Wiktionary
n. The seasonal harvesting of petrel chicks, especially shearwater species, for food, oil and feathers.
Wikipedia
Muttonbirding is the seasonal harvesting of the chicks of petrels, especially shearwater species, for food, oil and feathers by recreational or commercial hunters. Such hunting of petrels and other seabirds has occurred in various locations since prehistoric times, and there is evidence that many island populations have become extinct as a result. More recently ‘muttonbirding’ usually refers to the regulated and sustainable harvesting of shearwaters in Australia and New Zealand. These include the short-tailed shearwater, also known as the yolla or Australian muttonbird, in Bass Strait, Tasmania, as well as the sooty shearwater, also known as the titi or New Zealand muttonbird, on several small islands known as the Muttonbird Islands, scattered around Stewart Island in the far south of New Zealand.