The Ruamaahua Islands Trust wanted to use science and Hauraki mātauranga (traditional knowledge) to understand the long-term trends in oi numbers on the Ruamaahua Islands and identify what type of factors might be causing changes in the population.
They also wanted guidance about the numbers of oi chicks that could potentially be harvested from the islands without endangering the long-term viability of the population. So the Hauraki approached Manaaki Whenua with a request to establish a research project to address these questions.
To understand what is happening to a population, we need to understand what sorts of things cause it to grow or decline. For example, a population may decline because only some adults are breeding or maybe because a large number of adults or chicks are dying. The key question would be then why are only a few birds breeding or why are lots of adults or chicks dying? Could something have happened to their food supply as the result of climate change? Are adults being caught accidentally in commercial fisheries?
To address these kinds of questions, the scientists involved in the project came up with the following research aims:
- Initiate long-term monitoring programmes on the Ruamāhua Islands and Moutohora to measure ecological parameters such as oi productivity, burrow and chick densities, adult survival, diet and foraging behaviour
- Investigate what type of factors (e.g. commercial fisheries by-catch, climatic and oceanic conditions, and harvest) affect oi populations
- Develop models to determine population growth rates for oi, using current and long-term information from the Ruamāhua Islands and Moutohora
- Record Hauraki mātauranga (traditional knowledge) understandings to direct, support and/or cross-check the scientific interpretations
Field work for this research programme was initiated in April 2006 on the Ruamāhua Islands and Moutohora. Randomly placed 10 ×10-m plots have been established on islands to monitor annual variation in productivity, burrow density, chick density and number of chicks fledging. Banding plots (20× 20 m) have also been established on each of the islands, primarily to measure adult survival. Recaptured adults banded pre-1995 by Imber and Harrison (DOC) on Moutohora will provide information about longevity of the species.
Foraging ranges of adult oi from the Ruamahua Islands have been tracked using Sirtrack KiwiSat 202 Platform Transmitting Terminals (PTTs) over the 2006 and 2007 breeding seasons.
Long-term changes in prey abundance and/or availability for oi will be assessed using stable isotope signatures in feathers acquired from birds in museums around the world, and from the Ruamahua Islands and Moutohora. Prey species and annual variation in diet will be determined using stomach content samples from adults and chicks.
Databases of climatic (e.g. El Niño Southern Oscillation, wind patterns and strengths) and oceanic (e.g. sea-surface temperatures, chlorophyll-A concentrations) conditions will be constructed by scientists from NIWA. These data will be used to assess the influence climatic and oceanic conditions have on oi population parameters, diet, and foraging behaviour.
Information about the numbers of oi occurring as by-catch in monitored commercial fisheries around New Zealand will be provided by MFish for analysis. Also, over lap between oi foraging ranges and areas targeted by fishing fleets in New Zealand waters will be compared to determine the potential threat commercial fisheries pose to oi.