The Cape Verde Warbler (Acrocephalus brevipennis) is about 13 cm in length. It is also known as the Cape Verde Cane Warbler and the Cape Verde Swamp Warbler. It is endemic to Cape Verde. A medium-sized bird that is dull brown Acrocephalus with dark grey legs and an indistinct head pattern Although a diffuse pale line and eye ring are more obvious in fresh plumage, the only other resident warblers on the islands are Blackcap and Spectacled Warblers, which are unlikely to cause confusion.
The European Reed Warbler is a likely vagrant to the islands but has relatively longer primaries (primary projection is short and very blunt in Cape Verde), a relatively shorter tail, and is less brownish on the breast and flanks; it usually has paler legs. The bird keeps well concealed within the cover of trees and bushes, a habitat it shares only with blackcaps on the islands, revealing its presence through its distinctive song.
Fresh plumage, especially in first-years, is warmer, more rufous-brown on the upper parts, and has underparts washed with pale yellow. The call of Cape Verde Warbler includes a throaty pitch, a high, quick ‘chuk’, and a harsh, croaking “churr”. The song is quite unlike others of the genus: a strong, rich, vibrant rattle of three to five notes in the manner of Lesser Whitethroat in the tonal quality of a Common Nightingale. Some experts related its songs to bulbul, like a liquid bubbling.
Its natural habitat is endemic to the Cape Verde Islands (now restricted to São Tiago, but formerly occurring in Brava and São Nicolau). Locally, there are quite numerous well-vegetated parts of the island. Trees, bushes, and giant cane (Arundo donax) in valleys as well as areas of sugar cane, bananas, coffee, etc. Due to habitat destruction or the drought that has beset the islands, the bird population is declining. Hence, it is considered a vulnerable species by the IUCN.
