Mortality and behaviour of hihi, an endangered New Zealand honeyeater, in the establishment phase following translocation Original Research Article

We analysed mortality and behaviour of hihi, an endangered New Zealand honeyeater, in the first three months after translocation to 135 ha Mokoia island. Our aims were to assess: (1) whether mortality and behaviour were affected by the translocation process or post-release management, and (2) whether the fate of birds during this establishment phase affected the viability of the population. Forty hihi were translocated from the wild population on Little Barrier Island, released immediately in three different locations, and provided with sugar water feeders. Many of the birds suffered leg injuries due to the bands initially used, and up to 7 birds may have died from these injuries. Nevertheless, the mortality rate over the first three months was similar to the average rate over the first 3 years. Therefore, except for the bands used, there was no evidence of post-release mortality associated with translocation stress. Most hihi discovered the feeders quickly. However, feeder use varied greatly among birds and there was no evidence that access to feeders reduced mortality. Access to feeders also did not affect overall time spent foraging. However, birds using feeders allocated most of their foraging effort to invertebrate feeding, whereas birds not using feeders foraged mostly on flowers and fruits. Hihi dispersed quickly after release, and moved all over the island. Transmitters increased re-sighting rates over the first 3 weeks, but intensive observation during that period provided no useful information relevant to subsequent survival and reproduction. There was a slight tendency for birds to settle closer to their release sites than expected by chance, but there was no tendency for birds released together to form breeding pairs. We conclude that the viability of this population was not affected by any problems in the establishment phase. However, the population has had a consistently high mortality rate over the first 3 years, and its long-term viability appears poor. Our subsequent research is, therefore, addressing the factors that might be limiting the population in the long-term.