bROWN CREEPER (Certhia americana)
This diminutive, cryptically colored forest bird is the only treecreeper in the New World. Often seen hitching up the side of a large conifer, creepers use their decurved bills to glean invertebrates from furrows in tree trunks and their long, stiff tail feathers as a prop while foraging. In using their tail for support during trunk-climbing, creepers are evolutionarily convergent with woodpeckers. Because it is energetically cheaper to climb upward than to fly vertically (Norberg 1981), foraging creepers invariably work their way up a tree and then fly down to the base of the next tree to resume the process. They breed in forested habitats from s. Alaska east to Newfoundland and south through the Great Lakes states and New England to w. North Carolina and e. Tennessee in the east, and in the west from the Rocky Mt. and Pacific Coast states and provinces south through the highlands of Mexico to nw. Nicaragua. They winter within most of the breeding range as well as at lower elevations throughout the continental U.S. and ne. Mexico.
Subspecies: C. a. montana
Status and Occurrence: Uncommon to fairly common permanent resident in w. half of state and uncommon migrant, breeding resident, and winter visitor elsewhere. The easternmost breeding-season record is from Carter Co. near the South Dakota border. Little information on timing of annual events, but several nests have been found in Flathead and Lewis and Clark Cos. in Jun and Jul (MBD). The earliest initiation date for 19 nests found in w. Montana and ec. Idaho was 7 May, and the median date was 2 Jun (Hejl et al. 2002). Migrants are known from the e. half of the state in Apr, May, Sep, and Oct.
The oldest extant specimens are males taken by Charles Richmond in the Jefferson Valley on 23 Sep 1888 (USNM 123968; Richmond and Knowlton 1894) and by Vernon Bailey at Java on 19 Jun 1895 (USNM 136789).
Habitat: Breeds in coniferous and mixed coniferous-deciduous forests, preferring mature and old-growth stands with high canopy cover in the w. U.S. (Hejl et al. 2002). Hutto and Young (1999) found that creepers were more common in mature western redcedar-western hemlock, spruce-fir, and mixed-conifer forests than in pine or younger forests in w. Montana and Idaho. Winters in the same habitats used for breeding but also uses a wider diversity of forest types, including uplands dominated by deciduous trees, urban and suburban parks and residential areas that contain large trees, and riparian cottonwoods.
Brown Creepers are the only North American birds that build their nests behind loose pieces of bark on tree trunks. They prefer to nest in large dead or dying trees within dense forest stands, placing their nests from <1 m to >20 m above the ground (Hejl et al. 2002).
Conservation: Level I Priority in Montana. The BBS is poorly suited for monitoring this species (Hejl 1994). Data indicate a decline in numbers of 0.3% per year survey-wide from 1980 to 2007 and an increase of 12.8% per year in Montana during the same period; the Montana trend data are derived from small sample sizes and thus are not reliable. The global population estimate is 5.4 million birds (Rich et al. 2004).
Concern for this species results from its strong association with unlogged old-growth forest, especially stands of cedar-hemlock, which are uncommon in Montana and are highly productive for timber (Casey 2000). Summarizing studies of more than 60 species of forest birds in the Rocky Mts., Hejl et al. (1995: 230) found that Brown Creepers “exhibited the clearest difference between harvested and unharvested treatments; creepers were always less abundant in clearcuts or partially logged forests than in uncut areas.” Maintaining large blocks of unlogged old-growth and mature forest with high densities of large trees, dying trees, and snags would be especially beneficial to the species (Casey 2000, Hejl et al. 2002).
Historical Notes: No doubt because Brown Creepers are inconspicuous and breed in low densities, most early naturalists who visited Montana in summer failed to encounter them. Saunders (1921) believed that creepers were rare summer residents, and he was not aware of breeding records for the state. The earliest mention of the species is by Cooper (1869c: 296), who on 19 Jun 1860, while along the Missouri R. about 80 km above Fort Union, saw creepers that probably “had nests near there.” Brown Creepers have not been reported in the breeding season from this location since, making it difficult to know what to make of Cooper’s observation. As he continued west into Idaho in early Sep of that year, Cooper (1869b: 74) remarked that creepers were “Rather common, especially in the dark spruce forests of the Coeur d’Alene Range.” The creeper taken by Richmond in 1888 was “the only one seen” in two summers of field work in Gallatin Co. (Richmond and Knowlton 1894: 307).
Contemporary Work: U.S. Forest Service researchers Sallie Hejl and Mary McFadzen followed 19 nests in w. Montana and adjacent Idaho in the 1990s, obtaining data on nest-site characteristics, timing of nesting, incubation period, and reproductive success (Hejl et al. 2002). The ability of a Brown Creeper to use its cryptic coloration to avoid detection by a potential predator was well documented by Riley McClelland (1975) at a nest in the Flathead NF. When startled by a slight movement of McClelland’s leg, an adult that had been working its way up the trunk toward the nest suddenly froze, pressing its body and outstretched wings tightly against the tree. The bird was so well camouflaged against the bark that it took McClelland “several minutes” to relocate it in his binoculars after he had briefly averted his eyes from the bird. The creeper remained stationary for another 5 minutes after McClelland relocated it.
Sponsored by Jim and Sue Brown, Missoula
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