Swainson's thrush (''Catharus ustulatus''), also called olive-backed thrush and russet-backed thrush, is a medium-sized thrush. It is a member of genus ''

Catharus The genus ''Catharus'' is an evolutionary clade of forest-dwelling passerine birds in the family Turdidae (thrushes), commonly known as nightingale-thrushes. The extant species are widely distributed across the Americas and are descended from a c ...

'' and is typical of it in terms of its subdued coloration and beautiful, ascending flute-like voice. Swainson's thrush was named after William Swainson, an

English English usually refers to: * English language * English people English may also refer to: Peoples, culture, and language * ''English'', an adjective for something of, from, or related to England ** English national ide ...

ornithologist Ornithology is a branch of zoology that concerns the "methodological study and consequent knowledge of birds with all that relates to them." Several aspects of ornithology differ from related disciplines, due partly to the high visibility and th ...

Etymology

The genus name ''Catharus'' comes from the

Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic peri ...

''katharos'', "pure or clean" and refers to the plumage of the

orange-billed nightingale-thrush The orange-billed nightingale-thrush (''Catharus aurantiirostris'') is a species of bird in the family Turdidae. It is found in Colombia, Costa Rica, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Panama, Trinidad and Tobago, and Venezuela. ...

''C. aurantiirostris''. The specific ''ustuatus'' is

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

for "burnt", from ''urere'', "to burn".

Habitat

The breeding

habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...

of Swainson's thrush is

conifer Conifers are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single ...

ous woods with dense undergrowth across

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...

, and the northern

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

; also,

deciduous In the fields of horticulture and Botany, the term ''deciduous'' () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves, usually in the autumn; to the shedding of petals, aft ...

wooded areas on the

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

coast of

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

Range & distribution

These birds migrate to southern

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

and as far south as

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

. The coastal

subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...

migrate down the Pacific coast of North America and winter from

Costa Rica Costa Rica (, ; ; literally "Rich Coast"), officially the Republic of Costa Rica ( es, República de Costa Rica), is a country in the Central American region of North America, bordered by Nicaragua to the north, the Caribbean Sea to the no ...

, whereas the continental birds migrate eastwards within North America (a substantial detour) and then travel southwards via

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...

to winter from

Panama Panama ( , ; es, link=no, Panamá ), officially the Republic of Panama ( es, República de Panamá), is a transcontinental country spanning the southern part of North America and the northern part of South America. It is bordered by Cos ...

Bolivia , image_flag = Bandera de Bolivia (Estado).svg , flag_alt = Horizontal tricolor (red, yellow, and green from top to bottom) with the coat of arms of Bolivia in the center , flag_alt2 = 7 × 7 square p ...

. Swainson's thrush is a very rare vagrant to western

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

. It has also occurred as a vagrant in northeast Asia.

Threats

This species may be displaced by the

hermit thrush The hermit thrush (''Catharus guttatus'') is a medium-sized North American thrush. It is not very closely related to the other North American migrant species of ''Catharus'', but rather to the Mexican russet nightingale-thrush. The specific na ...

where their ranges overlap. Possibly, the latter species adapts more readily to human encroachment upon its habitat. At least in the winter quarters, Swainson's thrush tends to keep away from areas of human construction and other activity.

Description

This species is in length. The wingspan averages at and the wing chord is . The bill measures in length and the tarsus is long. This species' body mass can range from . This thrush has the white-dark-white underwing pattern characteristic of ''Catharus'' thrushes. Adults are brown on the upperparts. The underparts are white with brown on the flanks; the breast is lighter brown with darker spots. They have pink legs and a light brown eye ring. Birds in the east are more olive-brown on the upperparts; western birds are more reddish brown. This bird's song is a hurried series of flute-like tones spiralling upwards.

Diet

They forage on the forest floor, also in trees. Swainson's thrushes mainly eat insects, fruits and berries. They make a cup nest on a horizontal tree branch.

Subspecies

Four subspecies are recognised, ''Cathartus ustulatus alame'', ''C. u. swainsoni'', ''C. u. ustulatus'' and ''C. u. oedicus''. Subspecies ''Cathartus ustulatus alame'' and ''C. u. swainsoni'' summer east of the

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...

Coast Mountains The Coast Mountains (french: La chaîne Côtière) are a major mountain range in the Pacific Coast Ranges of western North America, extending from southwestern Yukon through the Alaska Panhandle and virtually all of the Coast of British Columbia ...

