The best of both worlds for seabird population management
Adult oi. Image – Morgan Coleman
A unique combination of traditional Maori knowledge and western science has provided fresh insights into the lives of one of New Zealand’s seabird species.
Hauraki mātauranga (traditional knowledge) has provided significant information about oi (grey-faced petrel) harvest trends and resource management strategies on the Ruamaahua (Aldermen) Islands, while the latest advances in Sirtrack satellite transmitter technology have provided new insights into the oceanic range over which the bird forages.
It’s all part of the Mauriora ki nga oi (Safe-guarding the life force of the grey-faced petrel) programme that over the past 5 years has been examining how fisheries by-catch, oceanic and atmospheric events as well as harvest affect the bird population. The customary take of plump chicks from the rugged islands is one of the few remaining seabird harvests in New Zealand and when Hauraki Maori gifted the islands to the crown in 1968 they did so on the condition of continuing the harvest.
Kaumātua (elders) tracked declines in the number of oi chicks harvested as well as the number of birders participating in the annual harvest over the past 50 years. The present annual harvest is approximately 1% of its 1950s tally, which is likely to be the result of fewer chicks available, a 93% reduction in the number of birders going out to harvest and the current inexperience of current generation of Hauraki birders.
Some of the Hauraki strategies for managing oi populations included: (i) protecting the source of future breeders by only harvesting chicks in the intermediate stage of growth allowing those in a more advanced stages to fledge; (ii) creating breeding space by splitting burrows; (iii) annual rotation of harvest around islands to alleviate harvest pressure in some years; and, (iv) assigning island refuges to ensure a non-harvested source population.
Adult oi fitted with satellite tags on the Ruamaahua Islands ranged across the Tasman Sea to Australia, 4000km east beyond the Chatham Islands, and 2000km north towards New Caledonia. Distance didn’t seem to be an issue for these birds, as they could comfortably cover 500 km per day. Most congregated around the Ruamaahua Islands, the central Tasman Sea or the Chatham Rise. Oi home ranges overlapped not only New Zealand Exclusive Economic Zone but also the High Seas and Australian Exclusive Economic Zone. These data will be used to assess the bycatch risk posed by fisheries in these different regions and characteristics of oceanic habitats influencing the distribution of oi.
By using both Hauraki guardianship strategies and knowledge from new scientific innovations, researchers can begin to understand what mixture of factors are influencing these birds, and what the future might look like for oi population on the Ruamaahua Islands.
The findings were recently published in a special volume of the Papers and Proceedings of the Royal Society of Tasmania highlighting the current and future challenges and opportunities for research and conservation of Austral seabirds. The team was honoured to have the opportunity to contribute to this volume, which was a tribute to celebrate the life and work of the late Dr Irynej Skira, an imminent seabird ecologist.