| Swainson's warbler | |
|---|---|
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Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Passeriformes |
| Family: | Parulidae |
| Genus: | Limnothlypis Stone, 1914 |
| Species: | L. swainsonii |
| Binomial name | |
| Limnothlypis swainsonii (Audubon, 1834) | |
 | |
| Range ofL. swainsonii Breeding range Winter range | |
| Synonyms[2] | |
Helinaia swainsoni | |
Swainson's warbler (Limnothlypis swainsonii) is a smallspecies ofNew World warbler. It ismonotypic, the only member of thegenusLimnothlypis. Swainson's warbler was named afterWilliam Swainson, anEnglishornithologist.
Swainson's warblers are a small and rather nondescript songbird, though are fairly large for a New World warbler. Adults grow to 12.5–16 cm (4.9–6.3 in) in length and 11–20.5 g (0.39–0.72 oz) in weight. The wingspan averages 23 cm (9.1 in).[3][4] They are a plain olive-brown above and pale yellow-white below. They have a whitish eyebrow stripe that runs above their eye, and the top of their head is a rusty brown. Unlike most other New World warblers that are mostlydimorphic, there is no difference in appearance between a male or female Swainson's warbler.
Swainson's warblers are uncommon, mostly found in floodedswamplands andcanebrakes of thesouth-eastern United States. More rarely, they will also occur inrhododendron thickets in the southernAppalachian Mountains. They are amigratory species, with part of the population migrating southeastwards to theGreater Antilles (where it overwinters in the Blue Mountains of Jamaica for example[5]) and the other southwestwards to theYucatán Peninsula region in winter.
This species begins breeding at about 10 months of age.[6] Pairs form, and stake out and defend a territory for nesting. Nests are fairly large and bulky, constructed from moss, grass, and small leaves situated above ground in a tangle of tall reeds or vines. The female will lay between three and five eggs. The eggs are white and sometimes, but rarely, speckled with brown. Incubation is done by the female only and lasts for about 14 days, after which the eggs will hatch. The young leave the nest about 12 days later. It is not known how long pairs stay together, although once a pair-bond has been established they do not usually mate with other birds at least in the currentnesting season. These birds live to as old as eight years.[6]
Nosubspecies are recognized. There appears to be some divergence between populations fromArkansas and others of the coastal plains. This does fit a pattern one would expect fromgenetic drift, but there seem to be nogeographical orecological barriers restrictinggene flow. Even during thelast ice age, when average temperatures,precipitation andsea levels were lower, there seems to have been ample contiguoushabitat. Clearly, some factor restricting gene flow is at work, but it is not presently known what it is. It is possible that thesubpopulations conform to the different wintering areas.[7]
In some migrant birds it is known that the initial direction of the migration is set by fairly simplehereditary mechanisms. Offspring of pairs comprising birds of different subpopulations will, in such species, attempt to migrate into an intermediate direction. Such a course would lead a Swainson's warbler deep into theCaribbean where there are no wintering or even stopover points, and the bird would almost certainly perish. More research such as analyzingbird banding data is needed to determine whether this mechanism applies in Swainson's warbler.[7]
