What caused the population decline of the Bridled White-eye on Rota, Mariana Islands?

Studies in Avian Biology
By:  and 


  • The Publications Warehouse does not have links to digital versions of this publication at this time
  • Download citation as: RIS | Dublin Core


The Bridled White-eye (Zosterops conspicillatus rotensis) was Once thought to be common and widespread on Rota, Commonwealth of the Northern Mariana Islands, but is now restricted to several patches of native limestone forest in and adjacent to the Sabana region. Surveys conducted in 1990 indicated that the population had declined by 87% between 1982 and 1990 for unknown reasons. The low density and restricted habitat association of the Bridled White-eye on Rota contrasts with the situation on Saipan, Tinian, Agiguan, and formerly on Guam, where the Bridled White-eye is the most common forest bird and occurs at all elevations and in all habitat types. We surveyed the entire range of the Rota Bridled White-eye in 1996 to estimate its current numbers and distribution. We also reviewed existing information on the white-eye and evaluated potential causes of its decline, including predation by Black Drongos (Dicrurus macrocercus), rats (Rattus spp.), and the brown tree snake Boiga irregularis); pesticides; avian disease; and habitat loss and alteration. We found that 94% of the extant population of 1,165 white-eyes on Rota was restricted to four patches of old-growth, native limestone forest covering only 259 ha. We believe that the population decline and current localized distribution is primarily a result of habitat changes due to agricultural development and typhoons, but the absence of white-eyes from several stands of native forest above 200 m remains unexplained. The Rota white-eye may be a different species from white-eyes found on Saipan, Tinian, Agiguan, and Guam, with different habitat preferences.

Study Area

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title What caused the population decline of the Bridled White-eye on Rota, Mariana Islands?
Series title Studies in Avian Biology
Volume 22
Year Published 2001
Language English
Publisher Cooper Ornithological Society
Publisher location Los Angeles, CA
Contributing office(s) Pacific Island Ecosystems Research Center
Description 7 p.
First page 274
Last page 280
Country Mariana Islands
State Rota