Saturday, March 30, 2013

Nature's Advance Man

This morning, an eastern phoebe flitted across the restored prairie at Forum Nature Area, in Columbia. Moving through chilly, moist air under gray skies that might rain or snow, the flycatcher seemed out of place.

Yet, this is his annual calling card.  Nature's advance man often arrives by mid March, six weeks ahead of many northern flycatchers.  Among the earliest signs of spring, eastern phoebes are generally found alone, flicking and spreading their tail as they alight on a sapling or dead wildflower stalk.  Until the insect supply catches up with their energy needs, they feast on berries and soft seeds as well; once the weather is reliably warm and hordes of insects fill the air, eastern phoebes pair off, nesting on cliff ledges, beneath bridges or along the eves and beams of barns and other out-buildings.

The hardiness of this flycatcher is also apparent in the fall, when they stop to winter along the southern tier of the U.S., well north of their cousins that head for the balmy air of Central and South America.  Why a bird that feeds on flying insects would evolve this pattern of behavior, matched only by the tree swallow in North America, is somewhat of a mystery.  Despite their habit of arriving before the last winter freeze and wintering in areas prone to cold weather, eastern phoebes thrive;  indeed, their population is increasing, partly in response to the varied nest sites that we humans provide.