Blane Klemek column: The brown creeper is an unusual feeder
Could it be that the brown creeper evolved the opposite foraging strategy of the similar behaving nuthatches so the species could co-exist in the same habitat?
Indeed, nuthatches and the diminutive brown creeper, though related, behave quite differently in their respective feeding behaviors.
If you watch nuthatches for any length of time, you quickly discover that their little bodies are perfectly adapted for the manner in which they forage. Nuthatches' (both the white-breasted and red-breasted species) typical feeding mode is creeping downward on the trunks and branches of trees headfirst.
Meanwhile, brown creepers, with their thin, decurved beaks, probe the bark of trees by traveling headfirst too, but instead of creeping downward, brown creepers inch along going upward. It's as if the food items that nuthatches might miss on their way down a tree, the brown creeper discovers on its way up a tree - or vice versa.
Few other birds could be mistaken for a brown creeper. As I've already mentioned, nuthatches possess similar behaviors and body designs, but no nuthatch is brown in color. So, too, the nuthatches' typical downward, headfirst approach to foraging, while brown creepers usually creep upward, headfirst, is one of the best ways to know in an instant that you're observing one or the other species.
Brown creepers blend into their environment better than most species of birds do. Whereas many birds, particularly male birds, display assortments of colors, the mottled brown backs of brown creepers are as cryptic a plumage as Nature provides.
As any birder can attest, picking out brown birds in natural environments is difficult at best. It is also why female birds of most species are generally less colorful than male birds. As such, those birds that do all or most of the incubation duties, especially ground nesting birds like ducks and upland gamebirds, are cryptically colored females. Nature has provided camouflage plumage because of female birds' vulnerability to predation.
Propped tightly against and creeping on the bark of trees, brown creepers are nearly invisible. Partly as innate defense against would-be predators and partly because the posture and mode of locomotion is good foraging strategy, creepers instinctively behave in ways that best equip themselves for survival.
By navigating and clutching firmly the trunks and major limbs of trees in the manner they do - that is, drawing their breasts snuggly into bark crevices, essentially flattening themselves - brown creepers appear to be a part of the tree itself. If threatened, creepers will sometimes freeze, spread their wings, and become motionless for several minutes until the perceived danger passes.
As creepers navigate on the boles of trees in search for food, they stop repeatedly to probe cracks in the bark with their thin, decurved beaks. The beak, perfectly adapted to the birds' specific foraging method, is shaped the way it is for a good reason: it works and works well. Any place where their beaks can fit into or underneath, brown creepers use it to probe for insects, insect pupae, and insect eggs. They also occasionally feed on nuts and seeds.
So at home within the bark of tree trunks and main limbs for their foraging activities, creepers also nest within the bark. Characteristic of brown creeper nesting behavior are nests constructed of bark bits, tiny sticks, some moss, and a few feathers neatly arranged into a small bowl tucked up against a tree trunk and sandwiched behind slabs of bark. True to their physical form, brown creeper nests are difficult to locate, let alone see. Cavities inside of trees are also utilized by nesting creepers.
Habitat components that are important for the rarely viewed brown creeper (although they are occasionally observed visiting backyard suet feeders) are the types of trees they prefer feeding from and nesting in. Commonly nesting within hardwoods, brown creepers tend to concentrate their searches for food on dead and dying trees where wood boring insects and other invertebrates are usually more abundant. Here is yet another avian species that depends on snag trees for their existence.
The inconspicuous brown creeper hasn't much of a song or call (the song is described as a "tinkling, descending warble"). But a well-tuned ear can pick up the faint, high-pitched lisped-call - a sort of "tsee" note, if you will. In any event, the brown creeper's voice is consistent with its minuscule size and unobtrusive presence. To compare, nuthatches vocalize louder and more often than do creepers.
Brown creepers are the only members of the treecreeper family, Certhiidae, that reside in North America. Other species of treecreepers can be found in Europe, Asia, Africa, India, Australia, and the Philippines.
Additionally, our species of treecreeper is the only North American bird that exhibits the combination of traits that make them so unique - mottled plumage, a decurved beak, and the upward creeping behavior regularly observed. To be sure, no other bird is quite like our little brown creeper.
Of all the species of birds that make Minnesota its home, the brown creeper is a bird I rarely observe. I find this interesting because of not only the amount of time I spend in the woods, but also because the brown creeper is a year-around resident. Every time I see a brown creeper, I stop to appreciate the encounter.
Sharing traits that remind us of woodpeckers, nuthatches, wrens and other brown or unremarkable birds, the brown creeper is a bird that's as exceptional as they come and as sure to please as we get out and enjoy the great outdoors.
Blane Klemek is the Bemidji area assistant wildlife manager, DNR Division of Fish & Wildlife. He can be reached at email@example.com.