Spring brings the return of music to our forests and fields: the dawn songs, daytime chattering, and evening vespers of migrating songbirds arriving in the Kingdom.
None give more lovely voice to this symphony than the thrushes. Males sing to stake out their breeding territories and perform their daily song for only two reasons: to attract a mate and to discourage competing rivals of the same species. These strict meanings of bird song are different from the chips, peeps, and squeaks known as bird calls, which are most often simply social contact chatter or alerts of nearby predators or other perceived dangers (including you).
Every species of songbird has its own song, a language recognizable to its own. But we comparatively tone-deaf humans struggle to distinguish these songs, often to the point of exasperation. Watch a singing Robin, Chickadee, or Song Sparrow, and you’ll see that song costs a lot of energy, so it is wasteful unless it reaches the receptive ears of the same species.
Some basics of birdsong include the following pattern. High-pitched, wheezy songs are usually associated with treetop singers such as the flame-colored Blackburnian Warbler, or birds of forest edges and open ground, such as Savannah Sparrows. Louder, lower-pitched songs, like the clear notes of the White-throated Sparrow, the insistent Ovenbird, and the thrushes most often emanate from the forest understory. These patterns have evolved to address how habitat affects the transmission of bird songs. The forest floor and understory are cluttered with obstacles that disrupt sound waves, but lower frequency songs, transmitted from singer to listener, have longer wavelengths and are thus less degraded by these obstacles.
Most of our local thrushes (a family unfortunately known as the Turdidae) are denizens of the understory and produce some of nature’s most beautiful, richest songs. These few species include Vermont’s State Bird, the Hermit Thrush (Catharus guttatus); the splendid Wood Thrush (Hylocichla mustelina); the ethereal Veery (Catharus fuscescens); the discreet Swainson’s Thrush (Catharus ustulatus); the seldom seen Gray-cheeked Thrush (Catharus minimus); and the rare Bicknell’s Thrush (Catharus bicknelli). Among these operatic specialists, their differences in appearance and habitat preference may be subtle, but their lovely songs are loud, complex, melodious, and distinctive.
Thrushes of the Backyard, the Back Forty, and the Woodlot
The song of the Hermit Thrush, the first of this group to arrive in the spring, is a series of flute-like phrases. Each phrase begins with a long, clear note, followed by a haunting series of soft notes. The Hermit Thrush repeats this phrase at a lower pitch, repeats it again at a higher pitch, and continues for about six phrases within two octaves before returning to the original pitch. Described by some as “melancholy,” the song of the Hermit Thrush is most often heard at dawn and dusk in fairly dry deciduous, coniferous, or mixed forests from northern New England to British Columbia.
The Veery may be named for its loud, sharp “veer” call, but its song is like a tumbling musical waterfall, a complex series of hollow notes like those of a breathy pan flute. Found in dense forest understory, most often near water, the Veery is hard to spot, but its song, especially heard in the early evening, confirms its abundant presence. My favorite place to listen for the Veery is in the groves of floodplain Ostrich Ferns beneath the Silver Maples and Black Willows along the Connecticut and Passumpsic Rivers.
As well-known as the Hermit Thrush is the Wood Thrush, slightly larger and more boldly marked than the other thrushes of the Kingdom. The Wood Thrush may be found in deciduous forest understory in most of the eastern states. Wood Thrushes prefer damp areas near babbling brooks, where they sing with gusto both morning and evening. The three-part song of the Wood Thrush is marked by a sequence of staccato notes, a signature “ee-oh-lay,” and bright piccolo trills, extolling the full possibilities of birdsong. Bird vocalization has two separate airways that may produce different sounds simultaneously. A careful listener may recognize that the Wood Thrush uses this anatomy to sing its own beautiful solo stereo duet.
Thrushes of Our Boreal and Alpine Forests
The boreal and alpine habitats in Vermont are very limited, but these are the places where you might hear the equally beautiful and complex songs of the Swainson’s Thrush and the Bicknell’s Thrush. The shy Swainson’s Thrush, widely distributed but seldom seen, prefers dense understory in damp upland locations such as swamps of alder and regenerating balsam fir. My encounters with them in the Kingdom have often involved scratchy, soggy bushwhacking in pursuit of a glimpse. The Swainson’s Thrush takes the Veery song and turns it upside down: a breathy, flute-like upward spiral, a lively spirit-lifting voice of wilderness.
Bicknell’s Thrush and Gray-cheeked Thrush share their own paragraph here. For most of the two centuries of scientific study of North American birds, these two were considered one species – Gray-cheeked Thrush. Brilliant Vermont ornithologists renewed an old challenge to that view. Chris Rimmer, the Director of the Vermont Center for Ecostudies, and his research colleagues, found that there was a population of these thrushes breeding only in the highest elevations of Vermont, New Hampshire, and the Adirondacks as well as the highlands of eastern Quebec and Cape Breton, Nova Scotia. Its preferred habitat is stunted montane balsam fir, spruce, and birch just below the tree line. This population also has highly restricted winter distribution in Hispaniola and Cuba. These factors, plus subtle plumage and behavioral differences, suggested that it might not be a form of the widely distributed, more common Gray-cheeked Thrush after all, but something very similar.
The songs confirmed the evidence of two species. Both sing a jumble of reedy Veery-like notes, but the Bicknell’s song ends in a brief upward sweep, while the Gray-cheeked Thrush’s song tips down at the end. To hear the rare Bicknell’s Thrush requires considerable effort: a day climb up Mt. Mansfield or a hike along the northern reaches of the Long Trail to Jay Peak. In some years the summit of Burke Mountain has supported breeding pairs. The best chance to hear the Gray-cheeked Thrush is during its spring pass through to Canada’s boreal forests.
If your ears can distinguish between Mozart and McCartney, you can certainly learn the gorgeous woodland songs of our thrushes. Your walks in the woods will be musically enriched forever.