Last winter, a bright spot in my day was watching a mated pair of Carolina Wrens fly in at dusk to roost on our porch. They had discovered the rusty can I hung the summer before to hold citronella candles, and after adding a bed of dried leaf skeletons, they moved in. Each evening just before dark, the male would appear. Except on the coldest nights, he sang a few bars of his chirily-chirily-chirily song before zipping into the can, followed by his mate.
It was comforting to know that something as simple as providing the pair a safe, dry place to spend the night helped them survive the brutally cold nights we can get in the Blue Ridge Mountains of southwest Virginia.
Carolina Wrens form lifelong pair bonds and stay together all year, defending a home territory of 1 to 15 acres, mainly against other wrens. In urban areas, their territory can be as small as a backyard. These adaptable birds are common in open woods, overgrown farmland, and brushy suburban backyards in the eastern half of the United States, extreme southern Ontario, and northeastern Mexico, where they busily explore the underbrush and leaf litter for insects. Owing to their small size and rounded wings, wrens are quite agile, darting from place to place with the quickness of a mouse. Primarily ground foragers, they use their curved bills to lift up leaf litter and snatch prey.
You’ll know if you have wrens around. They’re usually heard before they are seen and are not afraid to make their presence known. Their boisterous song rings out at any time of the day. Perhaps driven by curiosity, they seem attracted to human activity. Whether we are working in the garden, tending the honeybees, or walking the dogs, the wrens will come for a closer look as long as we pretend not to notice them, but give these shy birds so much as a glance, and they dive into the nearest cover.
Carolina Wrens may “duet” at any season; the female engages in chattering while her mate sings his heart out. His fearlessness in erupting into song from an exposed, elevated perch, combined with his unmistakable tea-kettle, tea-kettle, tea-kettle song, makes him easy to spot and identify. As if he can’t hold it in a moment longer, he energetically belts out his bubbly song. With a repertoire of 30 or so distinct songs, some appropriated from other species, males sing at different times of the year to attract a mate, strengthen the pair bond, and warn trespassers to stay out of their territory.
By the time the warblers, Red-winged Blackbirds, and Ruby-throated Hummingbirds return from their wintering grounds, the resident wrens are already choosing a nest site and building a nest. They tend to use the same territory year after year, so it’s a pretty safe bet that the pair that roosted on our porch the previous winter are the same birds that have raised their young around our house for the past three years.
Spring: Nesting on our doorstep
In the wild, Carolina Wrens nest in natural cavities like old woodpecker holes, the roots of upturned trees, or rotted tree stumps. But many have adopted a mi casa es su casa policy when it comes to nesting, choosing to build their nests close to human activity. Favorite places might be porch railings or windowsills, under shed overhangs, or in hanging planters, flowerpots, mailboxes, and the pockets of hanging coats. It’s possible they choose to raise their young in human-dominated structures because fewer predators hang out near people.
About the only predators that bother the wrens that nest around our house are black rat snakes. Although wrens are aggressive nest defenders, their loud squawking and diving at a snake that crawled onto the porch and was threatening their five nestlings did not deter the reptile from its mission. Snakes are beneficial because they eat rats and mice, but we relocate the ones that turn up on the porch or in the chicken coop (they eat the eggs). This one got a free ride into the woods behind our house.
This spring, the wrens started a nest in a 15-inch length of PVC pipe that my husband had attached to the electric fence around our bee yard to hold a pollen substitute until natural pollen became available. Ignoring the bees, the pair began stuffing leaves, moss, and small stems into the pipe, all gathered from right around the nest site. After a couple of hours, the male’s zeal seemed to flag, at which point he took frequent breaks to sing from a nearby limb, as if cheering his mate on.
A little later, trouble showed up in the form of a male House Wren, a notorious nest destroyer. In a matter of minutes, the contents of the wren nest lay strewn on the ground. A second attempt by the pair met the same fate. However, the third time the House Wren showed up, the male Carolina stood his ground, and there was a skirmish.
As if suddenly possessed, he repeatedly dove at and pursued his rival, issuing scat notes, until the interloper gave up on its mission and flew off. With that matter taken care of, the pair finished the nest, to which the female added a lining of dried grass, leaf skeletons, and chicken feathers. The nest was complete and ready for eggs, and unless something else went wrong, we would get to watch wrens fledge around our house for the fourth consecutive year.
About the time the female laid her eggs, we got a chilly spell, and she had to stay on the nest to keep the eggs warm. Her dutiful mate brought her food several times throughout the day. Once the weather warmed, she only left the nest long enough to feed herself while her mate stayed close by, guarding his family and engaging in frequent outbursts of song. After the eggs hatched, the pair spent their entire day fetching food for their fast-growing brood.
To provide the high-protein diet needed to nourish their young, the wrens tirelessly comb the yard, fields, and garden beds for insects. We only mow a small area around the house, leaving the fields to grow up to provide food and cover for wildlife. The abundant wildflowers, grasses, and shrubs lure in a cornucopia of insects. If you’re a gardener, one of the great things about having nesting wrens is the joy of watching them bring in a steady stream of garden pests to feed their young. We sure won’t miss the caterpillars, beetles, grasshoppers, snails, leafhoppers, and moths that round out the wren family’s high-protein menu.
