Swainson's warbler (Limnothlypis swainsonii )

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Swainson's warbler
IUCN Red List species status – Least Concern LEAST
CONCERN

Top facts

  • Swainson’s warbler is a migratory species which breeds in the south-eastern United States and winters in Central America and the Caribbean.
  • The large, bulky nest of Swainson’s warbler resembles a pile of leaves.
  • Swainson’s warbler has a loud, distinctive song which is described as having a ringing quality.
  • Swainson’s warbler is listed as a species of conservation concern by the U.S. Fish and Wildlife Service.
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Swainson's warbler fact file

Swainson's warbler description

KingdomAnimalia
PhylumChordata
ClassAves
OrderPasseriformes
FamilyParuidae
GenusLimnothlypis (1)

Swainson’s warbler (Limnothlypis swainsonii) is a very secretive, medium-sized wood-warbler (2) (4) with plain, olive-brown upperparts (2) (3) (4) (5). This species has a reddish-brown crown (2) (5), long whitish ‘eyebrows’ (2) (3) (4) (5) and a dark eyestripe (2) (3). The throat and underparts are white to yellowish-white (2) (3) (5) and are unstreaked (2).

Swainson’s warbler has a long, heavy, pointed bill (2) (3) which is greyish-pink (2) to flesh-coloured (2) (3). The legs and feet are pinkish (2) (3), and the eyes are brown (2).

Swainson’s warbler does not demonstrate any seasonal variation in plumage colouration (2), and unlike in most other New World warblers (5), the male and female of this species are similar in appearance (2) (3) (5). Juvenile Swainson’s warblers are mostly tawny-brown, with slightly paler cheeks, pale buff lower underparts and narrow, pale cinnamon wingbars (3).

Swainson’s warbler has a loud, distinctive song (2) (3) (4) which is described as having a ringing quality (2) (4) and is used to maintain the bird’s breeding territory and advertise to females (2). The song is formed of a descending series of slurred whistles (3) (4) followed by a few more rapid, warbled notes, which sound like ‘wee wee wee wee-tu-weeu(3). The primary call of Swainson’s warbler is a forceful yet sweet ‘sship’, while the flight call is a thin, high-pitched buzzy sound (3).

Synonyms
Sylvia swainsonii.
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Swainson's warbler biology

An apparent specialist of forest floor invertebrates (2) (3), Swainson’s warbler tends to feed on ants, beetles, centipedes and spiders (2) (3) (4), which are mostly found beneath the leaf litter (2) (3). This species tends to forage for its prey by probing under the leaf litter and flipping over dead leaves (2) (3) (4), and has even been seen sticking its bill into a curled-up leaf and opening it up to reveal prey (4). It will also glean prey from low bushes and may occasionally catch insects in flight (3). Swainson’s warbler is not known to eat fruit or nectar (2), but it has been recorded eating small lizards (3).

The breeding season for Swainson’s warbler lasts from May through to July (3), with the males arriving at the breeding grounds first to defend large territories (2). Monogamous breeding pairs are formed within a few days of the females arriving. The female Swainson’s warbler constructs the nest alone, building a large, bulky structure which takes between two and five days to complete (2). The nest is formed of leaves (3), sticks and vines (4), and is lined with moss, grass and pine needles (3) (4). The nest is typically placed in understorey vegetation (2) (3), and is either supported by small shrubs and trees or suspended on several thin vines (2).

The female Swainson’s warbler generally lays a clutch of between two and five eggs (4) which are incubated for a period of 13 to 15 days (3). Clutches of up to seven eggs have been observed (2), although three is most common (3). Swainson’s warbler eggs are white and are usually unmarked (2) (4), but can appear pinkish or bluish (2). Both the male and female adult feed the young chicks, which typically leave the nest around 8 to 12 days after hatching. Swainson’s warbler is thought to live for up to ten years (2).

Swainson’s warbler leaves the breeding area around August (2) (3), arriving in its wintering grounds from mid-September. It stays on the wintering grounds until spring migration begins again in March (3).

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Swainson's warbler range

Swainson’s warbler breeds in the south-eastern United States (1) (2) (3) (5), from southern Missouri through to Virginia, and from eastern Texas and Oklahoma (2) (3) eastwards through to Alabama and Tennessee (2). This species also occurs in Illinois, although it has been nearly extirpated in the state, now occurring mainly in the extreme south (2).

