Family: Acrocephalidae (Reed-warblers)

Authority: Yamashina, 1942

Red List Category

Criteria: A3bce+4bce

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Justification of Red List category
This species qualifies as Critically Endangered because the very rapid rate of decline in its very small global population observed over the past three generations is expected to increase owing to habitat loss and degradation combined with the impact of introduced predators including the possible arrival of Brown Tree Snake (Boiga irregularis) on Saipan. This snake is a likely factor in the reed-warblers sister species' extirpation from Guam.Should the recorded rate of decline be lower than suggested then the species may become eligible for downlisting in the future, though the number of extinctions within this species complex and the potential existential threat posed by accidental introductions would suggest that extreme caution be employed prior to any lowering of the threat status.

Population size: 2000-2499

Population trend: Decreasing

Extent of occurrence (breeding/resident): 2,500 km²

Country endemic: Yes