Muttonbirder selectivity of sooty shearwater (titi) chicks harvested in New Zealand

Sooty shearwater chicks (Puffinus griseus) harvested by Rakiura Maori on Putauhinu Island in the 1997-1999 muttonbirding seasons were larger and more developed than randomly available chicks. Early in the season, when muttonbirders extracted chicks from burrows during the day, this difference may have resulted directly from harvesters selecting areas with higher quality chicks, or indirectly from their selecting higher occupancy or more accessible areas. Later in the season, chicks were harvested after they emerged from burrows at night. Initially, relatively few, light chicks with more developed feathers emerged, and selection between them was relatively weak. As chicks became more abundant, muttonbirders selected heavier, less downy chicks with longer wings. Muttonbirders often rejected small chicks, but there was evidence for selection of larger, more developed chicks even above the estimated reject weight. When undisturbed, higher quality chicks would probably have higher survival and probability of recruitment. Harvesting larger chicks will therefore have a greater impact on the population than randomly harvesting chicks. Models investigating harvest impacts should incorporate chick quality to avoid under-estimating harvest when assessing the long-term sustainability of a culturally important traditional harvest for Rakiura Maori.