R.N. HOLDAWAY 11 Department of Zoology, University of Canterbury, Christchurch NEW ZEALAND'S PRE-HUMAN AVIFAUNA AND ITS VULNERABILITY Summary: In the past 1000 years New Zealand has experienced a major 'extinction event', losing 40-50% of the avifauna, at least 50% of the frog fauna, and unknown proportions of the lizard and invertebrate faunas. During this period, bird species became extinct at different times and rates depending on the particular aspects of their ecology and life history which made them vulnerable to habitat loss, hunting, predation, and competition for food resources. Three groups of species with different levels of vulnerability are recognised within this event: Group I, 1000-1200 AD - species susceptible to initial impact of hunting by Polynesians and dogs, and predation and competition for food after an explosive irruption of kiore (Rattus exulans); Group II, 1200-1780 AD - species more resilient but gradually reduced by Polynesian hunting and continuous clearance and fragmentation of habitat; Group III, 1780-present - species susceptible to hunting with European weapons and predation by Rattus norvegicus, R. rattus, mustelids, cats, and to competition by mammalian herbivores, and destruction of wet forest and wetland habitat. Climatic change is seen as a negligible influence relative to these major intrusions. Discussions of the pre-human avifauna have so far concentrated almost exclusively on moas (Aves: Dinornithidae, Anomalopterygidae), partly because information on the other extinct species is sparse. The ecology of 12 species in the pre-human avifauna is inferred from their anatomy, relationships to extant species, sub-fossil evidence of diets, and analogy with related forms elsewhere. Keywords: New Zealand; avifauna; extinction event Introduction The New Zealand avifauna was, when Europeans To reconstruct the ecology of extinct species in arrived, only a battered remnant of the fauna of pre- the pre-human avifauna, some of which are only human times, surviving in a much-altered distantly related to extant species, we need to consider environment. This remnant, supplemented by some functional clues in their anatomy, and information on late immigrants is, however, the fauna used in most their habitat, diet, and demography. Some biogeographic and faunistic analyses. Various lists of information can be obtained from the extensive, if extinct New Zealand birds are available (e.g. Kinsky, uneven, literature on avian sub fossil deposits in New 1970), tucked away as appendices where they attract Zealand, but we need many more, detailed studies of little attention. Most lists are out of date, and do not sites and individual species. provide information on ecology. They are easily Such studies as are available have concentrated on overlooked. the ecology of moas, and their influence on the It is important to consider the ecology of species evolution of the New Zealand flora. Moas (Aves: lost between 900 and 1800 AD in more detail, because Dinornithidae, Anomalopterygidae) were indeed only then can the causes and results of their extinction impressive members of the diverse avifauna in pre- be better assessed. Cassels (1984) pointed out general human New Zealand, but their effects on vegetation similarities between the species which went extinct, but in the Late Holocene cannot be discussed without the present paper is the first attempt to assign a considering the palaeo-ecosystem as a whole. Other general ecology to several extinct species and to herbivores were present and the moas (themselves a discuss faunal assemblages. As such, it may provide a much more diverse ecological group than is usually framework for future work on the palaeo-ecology of appreciated) were subject to the same pressures of the pre-human fauna, and a firmer conceptual base predation and dispersion of food resources as other for studies on the relative effects of moas, ungulates, animals. Several of the papers in this volume treat the and climate on the vegetation of New Zealand. group as 'the moa' and assign 'it' mammal-like New Zealand Journal of Ecology 12: ©New Zealand Ecological Society 12 NEW ZEALAND JOURNAL OF ECOLOGY, VOL 12, (SUPPLEMENT) 1989 characteristics. Others argue on very tenuous premises deposits, including a species much larger than L. for, say, flocking behaviour, and then attempt to hamiltoni. Frogs must have been a major feature of assess population size and grazing pressure. The the fauna of the pre-human forest floor, judging by results are not convincing. Although many authors the abundant remains being found in caves whose have discussed the cause(s) of moa extinction (e.g. entrances were once within forest. Fleming, 1953, 1962; Cumberland, 1962; Duff, 1964; A variety of skinks (Scincidae) and geckos Anderson, 1984; Cassels, 1984; Trotter and (Gekkonidae) still occurs on the main islands of New McCulloch, 1984), only a few aspects of moa ecology Zealand, but they are far more conspicuous and have been treated in detail (Hamel, 1979; Burrows et abundant on islands without mammals, particularly al., 1981; Anderson, 1983). To