by Pam Willison
Haunting, quavering, buzzy, isolated and resonant, lacking melody and fluidity, and musical but dissonant. The Varied Thrush (Ixoreus naevius) provides a challenge for those who seek to describe the song. Possibly the best description is polyphonous: 2 or 3 notes sounded simultaneously resulting in a sound that sometimes seems harmonious, and sometimes not. Like three different sounding whistles blown together for a couple seconds. Some people venture to identify the minor key of the Varied Thrush. But this member of the Turdidae, or thrush, family has a song in “varied” keys!!
The first time I saw a Varied Thrush was in early spring, and it was aggressively scratching and feeding under native evergreens and shrubs in my yard. I thought it was the oddest-looking Robin I’d ever seen – until I looked in a bird book. Varied Thrushes are often mistaken for or compared to the American Robin, a thrush cousin. This familiar reference point helps us picture a similar size, shape, and color for the Varied Thrush. With a slighter build and more bold patterning, Varied Thrushes sport greyish-blue feathers on the back, rump, tail, crown, and nape; a rich burnt-orange face, eyebrow, breast, and pair of wing bars; and a black eye stripe and necklace or breast band. Primary feathers are slate-grey dappled with orange, while secondary feathers are slate-grey tipped with orange. The female has similar markings, which are duller and brownish-olive instead of grey, making her hard to distinguish from a juvenile. The bill is pointed, and mostly black, and the legs and feet are tawny.
The behavior of Varied Thrushes might also lead to mistaken identity as a Robin, as you see it hopping across the ground and foraging in leafy debris for insects and invertebrates, eating berries, or harvesting seeds or fruit in the fall. However, for breeding they seek high elevation, dense, moist, forests, with a dark understory, so it’s unlikely you will observe much of their feeding behavior. Additionally, Varied Thrushes tend to be elusive, secretive, and mysterious – how fitting considering their haunting, minor-key song. Most often, we hear them, but aren’t successful at locating them. Springtime hiking to mountain lakes (Stanton, Avalanche, Strawberry), walking or bicycling Going-To-The-Sun Road, or wandering on Trail of the Cedars will likely provide an opportunity to hear the polyphonous call. Decide for yourself how it is best described.
The geographic range of the Varied Thrush is western North America with breeding from the forests of northern California to the boreal forests in Alaska and the Yukon, and east into Idaho, western Montana, and Alberta. Because of this limited range, they are short-distance migrators, wintering in central-Oregon and northern California. In mild Pacific forests, they can be altitudinal migrants – not leaving, just changing elevation for breeding. The male arrives in Montana very early in the spring to his preferred habitat of wet, dense or old-growth forest to begin singing to defend his territory, and aggressively chase away competitors. The female builds her cup-like nest in low bushes or near the trunk of a conifer tree, possibly near a stream. The nest contains an inner layer of soft grasses, dead leaves and moss; a dense middle layer of wet grass, moss, or mud; and a coarse outer layer of bark, twigs, lichen and leaves. She lays 3-4 eggs – pale blue with pale brown spots – which hatch in about 2 weeks. Both parents contribute to feeding the young and, if conditions are favorable, raise two broods. Outside of breeding season, Varied Thrushes can be wanderers, having been sighted in all 48 lower states.
Varied Thrushes are still common within their range, although from 1966-2015, they declined 2.5% per year for a cumulative decline of 73%. They are vulnerable to loss of habitat through logging of northwest forests, and to forest fragmentation as they seldom live in forest patches less than 40 acres. According to the climate vulnerability tool at Audubon.org, a temperature increase of +3 degrees Celsius will cause the loss of 68% of their habitat. Climatic changes will not only make them susceptible to decline but will reshape their range and shift them northward.
The Varied Thrush, so named because of the varied plumage, has a number of traditional or regional names: Canadian Thrush, Winter Thrush, Mountain Thrush, Alaska Thrush, and Oregon Thrush. Regardless of the moniker it bears, it’s a good bet that the haunting song of the Varied Thrush is memorable to those fortunate enough to hear it.