Pacific Islands Fish and Wildlife Office
Pacific Region

Endangered Species in the Pacific Islands

Mariana swiftlet / Aerodramus bartschi / Chachaguak

Photo of Mariana swiflet The Mariana swiflet is a small, narrow winged bird with dark sooty gray above and grayish brown below. The species is endemic to the Mariana Islands and populations currently exist on Guam, Aguiguan, and Saipan.
Mariana swiflet - Photo credit Curt Kessler

Habitat & Behavior:
Swiflets build their nests on the upper walls of natural and manmade caves. Nests are composed of moss held tightly together and sealed to the cave wall by hardened saliva. The species navigates through caves using echolocation.

Past & Present:
The Mariana swiflet was once found on Guam, Rota, Aguiguan, Tinian, and Saipan. The population on Rota was extirpated in the 1970s and except for sporadic observations, is only known from the fossil record on Tinian.

In 1987, The Guam Division of Aquatic and WIldlife Resources estimated that only one swiflet colony of 400 birds, the Mahlac Cave colony, occurred on Guam. Currently three colonies are known to occur on the island. In 2005, the Mahlac Cave colony included 600-800 birds. The Fachi Cave colony included 45-95 birds, and the Maemong colony included 70 birds.

In 1984 and 1985, the Commonwealth of the Northern Mariana Islands Division of Fish and Wildlife estimated a population of 970 birds on Aguiguan and over 3,000 birds on Saipan. Estimates from known caves in 2005 place the population on Aguiguan and Saipan at 300-500 and 5,300, respectively.

Conservation Efforts:
Swiflets were introduced on O‘ahu in the early 1960s. On August 27, 1984, the Mariana swiflet was designated as endangered. Pesticide poisoning, introduced predators such as the brown treesnake, disease, typhoons, disturbance or loss of nesting caves may have contributed to the decline of this swiflet.

Brown treesnake control around the colonies on Guam is being undertaken by the Navy. The CNMI has also initiated cockroach control in some of the caves on Saipan to reduce nest failures. Plans for reestablishing populations in northern Guam and Rota through translocation are also being considered.


Last updated: September 20, 2012
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