The Secret Life of Our American Treecreeper

By Cade Campbell

Brown creeper ( Certhia Americana )

Brown creeper (Certhia Americana)

The brown creeper (Certhia americana) is a bizarre bird. If you’re not looking for them, they are virtually invisible against the craggy bark of large trees. The only member of the Treecreeper family in North America, brown creepers are pretty aberrant when compared to their more typical companion species. Nonetheless, these birds are known for performing a highly sought-after role in mixed-species flocks during the winter. When frigid temperatures push these flocks of wintering birds south, chickadees, titmice, and nuthatches band together to forage more efficiently on each tree. Tufted titmice and chickadees share the branches and twigs of large trees, while nuthatches forage downwards along the trunk of the tree. When brown creepers join one of these flocks, they will begin foraging at the base of the tree and spiral upwards. Four or five species of these birds will engage in this behavior, encircling trees in search of tiny insects, cocoons, or seeds hidden in the bark.

The entire livelihood of the brown creeper is dependent on tree bark. When threatened by a predator, a brown creeper will freeze, pressing its grizzled, brown body against a tree trunk to camouflage itself. The brown creeper’s scythe-shaped bill enables them to stab, pluck, and pry invertebrate prey from cracks in bark. The toes, feet, and legs of brown creepers are positioned to allow the birds to adhere themselves to the tree trunk. The long, tawny tail of the bird allows it to stabilize itself while foraging vertically on tree bark. But most importantly, at least to this population, the reproduction of the species also occurs within tree bark. A pair of brown creepers generally constructs a nest in a thick stand of evergreens, such as the spruce forests of Canada and the Northeast. However, the high elevations of Whitetop Mountain and Mount Rogers also host a population of breeding brown creepers. While many Southern birders are familiar with the occurrence of this peculiar little bird during the winter months, few get to observe the remarkable nesting behavior of the species, even though they are nesting in the backyard of America, right in the mountains of Southwest Virginia, Eastern Tennessee, and Western North Carolina.

Brown creeper nest behind Blue Ridge Discovery Center.

Brown creeper nest behind Blue Ridge Discovery Center.

However, these habitats would not be very unique without the elevation changes of each mountain, as well as the constantly shifting plant and animal communities. As you begin the ascent towards Whitetop along a very steep embankment, there is a noticeable, clinal shift from a riparian, acid cove forest into a drier forest speckled with pines and hemlock. Songs of the hooded warbler and Louisiana waterthrush fade away and are replaced by the jingling of ovenbirds and the raspy whistling of black-throated green warblers. Eventually, one will reach the summit of Whitetop’s spruce-fir forest and high-elevation grasslands, one of the most unique and beautiful ecosystems in the entire world. Brown creepers nest in this habitat, where they build some of the coolest little nests imaginable. A pair will build a thick cup of shredded bark, pine needles, and other soft, fibrous material under a flap of bark peeling from one of these trees. The bark serves as a roof, protecting the young from the harsh wind and rain of the Southern Appalachian “cloud forest” where the temperature, weather, and wind speed is constantly shifting, sometimes quite dramatically. The opening of the nest is inconspicuous and resembles a window or a door in shape, a feature which creates a slight resemblance between the nest and a miniature tree house.

Currently, there is an active brown creeper nest in the Mount Rogers National Recreation Area behind Blue Ridge Discovery Center in an almost vertical grove of white pines. However, before I found the actual nest, I was led by a singing individual to a “dummy nest.” Whether the nest was constructed by brown creepers to serve such a purpose, or whether it is a repurposed nest from a previous year or another bird is questionable, but this individual was certainly utilizing its presence. A “dummy nest” is a fake, empty nest built by birds as a decoy to distract or deter potential predators. I have to admit that the “dummy nest” strategy worked on me, even though my intent was quite the opposite of harming any eggs or young I might have found.