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

Sooty shearwater chicks (Puffinus griseus) harvested by Rakiura Maori on Pu tauhinu Island in the 1997-1999 muttonbirding seasons were larger and more developed than randomly available chicks. Early in the season, when muttonb irders extracted chicks from burrows during the day, this difference may ha ve resulted directly from harvesters selecting areas with higher quality ch icks, or indirectly from their selecting higher occupancy or more accessibl e areas. Later in the season, chicks were harvested after they emerged from burrows at night. Initially, relatively few, light chicks with more develo ped feathers emerged, and selection between them was relatively weak. As ch icks became more abundant, muttonbirders selected heavier, less downy chick s with longer wings. Muttonbirders often rejected small chicks, but there w as evidence for selection of larger, more developed chicks even above the e stimated reject weight. When undisturbed, higher quality chicks would proba bly 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-te rm sustainability of a culturally important traditional harvest for Rakiura Maori.