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Perception Channels: visual ; tactile ; acoustic ; chemical
Varied Thrushes are currently neither endangered nor threatened in any portion of their range. Due to the fact that Varied Thrushes live in western old growth forests, deforestation and clear cutting pose potential threats to some population of Varied Thrushes. Flying into windows is a major anthropocentric cause of mortality (George, 2000).
Wells, et al. (1996) found that Varied Thrush populations undergo 2-3 year cycles of abundance and decline in most of the normal winter ranges.
US Migratory Bird Act: protected
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
Varied Thrushes may eat orchard fruit (Finley, 1936)
During migration they eat fruits, berries and acorns. During the summer they eat arthropods, fruits and berries (George, 2000). During the winter, Varied Thrushes eat arthropods, fruits and acorns and can be lured to backyard feeding stations and are fond of apples (Finley, 1936 and George, 2000). Wells et al. (1996) suggest that the population cycling of the Varied Thrush is tied to the fruiting cycle of oak trees in the thrush's habitat.
Western North America. The Varied Thrush breeds from Northern California north to the extent of the boreal forests in Alaska and the Yukon Territory. They range east into Idaho and western Montana and Alberta (Finley, 1936). Varied Thrushes are known to overwinter as far south as Southern California. These birds occasionally stray to eastern North America and have been recorded in every Canadian Province except Newfoundland and in every U.S. state except Arkansas, Mississippi, Alabama, North Carolina and Hawaii (George, 2000).
There may be four distinct subspecies of Varied Thrushes:
Ixoreus naevius naevius, a subspecies that breeds in southeast Alaska and along the coastline south to northern California,
Ixoreus naevius meruloides, a subspecies that breeds from interior Alaska south through interior British Columbia and into northwestern Montana, northern Idaho, eastern Washington and northeastern Oregon,
Ixoreus naevius carlottae, a subspecies that breeds on Queen Charlotte Island, British Columbia and
Ixoreus naevius godfreii, a subspecies that breeds from southern interior British Columbia to eastern Washington and western Montana (George, 2000).
Biogeographic Regions: nearctic (Native )
Varied Thrushes are most commonly found in dense, moist woodlands and low coniferous old growth forests. In California, Varied Thrushes prefer the forests of coastal redwoods, Sitka spruce and red alder; in Oregon and Washington they prefer wet coastal forests of Sitka spruce, western hemlock and western red cedar and wet montane forests with Douglas fir, western hemlock and western red cedar; in northwestern Montana they prefer forests of western larch and Douglas fir; in coastal British Columbia they prefer forests of Douglas fir, western hemlock, western red cedar and Sitka spruce; in interior British Columbia they prefer montane coniferous and taiga forests; and in Alaska they prefer wet coastal and taiga forests (George, 2000).
Terrestrial Biomes: taiga ; forest ; mountains
Average lifespan
Status: wild: 67 months.
Length 19.0-26.5 cm; Body mass 65-100grams
Male: Characteristics of male Varied Thrushes are a slate blue back and nape, an orange face, eyebrow, and breast with a black eye stripe and black necklace or breast band. Wings; Coverts are slate-grey with two orange bars. Secondaries are slate-grey and tipped with orange. Primaries are slate-grey and dappled with orange (Finley, 1936).
Female: Resembles the male but much more dull and with brownish-olive coloration replacing the slate-grey of the male (Finley, 1936).
Juvenile: Like the female but with a whitish belly (Finley, 1936).
There are four listed subspecies for the Varied Thrush based solely on plumage differences in the females (in George, 2000).
Range mass: 65 to 100 g.
Other Physical Features: endothermic ; bilateral symmetry
Varied Thrushes are difficult to study because of their retiring behavior, love of dark, wet forests and low population densities. The males usually choose territories that serve both for breeding and feeding in wet, mature forests. The males establish individual territories by singing. During the breeding season, a male Varied Thrush will chase rival males away from its territory (George, 2000).
Female Varied Thrushes build their nests in low bushes on or near a stream bank (Finley, 1936). Active nests are often found near old nests in the understory. The nests are three layered with a course outer layer of twigs, leaves, lichen and bark, a dense middle layer of rotten wood and moss or sometimes with mud and wet grass, and a fine inner layer of soft grasses, dead leaves and moss (George, 2000). The eggs are greenish-blue with sparse dark umber-brown spots (Finley, 1936). Along the coast, females tend to lay an average of 3 eggs with a range of 1 to 5, while the interior subspecies lay an average of 4 eggs with a range of 2-6. They may raise two broods a year and the hatchlings are altricial. Varied Thrushes are monogamous and both parents help feed the young (George, 2000).
