Birdfinding.info ⇒ Endangered but still locally common on Saipan, especially in the central hills, around the north end of the island, and at Lake Susupe. Very scarce and localized on Guam and an infrequent visitor to the other Mariana Islands. On Oahu, it has been found consistently at Aiea Ridge, which is near the colony site in the North Halawa Valley. Rarely seen elsewhere on Oahu, but there have been some intriguing sightings from cliff sites scattered around the island, including Ka’ena Point. The Oahu population is apparently the only known case of a swift as an introduced species.
Mariana Swiftlet
Aerodramus bartschi
Endemic to the Mariana Islands: Saipan, Aguijan, and Guam, where it breeds in caves and forages over all local habitats.
Formerly also resident on Tinian and Rota, but apparently extirpated from both around the 1970s. Sightings on both islands during the 2010s indicate at least occasional visits and possible natural recolonization.
Introduced to Oahu in 1962 and 1965, about 350 individuals combined. In 1978, a nesting colony was discovered in a manmade tunnel in the North Halawa Valley. Annual censuses of the colony have counted up to 54 nests (highest counts in 2000 and 2010), but rat predation has eliminated the colony in some years.
As of 2015, the global population was estimated between 6,500 and 7,000 in 19 known colonies: ~4,700 in eight colonies on Saipan (where a ninth, inaccessible colony was not surveyed), ~1,600 in three colonies on Guam, ~270 in six colonies on Aguijan, and ~140 in one colony on Oahu.
Entrance to the Mariana Swiftlet roosting and nesting tunnel in the North Halawa Valley, Oahu, Hawaii. © Nathan Christopher Johnson
Additional colonies were suspected but unconfirmed on Guam and Saipan. Many apparently suitable caves exist on all five islands of its natural range, and reintroduction efforts have been planned for Rota and northern Guam.
Identification
A typical Aerodramus swiftlet, but with comparatively pale underparts and uniform upperparts.
Mariana Swiftlet. (Commonwealth of the Northern Mariana Islands; March 2, 2020.) © sablan93
Mariana Swiftlet, flight silhouette. (Oahu, Hawaii; May 20, 2015.) © Colin Morita
Mariana Swiftlet. (Aiea Ridge, Oahu, Hawaii; December 15, 2010.) © Michael Walther
Mariana Swiftlet on tunnel wall. (North Halawa Valley, Oahu, Hawaii; May 2006.) © Nathan Christopher Johnson
Voice. “Described as weak chirps and twitterings.” (Chantler 2000)
Notes
Monotypic species.
IUCN Red List Status: Endangered.
More Images of Mariana Swiftlet
Mariana Swiftlet on tunnel wall. (North Halawa Valley, Oahu, Hawaii; May 2006.) © Nathan Christopher Johnson
Mariana Swiftlet, with light-neutral background allowing underparts coloration to show. (WWII Memorials, Saipan, Northern Mariana Islands; September 8, 2019.) © Joseph Morlan
Mariana Swiftlet. (Aiea Ridge, Oahu, Hawaii; December 15, 2010.) © Michael Walther
Mariana Swiftlet. (Aiea Ridge, Oahu, Hawaii; October 26, 2015.) © Michael Walther
Mariana Swiftlet. (Aiea Ridge, Oahu, Hawaii; December 15, 2010.) © Michael Walther
Mariana Swiftlet. (Aiea Ridge, Oahu, Hawaii; May 7, 2019.) © Zugunruhe Tours
Mariana Swiftlet. (Aiea Ridge, Oahu, Hawaii; January 29, 2018.) © Ray Duffy
Mariana Swiftlet. (Aiea Ridge, Oahu, Hawaii; September 24, 2016.) © Sharif Uddin
Mariana Swiftlet, showing “large-handed” silhouette typical of this genus. (Commonwealth of the Northern Mariana Islands; March 2, 2020.) © sablan93
Mariana Swiftlet. (Aiea Ridge, Oahu, Hawaii; December 4, 2016.) © Laura Keene
Mariana Swiftlet, incubating. (Lake Susupe, Saipan, Northern Mariana Islands; August 19, 2005.) © Eric Kershner
Mariana Swiftlet, nestling. (Lake Susupe, Saipan, Northern Mariana Islands; August 19, 2005.) © Eric Kershner
References
BirdLife International. 2016. Aerodramus bartschi. The IUCN Red List of Threatened Species 2016: e.T22728583A94990600. https://dx.doi.org/10.2305/IUCN.UK.2016-3.RLTS.T22728583A94990600.en. (Accessed May 23, 2020.)
Chantler, P. 2000. Swifts: A Guide to the Swifts and Treeswifts of the World (Second Edition). Yale University Press.
eBird. 2020. eBird: An online database of bird distribution and abundance. Cornell Lab of Ornithology, Ithaca, N.Y. http://www.ebird.org. (Accessed May 23, 2020.)
Johnson, N.C. 2015. Population Ecology of the Mariana Swiftlet (Aerodramus bartschi) on O’ahu, Hawaiian Islands. https://ir.library.oregonstate.edu/downloads/cf95jd83w. Oregon State University, Corvallis.
Pratt, H.D., P.L. Bruner, and D.G. Berrett. 1987. A Field Guide to the Birds of Hawaii and the Tropical Pacific. Princeton University Press.
Pratt, H.D. 1993. Enjoying Birds in Hawaii: A Birdfinding Guide to the Fiftieth State (Second Edition). Mutual Publishing, Honolulu, Hawaii.
Pyle, R.L., and P. Pyle. 2017. The Birds of the Hawaiian Islands: Occurrence, History, Distribution, and Status. Version 2 (January 1, 2017). http://hbs.bishopmuseum.org/birds/rlp-monograph/. B.P. Bishop Museum, Honolulu, Hawaii.