Swainson's Warbler
Limnothlypis swainsonii
Shy and difficult to see in deciduous forest with dense understory, often near water. Plain buffy-brown coloration with rufous crown and dark eyeline. Also note disproportionately large, sharp, pinkish bill and pink legs. Shimmies tail side-to-side as it slowly forages on the forest floor, investigating fallen leaf litter for insects. Fairly restricted breeding range in the southeastern U.S.; winters primarily on the Yucatan peninsula and in the Caribbean. Listen for loud, sweet song, similar to Louisiana Waterthrush but without the complex ending.
Identification
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). 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 mostly dimorphic, there is no difference in appearance between a male or female Swainson's warbler.
Taxonomy
No subspecies are recognized. There appears to be some divergence between populations from Arkansas and others of the coastal plains. This does fit a pattern one would expect from genetic drift, but there seem to be no geographical or ecological barriers restricting gene flow. Even during the last ice age, when average temperatures, precipitation and sea levels were lower, there seems to have been ample contiguous habitat. Clearly, some factor restricting gene flow is at work, but it is not presently known what it is. It is possible that the subpopulations conform to the different wintering areas.<p>In some migrant birds it is known that the initial direction of the migration is set by fairly simple hereditary 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 the Caribbean where there are no wintering or even stopover points, and the bird would almost certainly perish. More research such as analyzing bird banding data is needed to determine whether this mechanism applies in Swainson's warbler.
- Scientific name
- Limnothlypis swainsonii
- Authority
- (Audubon, 1834)
- Order
- Passeriformes
- Family
- Parulidae
- Genus
- Limnothlypis
Range and habitat
Swainson's warblers are uncommon, mostly found in flooded swamplands and canebrakes of the south-eastern United States. More rarely, they will also occur in rhododendron thickets in the southern Appalachian Mountains. They are a migratory species, with part of the population migrating southeastwards to the Greater Antilles (where it overwinters in the Blue Mountains of Jamaica for example) and the other southwestwards to the Yucatán Peninsula region in winter.
- Breeding range
- NA : se USA
- Non-breeding range
- MA and West Indies
- Migration
- Complete migrants
Behavior
This species begins breeding at about 10 months of age. 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 current nesting season. These birds live to as old as eight years.
Conservation
- Population trend
- rising
Photos
Distribution
Bird Calls
Other Birds
African Darter
Anhinga rufa
A long and slender cormorant-like waterbird that often swims with its body submerged and only the “S”-shaped neck protruding from the water. Adults are mostly black with white flecks and streaks. Males have a rusty neck and a white stripe running from the eye down the side of the head, which is duller when not breeding. Females and juveniles are muted and brown. African Darter is widespread in freshwater wetlands, preferring placid to fast flowing waters. Cormorants have proportionately larger heads, bulkier necks, and hooked rather than bayonet-shaped bills.
Fork-tailed Storm-Petrel
Hydrobates furcatus
Unique among storm-petrels in having an entirely silvery-gray plumage. Aside from overall plumage color, look for contrasting dark underwings, dark mask around eye, and deeply forked tail. Breeds on offshore islands across the North Pacific, from Japan to California. Fairly common over cool water, often not far from shore. Found singly or in large flocks, often mixed with other storm-petrels.
Spot-backed Antwren
Herpsilochmus dorsimaculatus
Small canopy antwren with a long, graduated tail. Males are largely gray with a black crown and a bold white eyebrow; the black spots on the back can be difficult to see. Females have a buff forehead and breast sides, with the black crown spotted white. Inhabits humid lowland forest and seasonally flooded forest in some regions. Almost invariably seen accompanying canopy mixed-species flocks. The song is a somewhat deep trill that slightly ascends and then descends: “wiwiwurrrrr.”
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