Have burrowing petrels recovered on Marion Island two decades after cats were eradicated? Evidence from sub-Antarctic skua prey remains

Published source details Cerfonteyn M. & Ryan P.G. (2016) Have burrowing petrels recovered on Marion Island two decades after cats were eradicated? Evidence from sub-Antarctic skua prey remains. Antarctic Science, 28, 51-57.
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Summary

Control mammalian predators on islands for seabirds

A before-and-after study in 1987–1988 and 2010–2011 on Marion Island, South Africa (Cerfonteyn & Ryan 2016) reported that following the eradication of feral cats Felis catus, there was only a small increase in the proportion of burrowing petrels in the diet of sub-Antarctic skuas Stercorarius antarcticus. The study suggests that this reflects a lack of substantial recovery in petrel populations on the island. Statistical significance was not assessed. In 1987–1989, when feral cats were present, petrels (all species combined) comprised around 22–27% of skua diets. In 2010–2011, around 20 years after cat eradication, petrels comprised 29–40% of skua diets. Cats were eradicated from Marion Island in 1991, after a presence of around 40 years. Diet composition was based on (a) the predominant prey at feeding sites (450–878 sites/period) and (b) closer identification of individual remains at a subset of feeding sites (101–136 sites/period). Data from the 1980s were taken from a previous publication.