Response to Comment on "Avian Extinction and Mammalian Introductions on Oceanic Islands"

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Abstract
Didham et al. (2) argue that we focused on a single-factor explanation and failed to consider other causes of extinction, notably habitat loss, that may correlate with the number of introduced predator species across islands, thus leaving open the question of causality. We certainly do not argue that extinctions are caused by a single factor; there is considerable unexplained variation in our data, and our other work has shown that, in addition to predation, factors such as habitat loss are important (3). Furthermore, we show that the number of introduced predator species fails independently to explain variation in the current levels of threat faced by island bird assemblages, so that other factors must be important (1). Nevertheless, our analyses do strongly suggest that mammal predators have played a major role in post-European avian extinctions on islands across the world. In this, they generalize the results of many studies linking the decline and extinction of birds on oceanic islands to the impact of exotic predators (4–7).