High predictability in introduction outcomes and the geographical range size of introduced Australian birds: A role for climate

1. We investigated factors hypothesized to influence introduction success a nd subsequent geographical range size in 52 species of bird that have been introduced to mainland Australia. 2. The 19 successful species had been introduced more times, at more sites and in greater overall numbers. Relative to failed species, successfully in troduced species also had a greater area of climatically suitable habitat a vailable in Australia, a larger overseas range size and were more likely to have been introduced successfully outside Australia. After controlling for phylogeny these relationships held, except that with overseas range size a nd, in addition, larger-bodied species had a higher probability of introduc tion success. There was also a marked taxonomic bias: gamebirds had a much lower probability of success than other species. A model including five of these variables explained perfectly the patterns in introduction success ac ross-species. 3. Of the successful species, those with larger geographical ranges in Aust ralia had a greater area of climatically suitable habitat, traits associate d with a faster population growth rate (small body size, short incubation p eriod and more broods per season) and a larger overseas range size. The rel ationships between range size in Australia, the extent of climatically suit able habitat and overseas range size held after controlling for phylogeny. 4. We discuss the probable causes underlying these relationships and why, i n retrospect, the outcome of bird introductions to Australia are highly pre dictable.