The Brown Creeper, also known by its scientific name Certhia americana, is a small songbird found throughout North America. It is known for its distinctive brown plumage and slender curved bill, which it uses to probe under bark crevices searching for insects. Though this inconspicuous bird blends into tree trunks, it has another more descriptive name that reveals its unique foraging behavior – the Tree Creeper.
Tree Creeper
The most common alternate name for the Brown Creeper is the Tree Creeper. This name refers to the bird’s habit of methodically creeping up the trunks of trees in search of food. Using its stiff tail feathers for support, the creeper slowly ascends the tree in a spiral pattern, meticulously exploring every crevice and groove in the bark for hidden insects. Its curved bill allows it to probe deep into cracks to pick out spiders, beetles, ants, and other invertebrates. Unlike nuthatches that move headfirst down trees, creepers creep upwards, steadily making their way up the trunk before flying down to the base of another tree to repeat the process. This distinguishing foraging behavior of creeping up tree trunks gives rise to its descriptive moniker – the Tree Creeper.
Habits and Identification
The Brown Creeper is a small, inconspicuous bird that can be challenging to spot among the bark of trees. Adults measure only 4.5-5.5 inches in length and weigh a mere 0.2-0.4 ounces. Their main plumage consists of streaked, cryptic brown upperparts and a white underside. This provides excellent camouflage as they creep up tree trunks. Other identification features include:
- Slender, curved bill specialized for probing under bark
- Stiff rictal bristles around the base of the bill to help guide prey into the mouth
- Brown streaked underparts
- Pale, thin bill
- Buffy undertail coverts visible in flight
- Distinctive high-pitched, thin call described as a “seeeep”
In addition to foraging on live trees, creepers will also search for insects on dead trees and fallen logs. They occasionally join mixed flocks with chickadees, nuthatches, and woodpeckers while foraging. Due to their cryptic coloration, faint calls, and quiet manner, creepers often go unnoticed as they methodically work their way up trunks and along branches.
Range and Habitat
The Brown Creeper has an extensive range across forested regions of North America. Its breeding habitat stretches from Alaska across Canada and the mountainous western United States down through the Appalachian Mountains into northern Georgia. Some isolated breeding populations exist in the western mountains of Mexico. The species migrates short distances in the winter, spreading south and downslope to occupy more low-elevation coniferous forests. However, some individuals, particularly in the western mountains, remain in breeding areas year-round.
Brown Creepers are strongly associated with mature coniferous or mixed forests, especially those with plenty of dead trees and fallen logs which provide foraging sites. They prefer taller forests with large-diameter trees and high canopy closure. Favored tree species include spruce, fir, pine, cedar, and hemlock. In the winter, they may also be found in deciduous forests. Standing dead trees (snags) and fallen logs provide essential habitat for nesting, roosting, and foraging.
Diet
Brown Creepers forage on live trees, dead trees, and fallen logs, searching the bark crevices and epiphytes for small invertebrates. The bulk of their diet consists of spiders, insects, and other arthropods. Typical prey items include:
- Spiders
- Caterpillars
- Beetles
- Ants
- Aphids
- Scale insects
- Bark lice
- Moth eggs
- Psocids
- Caddisfly larvae
Less commonly, they may eat small amounts of seeds and berries in the winter. Their fine curved bill allows them to extract insects and spiders from narrow crevices and holes in the bark. They can dig surprisingly deep beneath furrows in the bark to find concealed prey. Creepers sometimes scale peeling bark or hang upside down underneath branches and limbs to probe for food.
Nesting
Brown Creepers breed in mature coniferous and mixed forests across North America. They choose nest sites on live or dead trees, usually against a piece of peeling bark or in a cavity or behind a knot hole. Favorite nest trees include those that are deteriorating or have fungal infections that cause the bark to loosen. Unlike many other songbirds, creeper pairs do not maintain a nesting territory but may nest semi-colonially, sometimes with several pairs nesting on the same tree.
Nest building begins in late April or May. The female constructs the nest out of bark strips, small twigs, lichens, and conifer needles, binding them together with spiderwebs. She then lines the inner cup with fine materials like rabbit fur or feathers. Nest construction takes 1-2 weeks, after which the female lays a clutch of 5-8 tiny white eggs. She incubates the eggs alone for about 14 days. The chicks hatch synchronously and are cared for by both parents. They fledge the nest at 13-17 days old but remain dependent on their parents for several more weeks.
Migration
Most breeding populations of Brown Creepers in Canada and the northern U.S. migrate short distances south and downhill for the winter. They begin departing their breeding grounds in September and October, arriving on the wintering grounds in October and November. Spring migration back to the breeding grounds takes place from March through May. However, creepers that breed in southern regions and at lower elevations may remain in the same areas year-round.
Migrating individuals from northern areas travel at night in loose flocks, averaging about 24 miles per night. Their total migration journeys are relatively short, with most birds traveling less than 500 miles between breeding and wintering areas. Banding studies show the oldest known wild Brown Creeper was over 7 years old.
Conservation Status
Brown Creepers have a large breeding distribution and a global population estimated at 10 million individuals. Partners in Flight estimates a breeding population of 5.5 million in North America alone. They are therefore classified as Least Concern by the IUCN Red List. However, populations have declined by about 1% annually in recent decades according to data from the Breeding Bird Survey and Christmas Bird Count.
These declines are attributed primarily to habitat loss, particularly the harvesting of old-growth forests and loss of standing dead trees. Creepers rely on mature forests with plenty of cavities for nesting and loose bark for foraging. Timber harvesting and salvage logging removes vital nesting and foraging habitat. Use of wood in biomass energy production may also impact habitat availability in the future.
To support Brown Creeper populations, land managers can retain snags, fallen logs, and decaying trees in harvested forest patches. Preserving intact areas of old growth forest will also benefit Brown Creepers. Planting tree species favored by creepers, like firs and pines, can help provide future nesting and foraging habitat as secondary forests regrow after harvesting. With appropriate habitat conservation, the outlook for the Tree Creeper remains good across most of its range.
Summary
The Brown Creeper is a small songbird that forages by spiraling up the trunks of trees, using its specialized curved bill to probe for insects beneath bark crevices. This characteristic foraging behavior gives rise to its alternate common name – the Tree Creeper. Tree Creepers occupy mature coniferous and mixed forests across North America. Their populations have declined in recent decades, primarily due to ongoing loss of old-growth nesting and foraging habitat. However, with appropriate protection and management of standing and fallen dead trees, the future of this inconspicuous little bark bird remains promising.