A migratory species, Swainson’s warbler winters in the western Caribbean, including the Bahamas, Cuba, Jamaica and the Cayman Islands (1) (2) (3). Its wintering range also extends into south-eastern Mexico and north-eastern Central America (1) (2) (3), including Guatemala and Belize (2) (3). Swainson’s warbler has been reported to be a vagrant species in Venezuela (1) (2), Colombia, Panama and Puerto Rico (1).

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Swainson's warbler habitat

Swainson’s warbler can be found in a variety of habitats, such as bottomland hardwood forests (2) with thick undergrowth (2) (4). It is also often found in flooded swamplands and canebrakes (3) (4) (5). The habitat preference of Swainson’s warbler appears to change somewhat depending on its location. Individuals in Georgia tend to prefer open areas of forest with dense leaf litter and a thick understorey, while Appalachian populations are found in laurel and rhododendron thickets along streams and rivers (3).

In its wintering range, Swainson’s warbler is typically found in tropical and semi-deciduous montane forest, as well as in mangroves and wooded gardens (2) (3) (4).

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Swainson's warbler status

Swainson’s warbler is classified as Least Concern (LC) on the IUCN Red List (1).

IUCN Red List species status – Least Concern

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Swainson's warbler threats

Swainson’s warbler has a large population size which covers an extremely large range (6), and it is not considered to be globally threatened (3). However, this species’ population has declined in recent years, particularly in the north-western parts of its breeding range (3). In these areas, habitat destruction is believed to be the main cause of the decline (2) (3), with Swainson’s warbler’s wooded habitat being converted at a rapid rate to cropland, pasture and urban sites (2). Habitat destruction is also threatening Swainson’s warbler in its limited wintering range (2), and the fragmentation of remaining habitat poses an additional threat (2) (3).

The collection of adults and eggs has been known to decimate local populations in some areas, while collisions with objects, particularly during night-time migration, also negatively impacts Swainson’s warbler (2).

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Swainson's warbler conservation

Swainson’s warbler is listed as a high priority species of conservation concern by the U.S. Fish and Wildlife Service (2) (3). There are currently no known conservation measures in place for this species, but recommended actions include the management of forested areas to encourage the regeneration of canebrakes, therefore maintaining ideal habitat conditions (3).

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Find out more

Find out more about Swainson’s warbler:

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Authentication

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk

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Glossary

Deciduous
A plant that sheds its leaves at the end of the growing season.
Gleaning
The catching of prey by plucking it from or within foliage.
Incubate
To keep eggs warm so that development is possible.
Invertebrates
Animals with no backbone, such as insects, crustaceans, worms, molluscs, spiders, cnidarians (jellyfish, corals, sea anemones) and echinoderms.
Monogamous
Having only one mate during a breeding season, or throughout the breeding life of a pair.
Montane forest
Forest occurring in mountains.
Territory
An area occupied and defended by an animal, a pair of animals or a group.
Vagrant
An individual found outside the normal range of the species.
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References

  1. IUCN Red List (April, 2014)
    http://www.iucnredlist.org/
  2. Brown, R.E. and Dickson, J.G. (2010) Swainson’s warbler (Limnothlypis swainsonii). In: Poole, A. (Ed.) The Birds of North America Online. Cornell Lab of Ornithology, Ithaca. Available at:
    http://bna.birds.cornell.edu/bna/species/126/articles/introduction
  3. del Hoyo, J., Elliott, A. and Christie, D.A. (2010) Handbook of the Birds of the World. Volume 15: Weavers to New World Warblers. Lynx Edicions, Barcelona. Available at:
    http://www.hbw.com/
  4. All About Birds - Swainson’s Warbler (April, 2014)
    http://www.allaboutbirds.org/guide/Swainsons_Warbler/id
  5. MobileReference (2008) The Illustrated Encyclopedia of North American Birds: An Essential Guide to Common Birds of North America. MobileReference, Boston.
  6. BirdLife International - Swainson’s Warbler (April, 2014)
    http://www.birdlife.org/datazone/speciesfactsheet.php?id=9129
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Swainson's warbler  
Swainson's warbler

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