Scientific name Leucopeza semperi
Higher classification Leucopeza
Similar Saint Lucia warbler, Whistling warbler, White‑fronted whitestart, Pirre warbler, Barbuda warbler
The Semper's warbler (Leucopeza semperi) is an extremely rare or possibly extinct New World warbler which is endemic to Saint Lucia, part of the Lesser Antilles.
The common name and Latin binomial name commemorate Reverend John E. Semper, an amateur ornithologist who lived in St. Lucia.
The bird is about 14.5 centimetres in length. The plumage of the adults is dark gray at the upperparts and greyish white at the underparts. The immatures are brownish-grey above and have buffish underparts, and the long legs are pale yellow. It lives in the undergrowth of montane and elfin forests. The call consists of tuck-tick-tick-tuck noises. Nothing is known about its ecology but it is probably a ground-nesting bird.
It was rather abundant in the 19th century but there are only a few reports of this species in the 20th century. According to West Indian ornithologist James Bond, it was last collected on the summit of Piton Flores in 1934, another report was from March 1947 where it was sighted between the Piton Lacombe and the Piton Canaries. The last reliable sighting was in 1961. Though unconfirmed sightings were in 1965, 1972, 1989, 1995 and 2003 there is a weak hope for a rediscovery because suitable habitat still remains. A cause for its decline was probably the introduction of mongooses. Due to its possibly ground-nesting habits it was an easy prey for the mongooses. Another cause might be habitat destruction.