The Mariveles Mountains are in southern Bataan province, near the entrance to Manila Bay (PH010), and rise steeply from sea level to 1,420 m. An area of forest is shown there on recent forest cover maps, which is reported to include both lowland and montane forest, including mossy forest. This includes old reforestation plantations in the former Lamao Arsenal and old growth forest at the peak of Mt Mariveles.
Many of the threatened and restricted-range birds of the Luzon Endemic Bird Areas have been recorded in or near to this IBA, but there is little recent information on their status there. This is the only site in the Philippines where Ijima's Leaf-warbler has been recorded, although this species is difficult to locate and identify and presumably also winters elsewhere in the islands. It is also notable for the records of the highly threatened Isabela Oriole. This species, Luzon Striped-babbler and Furtive Flycatcher appear to have an unusual disjunct distribution, being recorded from the Bataan peninsula and the Sierra Madre in eastern Luzon. However, this may prove to be a result of gaps in the coverage of some other parts of Luzon by ornithologists. A subspecies of Elegant Tit, Parus elegans gilliardi, is only known from the Bataan peninsula.
Non-bird biodiversity: Baseline surveys of the mammals and herpetofauna have yet to be conducted in the area.
BirdLife International (2020) Important Bird Areas factsheet: Mariveles mountains. Downloaded from http://www.birdlife.org on 26/10/2020.