Among its other important attributes, Little Barrier supports two birds endemic to New Zealand—the rare black petrel (Procellaria parkinsoni), and one endemic honey-eater, the stitchbird (Notiomystis cincta), which was once widespread on the North Island but is now found only on Little Barrier in moderate numbers, and apparently in no immediate danger. The impact of feral cats on stitchbirds has not been determined, but it is known that cats are seriously affecting the black petrel especially: they kill at least 90% of the chicks and some adults annually. Their impact on a locally remnant population of Cook's petrels (P. cookii) is apparently less severe.
In 1968-69 the Wildlife Service, with veterinary advice and assistance, added an attempt at biological control to the campaign of poisoning ("1080" in fish was the poison and bait used), trapping, and shooting. The very specific viral disease—feline enteritis—was introduced by trapping island cats, infecting them, and then releasing them. Some estimates of the resulting mortality from the combined techniques were as high as 90%; but there has been a recovery since, and the campaign is expensive in both time and man-power. And, oddly enough, the control effort has met with some opposition. Nevertheless, another campaign is planned.
Habitat Rehabilitation by Destruction of Mammals
The Kermadecs are a group of small islands about 800 km north-northeast of the North Island. Their biological significance, insofar as this symposium is concerned, is that they are the southernmost breeding area in New Zealand seas for many elements of the Pacific tropic and subtropical marine avifauna. Unfortunately, goats were liberated on the two largest islands—Raoul (3,000 ha) and Macauley (300 ha)—almost 150 years ago and Macauley Island was burnt over; such forest cover as it had was severely damaged or destroyed, probably at about the same time. The goats were to be an emergency food supply for whalers and shipwrecked mariners. Cats, too, became feral on Raoul Island during one of its fitful periods of occupation. The New Zealand Wildlife Service, in spite of the distance and difficulties involved, has undertaken pest destruction campaigns on both islands, but I offer here only an account of the simpler, and more successful, Macauley operation.
In 1966, a 5-week expedition to this waterless and almost treeless island resulted in the shooting of what was then thought to be all of its 3,000-odd goats (a density of about 15/ha). Four years later, a follow-up expedition found and destroyed another 17 goats (a later brief inspection suggested that these were indeed the last), and rehabilitation of the island is well under way. Now that the short turf is disappearing, erosion of the soft volcanic soils is reduced. With compaction no longer occurring, it will be interesting to see what the effect will be on birds breeding on the island—six breeding species of petrels, three breeding species of terns, and other marine species.
Sociolegal Conservation
The taking of petrels and other procellariiform birds for food has always been part of the Polynesian economy and culture throughout the Pacific. In New Zealand, the practice now has only minor economic importance, but it is still an essential part of Maori culture and tradition. The most commonly taken species are the sooty shearwater (Puffinus griseus) and, until recently, the gray-faced petrel (Pterodroma macroptera). Although no formal study of the impact of the annual harvest of chicks on the population has yet been made, all the indications are that it is not significant. Nevertheless, the Maoris willingly accepted the limited amount of legislation that has been passed to afford the two principal exploited species at least token protection. However, on the Chatham Islands, where there is a strong tradition of taking some of the albatrosses, this tradition has persisted, even though all albatrosses are fully protected throughout New Zealand.
Enforcement of legislation in small and isolated communities is not always easy and sometimes may not be wholly politic. However, the Maoris of the Chathams have been specially informed of the conservation issues at stake, and a "gentleman's agreement" has been reached: If a planned survey shows that full protection of albatrosses in the Chathams is indeed essential, the Maoris will honor the legislation to the letter; on the other hand, if limited exploitation seems justified, the Wildlife Service has agreed that it will be allowed.
Conclusions
Insofar as conservation measures of a passive type are concerned, it is fortunate that the offshore and outlying islands not yet occupied, farmed, or set aside as reserves, are likely to remain unexploited, either because they are too remote for exploitation to be economical or because they are too inhospitable, or both. In any event, public opinion is now such that unmodified or otherwise biologically important islands not already reserved would be proclaimed as reserves if threat of exploitation arose unexpectedly, unless they were found to be major sites for oil or minerals. Even so, legislation exists that offers the possibility of protection even from this threat, and has already been used to exempt some important mainland areas from prospecting and the granting of mining rights.