Lessons from introductions of exotic species as a possible information source for managing translocations of birds

It has been previously suggested that the characteristics that are driving the taxonomic homogenisation of the global avifauna, through the extinction of native bird species and the establishment of exotic bird species, are opposite sides of the same coin. One of the most important tools that conservation biologists and wildlife managers have to ameliorate the extinction of a species is to reintroduce populations to stronghold areas from which they have been extirpated or were not previously common. In this paper, we address the question of what the study of exotic bird introductions can tell us to inform the translocation of native species. We review the relative importance of the five factors that have been suggested significantly to influence the successful establishment of non-native species: introduction effort, environmental matching, species’ interactions, species’ life histories, and phylogenetic relatedness. Current evidence suggests that introduction effort will be an important determinant of release, but how many individuals need to be released, and in how many separate release events, is contingent on characteristics of species and environment. The importance of climate matching for introduction success suggests that the success of translocations will depend greatly on the study and amelioration of the problem that caused the initial population decline. This is most problematic in situations where the decline is associated with human-induced climate change. Migratory and sexually selected species may be harder to re-establish, but related species may differ substantially in their likelihood of success. We suggest that further insights into the reintroduction process may be gained particularly by studying species that are experiencing a threat in their native range but which are also being widely released as exotics outside of this range.