Aguijan Reed-warbler Acrocephalus nijoi


Justification of Red List Category
There are no records of the species since 1995, despite extensive surveys in 2000, 2001, 2008 and 2009. Additionally it is possible that the last few records actually pertain to dispersing individuals of Acrocephalus hiwae (Marshall et al. 2009).  It is therefore classified as Extinct.

Population justification
A tiny population was reported to remain on the uninhabited island but has not been observed on the island since the mid-1990s despite extensive surveys in 2000, 2001, 2008, and 2009 (USFWS 1998, Esselstyn et al. 2003, Camp et al. 2009b, Amidon et al. 2014), and the species is now considered to be Extinct.

Trend justification
Considerable survey effort appears to have adequately documented the disappearance of a species of Acrocephalus from the island of Aguijan between 1982 and 1995 (Engbring et al. 1986, USFWS 21998, Marshall et al. 2009). 

Distribution and population

This species is historically known only from Aguijan in the Northern Mariana Islands (to USA). 


It inhabited formerly disturbed areas vegetated by groves of trees and thickets. (Engbring et al. 1982, Reichel et al. 1992, USFWS 1998).


Introduced predators, including feral cats (Felis catus) and rats (Rattus spp.), and possibly monitor lizard (Varanus indicus), may have been a large factor in the declines, or possibly the impact of Ivy Gourd Coccinia grandis (USFWS 1998, Mosher 2006).

Conservation actions

Conservation and Research Actions Underway
A recovery plan exists for the pre-split taxon (U.S. Fish and Wildlife Service 1998) but there has been little or no active management for the species to date and the milestones in the plan are now out of date. However, provisions to protect habitat and mitigate loss have generally been included in major land development projects. In 1989, a goat removal programme was begun on Aguijan but, by 1995, goat populations had begun to rebound with reduced hunting pressure. Trap lines for snakes are maintained at ports, night searches are conducted and a sniffer dog programme has recently been established. Publicity campaigns were conducted to raise the general awareness of island residents, including port workers, about the dangers of snake colonisation (USFWS 1998). Repeat surveys have been conducted in 2000, 2001, 2008, and 2009 (USFWS 1998, Esselstyn et al. 2003, Camp et al. 2009b, Amidon et al. 2014).

Conservation and Research Actions Proposed
Repeat surveys of the avifauna of Aguijan: should any Acrocephalus be discovered, enact measures from the Species Recovery Plan and additionally genetically sample the individuals to establish that they are A. nijoi and not a secondary arrival of A. hiwae. If the latter, enact measures from the Species Recovery Plan for that species.


18 cm. Large, lanky, scruffy-looking warbler with long bill and often dishevelled feathers and erect head feathers when singing. Dingy olive-yellow above, with dull yellow eyebrow and underparts. Voice Call was a loud chuck or tchack. Males sang long, loud, varied and complex song.


Text account compilers
Benstead, P., Bird, J., Calvert, R., Khwaja, N., Mahood, S., O'Brien, A., Stattersfield, A., Derhé, M., Symes, A. & Wright, L

Camp, R., Dutson, G., Freifeld, H., Saunders, A., Radley, P., Mosher, S., Amidon, F. & Gourley, J.

Recommended citation
BirdLife International (2019) Species factsheet: Acrocephalus nijoi. Downloaded from http://www.birdlife.org on 22/01/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 22/01/2019.