| Varied thrush | |
|---|---|
 | |
| Male | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Passeriformes |
| Family: | Turdidae |
| Genus: | Ixoreus Bonaparte, 1854 |
| Species: | I. naevius |
| Binomial name | |
| Ixoreus naevius (Gmelin, JF, 1789) | |
| Subspecies | |
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Breeding Year-round Nonbreeding | |
| Synonyms | |
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Thevaried thrush (Ixoreus naevius) is a member of thethrush family, Turdidae. It is the only species in themonotypic genusIxoreus.
The varied thrush wasformally described by the German naturalistJohann Friedrich Gmelin in 1789 under thebinomial nameTurdus naevius.[2] Gmelin based his description of the "Spotted thrush" that had been described byJohn Latham in 1783 from specimens owned byJoseph Banks. These had been collected nearNootka Sound (formerly King George's Sound) which separatesNootka Island fromVancouver Island on the Pacific coast of Canada.[3] The varied thrush is now the only species placed in thegenusIxoreus that was introduced byCharles Lucien Bonaparte in 1854.[4][5] The genus nameIxoreus comes from theAncient Greekixos meaning "mistletoe". This was asynonym of a former name for themockingbird genus,Mimus; Bonaparte assumed wrongly that, becauseWilliam Swainson had shown a mockingbird and this thrush on the same plate of his book, they were related. The specificnaevius isLatin for "spotted" fromnaevus 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, thewing chord is 11.8 to 13.6 cm (4.6 to 5.4 in), thebill is 1.8 to 2.3 cm (0.71 to 0.91 in) and thetarsus is 2.9 to 3.3 cm (1.1 to 1.3 in). It is similar in size to the widespreadAmerican 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, andcrowns. They also possess a tuftedsupraloral stripe and streaks of dark colors on itsflight 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 thecovert 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 Britishvagrant 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 westernNorth America fromAlaska to northernCalifornia. It ismigratory, with northern breeders moving south within or somewhat beyond the breeding range. Other populations may only move altitudinally. This species is an improbable transatlanticvagrant, but there are now two accepted westernEuropean records, both inGreat 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 predominantlyinsectivorous, though its diet varies throughout the course of the year. During the summer, ground-dwellingarthropods make up the bulk of its diet. During migration and winter, however, the focus of the thrush's diet shifts tofruits,seeds, andacorns, though arthropods are still taken in some quantity. Varied thrushes consume a wide variety of berries throughout the year, includingsnowberry,red huckleberry,California honeysuckle,madrone,salmonberry, andthimbleberry.[9]
Varied thrushes forage primarily on the ground, except when foraging for fruits and berries.[9]
The breeding habitat is denseconiferous forest, with two to five eggs being laid in a tree nest.
