Feral domestic cats are recognized as one of the most devastating non-native predator species to many bird species, particularly nesting colonies of the Red-billed Tropicbird (Phaethon aethereus) on Saba island. The species is especially prone to predation from cats and rats because it nests on the ground and eggs and fledglings are easily preyed upon.
Cats pose the more serious threat to tropicbirds because cats have only recently become a problem (since about 2000), which means the birds have had less time to adapt to this new predator. Saba Conservation Foundation together with Wageningen University Research Center of The Netherlands collected baseline data on cat and rat distribution, and cat diet and health. They also conducted 83 questionnaire interviews with Saba residents to assess their views on cats, rats, tropicbirds and the acceptability of different management options.
Thirty-six percent (36%) of Saban and 48% of expat residents valued the life of a tropicbird more than that of a single cat. The remainder considered cats somewhat more important than one tropicbird but only few (5% natives, 18% expats) considered feral cats more important than the combined sum of all their tropicbird prey. Between 70-80% of respondents thought registration, neutering and removal of cats from breeding colonies was a good idea. A significant majority of residents (80%) found euthanization to be an acceptable method for use in cat control, while 43% even thought that total eradication of all cats (domestic and feral) from the island would be a good idea.
Preliminary veterinary assessments on abandoned cats showed the animals to be in overall poor health. Based on these results and taking into account the welfare concerns of the tropicbirds preyed upon by cats, the local SPCA decided to discontinue its practice of releasing neutered unwanted cats into the wild (Trap-Neuter-Release, or TNR). Removal of 36 cats from one breeding colony increased tropicbird chick fledgling success from about 5% to 50%, which is very encouraging in terms of animal welfare, when including birds into the equation.