The Mariana swiftlet or Guam swiftlet (''Aerodramus bartschi'') is a species of

swiftlet Swiftlets are birds from the four genera ''Aerodramus'', ''Collocalia'', ''Hydrochous'' and ''Schoutedenapus'', which form the tribe (biology), tribe Collocaliini within the swift (bird), swift family (biology), family Apodidae. The group contain ...

in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Apodidae The Apodidae, or swifts, form a family of highly aerial birds. They are superficially similar to swallows, but are not closely related to any passerine species. Swifts are placed in the order Apodiformes along with hummingbirds. The treeswifts ar ...

Taxonomy

It was formerly lumped with the island swiftlet (''Aerodramus inquietus'').

Description

The swiftlet is about in length with a dark grey-brown head and upperparts. Its throat and upper breast are grey-white with the rest of the underparts darker grey. The tail has a shallow fork and the plumage lacks gloss.

Distribution and habitat

The swiftlet is found in

Guam Guam ( ; ) is an island that is an Territories of the United States, organized, unincorporated territory of the United States in the Micronesia subregion of the western Pacific Ocean. Guam's capital is Hagåtña, Guam, Hagåtña, and the most ...

as well as in

Saipan Saipan () is the largest island and capital of the Northern Mariana Islands, an unincorporated Territories of the United States, territory of the United States in the western Pacific Ocean. According to 2020 estimates by the United States Cens ...

and Aguiguan in the

Northern Mariana Islands The Northern Mariana Islands, officially the Commonwealth of the Northern Mariana Islands (CNMI), is an Territories of the United States, unincorporated territory and Commonwealth (U.S. insular area), commonwealth of the United States consistin ...

, and is locally extinct on Rota and

Tinian Tinian () is one of the three principal islands of the Commonwealth of the Northern Mariana Islands (CNMI). Together with uninhabited neighboring Aguiguan, it forms Tinian Municipality, one of the four constituent municipalities of the Northern ...

. It was also introduced successfully to

Oahu Oahu (, , sometimes written Oahu) is the third-largest and most populated island of the Hawaiian Islands and of the U.S. state of Hawaii. The state capital, Honolulu, is on Oahu's southeast coast. The island of Oahu and the uninhabited Northwe ...

in the

Hawaiian Islands The Hawaiian Islands () are an archipelago of eight major volcanic islands, several atolls, and numerous smaller islets in the Pacific Ocean, North Pacific Ocean, extending some from the Hawaii (island), island of Hawaii in the south to nort ...

in the early 1960s, though the population there remains small. Its natural

habitat In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...

s are tropical moist lowland forest,

mangrove forest Mangrove forests, also called mangrove swamps, mangrove thickets or mangals, are productive wetlands that occur in coastal intertidal zones. Mangrove forests grow mainly at tropical and subtropical latitudes because mangrove trees cannot withsta ...

and

grassland A grassland is an area where the vegetation is dominance (ecology), dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes such as clover, and other Herbaceo ...

Behaviour

In its natural range the swiftlet builds shallow nests high on the interior walls and ceilings of

limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

caves, including sites in zones of complete darkness, in colonies of a few to several hundred birds. A single egg constitutes a clutch, but the birds may breed more than once a year. The swiftlets utter twittering and chirping sounds as well as the echolocation clicks used to navigate inside the nesting and roosting caves. Most birds in a colony leave their cave at dawn to forage, returning at sunset to roost. They are aerial feeders that capture small insects in flight over forest and other vegetation.

Status and conservation

The Mariana swiftlet is considered to be Vulnerable after being listed as an

Endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching, inv ...

in 2016. The population on Guam declined because of predation by

brown tree snake The brown tree snake (''Boiga irregularis''), also known as the brown catsnake, is an arboreal rear-fanged colubrid snake native to eastern and northern coastal Australia, eastern Indonesia (Sulawesi to Papua), Papua New Guinea, and many island ...

s and the use of agricultural

pesticide Pesticides are substances that are used to control pests. They include herbicides, insecticides, nematicides, fungicides, and many others (see table). The most common of these are herbicides, which account for approximately 50% of all p ...

s, though it is believed to have subsequently increased to an estimated 900 individuals in 2006. The population on Saipan was estimated in 2005 to consist of about 5400 individuals, though this population is at risk if the

becomes established on the island. The estimated size of the Aguiguan population is about 400. The single known breeding colony on Oahu was estimated in 1997 to contain a minimum of 17 breeding pairs. Proposed conservation measures include continued population monitoring and limiting cave disturbance, the prevention of the establishment of brown tree snakes in the Northern Marianas Islands, control of introduced mud dauber wasps and

cockroach Cockroaches (or roaches) are insects belonging to the Order (biology), order Blattodea (Blattaria). About 30 cockroach species out of 4,600 are associated with human habitats. Some species are well-known Pest (organism), pests. Modern cockro ...

es where they damage nests, and the reintroduction of birds to Rota whence they were extirpated in the 1970s.

References