The Aguiguan reed warbler or Aguijan reed warbler (Acrocephalus nijoi) originally occurred on the Northern Mariana Island Aguigan. It was once considered a subspecies of the nightingale reed warbler. Of this subspecies there never have been reports of a substantial population. In 1982 only four up to possibly 15 birds of the subspecies have been counted, and since 1995 none has been sighted, despite extended efforts to find specimens.