Extinctions of Polynesian Birds
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IO Jack GoIson Haberle et al. (1991:30, 38) and Brookfield (1991:207) contrast the situation in the I ri an Jaya section ofthe Highlands, where novolcanic ash is present and the land is more susceptible to degradation and erosion. Brookfield (1991 :207) describes the intensively managed and densely peopled wetlands of the Baliem Valley and Paniai lakes as being separated by a wide expanse of sparsely populated degraded slopeland from agrarian settlements in tributary valJeys and at the forest edge. CONCLUSION The massive transfomlation that the practice of shifting cultivation wrought in the ecology of Highlands New Guinea-from which we have derived some basic features of Highlands societies-as well as in agricultural practice, pig 4 husbandry, and systems of exchange, took place over many millennia. The en Extinctions of Polynesian Birds: try of the sweet potato was a fairly recent event, and it brought about changes in settlement and pig husbandry whose ramifications were still being worked Reciprocal Impacts of Birds and People out at the time ofEuropean contact. Today, in the Papua New Guinea High lands the cash economy and rising populations are making new demands on David W. Steadman natural and social systems and are requiring adjustments from them of a scale and urgency unparalleled in the past. The loss ofbird life is now well recognized as one of the major environmental consequences of the human colonization of Oceania. The decline of birds is related mainly to predation and to landscape changes wrought by prehistoric peoples to accommodate agriculture. For birds, perhaps the most influential landscape change has been the elimination and alteration of indigenous for ests through cutting, buming, and the introduetion of nonnative plants (Kirch 1983). These activities have eliminated natural habitats and have rendered tlle surviving birds even more vulnerable to predation from humans and non native mammals (rats, dogs, pigs). The erosion of topsoil associated with de forestation has removed large areas of nesting habitat for burrowing seabirds, such as shearwaters and petrels. Ethnographic information gathered over the past two centuries is crucial for interpreting Polynesian uses of birds in prehistoric times. I shall concen trate as much as possibIe on the prehistoric and early historie relationships be tween birds and Polynesians, knowing that events of the post-European period have only exacerbated what already was a dismal situation from the birds' standpoint. II ,2 David W. Steadman Extlnctions of Polynesian Birds SJ The geographic area eonsidered here is all of Polynesia except the Hawai HUMAN IMPACTS ON BIRDS ian Islands and New Zealand. Although Hawaii (Olson and James 1982a, Background Extinction Hl82b, 1991; James and Olson 1991; James et al. 1987) and New Zealand (An derson 1984, 1989a; Cassells Hl84; Trotter and McCulloch 1984; Holdaway The Holocene extinction of vertebrates ou Oceanic islands has been cali 1989) both experienced major prehistoric losses of birds, the biotas of these brated by the fossil record of the Galapagos Islands (Steadman et al. 1991). two isolated archipelagoes are not closely related to those elsewhere in Poly Dnlike any other group of islands in the tropical Pacific, the Galapagos never nesia. supported human populations before tlleir discovery by Europeans in 1535 The prehistoric record ofbirds is much better known in Polynesia than in (Steadman 1986). As a result, human impact in the Galapagos is confined to Micronesia or Melanesia. Bones ofbirds from archaeological or paleontologi the past five centuries, and it was relatively minor until about 1800. The Holo cai contexts are now known from at least 20 Polynesian islands besides Hawaii cene fossil record of the Galapagos comprises about 500,000 bones, more and New Zealand. In Micronesia, studies have been completed thus far on than 90 percent ofwhich predate the arrival ofhumans. These paleofauna~ re olll)' hvo islands. From Rota in the Mariana Islands, several small cave depos veal the loss of only zero to three vertebrate populations in the 4,000 to 8,000 its have yielded bones of 13 species of extinet or extirpated birds, including years before human arrival, compared to the loss of21 to 24 populations in the sheanvaters, tems, ducks, megapodes, rails, pigeons, parrots, swifts, and pas past 150 to 300 years. Thus the rate ofbackground (prehuman) extinction in serines (Steadman 1992a). Assemblages of archaeological bird bones exca the Galapagos was at least a hundred times less than the rate of human-re vated on Fais (Yap) represent species ofindigenous resident birds, 12 ofwhich lated extinction. When undisturbed by humans, the natural processes of dis