The Birds of Christmas Island form a heterogeneous group of over 100 species. There is a core group of ten 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.
After over a century of human exploitation of the phosphate deposits covering much of the island, two thirds of the rainforest cover remains and is now protected as a national park. However, gaps where the forest has been cleared, and the introduction of exotic fauna, continue to destabilise the island’s biological diversity. The endemic Abbott's booby is threatened when nesting by wind turbulence caused by past forest clearance. However, the biggest immediate threat is the introduction and spread of yellow crazy ants, through both direct predation and ecosystem collapse. This has led to all the island’s endemic bird species and subspecies being classified as Critically Endangered.
Meanwhile, the number of species recorded from Christmas Island continues to increase as birders, especially from Australia, attracted by the island’s endemics, record a variety of vagrants previously unnoticed. Some of these may in time, as with the white-breasted waterhen, establish breeding populations. Christmas Island is now seen as a birding ‘hot spot’, not only for its endemics but also for the chance of recording new species for the Australian bird list, something reflected in the frequency of submissions of sightings to the Birds Australia Rarities Committee.
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