Varied Thrush

Ixoreus naevius

(c) Ron Wolf
  • TURDINAE
  • Thrushes
  • Passeriformes
  • Zorzal pechicinchado
  • Grive à collier
Introduction

Despite its high numbers, there is concern that the Varied Thrush may be decreasing. This secretive songbird is fond of wet, dense, inaccessible forests, so researchers have much to learn regarding even some of the basic aspects of its breeding biology.

U.S. Fish & Wildlife Service
Bird Sounds
© Lang Elliot, Nature Sound Studio
Appearance Description

This robin-sized songbird is uniquely patterned and unlikely to be confused with other birds. Adult males are a particularly striking mix of rusty orange, black and bluish gray. The bird's head is gray at the crown, with a thin orange supercilium (or "eyebrow"), a black mask around the eye, and a bright orange throat. A bold black band separates the throat from the orange breast and scaled belly. The wings are intricately marked with bright orange wing bars. Females are similarly pattern, but less brilliant, with a gray (rather than black) breast band. The best clue to this bird's presence is usually its ethereal song. On the breeding grounds, it gives a long, high, single-pitched whistle, which it repeats regularly in varying pitches. Each whistle is followed by a seemingly deliberate pause. The song often seems to emanate from the dark forest itself, and is generally unhelpful to observers wishing to locate the singer.

Range Map
Courtesy Kenn Kaufman
Range Distribution

This strikingly handsome thrush breeds in coniferous forests throughout most of Alaska, south through the Yukon, British Columbia, and in five northwestern states, where it is found as far south as northern California. In winter, its range shifts south, extending from Kodiak Island and British Columbia all the way to Baja California.

Habitat

Dark, dense, mossy northwestern pine forests are the favored haunts of the Varied Thrush. It breeds in a variety of coniferous habitats, but is most common in wet coastal stands of spruce, hemlock, or fir. In winter, it wanders into different forest types, but is most likely to be encountered in dense wooded areas near ravines or streams. It is also more likely to be found at feeders, in yards, or even on lawns at this time of year.

Feeding

The diet of the Varied Thrush changes from season to season. When breeding, it mainly searches the forest floor for arthropods and other invertebrates, which it often locates by using its bill to flip leaf litter into the air. It will also take a variety of prey, including worms, caterpillars and insects. In winter, its diet becomes especially dependant upon fruits and berries, but also upon seeds, acorns, and other nuts. In winter and during migration, it is often attracted to cultivated food sources such as berry patches, apples, olives, and other crops.

Reproduction

The female seems to choose the nest site, and takes responsibility for building the nest, leaving the male free to delineate his territory with his eerily whistled song. The nest is usually placed at the base of a branch along the trunk, but can also be constructed on buildings, or even directly on the ground. The bulky cup nest is lined with soft materials such as grasses, and 2-5 brown-speckled sky blue eggs are deposited. The female incubates her eggs for about two weeks, but both parents tend to the chicks following hatching. Chicks are blind, naked and helpless, requiring constant care for the first several days. They develop quickly, however, and fledge from the nest after about two weeks. The time spanned from egg laying to fledging is less than five weeks, which grants adult pairs plenty of time to raise a second brood.

Migration

Different Varied Thrush populations employ varying migration strategies. It seems that while interior populations migrate far to the south, coastal populations may only migrate short distances, if at all. The Varied Thrush is a hearty bird, capable of surviving through the roughest of winters, but most birds depart from the northernmost portions of its range in winter. The Varied Thrush is regularly found far south of its breeding range in winter, but numbers present vary widely from year to year in certain areas. This species is also highly prone to vagrancy in winter, when at least a few individual birds inevitably show up on the east coast almost annually. Bird watchers have reported rare winter records of vagrant Varied Thrushes from nearly every state and province in North America over the years.

  • 26,000,000
  • 26,000,000
Population Status Trends

Through the years, Audubon's Christmas Bird Count (CBC) data have indicated that the Varied Thrush is subject to biennial spikes in abundance, where it is present in good numbers one year and scarce the following year. This trend has been well documented for decades. Recently, however, CBC data have indicated a continual decline in numbers between 2001 and 2006, with no expected bi-annual spike. On the other hand, Breeding Bird Survey data (which cover only the southern portions of the breeding range) seem to indicate that numbers have remained relatively stable each spring during that same time period. Population trends need to be closely monitored over the coming years.

In the early 1990s, a breeding population was newly discovered in the San Mateo Mountains of coastal central California. This location is quite distant from the next nearest breeding population in the northern part of that state, and is thought to indicate a recent range expansion for the Varied Thrush.

Conservation Issues

There are no major specific leading causes of decline, but the Varied Thrush may be vulnerable due to a number of human induced factors. As with so many other species, habitat loss is a concern, particularly the dense old growth forests of the northwest that are equally attractive to both Varied Thrushes and logging interests. It is also affected negatively by fragmentation of habitat, as it prefers to breed in large, continuous tracts of forest. Many birds are killed annually due to collisions with cars, or window strikes around buildings. The central California population is thought to be particularly vulnerable to predation by domestic cats.

It is hoped that the Varied Thrush will benefit from any conservation protections extended to the northwestern Spotted Owl, which shares a similar habitat.

What You Can Do

Reduce threats to birds by keeping your cat indoors. Read Audubon at Home information about cats. 

Find out about actions you can take including Audubon programs and activities.

More Information

Learn more about this species and other birds through these resources

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Natural History References

Cornell Lab of Ornithology. All About Birds. 1999. Webpage accessed August 2007.

Cornell Lab of Ornithology. Macaulay Library Sound and Video catalog. Webpage accessed August 2007.

George, T. L. 2000. Varied Thrush (Ixoreus naevius). In The Birds of North America, No. 541 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA. 

Kaufman, Kenn. 1996. Lives of North American Birds. Houghton Mifflin Company, New York. 

Sibley, David. The Sibley Guide to Birds. National Audubon Society. Knopf, New York. 2000.


Conservation Status References

Cornell Lab of Ornithology. All About Birds. 1999.   Webpage accessed August 2007.

George, T. L. 2000. Varied Thrush (Ixoreus naevius). In The Birds of North America, No. 541 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA. 

Kaufman, Kenn. 1996. Lives of North American Birds. Houghton Mifflin Company, New York.

Sibley, David. The Sibley Guide to Birds. National Audubon Society. Knopf, New York. 2000.