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Scientific Bases for the Preservation of the Hawaiian Crow 5— RELEVANT PRECEDENTS IN ENDANGERED SPECIES PRESERVATION Avian extinction during historical times has been largely an island phenomenon. As noted by King (1985), about 93% of all recorded avian extinctions have involved insular species and subspecies and have resulted directly or indirectly from human activity. In light of the findings regarding recent fossil deposits on the Hawaiian islands (Olson and James, 1982a,b, 1991; James and Olson, 1991), and elsewhere in Polynesia (Steadman, 1989), the magnitude of human-caused extinction there is even greater than that noted by King. The increased vulnerability of insular species to extinction can be traced to some combination of their restricted distribution, demographic instability, inbreeding depression, absence of native predators and hence vulnerability to exotic ones, and adverse environmental conditions (Wilcox, 1980; Terborgh and Winter, 1980; Diamond, 1985), but an increasing number of continental species have assumed similar characteristics because of burgeoning human population. The results of continued fragmentation and alteration of natural habitat all over the world can be seen clearly by comparing the threatened corvid species in the International Union for the Conservation of Nature Red Data Book (King, 1977–1979) with more recent compilations (Collar and Andrew, 1988; International Union for the Conservation of Nature, 1990). Although the number of endangered corvid species has remained at two ('Alala and the Marianas Crow, Corvus kubaryi), 10 species (three insular and seven continental) have been added to the more recent compilations and are considered at risk (Table 5.1). The underlying objective of all endangered-species restoration programs is to minimize the probability of extinction by increasing the numbers and the distribution of the species. Such programs typically combine conventional, long-term management activities (protection and restoration of habitat, legal protection, and public education) with manipulative, or "clinical," techniques aimed at immediate enhancement of fecundity and survivorship. Manipulative techniques that have been successfully applied in recovery programs range from such in situ measures as predator control, nest-site provisioning, reproductive manipulation, and supplemental feeding to ex situ measures such as translocation, captive breeding and reintroduction, and cryopreservation of gametes and embryos (Temple, 1977b; Cade, 1986a, 1988; Conway, 1988; Seal, 1988). Some ex situ techniques, particularly captive breeding and reintroduction, remain controversial (cf. Derrickson and Snyder, 1992), although they have been incorporated in recovery programs for a variety of avian taxa (Table 5.2). Many recovery programs have direct relevance to the restoration of the 'Alala, and several relevant cases are described in this chapter.
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Scientific Bases for the Preservation of the Hawaiian Crow Table 5.1 Conservation status of corvidsa Common Namesb and scientific Conservation Status Geographical Distribution and Reason for Conservation Status Beautiful Jay Cyanolyca pulchra Insufficiently known Ecuador and Columbia; rare and local Dwarf Jay C. nana Insufficiently known Now restricted to Oaxaca, Mexico; logging White-Throated Jay C. mirabilis Insufficiently known Guerrero and Oaxaca, Mexico; habitat logging and grazing Azure Jay Cyanocorax caeruleu Insufficiently known Steep declines throughout most of range in Brazil and Argentina Sichuan Grey Jay Perisoreus internigrans Vulnerable Pine and coniferous forests of central China Sri Lanka Magpie Urocissa ornata* Vulnerable Endemic to Sri Lanka; forest degradation Hooded Treepie Crypsirina cucullata Vulnerable Central Burma; forest degeneration Ethiopian Bush-Crow Zavattariorinis stresemanni Rare Ethiopia; habitat alteration Banggai Crow Corvus unicolor* Rare Banggai, Indonesia; known from only two specimens; habitat degradation Flores Crow C. florensis* Rare Flores, Indonesia; habitat degradation; has not adapted to agriculture Marianas Crow C. kubaryi* Endangered Guam and Rota Hawaiian Crow C. hawaiiensis* Endangered Hawai'i a From Collar and Andrew, (1988); International Union for the Conservation of Nature Red Data Book, (1990). b * = Insular species.
