Dartford warbler

The Dartford warbler (Curruca undata) is a Sylviid warbler from the warmer parts of western Europe and northwestern Africa. It is a small warbler with a long thin tail and a thin pointed bill. The adult male has grey-brown upperparts and is dull reddish-brown below except for the centre of the belly which has a dirty white patch. It has light speckles on the throat and a red eye-ring. The sexes are similar but the adult female is usually less grey above and paler below.

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.

The Dartford warbler was first described in 1776 by the Welsh naturalist, Thomas Pennant. He introduced the English name and based his description on two specimens that had been obtained by the ornithologist John Latham from Bexley Heath, near Dartford in Kent. In 1783 Latham included the warbler in his A General Synopsis of Birds but did not coin the binomial name, Sylvia dartfordiensis, until the supplement to his work was published in 1787. However, in 1783, before the publication of Latham's supplement, the Dutch naturalist Pieter Boddaert introduced the name, Motacilla undata, based on a coloured plate of "Le Pitte-chou, de Provence" in Edmé-Louis Daubenton's Planches enluminées d'histoire naturelle. The specific epithet undata is from Medieval Latin undatus meaning "with wavy markings". The type locality is Provence in France.

This species 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 a resemblance to the wrentit, the only species of Sylviidae from the Americas. However, the wrentit is less closely related to the genus Sylvia than to the parrotbills. Its visual similarity to the Dartford warbler group is an example of convergent evolution.

Three subspecies are recognised:

The Dartford warbler is a small, 13 cm (5.1 in), passerine bird, distinguished by its long tail compared with that of other warblers. Its plumage comprises unobtrusive and muted tones, which blend in with the dry dead plants, old wood or sunny greyish wood found in its preferred habitats.

Like many typical warblers, the Dartford warbler has distinct male and female plumages. The male has a grey back and head, reddish underparts, and a red eye. The reddish throat is spotted with white. The sides are a dull greyish tone, being more clear about the abdomen. In some populations males have bluish-grey or brownish-grey backs and heads. The female is paler below, especially on the throat, and a browner grey above. The female's throat also has white spots, although they are smaller and less marked than in the male. Juvenile birds are similar to females.

The species is naturally rare. The largest European populations of Curruca undata are in the Iberian peninsula, others in much of France, in Italy and southern England and south Wales. In Africa it can be found only in small areas in the north, wintering in northern Morocco and northern Algeria.