Treecreepers

(Certhiidae)

Class Aves

Order Passeriformes

Suborder Passeri (Oscines)

Family Certhiidae

Thumbnail description
Small birds with long, thin curved bills, long tails, and highly cryptic coloration

Size
5–6 in (12–15 cm)

Number of genera, species
2 genera; 7 species

Habitat
Woodlands and forests

Conservation status
Not threatened; slight local declines for some species

Distribution
Widespread across the Northern Hemisphere, with occurrences in central and southwest Africa

Evolution and systematics

The taxonomy of the Certhiidae is somewhat problematic, and on the basis of DNA-DNA analysis comparisons some workers suggest placing 22 genera and about 100 species in the family. Sibley and Ahlquist have further divided the family into three subfamilies: wrens (Troglodytinae); gnatcatchers, gnatwrens, and verdins (Poliotilinae); and treecreepers (Certhiinae). Most workers, including the American Ornithological Union, still consider the family to consist of "typical" treecreepers of the Northern Hemisphere (Certhia) and spotted creepers (Salpornis spilonotus) of India and Africa.

Physical characteristics

Size, coloration, and markings allow creepers to blend almost flawlessly with their preferred habitat, the rough brown bark of trees. Treecreepers are small, about 5–6 inches (12–15 cm) in length, and have a long, thin, curved bill, a slender tail, and streamlined, teardrop-shaped bodies. The twelve stiff, pointed tail feathers have shafts that project beyond the vanes. In all but the bar-tailed treecreeper (Certhia himalayana), this results in giving the tail a bristly appearance at the terminus. Treecreepers use their highly specialized tails to help them climb, but spotted creepers, which hold their tails away from the trunk, do not.

The legs of treecreepers appear disproportionately short, but this very functional design, along with long toes and claws, enables them to cling closely to the side of trees as they search for food.

Plumage variation among species can be subtle and confusing. The cryptic upperparts are mostly shades of brown with streaks or streaky spots of black, gray, buff, and white. All species have a noticeable buff or white eyebrow, though it is less pronounced in some. Underparts are buff or white, with shades of cinnamon, rufous, or gray less common. Males and females are similar in appearance in both size and color. Juvenal plumage is somewhat duller and more streaky on the upperparts, but first-year birds are otherwise identical to adults. Spotted creepers are also highly cryptic but distinctively barred and more prominently spotted than treecreepers.

Distribution

Treecreepers are found throughout the forests and woodlands of Central America and temperate regions of the Northern Hemisphere. Short-toed (C. brachydactyla), Eurasian (C. familiaris), rusty-flanked (C. nipalensis), brown-throated (C. discolor), and bar-tailed treecreepers are found in Europe, central Asia, and Asia. Brown creepers (C. americana) are found in North and Central America. The spotted creeper is found in the woodlands of India and Africa in sparse and scattered populations.

Habitat

Depending on the species, creepers can be found anywhere from sea-level to mountain regions and from temperate to tropical climates. Creepers generally require mature forests and woodlands, which provide the type of bark that houses the small invertebrates on which they forage and the structures for securing their nests. Lack of suitable habitat for nesting may be the limiting factor in the expansion of breeding range in some species.

Behavior

Creepers forage singly, in pairs, or in mixed-species flocks. Foraging behavior is distinctive and consists of flying to the base of a tree, then gleaning and probing rough bark for insects while climbing the trunk. Creepers also forage for prey on limbs by clinging to the underside and creeping outward from the trunk almost to the tip of the main branch. Treecreepers typically climb the trunk in a jerky, spiral motion.

Treecreepers roost singly, in pairs, or sometimes in small groups during the nonbreeding season, probably for warmth. Some species roost arranged in a small circle with individuals facing one another.

Feeding ecology and diet

The Certhiidae use their thin, thorn-like bill to probe beneath bark for food, which primarily consists of small insects, spiders, and other small invertebrates. Treecreepers also eat seeds and nuts, usually in wintertime when invertebrates are scarce. There is only one known record of treecreepers storing food, which consisted of sunflower seeds taken from feeders one winter.

Reproductive biology

Male creepers establish and defend the breeding territory through vocalization. Songs are generally weak and quiet trills, and calls are high-pitched and thin. Though they may often go unnoticed, songs and calls may be the best way of locating these highly cryptic birds.

Breeding biology of the rusty-flanked treecreeper and the brown-throated treecreeper is not very well known. In all other treecreeper species, nests are usually constructed beneath a loose piece of bark on dead or dying trees. Occasionally creepers will construct nests on buildings, walls, crevices in trees, or in heavy vegetation such as ivy. Some species also infrequently use nest boxes. Height of nests from the ground varies from species to species and can range from 1.6 to 52 ft (0.5 m to 16 m).

