Years to extinction
In agreement with the first hypothesis, models with a log-transformed population size significantly outperformed those fit with non-logged population size (Δ AIC > 2) for data on all species combined, only birds and only non-avian species (Table S2). Also, in all three groups of data a positive interaction between body size and population size was included in a model within two AIC units of the best fitting model (Table 2); these models suggest that populations of smaller-bodied species are under imminent risk of extinction over a larger range of population size.