A structured decision-making approach for the recovery of tara iti/NZ fairy tern

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Executive summary

Tara iti/New Zealand fairy tern (Sternula nereis davisae) is Aotearoa New Zealand’s rarest indigenous bird, with only 12 known breeding pairs in 2020 and a conservation status of Threatened – Nationally Critical. Its range is restricted to northern Aotearoa New Zealand and breeding is confined to only four sites in the Auckland and Northland regions.

A scientific review of the tara iti management programme in 2017 produced a series of key management recommendations and identified some critical issues within the programme. However, there was a lack of clarity and support for how these issues should be addressed. Therefore, the Department of Conservation (DOC) initiated a structured decision-making (SDM) process that involved a facilitated working group of stakeholders (including DOC, iwi, non-government organisations, Auckland Zoo, New Zealand Defence Force, universities and the community) as the first step towards developing a collaborative and inclusive plan for tara iti recovery. The scientific review also highlighted an urgent need for reformation of the tara iti recovery group, which was re-established soon after the SDM process got underway.

The SDM framework enabled a range of management options to be identified and assessed against multiple objectives that are fundamentally important to tara iti recovery, including increasing the viability of the wild population, the integration of mātauranga Māori/traditional knowledge, wider ecosystem benefits, and the awareness and respect for tara iti amongst communities in Aotearoa New Zealand; and reducing the cost of management. Management options were later assembled by the authors, in consultation with members of the working group, into eight potential recovery strategies for further consideration. Options included a mix of intensive predator management, nesting shell patch creation and protection, pair management, egg supplementation, reinforcement of the wild population through the harvest of wild eggs and captive rearing of young, and creation of new breeding sites. The outcomes of the different recovery strategies were then predicted by analysing the available information both quantitatively and qualitatively.

The analysis showed that five of the management strategy alternatives had a high probability (≥ 0.94) of population persistence over the next 50 years, three of which were acceptable to the tara iti community (as judged by the tara iti recovery group). Among the acceptable strategies, two would also provide the opportunity to develop techniques for establishing additional populations in the future (not assessed in this report) and included a captive breeding component, but the strategy that was predicted to give the largest population size in 50 years is not currently aligned with mātauranga Māori. The predicted annualised cost over 50 years of implementing a strategy that includes captive breeding is NZ$940,000.

The recovery group agreed that the most workable solution would be to implement component actions building up from a set of in situ actions that are common to all five strategies that had a high probability of persistence and population size increase. A logical progression would be to immediately implement these in situ actions and then expand these to include new sites as quickly as possible (at predicted annualised costs over 50 years of $410,000 and $640,000, respectively). Meanwhile, work should continue with iwi and other stakeholders to refine a captive rearing component that maximises persistence and population size, can be resourced, and is acceptable to all stakeholders.

It is also recommended that partnership options for tara iti management are explored between DOC, the tara iti stakeholder group and wider community to allow the resources that are needed to fully fund a management programme to be identified and secured.