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Photo by Jim Parrish
Photo Copyright Jim Parrish
Brown Creeper
Certhia americana
NatureServe conservation status
Global (G-rank): G5
State (S-rank): S4
External links
General information
The brown creeper, Certhia americana, breeds in southern Alaska, a great deal of Canada, most of the United States, Mexico, and Central America. It remains in much of its breeding range during winter, although individuals breeding in northern areas or at high elevations may migrate to warmer climates. The brown creeper is a moderately common year-round resident of Utah, where it prefers forested areas in high mountains during summer and lower elevation scrublands and woodlands during the winter.
Nests are often built behind loose bark on dead trees, although nests are occasionally built behind bark on living trees, or in tree cavities. Four to eight, typically five or six, eggs are laid and incubated for about two weeks. Both parents tend the young, which can fly at about two weeks of age and become independent at about one month of age. Brown creepers are excellent climbers that walk up tree trunks foraging for their favorite prey items, insects and spiders.
Species range
Breeding range extends from southcentral Alaska across Canada to southcentral Quebec and Newfoundland; south to southern California, southern Nevada, central and southeastern Arizona; in the mountains of Middle America through Mexico, Guatemala, and Honduras to north-central Nicaragua; to western Texas, southeastern Nebraska, southern Iowa, southeastern Missouri, southern Illinois, southern Michigan, southern Ontario, central Ohio, West Virginia; in the Appalachians to western North Carolina and eastern Tennessee; and to lowlands of Virginia, Maryland, and Delaware (AOU 1998). During the nonbreeding season, the range extends from southern coastal Alaska and southern Canada southward throughout the breeding range, except higher latitudes and elevations, to southern Texas, the Gulf Coast, and northern Florida, and to lowlands of the western United States and northern Mexico (AOU 1998). The species is resident in the Queen Charlotte Islands and in mountains from southeastern Arizona and southwest New Mexico south to Nicaragua (AOU 1998).
Migration
South of a line from southeastern British Columbia, North Dakota, Minnesota, Ontario, to Nova Scotia, are year round residents and do not migrate. In the mountains of the west they undertake altitudinal seasonal migrations, moving down into the foothills and valleys during the winter (Ryser 1985). In the vicinity of Bozeman, Montana, elevational movements occur Feb 20 to Apr 20 and Sep 10 to Oct 30).
Habitat
Preferred habitat includes forest, woodlands, forested floodplains and swamps. Scrub and parks are also used in winter and during migration. Most often found in coniferous and mixed forests. A study by Franzreb (1985) describes the habitat in Arizona as mixed-coniferous forest, dominated by Douglas-fir, ponderosa pine and southwestern white pine. Within the habitat, birds selected the largest (tallest) trees most often for foraging. Hejl (pers. comm.) reported finding larger numbers in western redcedar stands than in the Douglas-fir/ponderosa pine stands in 1992 field work. In the eastern U.S. south of the northern conifer zone, populations occur regularly in forested floodplains, and sometimes swamps. Hamas (pers. comm.), based on his experience, suggested that floodplain forests may be important habitat in Michigan. Davis (1978) studied populations in Michigan in two different forest types. One was an old white cedar, balsam fir, and black spruce swamp, with components of sugar maple, red maple, white pine, basswood and paper birch. The other was more topographically varied and drier; tree species included red maple, American beech, with less common white oak, eastern hemlock, large-toothed aspen, butternut hickory, and American elm. In the wetter areas of this site, dead American elms were common, and in the wettest areas, white cedar and eastern hemlock occurred. Davis (1978) found that all nests were in dead trees, and all nest trees were near water. Two were in swamps, while all others were within 60 m of flowing streams. A component of dead trees is essential for nesting, so brown creepers tend to be associated with older forests. Hejl and Woods (1991) found them in old growth forests (200+ yr), but never in rotation-aged (80 to 120 yr) Douglas- fir/ponderosa pine stands in western Montana and adjacent Idaho. The birds have also been known to move into areas where many trees have died due to flooding or disease (Bent 1948). Temporary positive impacts have been created by Dutch elm and other forest diseases, and by artificial floodings in forested areas. Both diseases and floodings leave standing dead wood and create large numbers of good nesting sites. However, the suitability of the habitat is, of course, only temporary in these situations. Creepers have been reported to become abundant in such situations (Bent 1948, Davis 1978, Nicholson pers. comm.), suggesting a certain degree of opportunism. Forest, woodland, swamps; also scrub and parks in winter and migration. Negatively impacted by forest fragmentation in southern Wyoming (Keller and Anderson 1992). Nests usually behind loose slab of bark still attached to living or dead tree, average of 1.5-5 m above ground (Harrison 1979). Also occasionally in knot holes when loose bark is not available (Bent 1948). One observer (Bent 1948) noted that nests were often under the only remaining piece of bark on a dead tree. Davis (1978) found that tree canopy was partially open at each nest site in a Michigan study.
