been studied the African warblers are territorial and monogamous. Nest design varies within the family; the crombecs construct deep pocket-shaped nests suspended from a branch; whereas the Victorin's warbler, Cape grassbird and moustached grass warbler construct cup nests weaved from grass. Status and conservation The majority of this family are considered to be fairly secure and are listed by the IUCN as least concern. One species, the Pulitzer's longbill, is listed as endangered. This species is endemic to forests found on escarpments in western Angola, a habitat threatened by forest clearance and the spread of slash-and-burn agriculture, and the population is thought to number less than a thousand and is still declining. Another potential concern is Chapin's crombec, which is either a species or a subspecies of the white-browed crombec. The status of this bird is uncertain, as conflict has prevented surveys in its range, but it may be extinct. Species Genus Sylvietta – crombecs Green crombec, Sylvietta virens Lemon-bellied crombec, Sylvietta denti White-browed crombec, Sylvietta leucophrys Chapin's crombec, Sylvietta (leucophrys) chapini – possibly extinct (late 20th century?) Northern crombec, Sylvietta brachyura Philippa's crombec, Sylvietta philippae Red-capped crombec, Sylvietta ruficapilla Red-faced crombec, Sylvietta whytii Somali crombec, Sylvietta isabellina Long-billed crombec, Sylvietta rufescens Genus Melocichla Moustached grass warbler, Melocichla mentalis Genus Achaetops Rockrunner, Achaetops pycnopygius Genus Sphenoeacus Cape grassbird, Sphenoeacus afer Genus Cryptillas – formerly Bradypterus (now Locustellidae) Victorin's warbler, Cryptillas victorini Genus Macrosphenus – longbills Kemp's longbill, Macrosphenus kempi Yellow longbill, Macrosphenus flavicans Grey longbill, Macrosphenus concolor Pulitzer's longbill, Macrosphenus pulitzeri Kretschmer's longbill, Macrosphenus kretschmeri References Bird families Birds of Sub-Saharan Africa