Nest-predation by Siberian weasel Mustela sibirica, Large-billed Crows Corvus macrorhynchos and domestic cats is the main threat. Its population on Miyake-jima declined rapidly following the introduction of Siberian Weasels in the 1970s. The number of Large-billed Crows on Mikake-jima and the other Izu Islands has increased as a result of the dumping of raw garbage. During a survey on Miyake-jima in 1992, a total of 22 nests were found containing eggs, all of which hatched, but all nestlings were subsequently predated. The effects of predation are likely to have been compounded by habitat loss, associated with timber production, tourist developments and road construction. Volcanic eruptions on Miyake-jima in 2000 are likely to have negatively affected the population on that island.