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(as evaluated by BirdLife International – the official Red List Authority for birds for IUCN): Endangered
Justification This species qualifies as Endangered because it has apparently undergone a rapid decline owing to pesticide-use and predation by the introduced brown tree snake on one island, although the reasons on other islands are unclear. However, earlier population estimates were probably too large and the population appears to have stabilised in recent years, and thus past declines may not be as great as feared.
Family/Sub-family Apodidae
Species name author Mearns, 1909
Taxonomic source(s) AOU checklist (1998 + supplements)
Synonyms Aerodramus bartschi AOU checklist (1998 + supplements)
Taxonomic note Collocalia inquieta (Sibley and Monroe 1990, 1993) has been split into C. bartschi following Browning (1993) and AOU (1998) and C. inquieta following Browning (1993).
Identification 11 cm. Swiftlet with dark greyish-brown upperparts and head. Silvery grey-white throat and upper breast. Remainder of underparts darker and greyer. Shallow fork-tail. Plumage lacks any noticeable sheen. Voice Chirps and twitterings. Makes echolocation clicks inside caves.
Population estimate
Population trend
Range estimate (breeding/resident)
Country endemic?
3,200 – 3,500
decreasing
730 km2
No
Range & population Collocalia bartschi is endemic to Guam (to USA) and the Northern Mariana Islands (to USA), and was introduced to Oahu, Hawaiian Islands (USA) in the early 1960s. On Guam, it was very abundant but, from the mid-1960s to the early 1970s, it underwent a precipitous decline4. In 1999, only three colonies remained, the largest holding c.700 birds (total population c.800)8. In the Northern
Marianas, populations disappeared from Rota and Tinian in the 1970s, although, on Tinian, it was possibly only nomadic3. In 1982, estimates were 9,120 on Saipan and 1,022 on uninhabited Aguijan3 but, more recently, estimates are c.2,000 (five colonies) and 400-475 (seven colonies), respectively8. On Oahu, it survives in a single known breeding colony in a small tunnel in the Ko`olau Mountains, although similar irrigation tunnels are common and thus other small colonies may exist2. Observations in 1997 suggest a minimum of 17 breeding pairs (66 birds in total)7.
Ecology It feeds over coastal and interior forest and grassland (and formerly mangroves), capturing small insects in flight, preferring forest on Guam and Aguijan8. It breeds and roosts in colonies in caves that typically hold a few to 700 birds8. Nesting occurs year-round, but is greatest from late January to September or October. One egg is laid per clutch and pairs probably lay more than one clutch per year8.
Threats The causes of the decline on Guam may relate to former pesticide-use. Currently, predation by brown tree snake Boiga irregularis is the primary limiting factor and interactions with introduced mud dauber wasps Vespula sp. may interfere with recovery (the additional weight of wasps nests causing swiftlet nests to fall from cave walls). On Saipan, exotic cockroaches (which also damage and destroy nests by consuming nest material and swiftlet saliva gluing them to cave walls) and possible disturbance by humans and feral mammals are probably the main threats7,8.
Conservation measures underway On Guam, snakes have been trapped at the main colony. Colonies have been censused regularly, nesting has been observed and foraging ranges mapped. On Saipan and Aguijan, colonies have been censused periodically and insecticide applied to kill cockroaches9.
Conservation measures proposed Continue monitoring. On Guam, facilitate recolonisation of caves historically used by large colonies. On Rota, reintroduce birds9. On Saipan, prevent cave disturbance.
References 1. Browning (1993). 2. Chantler and Driessens (1995). 3. Engbring et al. (1982). 4. Jenkins (1983). 5. Lee et al. (1996). 6. Morton and Amidon (1996). 7. Wiles and Woodside (1999). 8. G. Wiles (unpublished data). 9. G. Wiles in litt. (2000).
Text account compilers Andrew O’Brien (BirdLife International), Alison Stattersfield (BirdLife International)
IUCN Red List evaluators Guy Dutson (BirdLife International), Alison Stattersfield (BirdLife International)
Recommended citation BirdLife International (2014) Species factsheet: Collocalia bartschi. Downloaded from http://www.birdlife.org on 29/9/2014
This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, and BirdLife International (2004) Threatened birds of the world 2004 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.
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