Food habits
Creepers feed on arthropods gleaned off the surface and in the crevices of tree bark. They feed primarily on the main trunk of trees, moving from bottom to top, almost invariably forward and upward, and then flying to a low point on the next tree when branch density begins to restrict their movement (Willson 1970). Willson (1970) found that brown creepers in southern Illinois had highly specialized feeding behavior. Among a group of six bird species that all fed on insects from tree trunk or branch gleaning, creepers were the most specialized to feeding site in terms of tree structure in both winter and spring. While they favored oaks and maple in winter, and hackberry in spring, they also used several other species fairly equally in spring (i.e. they were less fussy about tree species in spring) (Willson 1970). Eats mainly insects and other invertebrates, including immature stages, obtained from bark of tree trunks and branches; also eats some nuts and seeds (Terres 1980).
Ecology
Territories ranged from 2.3 to 6.4 ha in a study in Michigan (Davis 1978). Rough approximations of density, calculated from maps of nest locations at the study sites in Davis (1978) yielded these figures for three study sites: two ha per pair, and 1.5 ha per pair for two areas of swamp forest habitat; 5.6 ha per pair in a more upland site. In the latter area, nests were close to streams, so that the area of appropriate habitat may have been smaller than the overall study area, and 5.6 ha per pair may be exaggerated by the inclusion of inappropriate habitat away from streams. Few observations of predators appear in the literature. One incidence of a creeper chased (but not captured) by a northern shrike is recounted in Bent (1948). Creepers are known to respond defensively to the scream of a hawk (Bent 1948, Davis 1978). NON-BREEDING: Bent (1948) reported that creepers are quite solitary, but there have been reports of communal roosting and huddling in winter. Fledglings roost in a characteristic huddle (Davis 1978, Ryser 1985). They were reported to move in mixed-species flocks in the winter in Louisiana, Maryland, and in summer in Maine (Morse 1970). In Louisiana, they were nearly always observed in mixed-species flocks in winter rather than singly (Morse 1970).
Reproductive characteristics
Four to eight eggs, most commonly five or six, are laid (Bent 1948, Davis 1978). Incubation begins once the entire clutch is laid (Davis 1978). Incubation lasts 14 to 17 days, but 15 is apparently most common (Davis 1978). Young fledge in 15 to 16 days, and are fed by both parents for about two more weeks. Davis (1978) found that 58% of nests with at least one egg or nestling (out of 19 observed) succeeded in fledging young. Survival rates, calculated from a total of 94 eggs laid were 60% from laying to hatching, and 94% from hatching to fledging, or 52% overall (from laying to fledging).
Threats or limiting factors
On a range-wide scale, no major threats are known. Locally, this species may be threatened by loss of forested wetlands and floodplain forest (Herkert, pers. comm.), forest fragmentation (Keller and Anderson 1992), and forest management practices that eliminate dead trees. The species is apparently area-sensitive (i.e., requires large blocks of habitat) and is intolerant of heavy logging or thinning. Nest failures have been caused by alteration of the nest site by wind or rain, predation, human disturbance, and in one case, brood parasitism by a cowbird (Davis 1978).
References
- Biotics Database. 2005. Utah Division of Wildlife Resources, NatureServe, and the network of Natural Heritage Programs and Conservation Data Centers.
- Peterson, R. T., and V. M. Peterson. 1990. A field guide to western birds, 3rd ed. Houghton Mifflin, Boston. 432 pp.
