Abstract for presentation at Biodiversity Extinction Crisis Conference - A Pacific Response

Fiji has 300+ islands and for birds they provided an ‘ideal’ home until human-induced habitat changes and the introduction of mammalian predators occurred. Mongoose (Herpestes javanicus) have often been cited as the main predator responsible for the extirpation of many bird species in Fiji but much of this evidence is anecdotal. This study was carried out on 16 small offshore islands in the Fiji group, half of which have extant mongoose populations. Bird point counts were carried out for five days in four key habitat types on each island. The environmental variables: island size, elevation, distance of the offshore islands from the two main islands (Viti Levu and Vanua Levu), habitat quality, number of cats and rats present, and the absence or presence of mongoose were investigated in order to determine whether they influenced bird assemblages. Multivariate analysis, using canonical ordination showed that habitat quality and the presence of forest cover were the key variables influencing the bird assemblages. Additionally, some birds were primarily associated with islands free of mongoose. Any effects detected, however, were ‘historical’, as mongoose have been on these islands for at least 20 years. Bird assemblages on mongoose islands were dominated by introduced species that are relatively unaffected by predation and/or were somewhat secure native arboreal species that avoid predation as mongoose rarely venture up into the forest canopy. To actually test the effect of mongoose on island birds there are two options; introduce mongoose to an island and monitor their impact (but this would be ethically unacceptable), or, to eradicate them to see how the bird populations respond. Only then, could we say for certain that mongoose predation, and not human-induced habitat changes, is the reason we are losing our bird species in Fiji.