Laura Erickson's For the Birds

(Recording of a Nashville Warbler)

Today is the first day of National Warbler Awareness Week, another self-proclaimed occasion to celebrate some of the Northland’s avian treasures. People down in tropical Minneapolis or Madison would never dream of declaring a warbler week so late in May, but we in north country have the excellent fortune to keep most of our warblers throughout the summer. It’s possible to hear a good 15 or 18 species of warblers singing up here on a hot July day, something people further south can merely dream of.

Our featured warbler today is one that was rare back in the days of John James Audubon, but is now one of the most abundant breeders of the Northland, the Nashville Warbler. This bird was first discovered in 1808 by Alexander Wilson near Nashville, Tennessee, on migration. Wilson only found three in his lifetime, and Audubon himself only managed to shoot three or four.

The Nashville is a bird of early successional stages of 2nd growth northern forests, where birch, aspen, and balsam fir predominate in open stands with many clearings. It’s one of the most courteous of all warblers for beginners to observe, since it mainly sticks to the middle story of trees, usually on the outermost branches and twigs. The Nashville was the second warbler I ever identified on my own—there were several migrants at eye level that allowed close looks at all of their markings—the bright lemon-yellow throat, breast, and underside, the olive back and wings with no wingbars, the bluish gray face with white eye rings, and even the small orange-red crown patch. The Nashville’s a tiny sprite—only about 4 1/2 inches long, and weighs in at a mere 1/3 of an ounce. Like most warblers, it’s only easy to see if you’re alert to the possibility—even during the peak of warbler migration, most people pass right by these avian jewels without ever knowing what they’re missing.

The Nashville is one of the few warblers with an easy song to memorize. It is just about always given in two parts–I learned it as “see-bit, see-bit, see-bit, see-bit, see–weet, weet, weet, weet, weet.”

(Recording of a Nashville Warbler)

Like a surprising number of warblers, Nashvilles nest on the ground, although they feed mainly in trees. They escape the heavy tropical competition in their native land from Northern Mexico down to Guatemala each spring by migrating north to forage on our abundant insects. They scour the bark of trees and underbrush for insect eggs and pupae, and the leaves for larvae. I see them hovering in mid-air while snatching bugs on outer leaves, and occasionally flycatching within a swarm of insects.

They set up their territories in late May and June, and weave their nest from moss and bits of fern on a moss hummock at the foot of a stump or bush. Rabbit fur often cushions the 4-5 white eggs, dotted with reddish brown. The male defends the territory while the female incubates the eggs.The Nashville is one of the few warbler species that has benefited from the destruction of large tracts of the eastern forest for forestry and lumbering. It isn’t bothered much by cowbirds, compared to other warblers, and benefits from human activity which opens up edges unlike most warbler species, which require extensive tracts of forest for breeding. But like many of our northern warblers, Nashvilles are threatened by the Greenhouse Effect. If predictions come true and our spruce and fir forests recede further north, these precious jewels may once again become as rare as they were in the days of Audubon.

(Recording of a Nashville Warbler)

This is Laura Erickson, and this program has been “For the Birds.”