, the Cascades and the

Sierra Nevada The Sierra Nevada () is a mountain range in the Western United States, between the Central Valley of California and the Great Basin. The vast majority of the range lies in the state of California, although the Carson Range spur lies primarily ...

, and ''C. u. ustulatus'' and ''C. u. oedicus'' summer west of these ranges. There is a small area of overlap in the Coast Mountains. Recent

molecular systematics Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

work confirms that these two pairs of subspecies form two genetically distinct

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

s, referred to as the continental and coastal clades, which diverged during the Late

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...

era, probably about 10,000 years ago as the last ice age came to its end and habitats shifted across North America. The genetic differences between the subspecies, and the circuitous migratory route of the continental birds, strongly suggest that these species underwent a rapid range expansion following the end of the last

ice age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and gree ...

, with populations originally summering in the south-east of North America expanding their ranges northwards and westwards as the ice retreated. Details of the molecular genetic analysis support the hypothesis of rapid expansion of both coastal and continental populations. The current migratory routes of the continental birds, especially the western populations, are not optimal in ecological terms, and presumably represent an inherited, historical route pattern that has not yet adapted to the birds' modern population locations. These results notwithstanding, analysis of

mtDNA Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial DNA ...

cytochrome ''b'' and

NADH dehydrogenase NADH dehydrogenase is an enzyme that converts nicotinamide adenine dinucleotide (NAD) from its reduced form (NADH) to its oxidized form (NAD+). Members of the NADH dehydrogenase family and analogues are commonly systematically named using the for ...

subunit 2 as well as

nuclear Nuclear may refer to: Physics Relating to the nucleus of the atom: * Nuclear engineering *Nuclear physics *Nuclear power *Nuclear reactor *Nuclear weapon *Nuclear medicine *Radiation therapy *Nuclear warfare Mathematics *Nuclear space *Nuclear ...

β-fibrinogen

intron An intron is any nucleotide sequence within a gene that is not expressed or operative in the final RNA product. The word ''intron'' is derived from the term ''intragenic region'', i.e. a region inside a gene."The notion of the cistron .e., gene. ...

sequence In mathematics, a sequence is an enumerated collection of objects in which repetitions are allowed and order matters. Like a set, it contains members (also called ''elements'', or ''terms''). The number of elements (possibly infinite) is calle ...

dataWinker & Pruett (2006) shows that Swainson's thrush is the most ancient North American species of its genus; it is not closely related to other ''Catharus'' and the outward similarities with the other North American species are due to

convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...

Gallery

File:Swainson’s Thrush.jpg, Swainson's thrush on South Padre Island, Texas File: Swainson’s_Thrush_Tex.jpg , On South Padre Island, Texas File:Catharus ustulatus Charlie Lake.jpg, A Swainson's thrush in British Columbia

Footnotes

References

* Foster, Mercedes S. (2007):
The potential of fruiting trees to enhance converted habitats for migrating birds in southern Mexico.
''Bird Conservation International'' 17(1): 45–61. * Ruegg, K. C., & Smith, T.B. (2002).
Not as the crow flies: a historical explanation for circuitous migration in Swainson's thrush (''Catharus ustulatus'').
'' Proc. R. Soc. B'' 269(1498) 1375–1381. * Winker, Kevin & Pruett, Christin L. (2006):
Seasonal migration, speciation, and morphological convergence in the avian genus ''Catharus'' (Turdidae).
''

Auk An auk or alcid is a bird of the family Alcidae in the order Charadriiformes. The alcid family includes the murres, guillemots, auklets, puffins, and murrelets. The word "auk" is derived from Icelandic ''álka'', from Old Norse ''alka'' (a ...

'' 123(4): 1052–1068. rticle in English with Spanish abstract DOI: 10.1642/0004-8038(2006)123 052:SMSAMC.0.CO;2 PDF fulltext]

External links

Swainson's Thrush Species Account
- Cornell Lab of Ornithology

- USGS Patuxent Bird Identification InfoCenter

- naturesongs.com * * * {{Taxonbar, from=Q545006 Catharus, Swainson's thrush Native birds of Alaska Birds of Canada Native birds of the Northwestern United States Birds of South America Swainson's thrush Taxa named by Thomas Nuttall