understand the rats. Before humans arrived, lizards were probably as relationship between these large avian herbivores, the abundant on the mainland as they are now on the ecology of individual species and genera of moas must islands (Whitaker, 1973). Subfossil lizard material, be studied more deeply, in the context of a complete usually not identified to species, has been found in avifauna: it is that avifauna which is discussed here. caves and other deposits in many mainland areas (e.g. Rich et al., 1979). Worthy (1987b) reports Cyclodina alani, C. macgregori, C. whitakeri and Hoplodactylus Palaeo-environment duvauceli from widespread localities in the North Island. The pre-human avifauna was dominated by forest and The tuatara (Sphenodon punctatus) is now wetland birds. Forests covered most of the land below confined to offshore islands, and breeds successfully tree-line (McGlone, this volume), but the forest fauna only on those lacking the kiore or Polynesian rat, was radically different from that documented by Rattus exulans and other Rattus species (Crook, Europen explorers 100-200 years ago. Sub fossil 1973). Yet, the subfossil distribution of tuatara remains from caves and other deposits suggest that, includes most parts of both main islands (Bull and before the arrival of Polynesians about 1000 years Whitaker, 1975; Cassels, 1984). Its previous ago, the fauna was rich and diverse. distribution indicates that it was a widespread member Declines in relict populations of Powelliphanta of the ground fauna when Polynesians arrived. snails (Mollusca: Paryphantidae) (Meads et al., 1984) The endemic bat Mystacina tuberculata has and the large wetas (Insecta: Stenopelmatidae) (Watt, exploited an unusually diverse range of foods in the 1975) suggest that prehistoric populations were almost absence of mammalian competitors. Daniel (1979) certainly far greater in numbers and more continuous. reports that it feeds on the ground, foliage, and tree The great reductions in range, and the clear trunk, takes insects on the wing, and eats fruits and correlation between presence of introduced predators nectar. In some ways it was an analogue of shrews, and absence or extremely low numbers of large honey possums, and other bat groups. It also builds invertebrates, lizards, and tuatara, strongly suggest its own galleries in fallen trees and occupies petrel that extinctions have occurred and that many burrows. Not much is known about the only other mainland populations are now truly relict (Crook, New Zealand species, M. robusta, and it may even be 1973; Whitaker, 1973; Campbell et al., 1984). Many extinct (Hill and Daniel, 1985), but it used to be of the disjunct distributions in the lizard fauna (e.g. widespread and is frequent in cave deposits near Cyclodina) are in areas which were not greatly Waitomo (T. Worthy, pers. comm.). affected by climatic changes or physical disruption Remains of petrels are prominent in many cave during the Pleistocene (Towns et al., 1985). and dune deposits throughout New Zealand. Where Conversely, one of the extreme relicts is Leiolopisma the deposits are inland, in hills still covered with heavy acrinasum which presumably survived through the forest, they probably reflect former breeding colonies. worst of the glaciations in Fiordland or subsequently A few mainland colonies persist in some areas (e.g. recolonised the area within a few thousand years. Procellaria westlandica at Punakaiki, Puffinus huttoni Leiopelmatid frogs were widespread on both near Kaikoura) or at least have existed in European islands. Today, Leiopelma hamiltoni is restricted to times (Procellaria parkinsoni and Pterodroma Stephens and Maud Islands in the Marlborough inexpectata). Some of the dune deposits may indicate Sounds, but has been found in cave deposits as far former colonies rather than beach strandings south as Punakaiki, and at Waitomo and Hawkes Bay (Millener, 1981). Mainland cave deposits contain some in the North Island (Worthy, 1987a). Worthy (1987a) of the small prions (Pachyptila spp.) and various describes 3 new species of Leiopelma from cave HOLDAWAY: PRE-HUMAN AVIFAUNA 13 Pterodroma petrels now confined to offshore islands. prevailing in both regions from c. 10,000-1000 BP Indeed, some islands (e.g. South East Island in the (McGlone, 1983) had been replaced by tussock Chathams) still have diverse faunal assemblages grasslands with isolated patches of scrub and forest. resembling those inferred for many areas of the The effects of these vegetation changes on the fauna mainland (especially in forested hill country) before may have been catastrophic. Olson and James (1982a, Polynesian colonisation. For example, populations of b) proposed that the drier forests of Hawaii, which various burrowing petrels, tuataras, lizards, and large were removed during Polynesian settlement, were invertebrates are found on Stephens I and the Poor more diverse in structure than surviving wetter forests, Knights Is. and many of the endemic birds confined to them were When the drier eastern regions of Canterbury and exterminated when this habitat was destroyed.