Are islands more susceptible to be invaded than continents? Birds say no

island communities are generally viewed as bring more susceptible to invasi on than those of mainland areas, yet empirical evidence is almost lacking. A species-by-species examination of introduced birds in two independent isl and-mainland comparisons is not consistent with this hypothesis. In the New Zealand-mainland Australia comparison. 16 species were successful in both regions. 19 always failed and only eight had mixed outcomes. Mixed results were observed less often than expected by chance. and in only 5 cases was t he relationship in the predicted direction. This result is not biased by di fferences in introduction effort because, within species. the number of ind ividuals released in New Zealand did not differ significantly from those re leased in mainland Australia. A similar result emerged in the Hawaiian isla nds-mainland USA comparison: among the 35 species considered. 15 were succe ssful in both regions, seven always failed and 13 had mixed outcomes. In th is occasion, the results Bt well to those expected by chance, and in only s even cases was the relationship in the direction predicted. I therefore con clude that if true, the view that islands are less resistant than continent s to invasions is far from universal.