Northern Mariana Islands


Ko’ko’ (Guam rails, Gallirallus owstoni) are endemic to the island of Guam, but were extirpated by introduced brown tree snakes. However, some birds were taken into captivity in the mid 1980s before they were completely extirpated. A programme to introduce captive-reared ko’ko to snake-free Rota Island, 76 km N of Guam, was initiated in 1989 to conserve the species. Over 700 have been released on Rota to date, mostly at the eastern end of Rota, but the population there appears to be small and unstable, at least partially due to feral cats. In September 2006, when 46 ko’ko’ were released in Apanan, located in the southern part of the island. The release site was moved to Apanan as it contains more preferred habitat and is far from a development project currently underway in the east that will attract additional cats. Ko’ko’ have also been reintroduced to a 22-ha area on Guam where trapping and a perimeter barrier have been used to reduce abundance of brown tree snakes barrier. Contact Suzanne Medinaor Paul Wenninger, Department of Agriculture, Guam.


Biologists with the Marianas Avifauna Conservation Project have introduced the bridled white-eye (Zosterops conspicillatas) to Sarigan (16° 42′ N, 145° 47′ E), a 500 ha island in the Northern Mariana archipelago. This is viewed as a conservation introduction, and is part of a larger plan to conserve endemic bird species threatened by the exotic brown tree snake. 50 birds (29 male, 20 female, 1 unknown) were released on 3 May 2008, and these came from the island of Saipan (15º 15′ N, 145º 48′ E) which has a population of brown tree snakes. A total of 77 white-eyes were captured on Saipan from 22-24 April, and some were used in a trial to assess the degree to which white-eyes were likely to prey on Sarigan snail populations, specifically those of the humped tree snail (Partula gibba). The 50 birds selected for release were transported to Sarigan by helicopter on the day of release, and 14 fitted with transmitters (model LB-2N, Holohil Systems Ltd). These transmitters weigh 0.35 g and the white-eyes weigh about 7 g. The transmitterised birds were then monitored from 3-11 May 2008. Contact Paul Radley, Division of Fish & Wildlife, Commonwealth of the Northern Mariana Islands.

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