by
Gordon R. Williams
New Zealand Wildlife Service
Department of Internal Affairs
Wellington, New Zealand
Marine species (pelagic birds and those of exposed coasts) make up about 48% of New Zealand's native avifauna, excluding stragglers and antarctic species. The biological history that has led to the present status of marine birds in this archipelago of some 700 islands is outlined, methods of conservation are briefly described, and some illustrative case histories of management programs are given. In spite of the major environmental changes that have occurred in New Zealand during 200 years of European occupation, only one marine species has become extinct, although five such endemic species are currently regarded as threatened as are a few subspecies of widely distributed forms.
New Zealand, which lies some 2,000 km southeast of Australia, has been a changing archipelago for many millions of years. It has been separated from any major landmass (first, Gondwanaland and later, Australia) for at least 80 million years.
Before the arrival of man, probably between 1,000 and 1,500 years ago, New Zealand was free of any land mammals except two species of bats, and there were few avian predators. These, among a number of other biological peculiarities, reflect the archipelago's considerable and long-standing isolation.
There are nearly 700 islands 0.5 ha or more in area in the New Zealand region; and, if North, South, and Stewart islands are regarded collectively as the mainland, about 650 of these islands lie within 50 km of the coast and 30 beyond that limit, to about 850 km offshore (Atkinson and Bell 1973). The archipelago extends from about 30° to 52°S lat. (over a distance of about 2,400 km)—that is, from the subtropical to the subAntarctic—and from about 166° to 176°W long. (Fig. 1).
Pelagic and coastal birds must obviously be an important part of the avifauna and, in fact, aside from stragglers, antarctic species, and established introduced species, they make up about 48% of the 173 in the New Zealand Checklist (Kinsky 1970). Of the 83 species I have regarded as marine, 48 (28%) are pelagic and 35 (20%) shorebirds of exposed coasts. Ten of the 48 pelagics (21%) and 12 (34%) of the 35 shorebirds are endemic.
More than a thousand years of occupation by Polynesian man with his commensal Polynesian rats (Rattus exulans) and a peculiar breed of domesticated and feral dog (now extinct), did little damage to pelagic and open coast species, even though many, if not most, were used as food—especially the petrels, and particularly those belonging to the genera Puffinus, Procellaria, and Pterodroma. However, the Europeans, who arrived about 200 years ago, brought with them a menagerie of mammals and birds, and 33 species of each have become established and are now feral (Gibb and Flux 1973; Williams 1973). They also put into practice, on a large scale, European methods of land use that had unfortunate effects on almost the entire native avifauna. Although terrestrial, freshwater, and estuarine species suffered most, marine species suffered also. However, reduction in numbers and range rather than extinction was the rule, except locally.
Apart from habitat destruction by man and the various mammalian browsers and grazers, the most inimical agents have been black rats (Rattus rattus), Norway rats (R. norvegicus), feral cats, and feral pigs. One would expect the inhospitality or inaccessibility of an island to be a marine species' best protection, and so it has generally proved-the greatest losses have occurred on the two major mainland islands (North Island and South Island). Bourne (1967) suggested that Polynesians in pre-European times may have caused the extinction of numerous petrels in the Chatham Islands. There are still a few islands on which no exotic mammals occur, but modern transport, allied with human curiosity and cupidity, are stripping all but the most wild and remote of these of the protection against invasion they have had so far. Cruises by nature-hungry but sometimes environmentally illiterate tourists are beginning to be a local problem.
Fig. 1. New Zealand and its main offshore and outlying islands (from Atkinson and Bell 1973).
The matter of conservation of marine species in New Zealand has stemmed mainly from the recognition of the value of certain islands as refuges for whole ecosystems, as convenient areas for study, and as arks for the rescue of the threatened species that can be successfully established on them—an often highly hazardous and uncomfortable procedure for men as well as birds.
By statute, all feral species of birds in New Zealand are automatically protected unless specifically legislated for otherwise. (About 50 of our grand total of 285 species have been so legislated for.) One fortunate consequence of this provision is that all new arrivals—vagrants or new discoveries—are also fully protected. The legislation also states that it is illegal to have in one's possession the nests, eggs, feathers, skins, or bones of any fully protected species unless one has been issued a permit for this purpose. This restriction may apply to institutions as well as to persons.
