Lost and found in the Kaikouras

Press, 1 June 1984, Page 16

Lost and found in the Kaikouras

. . . the story of Hutton’s shearwater

By

GRAHAM M. WRAGG,

a student at

Lincoln College.

High in the Kaikouras breeds a species of seabird whose New Zealand home is a natural mountain fortress. Many thousands come every year, arriving from Australian coastal waters in early September, then leave with their young in March. Today, these Hutton’s shearwaters are restricted to the Seaward range but have died out from the Inland Kaikouras. These ranges rise to approximately 2500 metres. Both were formerly covered in chest-high snowgrass and native shrubs, and are divided by the deep Clarence River valley. But that is where their similarity ends. In the 1800 s tens of thousands of Hutton’s shearwaters nested in the Inland Kaikouras, but none remain today. The Inland Kaikouras have only half the rainfall of the Seaward Kaikouras, and they were found suitable for grazing sheep and cattle. The snowgrass was quickly killed off by cycles of heavy grazing and burning. The fires, because of the dry climate, burned out of control to the upper vegetation limits. The fire season, unfortunately, coincided with the height of the shearwater breeding season, and would have caught many adults still in their burrows incubating eggs and feeding chicks. The birds would also have been affected by the high numbers of feral animals present in the Inland Kaikouras during the first half of this century. Deer, goats, and sheep would have trampled their burrows, and cats, stoats, and ferrets would have preyed upon adults and chicks. In marked contrast, the Seaward Kaikouras have remained -relatively unmodified. There has been little grazing pressure, few fires, and predator numbers also seem low. Today, there are still two Hutton’s shearwater colonies in the Seaward Kaikouras, the larger of which is in the Upper Kowhai Valley. New Zealand contains the largest diversity of shearwaters anywhere in the world. Shearwaters (also known as muttonbirds) are. highly specialised, very ancient seabirds-(with a fossil record dating back more than 30 million years.

Related to albatrosses, their long narrow wings are adapted for longrange feeding flights and annual migrations. Six species of shearwater breed on New Zealand’s offshore islands, but only one breeds solely on the mainland. Hutton’s shearwater is a medium-sized member of the group, with a wing span of over 0.7 metres. What makes it unique is its strange breeding habitat. Evolution has left this shearwater breeding in dense colonies at over 1500 metres and up to 40 kilometres inland in the Kaikoura mountains and nowhere else. These are the highest known colonies of any seabird species. Every year in early spring, after overwintering in Australian coastal waters, Hutton’s shearwaters return to their mountain-top colonies. They begin their breeding season by cleaning out the burrows and pairing up, usually with the previous year’s partner. On the colonies, no birds can be seen during the day, but soon after dark the shearwaters fly inland. Many hundreds of birds fly over the colonies giving their cackling calls, “Ka he, ka he, ka how, ka how.” This call echoes around the vertical valley walls, and can be heard for many miles. Egg-laying begins in November, chick-rearing continues through January and February, and then in March the birds return to Australian waters. Mountain-top nesting has its advantages. In some years their colonies may be covered by deep snow until well into the normal breeding season. The adults are long lived, many living for 20 years or more. They are faithful to their place of birth; even when they suffer heavy predation or severe habitat destruction they will not move elsewhere. Hutton’s shearwater is named after F. W. Hutton, a former director of the Canterbury Museum. Its breeding site was a mystery until 1965. The significance of two early reports that recorded mutton birds in the Kaikouras had not been realised. The first record was by the surveyor, Mr J. W. Hamilton. On November 13, 1849, he noted in his

diary: “I was informed at Kaikoura Peninsula by the natives that the Titi (muttonbird) breeds in large numbers on the mountain (Tapuaenuku) and that many persons have been killed hunting for them.” The tradition was most likely broken in the 1820 s, with Te Rauparaha’s massacre of the Kaikoura Maoris. The second report of muttonbirds was on January 27, 1883, in the “Marlborough Express.” The author, “a gentleman mountaineer,” gave an excellent descriptive account of his party’s climb of Mount Tapuaenuku, and the birds and vegetation encountered along the way. “We made up on a long spur and it was on this spur of rich loamy soils that we came across the breeding places of the muttonbirds. They burrow in the ground like a rabbit, remaining out of sight all day, but at night venture out and set up a terrible row. One or two of the birds only were to be seen, but numerous feathers around the burrows gave evidence of a great many more.” The colony they found has since died out, and it was to be another 82 years before this unusual muttonbird was finally identified. In the early 1900 s two Hutton’s shearwaters were collected at sea near the Snares Islands (100 km south of Stewart Island.) These were described as a new species in the 1912 edition of "The Birds of

Australia.” The author, an eccentric English naturalist called Gregory M. Mathews, gave these specimens the common name of “Snares brown-backed petrel,” and listed them as breeding on the Snares Islands. This incorrect assumption caused much confusion about the breeding locality of Hutton’s shearwater. During the first half of this century, people living on the large stations of the Inland Kaikouras knew that muttonbirds bred in the mountains and often heard their strange cackling call on the still dark nights of spring and summer. Deer stalkers came across large numbers of burrows in the Seaward Kaikouras. This information came to the notice of Geoff Harrow, a well-known Canterbury mountaineer and naturalist. Suspecting he may have a clue to the breeding place of Hutton’s shearwater, he set off up the Kowhai River in the Seaward Kaikouras, on February 20, 1965. He found a large colony site and a number of corpses. The National Museum identified those specimens as Hutton’s shearwater and the mystery was solved. Recent surveys have shown the Upper Kowhai Valley colonies contain more than 50,000 birds. There is also a small colony at the norhern end of the Seaward Kaikouras, but this represents the total known distribution of this unique New Zealand seabird.