Baby wrens develop at an incredible rate and are capable of flying in 12 to 14 days. When it came time for the nestlings to fledge, mama stationed herself on a nearby limb and repeatedly issued a sharp, plaintive note to persuade them to leave the nest. The male sang with great fervor to help lure the nestlings out. Two nestlings came out to the edge of the tube but quickly retreated back inside. Dusk arrived, and all of the young were still in the nest. Early the following morning, with the encouragement of their parents, the chicks finally got up the nerve to leave. One by one, five chicks clumsily fluttered from the nest. Knowing the fledglings were vulnerable on the ground, the parents called frantically, and there was much confusion until all five were safely gathered in the trees.
The family remained in the tree cover near the nest for a couple of days, giving me the opportunity to watch the young chase each other around the yard in between learning basic survival skills. In a few weeks, the young birds would be ready to strike out on their own to find their own territory and be ready to breed and raise a family the following spring. In the northern parts of their range, wrens might only raise two broods, while here in Virginia, with the longer breeding season, they often raise three.
At the end of the breeding season, many non-migratory birds, including jays, crows, nuthatches, and bluebirds, rejoin their flock mates as a winter survival tactic. By banding together, the birds have more eyes to find food and spot predators, which helps the entire flock. Flocking birds also take advantage of roosting together at night for warmth. Every winter, a half dozen or so bluebirds fly in at dusk and huddle together in a corner eave of our porch, using each other’s body heat to survive the cold nights.
Rather than flocking, mated Carolina Wrens stay together year-round in their home territory searching for food, aggressively chasing off intruders, and raising their young. On my walks around the farm, I frequently hear the male chirping while the female squawks, rebuking me for disturbing them. The wren pair are totally dependent on each other for companionship and survival. Working as a team throughout their lives, they develop the exceptionally strong pair bonds they will need to get through the long, cold months of winter.
Unlike many other birds, they do not cache food. To maximize their foraging success, they eat a broad diet, including spiders, moths, and insects, as well as lizards, tree frogs, snails, and small snakes. The remaining part of their diet is vegetable matter such as seeds from bayberry, sweet gum, poison ivy, sumac, pine, and weeds, and they eat some fruits. Their varied diet makes it easier for the wrens to find food throughout the year. When wild food sources become scarce, they will come to feeding stations, especially if the feeders are placed near brush piles, thickets, or other cover.
Winter can be a dangerous time for Carolina Wrens. Belonging to a genus of tropical origin, they have a limited capacity to deal with cold weather and snow, and severe winters can take a toll on northern populations. Primarily ground feeders, they may struggle when heavy snow and ice cover their foraging areas, especially in the northern reaches of their range. Unmated or young birds that move farther north to find new territory often fall victim to cold winters. Those lucky enough to make it through long northern winters generally have access to bird feeders and sheltered places to roost. During very cold winters, Carolina Wrens will take shelter in nest or roost boxes.
Unlike flocking birds that roost together for warmth at night, the wren pair rely solely on each other to maintain body heat, and the loss of a roosting partner during the winter can spell disaster for the survivor. A severe cold snap at the end of December last year gave us concern for the wren pair roosting on our porch, but our concern was unfounded. They came through just fine.
It’s important to keep the feeders filled in winter to provide wrens and other ground foragers with the fuel needed to produce body heat. And if you start feeding them, don’t stop until spring! This can be a life saver in extreme cold or heavy snows. Wrens prefer peanuts from tube feeders and sunflower seed from platform feeders, and they’ll regularly visit your suet feeder. They will also roost in nest boxes in winter, preferring the type with a slotted entrance over those with the traditional entrance hole.
Carolina Wrens are a favorite of backyard birders for their fidelity to their home territory, ebullient year-round song, boundless energy, and curiosity about everything going on around them. We keep the feeders stocked in winter and hope the handsome, honey-voiced birds continue to raise their young here, ensuring a yard full of music throughout the year.
Unusual winter roosts: hornet nests
It’s well-known that warm winters spur Carolina Wrens to extend their breeding range northward; however, when colder years arrive, many birds are unable to survive, and populations plummet. On the whole, however, populations have been pushing slowly northward and westward over the past century with the rising average winter temperatures. The species has benefited from forest fragmentation in some areas and from reforestation in others — both processes create the tangled, shrubby habitat that the birds use.
In late 2017, father-and-son naturalists Doug Elliott and Todd Elliott of North Carolina reported on a little-known behavior that may help the wrens survive cold winters. They reported in The Chat, the official publication of the Carolina Bird Club, their observations of Carolina Wrens roosting inside hornet nests on winter nights (long after the year’s hornets had died). Here’s a blog post about the finding.
“Every year for the last ten years, we have collected one or more large Bald-faced Hornet nests and hung them under the roof of a porch,” the Elliotts wrote. “We have yet to observe a winter during which one or more wrens have not roosted in the hornet nest. Although this roosting behavior appears to be common, at least in our region, it has seldom been reported in the literature.”
They noted two descriptions of the behavior published in 1932 in The Auk but say otherwise it seems to have been unnoticed by researchers. The Elliotts contend the behavior “may play a vital role in the bird’s ability to overwinter. Further research is needed to understand how widespread and important this roosting behavior is among Carolina Wrens and other related bird species.”