Liguasan Marsh is in south central Mindanao, and is the largest swamp and marsh area on the island. It is a vast complex of river channels, small freshwater lakes and ponds, extensive freshwater marshes and arable land subject to seasonal flooding in the basin of the Mindanao River. Most of the area is underwater during periods of heavy rainfall, but some 140,000 ha dry out during dry periods and are cultivated. The marsh, although generally known as Liguasan, actually consists of two adjoining marshy basins, Liguasan Marsh and Libungan Marsh, with different water regimes. Liguasan lies at the confluence of the Pulangi, Maganoy, Buluan and Allah Rivers, and Libungan lies at the confluence of Libungan and Mindanao Rivers. There is c.5,000 ha of old growth forest within the marsh. The marsh is home to 112,000 Maguindanaon families whose primary means of livelihood are fishing when water levels are high and agriculture when they are low. Because of its very rich wildlife, the marsh has considerable potential for nature tourism. However, the area is a stronghold of insurgents, and access is restricted. The Government has recognized the importance both economically and politically of Liguasan Marsh and, in the Cotabato Agusan River Basin Development Project, has initiated the construction of a cut off channel from the Pagulungan sector of the Rio Grande de Mindanao to prevent and control floods.
Several threatened species have been recorded at Liguasan Marsh, including Philippine Eagle, but there is little recent information on their status there. It is likely that the relatively extensive lowland forests in this IBA support populations of more of the threatened and restricted-range birds of the Mindanao and Eastern Visayas Endemic Bird Area. The marsh is an important wetland site and supports resident or non-breeding populations of many waterbird species, including herons and egrets, rails, shorebirds and ducks. These include a Mindanao endemic subspecies of Little Grebe, Tachybaptus ruficollis cotabaco, and Comb crested Jacana Irediparra gallinacea, for which Liguasan is the only locality in the Philippines.
Non-bird biodiversity: The marsh supports a great variety of aquatic wildlife. It is one of the last strongholds for the endangered Philippine crocodile Crocodylus mindorensis, and the estuarine crocodile C. porosus also occurs. The marsh is particularly rich in orchids.
BirdLife International (2017) Important Bird Areas factsheet: Liguasan marsh. Downloaded from http://www.birdlife.org on 26/02/2017.