A new brush-finch in the Atlapetes latinuchus complex from the Yariguíes Mountains and adjacent Eastern Andes of Colombia by Thomas M. Donegan & Blanca Huertas Received 28 May 2005; final revision received 13 February 2006 The brush-finches Atlapetes are Neotropical passerines which achieve greatest diversity in the Andes and whose taxonomy and ecology have received much recent attention. Atlapetes shows a high degree of geographical variation, with various forms restricted to particular elevations, mountains or slopes, but few cases of true sympatry. The group is therefore ideally suited to studies of the patterns and mechanisms of speciation (Remsen & Graves 1995a, García-Moreno & Fjeldså 1999). Even recently, localised taxa have been described, both at species and subspecies level (e.g. Fitzpatrick 1980, Remsen 1993, Valqui & Fjeldså 1999), and a species thought possibly extinct was rediscovered (Agreda et al. 1999). Serranía de los Yariguíes and the Eastern Cordillera The Eastern Cordillera (Eastern Andes) is one of Colombia’s three principal mountain ranges, extending from dpto. Cauca (01 o N), to the Serranía de Perijá, on the Caribbean coast (11 o N). It is characterised by a varied habitats, with slopes bordering Amazonia, the llanos and Magdalena Valley, humid and dry regions, plateaux, steep slopes and wetlands. The cordillera’s cool climate and high- elevation savannas have long been subject to human development. It is also one of the world’s major centres of avian endemism, the Colombian East Andes Endemic Bird Area (Stattersfield et al. 1998). The Serranía de los Yariguíes (dpto. Santander) is an isolated western spur of the East Andes, rising to c.3,400 m and isolated from the rest of the cordillera to the north and east by the Sogamoso Valley, and to a lesser extent to the south by depressions associated with the ríos Horta, Quirola and Opón and their tributaries. A collection of 60 bird species was made below 1,000 m near San Vicente de Chucurí in November 1956 (Borrero & Hernández 1957), and a few specimens were taken elsewhere on the massif, generally on the drier eastern slope (e.g. Romero 1983), but the humid western slope and highest elevations were very poorly known ornithologically prior to our field work (for general results see Donegan & Briceño 2005, Donegan & Huertas 2005, Donegan & AvendaZo 2006, Huertas & Donegan 2006). Amongst the birds we recorded was one which initially appeared to be of the ‘Northern Rufous-naped Brush-finch’ or ‘Yellow-breasted Brush-finch’ complex, A. latinuchus. Paynter (1978) specifically commented on the absence of records of A. latinuchus (then classified as A. rufinucha) from the central part of the Eastern Cordillera, noting ‘While it is present in the Sierra de Perijá, a northward extension Thomas M. Donegan & Blanca Huertas 94 Bull. B.O.C. 2006 126(2) boc1262-060606.qxp 6/6/2006 3:09 PM Page 94