Varied Thrush

Varied Thrush

text and photos by Dan Gleason,  ©2008

Varied Thrush

Like many of us, bird enthusiasts anticipate the seasonal changes that occur throughout the year, but they are most aware of changes happening in the local bird populations. For instance, you might have noticed that robins have become more numerous in some places and that they are now often seen in small groups. Perhaps some are feeding in your yard as you read this. Then one day, you might notice a “stranger” amidst the robins; much like a robin, yet strikingly different in some ways. This bird has a rusty-colored breast but instead of being a solid color, this bird’s breast has a black V-shaped band running across it. There is an orange stripe above the eye and similar-colored spots over the wings. The bird’s shape, its beak and its colors all suggest American Robin but the pattern is more complex. Growing up here, I heard them called “Winter Robins” and “Canadian Robins.” Later, I also heard others call them “Alaska Robins” and “Oregon Robins.” Birders will know these birds as Varied Thrushes. “Varied” refers to the varied plumage and, while these birds are thrushes, they are certainly not robins, despite the somewhat superficial resemblance.

The Varied Thrush is a uniquely western bird that prefers the dense, moist coniferous forests west of the Rockies. It was known, of course, to the native peoples of the region but the Europeans and their descendants in America knew nothing of this bird until 1778 when specimens were collected at Nootka Sound on Vancouver Island by crew members of Captain James Cook’s third Voyage of Discovery. Later explorers, including Lewis and Clark, confirmed its existence but the habits of this species remained a mystery for many years. In the dense, old forests where it breeds, it is a secretive bird that is usually heard more frequently than it is seen. Even today, there are still many details of this bird’s natural history that we do not know.

During cold winter weather, Varied Thrushes are often found on lawns and yards in urban environments, where they feed alone or in association with robins. They are especially attracted to acorns, but also to winter berries and other seeds. During the summer, they mostly eat insects and ground-dwelling arthropods such as centipedes and millipedes. In late summer, they begin to eat more fruits and berries when they become available. As these birds feed on your lawn during the winter, watch as they move leaves and other ground litter aside with their beaks then hop backwards to more closely examine the “cleaned” area to see what food might be exposed.

Varied Thrush

When the breeding season arrives, Varied Thrushes retreat from the valley’s lower elevations to head back to old-growth forests at higher elevation. In this habitat, they are more easily heard than seen. Their song is unlike any other bird song and I describe it as a long, drawn out “buzzy whistle” on a single pitch. It is often followed one or two seconds later by a similar note on another pitch, and some people consider it a haunting, eerie sound…but the singer often remains unseen.

It is this secrecy and propensity for old forests that kept the biology of the Varied Thrush a mystery for many years, and even today we know less about this bird than about many others. Recent research shows that many populations of this bird are in serious decline. Breeding is restricted to old coniferous forests and as these forests are logged and become increasingly fragmented, suitable breeding habitat is disappearing. Varied Thrush have done well in some of the old growth reserves that were set aside for Spotted Owls.

The breeding season of the Varied Thrush is certainly long enough to allow two broods to be raised but we lack the data to know if two broods is normal or if it is the exception to the norm. We do know that a few eggs or young may be lost to squirrels or jays, but this loss is small when compared to the numbers killed in winter when these birds come into our urban environment. Window strikes and collision with towers kills many birds but the greatest number of winter deaths is due to predation from cats, both feral and pets. The secretive nature of Varied Thrushes changes during the winter and they become bold, fighting with one another or chasing away other birds. This assertiveness makes them less willing to quickly take flight from the ground, and thus, they become more vulnerable to cats.

Migration patterns differ within the various populations of Varied Thrushes. Most of the birds seen here in the Willamette Valley have probably come from higher elevation forests. But, birds that bred in Alaska and northern British Columbia will fly the farthest south, going beyond the wintering areas of the birds from southwestern Washington and northwestern Oregon. This “leap-frog” migration pattern is used by some other bird species as well. With food readily available throughout the year, individuals in the central portion of their range tend to migrate only a short distance. Rather than compete with such existing populations, the more northerly individuals find it easier to fly over the center-most populations to avoid the competition for food.

Wherever our winter Varied Thrushes come from, they are colorful and welcome visitors. Enjoy them whether you know them by their official name or by one of their many local names: Alaska Robin, Canada Robin, Golden Robin, Marsh Robin, Oregon Robin, Snow Thrush, Winter Robin, Wood Robin or some other moniker. And, if you hear that haunting buzzy trill while out hiking next summer, bring to mind the image of the Varied Thrush that may be feeding on your lawn this winter. You will then have the singer fixed in your mind, even if your eyes cannot find it on an overhead branch.

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