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The spread and status of the Gough Moorhen Gallinula comeri on Tristan da Cunha

Published online by Cambridge University Press:  24 June 2025

Harry H. Marshall ,
Coleen L. Moloney ,
Trevor Glass ,
Richard Grundy ,
Andy Schofield  and
Peter G. Ryan
Harry H. Marshall*
Affiliation:
https://ror.org/0138va192 Royal Society for the Protection of Birds , The Lodge, Sandy, UK
Coleen L. Moloney
Affiliation:
Department of Biological Sciences, https://ror.org/03p74gp79 University of Cape Town , Rondebosch, Cape Town, South Africa
Trevor Glass
Affiliation:
Tristan da Cunha Government, Edinburgh-of-the-Seven-Seas, Tristan da Cunha
Richard Grundy
Affiliation:
Tristan da Cunha Association, Glastonbury, UK
Andy Schofield
Affiliation:
https://ror.org/0138va192 Royal Society for the Protection of Birds , The Lodge, Sandy, UK
Peter G. Ryan*
Affiliation:
FitzPatrick Institute of African Ornithology, https://ror.org/03p74gp79 University of Cape Town , Rondebosch, South Africa
*
Corresponding authors: Harry H. Marshall and Peter G. Ryan; Emails: harry.marshall@rspb.org.uk; pryan31@gmail.com
Corresponding authors: Harry H. Marshall and Peter G. Ryan; Emails: harry.marshall@rspb.org.uk; pryan31@gmail.com
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Summary

Rallidae are frequent colonists of oceanic islands and are often susceptible to introduced predators. The Tristan Moorhen Gallinula nesiotis was endemic to Tristan da Cunha, South Atlantic and is thought to have gone extinct in the late nineteenth century. The closely related Gough Moorhen G. comeri was introduced to Tristan da Cunha from neighbouring Gough Island in 1956. We report historical records of their spread across Tristan da Cunha and the results of a population survey undertaken in February–March 2024. Gough Moorhens are now found across the entire island wherever there is suitable habitat from sea level to above 900 m elevation. Gough Moorhens prefer fern bush habitat on the Base, the plateau above the steep coastal cliffs. The total population is approximately 41,500 birds (95% confidence interval 24,000–72,000). Our density estimates (3–6 birds/ha) are similar to estimates for Gough Moorhens on Gough Island before the post-2021 population decline and are at the higher end of densities reported for oceanic island rallids, suggesting that the Tristan da Cunha population may be near carrying capacity.

Keywords

Gallinula comeriOceanic IslandsPopulation sizeRallidaeRange spread

Information

Type
Research Article
Information
Bird Conservation International , Volume 35 , 2025 , e20
Copyright
© The Author(s), 2025. Published by Cambridge University Press on behalf of BirdLife International

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