Key Reproductive Features: iteroparous ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous
Average time to hatching: 14 days.
Average eggs per season: 3.
The varied thrush (Ixoreus naevius) is a member of the thrush family, Turdidae. It is the only species in the monotypic genus Ixoreus.
The varied thrush was formally described by the German naturalist Johann Friedrich Gmelin in 1789 under the binomial name Turdus naevius.[2] Gmelin based his description of the "Spotted thrush" that had been described by John Latham in 1783 from specimens owned by Joseph Banks. These had been collected near Nootka Sound (formerly King George's Sound) which separates Nootka Island from Vancouver Island on the Pacific coast of Canada.[3] The varied thrush is now the only species placed in the genus Ixoreus that was introduced by Charles Lucien Bonaparte in 1854.[4][5] The genus name Ixoreus comes from the Ancient Greek ixos meaning "mistletoe". This was a synonym of a former name for the mockingbird genus, Mimus; Bonaparte assumed wrongly that, because Swainson had shown a mockingbird and this thrush on the same plate of his book, they were related. The specific naevius is Latin for "spotted" from naevus meaning "spot".[6]
Four subspecies are recognised:[5]
The varied thrush is a fairly large thrush species. It can range from 20 to 26 cm (7.9 to 10.2 in) in length and can span 34 to 42 cm (13 to 17 in) across the wings. Body mass can vary from 65 to 100 g (2.3 to 3.5 oz). Among standard measurements, the wing chord is 11.8 to 13.6 cm (4.6 to 5.4 in), the bill is 1.8 to 2.3 cm (0.71 to 0.91 in) and the tarsus is 2.9 to 3.3 cm (1.1 to 1.3 in). It is similar in size to the widespread American robin, though the varied is on average shorter with a heavier, more robust build.[7][8] In general, varied thrushes feature intense orange and black feathers.[9] Adult males exhibit medium orange with a curved gray pattern at the breasts and throats, with grayish-blue tail ends, scruffs, and crowns. They also possess a tufted supraloral stripe and streaks of dark colors on its flight feathers. Its bill is also achromatic, but tan near the bottom of the lower jaw. Its legs are often tawny or dark brown. Females' markings are not as well-defined, with olive-browns and grays, brown hind feathers, and indiscernible gray-brown plumage near the breasts. Young varied thrushes are generally brown, though their stomach feathers are white, and initially harbor two orange stripes at the covert feathers.[10]
Eggs are generally 3-4 per nest, but sometimes 2–5. Pale blue, lightly dotted with brown. Incubation is by female, probably about 2 weeks. Young: Both parents feed nestlings. Development of young and age at which they leave the nest are not well known. Probably 2 broods per year.
There is an extremely rare variant of this species in which all the orange in the plumage is replaced by white.[11] A very rare British vagrant in 1982 was of this type, leading to speculation that whatever mutation causes the colour variation also affects the navigational abilities of this thrush. There have been only five recorded sightings since 1921.[12]
The varied thrush breeds in western North America from Alaska to northern California. It is migratory, with northern breeders moving south within or somewhat beyond the breeding range. Other populations may only move altitudinally. This species is an improbable transatlantic vagrant, but there are now two accepted western European records, both in Great Britain, in 1982 and on Papa Westray in the Orkney Islands in October 2021.[13][14]
Nests in Alaska, Yukon Territory, and mountains in British Columbia, Washington, and Oregon. Prefers moist conifer forest. Most common in dense, older conifer forests in high elevations. Moves to lower elevations during the winter where it is often seen in towns and orchards and thickets, or migrates to California. Seen in flocks during winter of up to 20 birds. It is well known for individual birds to fly eastward in winter, showing up in just about any state, then returning to the west coast for breeding.
The varied thrush is predominantly insectivorous, though its diet varies throughout the course of the year. During the summer, ground-dwelling arthropods make up the bulk of its diet. During migration and winter, however, the focus of the thrush's diet shifts to fruits, seeds, and acorns, though arthropods are still taken in some quantity. Varied thrushes consume a wide variety of berries throughout the year, including snowberry, red huckleberry, California honeysuckle, madrone, salmonberry, and thimbleberry.[9]
Varied thrushes forage primarily on the ground, except when foraging for fruits and berries.[9]
The breeding habitat is dense coniferous forest, with two to five eggs being laid in a tree nest.
Varied thrush, Bellevue, WA, USA
Male. Distinguishing features include a black breast band on a bright orange breast
The varied thrush (Ixoreus naevius) is a member of the thrush family, Turdidae. It is the only species in the monotypic genus Ixoreus.
