The Dartford Warbler, Sylvia undata, is a typical warbler from the warmer parts of western Europe, and northwestern Africa. Its breeding range lies west of a line from southern England to the heel of Italy (southern Apulia). The Dartford Warbler is usually resident all-year in its breeding range, but there is some limited migration.
Description and systematics
Like many typical warblers, this small (13 cm) passerine bird has distinct male and female plumages. The male of this small Sylvia has a grey back and head, reddish underparts, and a red eye (see below for photo). The reddish throat is spotted with white. The female is paler below, especially on the throat, and a browner grey below. The song is a distinctive rattling warble.
The type locality is the Provence in France. The Dartford Warbler probably forms a superspecies with Tristram's Warbler and this in turn seems close to Marmora's Warbler and the Balearic Warbler. Altogether, this group of typical warblers bears an uncanny resemblance to the Wrentit, the only species of Sylviidae from the Americas (compare Wrentit with Dartford Warbler photo linked below). Still, the Wrentit is less closely related to the genus Sylvia than to the parrotbills. Its visual similarity to the Dartford Warbler group is an astounding example of convergent evolution between birds closely related enough to already share many similarities evolving half a world apart in similar Mediterranean scrub habitat.
Ecology and status
This small "warbler" species breeds in heathlands often near coasts, with gorse bushes for nesting. Like its relatives, the Dartford Warbler is insectivorous, but will also take berries. The nest is built in low shrub, and 3-6 eggs are laid.
Dartford Warblers were named for Dartford Heath in NW Kent, where the population became extinct in the early 20th century. They almost died out in the United Kingdom in the severe winter of 1962/1963 when the national population dropped to just 10 pairs. However, this species can recover well in good-quality habitat, because of repeated nesting and a high survival rate for the young. Indeed they recovered in some areas of the UK, but numbers are once again on the decline in other regions of that country, as well as elsewhere.
Formerly classified as a Species of Least Concern by the IUCN, it was suspected to be rarer than generally assumed. Following the investigation of the apparent decline, this was confirmed, and the Dartford Warbler is consequently uplisted to Near Threatened status in 2008.