Saipan reed warbler

The Saipan reed warbler or gå'ga' karisu in Chamorro (Acrocephalus hiwae) is a critically endangered songbird of the Northern Mariana Islands.

Taxonomy
It is sometimes considered a subspecies of the extinct nightingale reed warbler (A. luscinius) by some taxonomists.

Distribution and habitat
It occurs on two islands: Saipan and Alamagan. An estimated population of 2700 birds was reported in 2009 on Saipan, and on Alamagan 950 birds were reported in 2010. It inhabits wetlands, thickets and the margins of forests.

Description
The Saipan reed warbler is approximately 17 cm long, and is greyish olive-brown above with a pale-yellow underside. The female is slightly smaller than the male. Both sexes have a long bill compared to other reed warbler species.

Conservation
Threats to the survival of the Saipan reed warbler include habitat destruction resulting from urban development and agriculture, the introduction of invasive species, and volcanic eruptions.