Basilan Island lies c.20 km south of the tip of the Zamboanga Peninsula of south-western Mindanao. It is a hilly island, with several peaks that ascend to almost 1,000 m, including Mt Kebang (Twin Peak) and Mt Mohadji. This IBA includes the forests that remain in the hilly central part of the island, which are recommended by the DENR-9 for protection under the NIPAS as the Basilan Natural Biotic Area. An area of 234 ha of primary forest is reported to remain on Mt Mohadji, which also has patches of secondary forest which cover a total area of 2,500 ha. These areas were logged more than 20 years ago, but have now regenerated. Most of this is lowland forest, with limited areas of mossy forest around the highest peaks.
Many of the threatened and restricted-range species of the Mindanao and Eastern Visayas Endemic Bird Area have been recorded on Basilan, but there is little recent information on their status there. Several of these birds were found to be relatively abundant there in the past, notably the threatened Mindanao Bleeding-heart and Celestial Monarch. It is possible that the remaining forests on the island could prove to be very important for the conservation of some of these birds. The Zamboanga Bulbul is known only from Basilan and the western half of Mindanao, a distribution that it shares with several subspecies of birds. A total of 12 subspecies are endemic to Basilan alone, the four listed above in the table plus Colasisi Loriculus philippensis dohertyi, Philippine Fairy-bluebird Irena cyanogaster melanochlamys, Streaked Ground-babbler Ptilocichla mindanensis basilanica, Brown tit-babbler Macronous striaticeps striaticeps, Philippine Tailorbird Orthotomus castaneiceps mearnsi, Rufous-tailed Jungle-flycatcher Rhinomyias ruficauda ruficauda, Yellow-bellied Whistler Pachycephala philippensis basilanica and Little Spiderhunter Arachnothera longirostra randi.
BirdLife International (2017) Important Bird Areas factsheet: Basilan Natural Biotic Area. Downloaded from http://www.birdlife.org on 23/09/2017.