probably or certainly no longer live on Fais (Steadman and Intoh 1994). In persal, colonization, and evolution may resuIt in a very low rate of extinction spite of the small amount of data currently available from Micronesia, I see no for reptiles, birds, and mammals on tropical Oceanic islands. cultural, geographical, or biological reason why the extent of human-caused The Polynesian Record a\lan extinctions in this region of Oceania, when more fully studied, will differ in ,Uly major way from that ofPolynesia. Mo\ing west from the Galapagos to Oceania, we find that \irtllally all islands Thc islands of Melanesia tend to be larger, and to support richer floras and were inhabited at one time or another in prehistory and that a significant faunas today, than the islands ofPolynesia or Micronesia. The prehistoric re amount of prehistoric extinction has taken place. The prehistorie record ol' cord of Melanesian birds has been studied only on Fiji (Steadman 1989b), Polynesian birds is based on data collected from arehaeological and paleon New Caledonia (Balouet and Olson 1989), New Ireland (Steadman, White, tological sites in the Marquesas Islands (Steadman 1988, 1989a, 1991a, and Allen n.d.), and Mussau (Steadman n.d.). As in Polynesia and Micronesia, 1992b; Steadman et al. 1988; Steadman and Zarriello 1987; Dye and Stead the Iimited record in Melanesia shows losses of a variety ofboth seabirds and man 1990), the Society Islands (Steadman 1989a, 1992b; Dye and Steadman landbirds, tllC latter dominated by hawks, megapodes, rails, pigeons, parrots, 1990; Steadman and PallIavan 1992), tlle Cook Islands (Steadman 1985, 1987, and owls but also induding herons, ibises, buttonquails, snipe, owlet-night 1989a, 1991b, 1992b; Allen and Schubel 1990; Allen and Steadman 1990, jars, and crows. Preliminary data from the very large, high island of New Ire Steadman and !Grch 1990; !Greh et al. 1991; !Grch et al. 1992), Henderson Is land indicate that evcn its relatively rich avifauna (currently about 108 species land (Steadman and Olson 1985; Schubel and Steadman 1990), Easter Island ol' resident landbirds) has lost about 25% of its species. A greater percentage (Steadman et al. 1994), Samoa (Steadman 1993b), Tonga (Steadman 1989a, ofbirds has survived on tlle larger islands of Melanesia than on typical Polyne 1989b, 1993a; Dye and Steadman 1990), and the Polynesian Outliers in Mela siml or Mierouesian ishUlds, or on small Melanesian islands. This seems to be nesia (Balouet and Olson 1987; Steadman et al. 1988; Steadman, Pahlavan, due to tlw buffering effects that large island size, steep terrain, and diseases and !Grch 1990). I shall review this record briefly, using specific examples (such as malaria) have had on hUmaIl impact. Common sen se dictates that in from several island groups. sular floras and faunas are easiest to deplete on low, small islands. In addition, The losses of birds in Polynesia fall into three categories: (l) extinetion many parts of island Melanesia have been occupied for tens of millennia (loss of all populations of a species); (2) extirpation (los s of a species Oll an indi longer than anywhere in Polynesia or Micronesia (Jones 1989; see Chapter 2, vidual island, although one or more populations of the species survive else this volume). where); and (3) reduced population (loss without replacement of indi\iduals 1-4 David W. Steadman Extlnctions of PoJynesian Blrds ss from a surviving population on an island). A single locality (Mangaia, the Cook Table 4.1 Resident Birds from Ua Huka, Marquesas Islancl~ Islands) ean exemplif)' eaeh eatego!)'. The Conquered Lorikeet (Vini vidivici) is extinct because it has been extenninated on Mangaia as well as on eve!)' Bones from Exists today other island where it ever oceurred. The Society Islands Pigeon (Ducula HaneSite on UaHuka aurorae) is extirpated on Mangaia (and several other islands) but survives on SEABIRDS Makatea (Tuanlotus) and Tal1iti. Audubon's Shearwater (Puffmus lher Wedge-tailed Shearwater (Puffinus pacificus) x x minien), a pantropical seabird, has a reduced population on Mangaia today, Christmas Island Shearwater (Puffinus nativitatis) x sllIviving in numbers of less than 100, whereas arehaeological and ethno Audubon's Shearwater (Puffinus lhenninieri) x graphic evidence suggests that once it was com mon and widespread on the is Bulwer's Petre! (Bulweria ef. bulwerii) x x land. Tahiti Petre! (Pterodroma rostrata ) x Phoenix Petre! (Pterodroma cf. alba) The loss of seabirds in Polynesia has been particularly severe for petrels x Unknown petre! (Pterodroma smal! sp.) and shearwaters, although the ranges and numbers of many other kinds of x Polynesian Storm-Petre! (Nesofregetta fuliginosa) tropical seabird (various albatrosses, stonn-petrels, tropicbirds, frigatebirds, x x White-bellied