Modest increases in densities of burrow-nesting petrels following the removal of cats (Felis catus) from Marion Island

Published source details Dilley B.J., Schramm M. & Ryan P.G. (2017) Modest increases in densities of burrow-nesting petrels following the removal of cats (Felis catus) from Marion Island. Polar Biology, 40, 625-637.
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Summary

Control mammalian predators on islands for seabirds

A before-and-after study in 1979 and 2013 on Marion Island, South Africa (Dilley et al. 2017) reported that populations of petrels generally increased following control and eradication of feral cats Felis catus, but to a smaller degree than predicted. The study area contained 156,214 petrel burrows in 1979 (before cat control) but 243,613 in 2013 (22 years after cat eradication). White-chinned petrels Procellaria aequinoctialis increased at the highest rate (from 3,727 burrows in 1979 to 12,123 burrows in 2013). Salvin’s prions Pachyptila salvini increased from 126,338 to 182,643 burrows. Grey petrels Procellaria cinerea, already very rare in 1979 (3.1 burrows/ha), appeared to become less abundant by 2013 (1 burrow/ha). Common diving petrels Pelecanoides urinatrix, which had been extirpated by cats, were still not breeding in 2013. Before control started, cats killed 450,000 petrels/year on Marion Island. Cat control involved releasing the viral cat disease panleucopaenia, shooting, trapping and poisoning over 14 years, with eradication by 1991. House mice Mus musculus, also introduced, were not eradicated. Petrel burrows were surveyed in 13 sites (1,040 ha) across the island in 2013, replicating a survey done in 1979.