where does the muttonbird migrate ?

Answer 1

Seeing as this is an Australian rather than a New Zealand section I presume you are talking of the short-tailed shearwater which is known as the "mutton bird" in Bass Strait. Australia also has sooty shearwaters (the New Zealand muttonbird), wedge-tailed shearwaters, little shearwaters, fluttering shearwaters and fleshy-footed shearwaters. There are occasional visits from manx and bullers shearwaters.

While there are different migration routes for the Indian ocean and Pacific ocean birds, the short-tailed shearwater heads north from Bass Strait up the Australian coast then crosses the equator heading north to Japan and the Bering Sea. It then crosses to Alaska and follows the coast down to California before heading directly across the Pacific back to Australia where it breeds along the southern coast and particularly on the Bass Strait islands.

Answer 2

Scientists have long known that sooty shearwaters breed in New Zealand and Chile and migrate to feeding grounds in the Northern Hemisphere.

The details of this remarkable transequatorial migration have emerged from a study by a team of Californian, New Zealand and French scientists using electronic tracking tags to follow the paths of individual sooty shearwaters.

I hope it helps!