Detecting change in the status and habitat of Hinde's BabblerTurdoides hindei: 2000 to 2011

Abstract

Department of Zoology, National Museums of Kenya,PO Box 40658-00100, Nairobi, KenyaBACKGROUNDThe globally Vulnerable Kenyan endemic Hinde’s Bab-bler Turdoides hindei has its stronghold in the foothills ofMt Kenya and the Aberdares, where it is associatedmainly with patches of scrub and riverine thicket (Statt-ersfield et al. 1998, Njoroge & Bennun 2000, BirdLifeInternational 2012). A decline in its known range, firstdescribed in the 1970s, was attributed to scrub clearancefor cultivation, perhaps compounded in some areas byhuman disturbance and hunting (Plumb 1979, Njorogeet al. 1998). Surveys in 1994 and 2000–2001 showedthat the species was much less abundant within pro-tected areas than in fertile, densely populated farmland,offering limited scope for conservation through furthersite designation (Shaw & Musina 2003).The global range of Hinde’s Babbler lies predomi-nantly within the catchments of the upper Tana River,with outlying populations in Meru District, Machakos,Kitui and Nziu (Shaw et al. 2003). By 2001 the specieswas known from just seven main areas, and was thoughtto have a global population of c. 1500–5600 birds.Although scrub clearance has impacted on the species’range and population, its effect may have been partlymitigated by the spread of the exotic invasive Lantanacamara, which provides scrub cover in areas previouslycleared of native shrubs, enabling the Babbler to persistin, and possibly to re-colonize, intensively farmed land(Njoroge & Bennun 2000).Like most members of its genus, Hinde’s Babblerbreeds cooperatively, groups typically comprising threeto four adults (range 1–8), often accompanied by one ortwo juveniles (Njoroge & Mutinda 1996, Shaw & Musi-na 2003). Some groups include individuals with exten-sive light feathering on the chest, head and back,sometimes distributed asymmetrically, a trait interpretedby Plumb (1979) as possible evidence of inbreeding.In 2011 we reassessed the global range of Hinde’sBabbler and resurveyed three sites previously surveyedin 2000–2001, to determine whether changes hadoccurred in its known range, abundance, demography orhabitat over the intervening decade. To determine therelationship between plumage type, population densityand breeding success we assigned a plumage score to allindividuals seen sufficiently clearly, noting their age classand group composition.GLOBAL RANGEChanges in Hinde’s Babbler’s global range were estimatedfrom the number of occupied 10 9 10-km squares (itsArea of Occupancy) and from the number of squaresbounded by these known sites (its Extent of Occurrence).Three time periods were compared: 1900–1970,1971–1990 and 1991–2011. Since its discovery in 1900,Hinde’s Babbler has been recorded in 53 squares, indicat-ing an Area of Occupancy of c. 5300 km