How have feral cats contributed to bird extinctions on islands?

Feral cats have contributed to the extinction of approximately 30 island bird species worldwide. Their devastating impact is primarily attributed to the following factors:12

• Ecological Naivete: Many island bird species evolved without exposure to mammalian predators, leaving them "unwary" and lacking the defensive behaviors necessary to survive encounters with efficient hunters like domestic cats.13
• Efficient Predation: Cats are highly effective predators of vertebrates that have no prior experience with them. Because islands are small and isolated, these predators can exert immense pressure on local populations.12
• Population Impact: The scale of this predation can be extreme. For example, on Marion Island, a population of roughly 2,000 feral cats—descended from just five individuals—was estimated to kill 450,000 seabirds annually, severely threatening their survival.2

The introduction of cats to these environments, often by humans, has created a significant conservation challenge, as removing these invasive species is frequently a complex, expensive, and long-term process.12