The island of Borneo, located in southeast Asia at the southern edge of the South China Sea, is home to one endemic bird family, three endemic bird genera and 59 endemic bird species. All but one of the latter are forest dwellers, with most restricted to the spine of hills and mountains running down the middle of the island. The avian endemism has been shaped by the island's geological history. Borneo sits on a continental shelf. During glacial periods, when water levels were lower, Borneo was linked with other islands on the shelf and with the Malay peninsula in a large landmass known as Sundaland. This allowed bird species to move freely throughout the region until the waters rose again as the glaciers melted. Separated from their relatives by the sea, some of these species evolved over millennia into the endemics now found on the island. BirdLife International has designated the mountainous central spine of the island as an Endemic Bird Area (EBA) because of the number of endemic species found there, and has further designated several lowland regions and nearby islands as secondary EBAs. Habitat destruction is a major threat to Borneo's endemic birds, as forests are lost to palm oil plantations and timber harvesting. Geology and geological history Borneo is an island located in southeast Asia, on the continental shelf at the southern edge of the South China Sea. It lies south of the Philippines, west of Sulawesi, north of Java, and east of peninsular Malaysia. With an area of , it is the world's third largest island. More than half of the island is lowlands, rising to less than . However, a spine of mountains runs down much of the central portion of the island. These include Mount Kinabalu, which at is the tallest mountain between the Himalayas and West Papua. The island is shared by three countries: Indonesia, Malaysia, and Brunei. While the lowlands are the most productive habitat in terms of the number of bird species found there, the mountains are the seat of Borneo's endemism. This is in large part due to the island's geological history. During the Pleistocene, the world's polar caps repeatedly advanced and retreated, alternately locking vast amounts of water into ice, and releasing it back into the world's oceans. This caused the water level in the oceans to repeatedly rise and fall. During glacial periods, when water levels were at