Volume 52, No. 1

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Rapid increase in size of Wedge-tailed Shearwater Ardenna pacifica colony following rat eradication.



1Department of Science and Technology/National Research Foundation Centre of Excellence at the FitzPatrick Institute for African Ornithology, Department of Zoology, Nelson Mandela University, Gqeberha, South Africa *(
2Marine Apex Predator Research Unit, Institute for Coastal and Marine Research, Nelson Mandela University, Gqeberha, South Africa
3Save Our Seas Foundation, D'Arros Research Centre, Rue Philippe Plantamour 20, CH-1201 Geneva, Switzerland


KEYS, D.Z., BULLOCK, R.W., KEATING, C. & PISTORIUS, P.A. 2024. Rapid increase in size of Wedge-tailed Shearwater Ardenna pacifica colony following rat eradication. . Marine Ornithology 52: 149 - 155

Received 23 February 2023, accepted 12 July 2023

Date Published: 2024/04/15
Date Online: 2024/04/09

Key words: Ardenna pacifica, Wedge-tailed Shearwater, invasive species, population census, biodiversity, phenology, Seychelles


Invasive mammalian predators have devastating effects on seabird nesting colonies. A census was conducted on breeding Wedge-tailed Shearwaters Ardenna pacifica in 2016 and 2021 on D'Arros Island, Seychelles, which has been rat-free since 2003. Results were compared with an earlier population estimate to assess population growth following the rat eradication. Compared to counts in 2009, we estimated a 10-fold increase in breeding population size, with 2768 (95% confidence interval (CI) 2424-3112) and 2406 (95% CI 2143-2667) breeding pairs in 2016 and 2021, respectively. While the estimated increase is partly attributable to differences in the timing of the conducted census between the two studies, we also observed an increase in the areal extent of the population, from 3.00 to 3.85 ha (0.0300-0.0385 km2), and an increase in nesting density. Cumulatively, this indicates a true population increase.


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