The Brown creeper is a tiny woodland bird with an association with the biggest trees it can find. This common species is like a piece of bark that has come to life: this bird crawls up tree trunks, foraging for insect eggs and other food missed by more the active birds. Easily overlooked, its thin, reedy, piercing call indicates its presence. Reaching the top of a tree, it flutters to the base of the next, to begin spiraling its way up again.
Brown creepers live throughout North America, from northern Nicaragua up to Canada, Alaska and Newfoundland. In most of the range it is resident, but populations in the north migrate southwards in winter, apart from high mountain regions. Brown creepers breed in coniferous or mixed forest areas. They need large trees, alive or dead, for nesting and foraging.
A Brown creeper usually flies short distances between trees. It begins to forage at the base of a tree and upon reaching the top it flies to the base of the next tree and starts again. This species is solitary and arboreal outside the breeding season, though sometimes it may join a foraging flock of song birds. Communal roosting may take place during winter. Brown creepers are diurnal and an active type of bird, usually seen creeping up a tree trunk and foraging. When alarmed, it uses it camouflage pattern, landing on a tree trunk, flattening its body and spreading its wings. When remaining motionless, it looks just like bark. Brown creepers communicate mainly through vocalizations. When fighting for territory, males will sing a high-pitched song. Males also use vocalizations during the breeding season, making high and thin sounds that vary within a population.
A Brown creeper is serially monogamous and a pair remains together for several weeks after fledging. The male uses his songs when attracting a mate. Then the male and female chase each other, fluttering rapidly while displaying their white underparts. These birds breed from mid-May until mid-June. Their nesting site is chosen by the pair, but the female builds the nest, with the male sometimes bringing her nest material. The nest is 5 to 15 feet from the ground and often situated between the trunk of a dead tree and some loose bark, or in a natural cavity. 3 to 7 creamy or white eggs are laid, having fine, small, brown dots. Incubation is for 13 to 17 days, starting when the last egg has been laid. Only the female incubates, but the male feeds her at this time. The female broods the altricial chicks during bad weather, and both the parents feed them. Young fledge at around 15 to 17 days, but their parents feed them for 15 more days at least. They reach maturity at around one year.
Brown creeper populations are listed as threatened or endangered in several states, being threatened by habitat loss as well as degradation of the population’s breeding range, and the disappearance of large wooded regions.
According to the University of Michigan (Museum of Zoology) resource, the total population size of the Brown creeper is around 5,400,000 individuals. The All About Birds resource states that the total breeding population is 9.3 million individuals, 65% of them spending some of their time in the U.S., while 43% are in Canada, and 8% of them in Mexico. Overall, currently Brown creepers are classified as Least Concern (LC) on the IUCN Red List and their numbers today remain stable.