This is because they may have picked up a radiation dose (presumably via the food chain) when in their non-breeding quarters in the North Pacific that emanated from Japan's Fukushima nuclear plant, which allowed radiation to escape following the Japanese earthquake and tsunami earlier this year.
"A [Parks and Wildlife] spokeswoman says suggestions of radiation exposure in birds are being further investigated." But the department says it is not seeking samples and discourages people unfamiliar with wildlife from collecting them. You have been warned!
Click here to read that another "Mutton Bird", the Sooty Shearwater P.g riseus is considered safe to eat after testing for pesticides.
John Cooper, ACAP Information Officer, 4 October 2011