The Brown Creeper is a delightful find, and can be seen throughout winter in Wisconsin scuttling in spirals up big old trees, from floodplain silver maples to backyard elms. When threatened, Brown Creepers stay incredibly still, their perfectly camouflaged plumage making a believable chunk of bark. Uniquely, the Brown Creeper is the only member of its family to occur in North America.
Brown Creeper (photo by Kelly Colgan Azar).
On freezing days like today, it’s hard to wrap your head around how a bird so small can stay warm. For Brown Creepers, constant movement and feeding on insects and seeds keeps body temperature up. The birds are also known to huddle together in tree cavities at night.
The secrets of the Brown Creeper intensify during breeding season. It is possible to find breeding birds in southern Wisconsin, though rare, with scant records in lowland forests and bottomlands. In our state’s second Breeding Bird Atlas, Jefferson County recorded only one breeding pair along the bottomlands of the Rock River where it enters Lake Koshkonong.
Brown Creepers construct nests in a delicate way—they layer cocoons and spider egg cases together with twigs and strips of bark, nearly always situating nests behind a strip of bark hanging off a tree. Because of this habit, creepers need forests with old growth characteristics: plenty of standing dead wood to provide excellent foraging and nesting opportunities. In fact, in the western U.S., Brown Creepers are considered an indicator species for old growth forest because they prefer a dense upper canopy with tall trees. Trees stand almost 50% taller at creepers’ occupied sites compared to unoccupied ones.
Using their long bills to pry away strands of bark is a favorite activity of creepers, and their process of foraging involves starting at the base of the tree and moving upward, then diving to the bottom of the next tree.
Some research suggests that Brown Creepers exhibit habitat partitioning with co-occurring birds like nuthatches. Creepers will forage lower on trees and on thicker branches while nuthatches prefer slimmer branches and higher points of the tree. However, in areas where forest has been fragmented or logged, the Brown Creeper is in competition with these other species. Thus, large blocks of forest with large diameter trees are important for both overwintering and breeding grounds.
You can find Brown Creepers throughout Faville Grove Sanctuary, wherever there are good-sized trees. It’s unlikely that you’ll hear their high-pitched call during winter, so look for them mingling in flocks of nuthatches, chickadees, and titmice. Their presence might alert you to this hidden, secretive species.
Written by Drew Harry, Faville Grove Sanctuary land steward
Cover image: A rotund Brown Creeper, with streaky plumage and a pale underside, points a long curved bill upwards while climbing up a tree trunk. (photo by Kelly Colgan Azar).
