Site description This IBA includes the large mountain range that extends north to south from South-eastern Pangasinan Province southwards along the border between Zambales and Tarlac Provinces. The mountains reach a maximum altitude of 2,037 m at Mt High Peak, and there are several other peaks over 1,000 m, including Mt Dinampang and Mt Iba. A large block of old growth forest is shown in these mountains on recent forest cover maps, composed of closed canopy dipterocarp and mossy forest ranging in elevation from 990 m to the highest peaks. Ground-based surveys in 1992 confirmed the presence of a large expanse of virtually untouched forests around Mt High Peak.
Key Biodiversity The extensive forests that are reported to remain in the Zambales Mountains are remarkably poorly known ornithologically, given their proximity to Manila. Several of the threatened and restricted-range species of the Luzon Endemic Bird Area were recorded there during a survey in 1992, including the threatened Flame-breasted Fruit-dove, Spotted Imperial-pigeon and Green-faced Parrotfinch, and the poorly known Furtive Flycatcher. Several of these are lowland birds, but most of the remaining forest in this IBA is likely to be montane, with limited areas of lowland forest on the lower slopes. It is possible that many of the endemic montane birds of Luzon occur in the Zambales Mountains, and that the avifauna there will prove to be similar to that of the Cordillera Central of Luzon (e.g. Mt Pulog National Park: PH004).
Non-bird biodiversity: An extremely healthy population of horseshoe bats, of the poorly known family Rhinolophidae, has been found, plus the Endangered Luzon Pygmy Fruit-bat Otopteropus cartilagonodus, previously known only from six specimens. The threatened golden-crowned flying fox Acerodon jubatus is also reported to occur in the area.
Surveys in 1992 recorded a total of 17 individuals of a skink, Sphenomorphus beyeri, which was previously known from a single specimen collected in the 1920s, and found another skink, Lipinia sp., which may represent a new species.