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Scientific Bases for the Preservation of the Hawaiian Crow Table 5.2 Translocations and reintroductions of threatened avian species Common and Scientific Names; Locality Methodsa References Yellow-Crowned Night Heron, Nycticorax violacea; Bermuda CR/R Wingate (1982, 1985) White Stork, Ciconia ciconia; Europe CB/R Bloesch (1980), Blackwell (1990) Atlantic Puffin, Fratercula arctica; United States T Kress (1977), Cade (1986a) Bean Goose, Anser fabalis; Sweden CB/CF Von Essen (1982), Morner (1986) Lesser White-Fronted Goose, Anser erythropus; Sweden CB/CF Von Essen (1982), Morner (1986) Hawaiian Goose, Branta sandvicensis; Hawaiian Islands CB/R Kear (1986), Kear and Berger (1980), Hoshide et al. (1990) Aleutian Canada Goose, Branta canadensis leucopareia; United States CB/R;T Springer et al. (1977), Kear (1986) Brown Teal, Anas auklandica chlorotis; New Zealand CB/R Reid and Roderick (1973) New Zealand Scaup, Aythya novaesaelandiae; New Zealand CB/R Reid and Roderick (1973) California Condorb, Gymnogyps californianus; United States CR,CB/H Toone and Risser (1988), Wallace (1990, 1991), Kuehler et al. (1991), M. P. Wallace (pers. comm. 1992) a T = translocation of wild eggs, young, or adults; CR = captive rearing of wild-origin stock; CB = captive breeding; R = release of young; H = hacking of young; F = fostering of eggs or young; CF = cross-fostering of eggs or young. b Discussed in the text of the chapter.
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Scientific Bases for the Preservation of the Hawaiian Crow Common and Scientific Names; Locality Methods References Andean Condor Vultur gryphus; Peru, Colombia, United States CB/H Wallace and Temple (1987), USFWS and California Dept. of Fish & Game (1988) Wallace (1990, 1991), Lieberman et al. (1991) Bald Eagle, Hailiaeetus leucocephalus; United States CR,CB/F,H Cade (1986a, b), Nye (1988), Laycock (1991) White-Tailed Sea Eagle, Hailiaeetus albicilla; Europe CB/H Love (1984), Fentzloff (1984), Cade (1986a) Bearded Vulture, Gypaetus barbatus aureus; Europe CB/H Anderegg et al. (1983) Griffon Vulture, Gyps fulvus; Europe CB/H Terrasse (1983), Snyder (1986) Mauritius Kestrelb, Falco punctatus; Mauritius CR,CB/H,F Temple (1977a), Jones and Owadally (1988), Jones et al. (1991) Seychelles Kestrel, Falco araea; Praslin Island, Seychelles T Cade (1986a), Watson (1989) Peregrine Falcon, Falco peregrinus; United States, Europe CR,CB/H,F,CF Cade and Hardaswick (1985), Cade (1986a, 1990), Cade et al. (1988) Masked Bobwhite, Colinus virginianus ridgwayi; United States CB/F Ellis et al. (1977), Carpenter et al. (1991) Cheer Pheasant, Catreus wallichi; Pakistan CB/R Grahame (1980, 1988), Ridley (1986) Mississippi Sandhill Crane, Grus canadensis pulla; United States CB/H,F Zwank and Derrickson (1981), Zwank and Wilson (1988), McMillan et al (1987) Whooping Crane, Grus americana; United States CB/CF,H Drewien and Bizeau (1977), Derrickson (1985) Derrickson and Carpenter (1987), Lewis (1990)
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Scientific Bases for the Preservation of the Hawaiian Crow Common and Scientific Names; Locality Methods References Guam Rail, Rallus owstoni; Rota, Mariana Islands CB/R Witteman et al. (1990) Weka, Gallirallus australis greyi; New Zealand T,CB/R Anon. (1991a) Lord Howe Island Woodhenb, Tricholimnas sylvestris; Lord Howe Island CB/R Lourie-Fraser (1983), Miller and Mullette (1985), Fullager (1985) Takaheb, Notornis mantelli; New Zealand T;CR/R;CB/R Reed and Merton (1991), Anon. (1991b) Black Stilt, Himantopus novaezelandiae; New Zealand F/CF;CB/R Bryant (1985), Reed and Merton (1991) Pink Pigeon, Columba mayeri; Mauritius CB/R Todd (1985), Jones and Owadally (1988), Jones et al. (1988) Red-Crowned Parakeet Cyanorhamphus novaezelandiae; New Zealand CB/R Taylor (1985), Wiley et al. (1992) Military Macaw, Ara militaris; Guatemala CB/R Clubb (1991) Thick-Billed Parrot, Rhynchopsitta pachyrhyncha; United States T,CB/R Snyder and Wallace (1987), Snyder and Johnson (1988), Wiley et al. (1992) Puerto Rican Parrot, Amazona vittata; Puerto Rico CB/F Snyder et al. (1987), Wiley et al. (1992) Kakapob, Strigops habroptilus; New Zealand T Merton and Empson (1989), Triggs et al. (1989), Moorehouse and Powlesland (1991) Eagle Owl, Bubo bubo; Sweden, Germany CB/H Broo (1978), Von Frankenburg et al. (1984)
