LOW REPRODUCTIVE SUCCESS OF THE ENDANGERED TAKAHE PORPHYRIO-MANTELLI ON OFFSHORE ISLAND REFUGES IN NEW-ZEALAND

Many of New Zealand's endangered birds have been transferred from the ''mainland'' of the North and South Islands to smaller coastal islands free from introduced predators and competitors. The transfer of Takah e Porphyrio mantelli (Plate 1) to offshore islands is unique because t hese highly endangered, flightless rails are being moved from alpine-t ussock habitat of Fiordland, the last remaining natural population, to substantially different lowland habitat on island refuges, Despite th e fact that 30% of the approximately 160 Takahe left in the wild now l ive on coastal islands, a detailed analysis on the success of the isla nd populations has never been undertaken, Using data available from Ne w Zealand's Department of Conservation, we found that while adult surv ivorship of Takahe on islands is high, reproductive success is signifi cantly lower than in Fiordland. Most factors examined, including inbre eding and nutrient deficiency, had no significant effect on reproducti ve success of Takahe breeding on islands, Island pairs produced fewer eggs and juveniles in the first year of their pair bond relative to al l other years. Hence the large number of transfers of birds between is lands during the initial stages of the relocation program may have res ulted in a higher frequency of pair formation and thus may have contri buted to the islands' lower reproductive success. Why first clutches d id so poorly (four juveniles from 43 clutches) compared with second (1 1 from 36) and third (six from 13) clutches is not known but was one o f the main contributing factors for island pairs making greater nestin g effort but significantly lower returns than birds breeding in Fiordl and. In addition, some individual birds have been very successful in p roducing young relative to other birds, suggesting that important diff erences in quality of some breeders may also exist. We expect island p roductivity will improve over time as the number of interisland transf ers of Takahe decreases and as the proportion of breeding birds raised in the island environment increases.