Varied thrush

Varied thrush
Male
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Turdidae
Genus: Ixoreus
Bonaparte, 1854
Species: I. naevius
Binomial name
Ixoreus naevius
Gmelin, 1789
Subspecies
  • I. n. meruloides
  • I. n. naevius
  • I. n. carlottae
  • I. n. godfreii
Synonyms

Zoothera naevia

The varied thrush (Ixoreus naevius) is a member of the thrush family, Turdidae.

Taxonomy

The German naturalist Johann Friedrich Gmelin described the varied thrush in 1789. Four subspecies are recognised:[2]

The genus name Ixoreus comes from the Ancient Greek ixos, "mistletoe". This was a synonym of a former name for the mockingbird genus, Mimus; the genus creator 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, " spot".[3]

Description

Female

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.[4][5] In general, varied thrushes feature intense orange and black feathers.[6] 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.[7]

There is an extremely rare variant of this species in which all the orange in the plumage is replaced by white.[8] 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.[9]

Distribution and habitat

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 is an accepted western European record in Great Britain in 1982.

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.

Feeding

The varied thrush is predominantly insectivorous.

Breeding

The breeding habitat is dense coniferous forest, with two to five eggs being laid in a tree nest.

References

  1. ↑ BirdLife International (2012). "Zoothera naevia". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013.
  2. ↑ Gill, F.; Donsker, D., eds. (2014). "IOC World Bird List (v 4.1)". doi:10.14344/IOC.ML.4.1.
  3. ↑ Jobling, James A (2010). The Helm Dictionary of Scientific Bird Names. London: Christopher Helm. pp. 208, 265. ISBN 978-1-4081-2501-4.
  4. ↑ https://web.archive.org/web/20131022204024/http://www.polarconservation.org/education/arctic-animals/arctic-birds/thrushes-and-chats/varied-thrush. Archived from the original on October 22, 2013. Retrieved August 27, 2012. Missing or empty |title= (help)
  5. ↑ Peter, Clement (2001). Thrushes. Princeton University Press. ISBN 978-0691088525.
  6. ↑ George 2000, p. 1
  7. ↑ George 2000, p. 2
  8. ↑ Scott, Shirley L., ed. (1987). Field Guide to the Birds of North America (2nd ed.). National Geographic Society. p. 328. ISBN 0-87044-692-4.
  9. ↑ "Bird Walk 71 (photo gallery including photos of rare colour variant)".

Further reading

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