October. Studies in Illinois, Kentucky, Florida, Alabama, Georgia and Kansas found that most eggs are laid between late March to June or early July.
Some pairs raise three broods in one season, each taking slightly longer than 50 days from start to finish. This results in a very long breeding season of over 160 days. Some pairs have been recorded laying eggs and raising young for a total of 192 days, from the day the first egg is laid to the day the last chick fledges.
Carolina wrens raise between two to three broods in a typical year, which means their breeding season is quite long, stretching from as early as early March to August, September or rarely even October.
Studies found that some couples of Carolina wrens nest for around 192 days from the start to finish of the breeding season.
Carolina wrens lay eggs from as early as March to as late as September.
First chicks typically arrive between mid-March to April. As many as three broods are raised throughout spring and summer.
Carolina Wren perched on the branch of a tree
According to one study, males sometimes pre-build nests in the breeding ground at the start of the breeding season, though many are never used. The female and male then pick one of these pre-built nests and continue to build and refine it for the first brood.
These early-season nests are typically built on or near the ground; later nests are usually built above the ground.
Both the male and female Carolina wrens build the nest, but the male contributes more material as the female handles construction duties. One bird builds as the other delivers the material, but sometimes they build together, and the male sings as they work.
Most construction occurs in the morning. Once the nest nears completion, the female begins lining the inside of the nest with softer materials. Carolina wrens make around 100 trips back and forth with nesting material, and construction takes approximately four days to 1 week.
Carolina Wren gathering materials to build the nest
Carolina wren eggs are small, measuring 0.7 to 0.8in (1.7 to 2.1cm) long by 0.6 to 0.7in (1.4 to 1.6cm) wide. They’re white to pinkish white with finely spotted brown flecks concentrated at the larger end.
One of the eggs seems less pigmented than the others for reasons unknown.
Carolina wrens lay between 4 to 6 eggs on average, sometimes as many as 8. Incubation takes around two weeks, and the chicks are ready to fledge after another two weeks.
The entire breeding cycle per brood takes about 50 days.
The female Carolina wren takes care of incubation, and the male delivers her food and checks up on incubation progress. The male is attentive to the nest and sings to the female from nearby.
Carolina Wren eggs inside the nest
Carolina nests fledge after 13 to 14 days but can leave the nest after just nine days if they need to, e.g. if the nest is disturbed.
Fledglings remain together and roost together in nearby trees or disused nests. The parents continue to look after them for several days - the male will handle the majority of care when the female starts preparing for the next clutch.
Carolina broods have 1 to 3 broods. It’s very common for them to have two broods and less common to have 3.
Three broods are more common in the southernmost regions of their range, including Alabama, Georgia, Florida, South Carolina, Louisiana, Mississippi, Texas, and northern Mexico’s Yucatan region. Four broods have been recorded on rare occasions.
A recently fledged Carolina Wren chick
Carolina wrens only abandon their nests if they’re attacked by predators or destroyed.
Nests fail due to adverse weather, predators, and nest parasitism by cowbirds. Cowbirds sometimes remove Carolina wren eggs from the nest and lay their own larger eggs which the Carolina wrens incubate.
Carolina wrens may abandon nests hijacked by cowbirds, but the wrens can raise Cowbird chicks to adulthood.
Carolina wrens nest in small hollows and holes, including synthetic objects like buckets, mailboxes, old shoes, and coat pockets.
They commonly nest in backyards across the southernmost regions of their range, especially when eligible synthetic nesting sites are strewn around, such as abandoned cars and machinery.
Carolina wrens are cavity nesters and sometimes use nesting boxes, though they generally prefer more unusual synthetic nesting sites like mailboxes, buckets, tin cans, etc.
Carolina Wren gathering materials to build the nest
Carolina nests occasionally nest in tree hollows, upturned roots, and the lower section of trees. They’re flexible nesters that nest anywhere that loosely resembles an enclosed space or hollow.
Live trees aren’t their preferred nesting site unless they can find a cavity close to the ground.
Carolina wrens frequently nest on the ground in small holes, cavities, and other enclosed spaces.
The first nests of the season are more likely to be built on the ground. Subsequent nests are built off the ground at the height of 3 to 6ft or so.
During incubation, the female Carolina wren sits on the nest for around 73% of the day or more. The male doesn’t incubate but won’t be far away.
Carolina wrens roost in trees or humanmade structures, e.g., farmyard structures and abandoned buildings.
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