Kia Mau Te Tītī Mo Ake Tonu Atu: Marine ecology perturbations, climate change, and sustainability of a Māori customary seabird harvest
Principal investigator: Professor Henrik Moller
Staff involved: Henrik Moller, Corey Bragg
Kia Mau Te Tītī Mo Ake Tonu Atu ("Keep the Tītī Forever"), a 14-year research partnership between the University of Otago and Rakiura Māori , reached a climax in 2008 with the formulation of the first mathematical model predictions of the sustainability of the traditional harvest of sooty shearwater (Puffinus griseus) chicks ('tītī').
We combined mark and recapture models, measures of harvest intensity, population monitoring using ecological surveys, and data from eight detailed muttonbirder 'hunting diaries' (up to 2002) in a Bayesian modelling approach. This data discovered a highly contentious link between population knockdowns and oncoming La Niña climate phases. Additionally, it has allowed computer simulations of the impacts of 50 more years of climate change on future tītī population abundance and sustainability of an iconic customary harvest that is a culturally defining tradition of Kai Tahu.
The models showed that the observed fluctuations in hunting success revealed by the seven diaries could not be explained unless adult shearwaters were being killed by some unknown ecological mechanism appearing in the very early stages of El Niños. This finding challenges the mātauranga (Traditional Ecological Knowledge) of the birders, as well as the prevailing view of seabird ecologists, that seabirds can maintain high adult survival even when feeding conditions decline.
Some Rakiura Māori were extremely sceptical of our sustainability predictions that around 25% of the whanau (families) were taking too many chicks for tītī to remain abundant. Scepticism was further heightened by their experience of two remarkably good seasons just as we presented our model predictions. (For example, in the 2007 season, elders reported there to have been more adults and chicks than when they were children. 2008 brought a similar but slightly less spectacular season. However, the 2009 season was considered the worst in living memory of the old birders.)
This UORG grant updates the eight diaries to 2010, in order to track bird numbers and conditions through the huge recent oceanic fluctuation and to complete data from the past 70 years. They will provide a strong test for all 14 years of research and modelling, a litmus test for whether the community will believe our sustainability analysis and act upon its results, and an unprecedented gift for identifying the oceanic and/or climate mechanism driving tītī population fluctuations.
The new diary data will also check a remarkable and globally important phenomenon; remarkably, our harvest rate index (based on data to 2002) predicts the phase and intensity of ENSO five months earlier than NIWA, and a host of international meteorologists using their computer models can accurately forecast it. An early warning index of El Niño has huge economic, human health, and environmental management implications, which we would like to explore formally in future FRST bids, should this UORG confirm our preliminary model.