There are four to six eggs in the treecreeper clutch, and they are white and faintly spotted red or reddish brown; Spotted creepers have fewer eggs in each clutch (one to three) and the eggs are usually gray, greenish gray, bluish, or greenish blue with black or brown spots. Only the female incubates the eggs, but both sexes feed the young. Duration of brooding varies from species to species, but lasts from 13 to 17 days. Treecreeper pairs frequently double brood. Treecreepers usually form family parties for two to three weeks after the young fledge.

Conservation status

Brown creepers might be in slight decline in some regions of North America. Competition with wood ants for prey may be causing a decline in some populations of Eurasian tree-creepers.

Significance to humans

None known.

Species accounts

List of Species

Eurasian treecreeper

Certhia familiaris

taxonomy

Certhia familiaris Linnaeus, 1758.

other common names

English: Northern, common treecreeper; French: Grimpereau des bois; German: Waldbaumläufer; Spanish: Agateador Norteño.

physical characteristics

Length 5 in (12.5 cm). Upperparts brown, spotted and streaked with white or buff, rufous rump; underparts white to buff.

distribution

Widespread in Europe, Central Asia, and Asia.

habitat

Forest and woodland.

behavior

Roost singly, in pairs, or sometimes in small groups during the nonbreeding season.

feeding ecology and diet

Spiders, insects, and other small invertebrates.

reproductive biology

Nest behind loose bark or in crevice; will also use dead leaves and heavy vegetation to hide nest. Three to five eggs, eggs white with pink or reddish spots.

conservation status

Not threatened. Common and widespread.

significance to humans

None known.

Brown creeper

Certhia americana

taxonomy

Certhia americana Bonaparte, 1838, North America.

other common names

English: American treecreeper; French: Grimpereau brun; German: Andenbaumläufer; Spanish: Trepador Americano.

physical characteristics

Length 5.25 in (13 cm). Populations highly variable, but generally upperparts dark brown, spotted and streaked with white, buff, or pale gray; cinnamon-colored rump and undertail coverts, underparts white to buff; western and Mexican populations darker and smaller.

distribution

North and Central America.

habitat

Forest and woodland.

behavior

Fly to base of tree and search for insects while climbing upwards.

feeding ecology and diet

Spiders, insects, and other small invertebrates; sometimes seeds from feeders in winter.

reproductive biology

Nest behind loose bark or crevice within 197 ft (60 m) of water. Nest cup shaped with "horns." Five to six eggs, eggs white with reddish brown spots.

conservation status

Possibly declining, but not threatened at this time.

significance to humans

None known.

Short-toed treecreeper

Certhia brachydactyla

taxonomy

Certhia brachydactyla Brehm, 1820.

other common names

French: Grimpereau des jardins; German: Gartenbaumläufer; Spanish: Agateador Común.

physical characteristics

Length 5 in (12.5 cm). Resembles Eurasian treecreeper and is hard to distinguish on the basis of physical appearance.

distribution

Western Europe.

habitat

Mixed forest and woodland.

behavior

Forage for prey by clinging to the underside of tree branches.

feeding ecology and diet

Spiders, insects, and other small invertebrates.

reproductive biology

Nest behind loose bark or in crevice. Will use nest box. Five to seven eggs, white with reddish purple or reddish brown spots.

conservation status

Not threatened.

significance to humans

None known.

Resources

Books

Harrap, Simon, and David Quinn. Chickadees, Tits, Nuthatches, and Treecreepers. Princeton: Princeton University Press, 1995.

Kaufmann, Kenn. The Lives of North American Birds. New York: Houghton Mifflin, 1996.

Sibley, Charles G., and Burt L. Monroe, Jr. Distribution and Taxonomy of Birds of the World. New Haven: Yale University Press, 1990.

Periodicals

Aho, Teija, Markku Kuitunen, Jukka Suhonen, Ari Jäntti, and Tomi Hakkari. "Reproductive Success of Eurasian Treecreepers, Certhia familiaris, Lower in Territories with Wood Ants." Ecology 80 (1999): 998–1007.

Aho, Teija, Markku Kuitunen, Jukka Suhonen, Ari Jäntti, and Tomi Hakkari. "Behavioral Responses of Eurasian Treecreepers, Certhia familiaris, to Competition with Ants." Animal Behavior 54 (1997): 1283–1290.

Baptista, Luis F., and Robin Krebs. "Vocalizations and Relationships of Brown Creepers Certhia americana: A Taxonomic Mystery." Ibis 142 (2000) :457–465.

Davis, Cheyleen. "A Nesting Study of the Brown Creeper." The Living Bird 17 (1978): 237–263.

Susan L. Tomlinson, PhD