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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

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.

Key Biodiversity 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.

Non-bird 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.

Populations of IBA trigger species

Species Season Period Population estimate Quality of estimate IBA Criteria IUCN Category
Band-rumped Storm-petrel Hydrobates 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  20,000-49,999 individuals  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 -

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 (2015) Important Bird Areas factsheet: Boatswainbird Island. Downloaded from on 05/05/2015

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