Kiwi translocation review: are we releasing enough birds and to the right places?

Abstract

Translocations of kiwi (Apteryx spp.) are one of the most common and growing types of conservation translocations in New Zealand. However, their outcomes remain mostly unpublished, which does not allow for sharing of lessons learnt from past developments. We reviewed 102 kiwi translocations from the 19th century until 2018, and identified factors affecting their outcome. North Island brown kiwi (A. mantelli) was the most translocated species, but the highest impact of translocations on the improvement of conservation status was for the rarest taxa: little spotted kiwi (A. owenii), rowi (A. rowi), and Haast tokoeka (A. australis ‘Haast’). Translocations are typically used for creating secure populations and, more recently, for ecosystem restoration objectives and meta-population management. We developed a set of criteria to evaluate the outcome of introductions and reintroductions based on demographic parameters alongside current recommendations on genetic make-up of translocated populations. These criteria allowed us to categorise historical and recent translocations that were carried out for a wide array of objectives. Currently, based on these criteria, only a few translocated populations can be considered successful in the medium–long term: 15+ years following the release of a genetically diverse population (40+ unrelated individuals). Most historical translocations failed or require further genetic and habitat management. However, a majority of kiwi translocations have occurred over the last two decades and, while several populations have successfully established, for most of them, it is too soon to assess their medium-long term outcome. An analysis of factors affecting translocation outcomes revealed that, despite ongoing predator control, populations at small, unfenced sites on the mainland suffer from dispersal and predation, which has negative demographic and genetic consequences. Releases to larger mainland sites and predator-free areas have increased survival times, which indicates higher chances for a positive translocation outcome. Moreover, translocated wild-caught and captive-sourced birds survived longer compared to birds from the Operation Nest Egg programme, particularly at sites that were not predator-free. We highlight the need for genetic considerations in the planning and adaptive management of proposed and existing translocated populations. Specifically, we suggest that differences in kiwi survival, based on the type of released birds and release site’s area size and predator status, should be considered during translocation planning. Similarly, we encourage a standardised monitoring approach, increased reporting, and publishing the outcomes of translocations.