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Scientific Bases for the Preservation of the Hawaiian Crow Common and Scientific Names; Locality Methods References San Clemente Loggerhead Shrike, Lanius ludovicianus mearnsi; United States CR/H Scott and Morrison (1990), Morrison (1991), Kuehler (in press) Seychelles Brush Warbler, Acrocephalus sechellensis; Aride Island, Seychelles T Anon. (1988), N. J. Collar (pers. comm., 1990) Chatham Island Black Robinb, Petroica traversi; New Zealand T/F,CF Merton (1975), Flack (1977), Reed and Merton (1991) White-Eye Vireo, Vireo griseus bermudianus; Bermuda T wingate (1985) Laysan Finch, Telespyza cantans; Hawaiian Islands T Conant (1988) Bali Mynah, Leucopsar rothschildi; Indonesia CB/R Van Balen et al. (1990), Anon. (1991c), Quammen (1991), Van Bali, Balen and Soetawidjaya (1991) Saddleback, Creadion carunculatus; New Zealand T Merton (1975), Mills and Williams (1979) California Condor (Gymnogyps californianus) The recovery program for the California Condor is probably one of the most controversial ever undertaken. Although a succession of biologists tracked the condor's decline for over 40 years, the causes remained undetermined. In 1979, the population had dropped to about 30 birds, and a new research program was initiated primarily under the supervision of the U.S. Fish and Wildlife Service (USFWS) and the National Audubon Society. Initial proposals to trap condors for radiotelemetry and captive propagation brought forth a large opposition. Through the effective use of the press and political pressure, opponents sought to stop all intensive research and ''hands-on" management activities. The death of a wild nestling during handling in 1980 reinforced their case, and intensive procedures had to be abandoned.
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Scientific Bases for the Preservation of the Hawaiian Crow For the next several years, research activities were limited to observation and photography. During that time, it was learned that most of the adult birds in the wild were breeding, and the first accurate census count—20 birds—was completed by photographing individual molting patterns (Snyder and Johnson, 1985; Snyder and Snyder, 1989). In 1981, a pair that had lost its first egg was observed to relay; this convinced authorities that a captive population could be successfully established by removing first eggs without harming the wild population. Permission to begin radiotelemetry studies was granted in late 1982. In spring of 1983, the first eggs were removed from every nesting pair, and four young were successfully hatched at the San Diego Zoo (Kuehler and Witman, 1988). Because condors only lay every 2 years if they are rearing a chick, two wild nestlings were also taken into captivity to ensure that the adults would breed again the next year (Snyder and Snyder, 1989). Field studies soon revealed that one of the principal causes of mortality was lead poisoning that resulted from the ingestion of lead bullet fragments in deer carcasses, and the sudden loss of six wild adults during the winter of 1984–1985 convinced many that all the wild birds should be brought into captivity. That proposal culminated in an expensive lawsuit against the USFWS by the National Audubon Society. The Court found in favor of USFWS. The last wild condor was brought into captivity in 1987, and the captive population at the San Diego Wild Animal Park and Los Angeles Zoo was thus raised to 27 birds. Captive condors began breeding in 1988, and the captive population has grown steadily to its current number of nearly 50 birds. The California Condor Recovery Team has established three criteria that must be met before individual condors will be eligible for release to the wild: at least 90% of the genetic material of the founders, from which the released birds have descended, would still be represented in captivity; at least three birds must be physically and behaviorally ready for release at the same time; and at least three pairs must be successfully reproducing in captivity (Kiff, 1986, 1989; Wallace 1990). In anticipation of successful propagation of the California Condor, Andean Condors (Vultur gryphus) were used as research surrogates to develop methods for releasing captive-reared Condors to the wild. A total of 13 Andean Condors were released in southern California between 1988 and 1990 to test release and supplemental feeding procedures (Wallace, 1990, 1991), and the first captive-raised California Condors were released in the fall of 1991. Magpie Robin (Copsychus sechellarum) Once widespread and common on six islands in the Seychelles, the Magpie Robin by 1960 was restricted to Frigate Island, primarily as a result of the introduction of feral cats and rats (Rattus spp.) on the other islands (Gretton et al., 1991). Beginning in 1977, with about 41 birds remaining in the population, Jeffery Watson initiated a detailed field study under the auspices of the International Council for Bird Preservation and the World Wildlife Fund to determine the factors responsible for the species decline. He found that predation on adults by feral cats was a major problem, and personnel of the New Zealand Wildlife Service conducted a successful eradication program. Later investigations by Jan and Mariette Komdeur indicated that the population was failing to increase because of several additional factors, including nest predation
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Scientific Bases for the Preservation of the Hawaiian Crow by skinks, snakes, and the introduced Indian Mynah (Acridotheres tristis), a shortage of suitable nest cavities, and a shortage of feeding sites resulting from the regeneration of secondary scrub forest. Consequently, a recovery plan outlining potential management activities was prepared and endorsed by the Seychelles government and Frigate's owner in 1990, and implementation began the next year. Management activities—including supplemental feeding, provisioning and protection of nest sites, and habitat improvement and forest restoration—appear to have stemmed the population's decline, but remaining population is very small (22 birds) and vulnerable to catastophes, such as fire, disease, and storms. Plans are now under way to establish a second population on another island as soon as the population increases to 30 birds. As with the Seychelles Brush Warbler (Acrocephalus sechellensis) (See Table 5.2), this action will be accomplished by translocating wild birds into suitable habitat (Gretton et al., 1991). Lord Howe Island Woodhen (Tricholimnas silvestris) This flightless rail is endemic to the subtropical Lord Howe Island in the southwestern Pacific Ocean. Although once numerous and widespread across this small subtropical island, the Woodhen by 1969 was reduced to about 20–25 birds on the heights of Mt. Gower as a result of the introduction of dogs, cats, rats, and goats. The remnant population of birds had survived on Mt. Gower in extremely poor habitat. The area was free of predators, but was marginal in all other respects (Fullagar, 1985). Field studies were initiated in 1971 to determine the status and ecology of the species, and a vigorous predator-control program was begun in 1976. Both programs continue. Beginning in 1980, a captive-breeding facility was established, and three wild pairs were trapped for breeding purposes. A total of 78 captive-raised and 13 wild-origin Woodhens were eventually released at various locations throughout the island, and by June 1984 the wild population exceeded 150 as a result of substantial reproduction (Lourie-Fraser, 1983; Miller and Mullette, 1985). Takahe (Notornis mantelli) Populations of this flightless gallinule, endemic to the alpine tussock grasslands of the Murchison Mountains on the South Island of New Zealand, declined precipitously as a result of predation by introduced mammals, competition with introduced deer for its principal food plant, and egg predation by Wekas (Gallirallus australis greyi) (Williams and Given, 1981). The bird was thought to be extinct until the rediscovery of a single population numbering about 200 birds in the alpine grasslands near Te Anau on the South Island, but this population declined to about 120 birds by 1983. Biologists determined that Takahes normally lay two eggs but raise only a single offspring, so in 1985 they began removing a number of eggs from the wild each year to establish a captive-breeding population and to hatch and rear young for release in other suitable areas. Between 1987 and 1989, 25 birds were released in the Glaisnock catchment of the Murchison Mountains, and additional populations were established on two predator-free islands. As a result of those manipulative procedures, the Takahe numbers increased to over 200 in 1990 (Hay, 1990; Reed and Merton, 1991).
