Individual study: Control of black rats Rattus rattus increases breeding performance of Cory’s shearwater Calonectris diomedea Congreso Island, Chafarinas Archipelago, Spain
Igual J.M., Forero M.G., Gomez T., Orueta J.F. & Oro D. (2005) Rat control and breeding performance in Cory's shearwater (Calonectris diomedea): effects of poisoning effort and habitat features. Animal Conservation, 9, 59-65
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Control mammalian predators on islands for seabirds
A before-and-after study on Congreso (25.6 ha), Chafarinas Islands, Spain, between 1997 and 2004 (Igual et al. 2005) found breeding success of Cory’s shearwaters Calonectris diomedea at two sub-colonies increased when black rats Rattus rattus were intensively controlled and fell when control was relaxed. Success was 27-44% and 51% during two periods of little or no control (1997-8, 2000), compared with 70% and 71% during intensive control (2000 and 2002-4). Increases were due to decreased chick mortality from 52% and 23% in 1999 and 2001 to 11% in 2000. The increase in breeding success after control was greater at the more easily accessible colony, although that colony had lower breeding success overall. Between 208 and 280 nests were studied each year.