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

Abstract

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.

Traditional Ecological Knowledge and scientific inference of prey availability: Harvests of sooty shearwater (Puffinus griseus) chicks by Rakiura Maori

“…However, they formed their TEK construct for the whole island by sharing knowledge of each others' rhythmsespecially the date of starting and completing the rama, but also relative date that the whānau leaves the island. There is intense interest in the number of emerging chicks and condition of the chicks (size, stage of feather development) in the initial days of the rama in particular (Hunter et al 2000).…”

“…We recorded the weight of 20-40 harvested chicks after they had been "spewed" (stomach contents expelled; see Hunter et al 2000 for a description of this and its effect on chick weights). These data were organised into weekly time periods.…”

Matauranga Maori, science and seabirds in New Zealand

“…Muttonbirders target the well-developed and fatter chicks. These would have had higher probability of recruitment back into the population than smaller chicks (Hunter et al 2000). Photo: Tītī research team.…”

The importance of seabird research for New Zealand

“…Changes in seabird abundance are therefore likely to affect soil nutrification and aeration, plant regeneration and succession, and abundance of other animal species living in the vicinity. The Kia Man Te TTtl Mo Ake Tonu Atu ("Keep the TTtT forever") research project (described by Moller 1996;Moller et al 2000) featured in five of the papers in this special edition (Hunter et al 2000;Jones 2000;Kitson et al 2000;Lyver 2000a;Sohle et al 2000) is particularly salient because titl (sooty shearwaters, Puffinus griseus) are probably New Zealand's most abundant seabird (Marchant & Higgins 1990). Their influence dominates over 35 nature reserves around the Marlborough Sounds, Fiordland, Rakiura (Stewart Island) and the subantarctic.…”

“…Patterson & Wallis (2000); 11. Hunter et al (2000), Kitson et al (2000), Lyver (2000a); 12. Stahl & Sagar (2000b).…”