When the Indian Ocean atoll of Aldabra was added to the World Heritage List in 1982 it concluded 20 years of conservation effort to gain international recognition of its scientific importance. Its native wildlife, which is still remarkably intact, is, however, under threat. Only 27 km away, on Assumption Island, introduced bird species have established and are breeding. The author made a survey in October 1986 and among his findings was the particularly alarming discovery of a large population of red-whiskered bulbuls Pycnonotus jocosus, a nest predator of small passerines. Urgent action is required to remove the introduced species from Assumption, not only to protect Aldabra, but also to pave the way for conservation efforts on Assumption itself.