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close| Location | St Helena (to UK), Ascension Island |
| Central coordinates | 14o 18.00' West 7o 56.00' South |
| IBA criteria | A1, A4i, A4ii, A4iii |
| Area | 5 ha |
| Altitude | 0 - 104m |
| Year of IBA assessment | 2001 |
Ornithological information See Box for key species. Of the 11 resident species of seabirds one, Anous stolidus, does not breed, breeding instead on the main island and stacks (SH001). Breeding species are Oceanodroma castro, Phaethon aethereus, P. lepturus, Sula dactylatra, S. sula, S. leucogaster, Fregata aquila, Sterna fuscata, Anous minutus and Gygis alba. Puffinus lherminieri is thought to have once bred. The world population of F. aquila breeds at this site.
Site description The site is a barren, steep-sided trachytic rock, about 340 m by 220 m in size, rising to 104 m, with a relatively flat basaltic top nearly 3 ha in extent, located 305 m north of the eastern part of Ascension Island (SH001). Included also is a small, isolated rock 670 m east of the southern end. The site is heavily overlaid with guano, and there are traces of a guano industry that operated in the 1920s.
Populations of IBA trigger species
| Species | Season | Period | Population estimate | Quality of estimate | IBA Criteria | IUCN Category |
|---|---|---|---|---|---|---|
| Madeiran Storm-petrel Oceanodroma castro | breeding | 1959 | 1,500 breeding pairs | medium | A4ii | Least Concern |
| Red-billed Tropicbird Phaethon aethereus | breeding | 1959 | 500 breeding pairs | medium | A4ii | Least Concern |
| White-tailed Tropicbird Phaethon lepturus | breeding | 1959 | 1,000 breeding pairs | medium | A4ii | Least Concern |
| Ascension Frigatebird Fregata aquila | breeding | 1997 | 6,000 breeding pairs | medium | A1, A4ii | Vulnerable |
| Masked Booby Sula dactylatra | breeding | 1990 | 1,300 breeding pairs | medium | A4ii | Least Concern |
| Black Noddy Anous minutus | breeding | 1990 | 5,000 breeding pairs | - | A4i | Least Concern |
| A4iii Species group - seabirds | breeding | - | - | unknown | A4iii |
Protected areas
| Protected area | Designation | Area (ha) | Relationship with IBA | Overlap with IBA (ha) | |
|---|---|---|---|---|---|
| Boatswainbird Island | Protected Area | 5 | is identical to site | 5 |
Land use
| Land-use | Extent (% of site) |
|---|---|
| fisheries/aquaculture | - |
| nature conservation and research | - |
Other biodiversity The dolphins Steno bredanensis (DD) and Tursiops truncatus (DD) occur, the former common around the island. There are several invertebrates, including the endemic pseudoscorpions Garypus titanius, Neocheiridium sp. and Stenowithius duffeyi.
Management considerations Initial restrictions on access were instituted in 1977, and permits to visit can only be granted by the Administrator, now only seldom given. Besides the accidental introduction of mammalian predators such as cats and rats, the main threat is disturbance. Supervision is poor due to the location of the site at the opposite end of Ascension, away from the authorities at Georgetown. The adjacent mainland, from where the site can be monitored, is seldom visited due to a lack of vehicular access—tracks are poor. Boatloads of visitors have landed illegally, and captains of passing vessels have been known to blow the ship’s whistle to put up the birds as a ‘spectacle’ for passengers and crew. This displaces eggs and chicks, which are lost due to exposure to the sun, and predation. A further threat is commercial fishing; there is potential for over-exploitation of fish stocks.
References Allan (1962), Ashmole (1962, 1963a, b), Ashmole and Ashmole (1997, 2000), Ashmole, Ashmole and Simmons (1994), Blair (1989), Dorward (1962a, b, 1963), Dorward and Ashmole (1963), Duffey (1964), Hughes (1992b), Hughes et al. (1994), Nash et al. (1991, 1992), Osborn (1994), Packer (1983), Ratcliffe (1997), Simmons (1967, 1968, 1970, 1990), Stonehouse (1960, 1962 a, b), Stonehouse and Stonehouse (1963).
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Recommended citation BirdLife International (2013) Important Bird Areas factsheet: Boatswainbird Island. Downloaded from http://www.birdlife.org on 23/05/2013
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