Eighteen million of these arrive in Tasmania each year. There are known to be at least 167 colonies in Tasmania and an estimated 11.4 million burrows. The largest colony is on Babel Island which has three million burrows. Their colonies are usually found on headlands and islands covered with tussocks and succulent vegetation such as pigface and iceplant. Headlands allow for easy take off and landing.
Early accounts suggest that the population was once considerably higher.
In 1798, Matthew Flinders estimated that there were at least one hundred million birds within a single flock sighted in Bass Strait. Their migratory path is difficult to define because they don't come to shore during the months of the migration. Exhausted and starved birds are often washed up on beaches of Japan, the Aleution Islands, North America and Australia. Originally this led scientists to believe that the birds flew a figure of eight course across the Pacific Ocean. Recent studies suggest the majority of birds merely fly north along the western part of the Pacific Ocean to the Arctic region and return southwards through the centre of the ocean.