This IBA includes several substantial blocks of old growth forest that are shown on recent forest cover maps in the Sierra Madre mountains in south-eastern Isabela Province and north-eastern Aurora Province. It lies between the Northern Sierra Madre Natural Park (PH015) to the north and Maria Aurora Memorial Park (PH017) to the south. The topography of this remote region is mountainous, with several peaks rising to over 1,000 m, the highest point being Mt Dos Hermanos at 1,613 m. The vegetation is similar to that of the Northern Sierra Madre Natural Park, with areas of montane forest around the peaks, and substantial areas of lowland forest on the lower mountain slopes. A survey was completed at Diagopanay, near Dinapique, in 1991 in primary forest at 300-675 m, although this forest was being logged while the survey was taking place.
Many of the threatened and restricted-range birds of the Luzon Endemic Bird Area were recorded in this IBA during surveys in 1991-1992 by a team from the DENR, BirdLife International, Danish Ornithological Society (DOF) and Zoological Museum of Copenhagen University. The avifauna there is similar to that of Northern Sierra Madre Natural Park (PH015), with important populations of many birds of conservation concern, and it is likely that further surveys would find some other important species. The recent sightings of Philippine Eagle suggest that this IBA is an important part of the network of sites required to conserve the population of this critically endangered species in the Sierra Madre mountains.
Non-bird biodiversity: Surveys in 1996-1999 found several endemic mammals, including Luzon Shrew Crocidura grayi, Common Philippine Forest Rat Rattus everetti, and two Luzon endemic species, Luzon Montane Forest Mouse Apomys datae and Large Luzon Forest Rat Bullimus luzonicus. A new frog species, Platymatis sierramadrensis was recorded in this IBA. Seven more frogs discovered there are still in the process of identification, and two Sphenomorphus species recorded from the area are believed to probably be new species.
BirdLife International (2023) Important Bird Areas factsheet: Central Sierra Madre mountains. Downloaded from http://www.birdlife.org on 06/02/2023.