Wedge-tailed Shearwaters increase on now rat-free D’Arros Island in the Seychelles

Wedgie Danielle Keys
A Wedge-tailed Shearwater on D’Arros Island, photograph by Danielle Keys

Danielle Keys (Marine Apex Predator Research Unit, Nelson Mandela University, Gqeberha, South Africa) and colleagues have published in the open-access journal, Marine Ornithology on the increasing numbers of Wedge-tailed Shearwaters Ardenna pacifica on a Seychelles island following eradication of Norway Rats Rattus norvegicus.

15 352 Danielle van den Heever October2016 CKD
Danielle Keys burrow scopes a Wedgie burrow on on D’Arros Island, photograph by
Clare Keating

The paper’s abstract follows:

“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.

Wedgie burrows Danielle Keys
Wedge-tailed Shearwater burrow entrances on on D’Arros Island, photograph by Danielle Keys


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.

13 May 2024

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