The Birds of Christmas Island form a heterogeneous group of 162 species. There is a core group of 4 endemics that have evolved on the remote island in the eastern Indian Ocean for thousands of years, attended by a suite of regular migrants, opportunists and occasional visitors. Some 200 km from the nearest land, Java, Christmas Island was not occupied by humans until the late 19th century. It is now an Australian territory. The natural vegetation of most of the 140 km² island is rainforest, to which the endemic landbirds are adapted, while the seabirds have taken advantage of a breeding location which had no major natural predators.