Blane Klemek: Creepers are at home in the trees
In late November, on a very calm and cold morning in the La Salle Lake State Recreation Area located a dozen miles north of Lake Itasca, I heard a high-pitched, but thin sounding call-note of a familiar, yet not-often-seen, avian friend of mine.
While standing in a lowland forest not far from La Salle Creek and an adjacent cedar swamp, I searched the immediate area for the little brown bird and quickly located it. To some people not familiar with the bird’s voice, the whisper-like note — delivered as seee or sreee — might go unnoticed, or possibly thought to be more distant than its actual location.
Indeed, my little brown friend was none other than the frequently described “diminutive” brown creeper. The brown creeper’s Latin genus name, Certhia — shortened from certhius, which was derived from the Greek word “kerthios,” or a small tree-dwelling bird — means “a creeper.” Spiraling vertically up the trunks of trees, the five-inch long birds are aptly named.
I can think of only a few other birds that could be mistaken for a brown creeper. Nuthatches possess similar behaviors and body design, but no nuthatch is brown in color. As well, nuthatches typically creep downward on a tree trunk or limb head first ,while the brown creeper usually creeps upward, again head first. And though nuthatches and creepers are vocal, nuthatches vocalize louder and much more often than do creepers. As well, creepers share characteristics with species of woodpeckers, too; albeit unrelated to woodpeckers.
Brown creepers blend into their environment better than most species of birds do. Whereas many birds, particularly male birds, display assortments of color, the mottled brown backs of brown creepers is as cryptic a plumage as Nature provides. As anyone can attest, picking out brown birds in natural environments is difficult at best.
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, de-curved beaks. The beak, perfectly adapted to the birds’ specific foraging method, is shaped the way it is for a good reason. Any place where their beak 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 depend on snag trees for their existence.
The inconspicuous brown creeper hasn’t much of a song or call. But a well-tuned ear can pick up the faint, high-pitched lisped-call — a sort of “tsee” note, if you will; and the song is described as a “tinkling, descending warble.”
In any event, the brown creeper voice is consistent with its minuscule size and unobtrusive presence.
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, to name some. 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 de-curved beak, and the upward creeping behavior regularly observed. To be sure, no other bird is quite like our little brown creeper.
Reminding us of woodpeckers, nuthatches, wrens, and other little brown unremarkable birds of the forest, the brown creeper, unique in every way, is a bird that’s sure to please as we get out and enjoy the great outdoors.
BLANE KLEMEK is a Minnesota DNR wildlife manager. He can be reached at bklemek@ yahoo.com