Insights to the functional relationships of Māori harvest practices: Customary use of a burrowing seabird

We used a deterministic age-structured model of a population of grey-faced petrels (Pterodroma gouldi). By harvesting pre-fledging chicks, rather than adult birds, Māori harvesters had less of an impact on population growth rates; annual population growth rate dropped below 1.0 if 2% or more of adult birds were harvested compared with threshold harvests of 25% or more of either eggs or chicks. Restrictions such as prohibition of the digging out of burrows or the use of a snaring pole to catch chicks would lead to an annual harvest of less than our estimated deterministic threshold for a sustainable harvest of 25% of chicks even if all the chicks within arm’s reach down the burrows were caught. The cultural practice of rotating harvests or resting populations was also effective; harvesting every 3 years allowed up to 75% of chicks to be taken without causing the theoretical population to decline.