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Ascension Island

​Ascension is a small island of volcanic origin and is found in the South Atlantic Ocean roughly midway between South America and Africa (7° 57' S, 14° 22' W) and forms part of the British Overseas Territory of St Helena, Ascension and Tristan da Cunha.  

From a natural history perspective Ascension is a breeding site for the green turtle (Chelonia mydas) and a number of seabird species of which the Sooty Tern is the most numerous. Ascension played a key role as a staging post during the 1982 Falklands conflict and still provides the link between the UK and the South Atlantic.

  • Our Work on Ascension Island

    British military ornithological societies have monitored the colony of Sooty Terns Onychoprion fuscatus and other seabirds on Ascension Island in the South Atlantic since 1987. The first population census was completed in 1990 ten years prior to the commencement of the RSPB cat eradication on the Island. Sooty Terns were closely monitored during the two years when cats were culled and now we continue the monitoring in the post eradication phase. The longitudinal study has focused on the breeding biology of the Sooty Tern and concentrates on establishing trends in the breeding population, identifying and recording levels of predation, site fidelity, sub-annual breeding, investigating nest and adult survival rates, and more recently to identifying their migration sites.

    The long term monitoring programme on Ascension was not planned and there is no lead organisation dictating the direction of the project. The programme has evolved over time and the focus now is on publishing the information that has already been gathered, filling gaps in existing data sets and to continue with the monitoring work. Over the years the lead role has changed hands a number of times. The organisations involved are:

    • The Royal Air Force Ornithological Society (RAFOS) which mounted the first expeditions in Feb 87 and Nov 88 and has contributed to most expeditions since.
    • The Army Ornithological Society (AOS), the main contributor, mounting expeditions in 1990, 1991, 1994, 1996, 1998, 2000, 2002, 2004, 2005, 2006, 2007, 2008, 2009, 2011 and the most recent in 2012.
    • The Royal Navy Bird Watching Society (RNBWS) which has contributed field workers, ringers and boat surveys.

    The main aim of this long term monitoring programme is to facilitate the expansion of the breeding population by identifying and reducing threats to the Sooty Tern colonies. The following tasks are conducted:

    • Surveys of the breeding population are undertaken at regular intervals.
    • The levels of predation in the colony are measured and recorded.
    • A ringing and re-trap programme is maintained so that inter and intra colony movements can be monitored and survival rates determined.
    • Perceived threats to the colony are investigated.
    • Long term, quantifiable data that can be used as evidence for making conservation management decisions on Sooty Terns is collected and made available to interested parties.

    Ascension Island Overview Map (Imagery © 2009 DigitalGlobe)

    Ascension Island Overview Map (Imagery © 2009 DigitalGlobe)

    Useful Ascension Island References

    CIA - The World Factbook
    Ascension Island Government
    Foreign and Commonwealth Office profile on Ascension Island

  • Birds of Ascension Island

    Ascension Island is home to 15 species of bird, both native and non-native.  This section provides a short introduction to 5 species and, over time, will be expanded to cover all 15.  For those who wish to learn more there are downloadable information sheets which include further references and, where possible, these are linked to the relevant research papers.

    Masked Booby (Sula dactylatra)

    Sooty Tern (Onychoprion fuscatus)

    White Tern (Gygis alba)

    Brown Noddy (Anous stolidus)

    Common Mynah (Acridotheres tristis)

  • Trend in the population of Sooty Terns breeding on Ascension Island, South Atlantic

    Using geolocators to discover where Sooty Terns go between breeding seasons on Ascension Island in the South Atlantic

    Avian deformities

    The use of Google Earth imagery to identify seabird nests

    Ascension Island KML File For Google Earth - Maps of the Sooty Tern Colonies

    Age categories P1-P7 of Sooty Tern chicks

    Plasticity in breeding periodicity: the sub-annual cycle of Sooty Terns on Ascension Island

    Sooty Tern Ringing Data

    Study Sites Interactive Map

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