Pity the brown creeper. A prisoner of the forest, the creeper seems unable to escape the gravitational pull of the tree trunk on which it creeps, ever upward, gleaning insects, spiders, and their eggs along the way.
Rarely does the creeper fly free or far like the warbler, or even the woodpecker with whom it shares life on the bark. The brown creeper is generally considered a “permanent resident” of our forests – like the trees themselves, stuck here year-round. Squirrels and forest moths are more ambitious in their travels.
Or so it might seem.
One fall, on Maine’s Monhegan Island, brown creepers tumbled at dawn from the skies like autumn leaves (which they resemble). They crept on front lawns, on cedar shakes, and on trees scattered throughout the forest. These voyagers from the north help shatter our tidy notions about birds that either stick around or migrate. Birds sometimes do both.
Sorting out which creepers migrate and which remain isn’t so easy, mostly because creepers seem to get little respect – or, at least, attention – from ornithologists. Perhaps because creepers are so cryptic, we know relatively little about their breeding biology, including territory requirements, and their population trends.
What we do know about creeper migration reveals a hodgepodge of movement to and from breeding grounds across North America. Eastern and northern creeper populations, particularly those breeding across eastern Canada, seem most inclined to migrate. A creeper banded in Ontario later turned up 545 miles away in North Carolina. Another banded in Massachusetts flew 262 miles to New Jersey. Elsewhere on the continent, creepers might migrate only longitudinally (generally east or west) or attitudinally (dropping in elevation for winter); southern populations seem to be sedentary or to move only short distances.
This kind of mixed migration pattern isn’t so unusual among birds. Red-tailed hawks breeding here in the Northeast, for example, either over-winter not too far away or leave us for short periods. Red-tails from farther north sometimes migrate here to spend at least a portion of the winter with our year-round hawks.
So what about the brown creepers now creeping around your woods? Migrants or residents? Who knows? Finding one is hard enough. Among the most widespread forest birds on the continent, creepers are nonetheless inconspicuous. To find one, your best bet is to go spishing, as we call the practice of mimicking the scold or warning notes of wrens and a few other songbirds by repeating, “Spshsh-spshsh spshsh-spshsh. Psssp-psssp-psssp-psssp-psssp.”
Creepers are suckers for spishing. When it works, usually a lone bird will fly in, land low on a tree trunk, and work its way upward. Once your creeper gets high enough, it will fly to the base of a nearby tree to repeat its unique foraging pattern. The lone member of its family (Certhiidae) here in North America, no other bird gleans like a creeper.
If you’ve been seeing creepers this past winter, they may soon depart for points north – if they’re migrants, that is. But fear not, other creepers may arrive to take their place. I think of March and April – sugaring season – as creeper season here in the Northeast. It could be that we encounter more creepers this time of year because they’re migrating through. More likely, we find more creepers because they begin to vocalize.
For some of us, hearing a brown creeper is like hearing tree bark. The tumbling notes are thin and high enough to be inaudible to certain people (yeah, okay, to “older” people like me). But if you manage to detect the creeper’s small, sweet, tinkling song, your bird is advertising for a mate and will probably stick around for the season.
As best we can tell, creepers don’t sing much during migration. A brown creeper singing in March is one of the first signs that spring is indeed creeping our way.
Bryan Pfeiffer is an author, wildlife photographer, guide, and consulting naturalist who specializes in birds and insects. He lives in Montpelier, Vermont.