After this good start and the setting aside of conservation reserves of various kinds, active conservation measures depend on making careful and comprehensive surveys of the species and its ecosystem—often none too easy a task in the New Zealand region because of the rough seas, the relative inaccessibility of many of the important islands and their ruggedness, and the near-impenetrability of some of the vegetation types they support. Having decided that positive action is necessary, the next step is to use all available media to inform the public (local as well as national, if the island is inhabited) of the situation and the proposals for remedying it. As in most other countries, uninformed emotionalism is one of the most pervasive and serious obstacles to effective conservation because of the political pressure it can generate.
Apart from formal ecological studies, the New Zealand Wildlife Service uses three main methods to support threatened species (other than the attempts we are making to breed certain freshwater and terrestrial species in captivity):
• The translocation and founding of new colonies in promising or unmodified habitat. Such habitats are not common in New Zealand because of the ubiquity of the introduced mammalian browsers, grazers, and predators (Williams 1977).
• The destruction, or at least the reduction, of such browsers, grazers, and predators by physical, chemical, or biological methods, or combinations of these.
• The exertion of social influences to promote changes in methods of land use or in traditional harvest for food (the latter can be particularly important as far as the Polynesian [Maori] population is concerned, as nowadays the taking of birds for food is predominantly a cultural rather than an economic matter).
Translocation has been a valuable technique for increasing the numbers and ranges of a few threatened terrestrial species. The very nature of most marine species, however, limits its application as far as they are concerned. Nevertheless, we have considered it worth trying for one nonmigrant wader; and no doubt it could be tried under similar circumstances elsewhere.
Convincing local experiences have shown that predator or competitor destruction is likely to be practical only on small, not-too-rugged islands, usually no larger than about 500 ha. However, special circumstances have prompted us to attempt destruction, or at least control, on much larger and more difficult islands. It is implicit that the predators or competitors are exotic, not indigenous. Recently, on those rare islands that are inhabited but still free of either black or Norway rats, we have set up permanent bait stations (at which sodium fluoroacetate—"1080"—is used as the poison) on wharves and jetties in the hope that such a precaution will, with the addition of a propaganda campaign calling for the regular fumigation of visiting vessels, prolong the charmed lives that these fortunate islands have so far enjoyed. It goes without saying that we ask that the greatest care be taken when expeditions land stores on uninhabited, rat-free islands which, if by "rat-free" we mean also free of R. exulans, are even rarer in our seas.
The sociolegal approach is effective only when ecosystems or communities have not been seriously modified, otherwise it is no substitute for either of the other two measures discussed.
Last century, an endemic monotypic genus of wader—the New Zealand shore plover (Thinornis novaeseelandiae)—was widespread and occasionally very common around the coasts of the North and South islands and the Chatham Islands. As a result of European settlement and the accompanying predation by feral cats and rats, the species now occurs only on South East Island in the Chatham group (860 km east of the mainland), where it at present seems safe, since there are no rats on the island and it is now a reserve. However, the population numbers only about 120 individuals. Because calamities can always occur (for example, ship rats recently reached shore on three important islets off the southwest coast of Stewart Island), the Wildlife Service is anxious to spread the shore plover to other suitable islands, if they can be found. The species is not a migrant and is rather sedentary. The first translocation attempts failed, probably because mainly adult birds were used, and we are now continuing our studies of the species with the thought in mind, among others, that success may come if young birds are used instead; the question is—how young?
As is widely known, the New Zealand Wildlife Service has been remarkably successful in recent years in translocating one species of the endemic wattlebird family—the forest-dwelling saddleback (Philesturnus carunculatus)—to other islands than the four small ones it had been reduced to by the early 1960's; three of these islands were the ones recently invaded by ship rats, referred to above.
Some 25 km off the North Island's east coast lies the 3,000-ha, very rugged and forested Little Barrier Island, which has now been a reserve for the protection of flora and fauna for about 80 years. Before that, it had been almost continually occupied by Maoris since their arrival in New Zealand, and about one-third of its forest was felled or burnt, especially after European settlement of the adjoining New Zealand mainland began.
Most unusually, Little Barrier is now free of any grazing or browsing mammals, and has only the Polynesian rat (a reminder of the Maori occupation) and feral cats (a European legacy) to impair its extreme importance as a reserve. The rats have been unmolested by man because, rightly or wrongly, they are considered ineffective predators generally; however, their impact has probably been under-rated. More than half a century of trapping and hunting of cats by successive caretakers on the island has not effectively reduced that population.
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.
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.
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.
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.
It is gratifying to realize that, although some endemic marine subspecies (generally not very different from neighboring subspecies) are endangered to varying degrees, there are very few whose disappearance would result in the disappearance of the species itself from the New Zealand area. Only one endemic marine species has become extinct in recent times, the Auckland Island merganser (Mergus australis) in about 1905, and only six are currently in any real danger: the Chatham Island taiko (Pterodroma magentae), the black petrel, Hutton's shearwater (Puffinus huttoni), the Westland black petrel (Procellaria westlandica), the shore plover, and the Chatham Island oystercatcher (Haematopus chathamensis). However, a list of this kind is often a matter of some controversy. Something is at present being done to help all but the first and last of these. The Chatham Island taiko had not been positively identified for about 50 years, until 1977 when this species was "rediscovered" on the main island of the Chatham group; though its numerical status is unknown, it is rare. The Chatham Island oystercatcher, although certainly "threatened" (only about 50 are known to exist), does occur on four islands, two of which are reserves. Although this species has not been actively studied until now, it is soon to be the subject of a full ecological survey.
A few words about the hunting of marine species: Mutton-birding aside—that is, apart from the taking by Maoris of the young of the sooty shearwater and the gray-faced petrel—there has been no legal hunting of any marine birds in New Zealand for 35 years now, nor is there likely to be. This situation reflects the consistently increasing weight of informed public opinion in favor of, let alone scientific concern for, transoceanic migrants. The pro-hunting lobby for some species of waders, in particular the eastern bar-tailed godwit (Limosa lapponica baueri), is a small one, the numbers of which decrease yearly. However, small-scale poaching occasionally occurs; it is punished when discovered.
Protection for marine species extends only to the 3-mile limit of New Zealand's territorial waters, but it would be extended further should New Zealand follow the present trend of including as territorial waters all those that cover the continental shelf or beyond. [This extension occurred in 1977; the marine fishing zone for New Zealand waters has been extended to 200 miles (360 km) around all coasts.]
Only three marine species are not afforded full protection under the Wildlife Act: two, the black-backed or Dominican gull (Larus dominicanus) and the black shag (Phalacrocorax carbo), are totally unprotected—the first because of its predation on some rare shorebirds during the breeding season and for its attacks on sheep and lambs at a similar time, and the second because of its depredations (seldom serious) on the introduced trout and salmon, mainly in fresh waters—the third species, the southern skua (Stercorarius skua lonnbergi), may be destroyed only when it is actually attacking sheep or lambs, an occasional event confined to the Chatham Islands. Destruction of these three common species is not encouraged by the Wildlife Service except when black-backed gulls become too active among colonies of, say, the fairy tern (Sterna nereis), which is very rare in New Zealand but not elsewhere in its range. Otherwise, control of the species is left in the hands of those most affected by their depredations but whose judgment is usually reasonable.
Marine birds, therefore, are generally satisfactorily protected by law or managed for conservation in New Zealand—especially when one considers the remarkable changes that have occurred in the New Zealand archipelago over the last 200 years. Although the situation could be better, it would certainly have been worse if the Wildlife Service (and other conservation organizations) had not been untiring in keeping the general public and the legislature aware of the issues at stake and seen to it that as much as possible of the necessary conservation work was done—and done before it was too late.
I thank my Wildlife Service colleagues, B. D. Bell, M. J. Imber, D. V. Merton, and C. J. R. Robertson, for valuable comments and advice on the preparation of this paper.
Atkinson, I. A. E., and B. D. Bell. 1973. Offshore and outlying islands. Pages 372-392 in G. R. Williams, ed. The natural history of New Zealand. A. H. & A. W. Reed, Wellington.
Bourne, W. R. P. 1967. Subfossil petrel bones from the Chatham Islands. Ibis 109:1-7.
Kinsky, F. C. 1970. Annotated checklist of the birds of New Zealand. A. H. & A. W. Reed, Wellington.
Gibb, J. A., and J. E. C. Flux. 1973. Mammals. Pages 334-371 in G. R. Williams, ed. The natural history of New Zealand. A. H. & A. W. Reed, Wellington.
Williams, G. R. 1973. Birds. Pages 304-333 in G. R. Williams, ed. The natural history of New Zealand. A. H. & A. W. Reed, Wellington.
Williams, G. R. 1977. Marooning—a technique for saving threatened species from extinction. Int. Zoo Yearb. 17:102-106.