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Scientific Bases for the Preservation of the Hawaiian Crow Kakapo (Strigaps habroptilus) This large, flightless parrot, endemic to New Zealand, is unusual in that it is nocturnal, solitary, and polygynous with males forming leks for mating. Although at one time widespread on all of New Zealand's main islands, by 1976 it was believed to be effectively extinct, inasmuch as only a few males could be located (Merton, 1975). However, in 1977, a population of 100–200 birds was discovered on southern Stewart Island. Because predation by introduced mammals was a major impediment to recovery, biologists with the New Zealand Wildlife Service moved about 50 birds to three predator-free offshore islands beginning in 1982, and additional birds have since been moved between islands. When studies determined that the absence of reproduction in the translocated populations might be the result of inadequate nutrition, a supplementary feeding program was initiated in 1989 on Little Barrier Island. In 1990, male reproductive activities increased, and two females that were known to take the supplemental provisions (i.e., sweet potatoes, apples, brazil nuts, almonds, walnuts, and sunflower seeds) nested and laid eggs. In 1991, four of five females receiving supplemental food laid eggs, and two renested. Efforts to effect successful reproduction through supplemental feeding continue, and the populations are being closely monitored (Triggs et al., 1989; Moorehouse and Powlesland, 1991; Wise, 1991). Chatham Island Black Robin (Petroica traversi) Once widespread throughout the Chatham Islands of New Zealand, the Black Robin disappeared from all the larger islands after European colonization, until only a remnant population of 25 birds survived on Little Mangere Island. As a result of habitat degeneration in the 1970s, the population declined from 18 in 1972 to seven birds (two females and five males) in 1976, and the population was later transferred to 4 hectares of suitable habitat on Mangere Island. By 1979, only one female and four males remained, and an intensive effort to augment reproduction by removing eggs and stimulating renesting was begun. The eggs were initially cross-fostered to incubating Chatham Island Warblers (Gerygone albofrontata), but this effort was abandoned when it was determined that the chicks could be raised only to about 10 days of age. Eggs were later transferred 15 km by sea to South East Island and fostered to nesting pairs of Chatham Island Tomtits (Petroica macrocephala). To increase nest security and allow intensive manipulation, all Robin and Tomtit nests were slowly transferred to nest boxes. First and second clutches were generally removed from Robins for fostering, and third clutches were left with the Robins for incubation, hatching, and rearing. Owing to improper song-learning by male Robins raised to independence by Tomtits, fostering procedures were refined to return chicks to Robin nests at about 15 days of age, and supplemental feeding of both Robins and Tomtits was instituted to enable the parents to raise enlarged broods. Between 1980 and 1988, transfers between islands included over 40 Robin eggs, 10 nestlings, and 25 independent birds. A second populations of Black Robins has been established on South East Island, and the total wild population has increased to over 100 birds (Flack, 1977; Reed and Merton, 1991).
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Scientific Bases for the Preservation of the Hawaiian Crow Mauritius Kestrel (Falco punctatus) Once common almost throughout the island of Mauritius, by the early 1970s the kestrel was restricted to native forest in the Black River Gorges region as a result of deforestation, and the known population consisted of only two breeding pairs. Like the 'Alala, this species existed for several decades at an effective population size of fewer than 20 pairs, and it was the subject of a poorly managed breeding program for nearly 10 years before success was achieved and significant reintroductions were begun (Jones et al., 1981, 1991; Cade and Jones, in press). From 1974 to 1986, the wild population grew slowly and irregularly from two known pairs to about eight pairs (one to six productive pairs). The species essentially survived on its own during those years, despite attempts at captive breeding. Eight birds (five adults, and three nestlings) were removed from the wild for captive breeding between 1974 and 1978, but only a single young was produced in captivity. All nine birds died from one cause or another by 1980 (Jones, 1987). Although many conservationists lost hope for the kestrel, the program came under new direction when Carl Jones, of the Jersey Wildlife Preservation Trust, arrived on the island in late 1979. To minimize the impact on the wild population, he rebuilt the captive flock by removing first clutches for artificial incubation and rearing, thus allowing the wild pairs to renest and fledge young. The first captive-produced young were produced in 1984. With the help of Willard Heck, of the Peregrine Fund, more than 30 young had been produced in captivity by 1987, and more than 140 by 1992 (Cade and Jones, in press). As the number of breeding pairs increased in the wild during the 1980s, further manipulations to enhance productivity were implemented. A total of 146 fledglings derived from 190 fertile eggs collected from the wild were hatched in the laboratory and later returned to the wild by fostering or hacking (Sherrod et al., 1981). In all, some 230 captive-produced and wild-origin young have been released since 1984. By the end of the 1991–1992 breeding season, the wild population totaled some 170 and included 30 known breeding pairs distributed in four areas of the island. Many of the birds that have been returned to the wild have survived and bred in extensively modified habitat (Cade and Jones, in press). Conclusions The recovery programs described here demonstrate a number of important points that are especially relevant to preservation efforts for the 'Alala: Wild populations of many threatened species have declined to extremely low numbers, but have responded positively to well-conceived and carefully implemented programs. The case studies cited here, as well as those for many other species, clearly indicate that, as long as a single male and female survive, it is never too late to try to save an endangered species. Most seemingly hopeless cases turn out to be much more hopeful when imaginative research and conservation programs are implemented (Derrickson and Snyder, 1992).
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Scientific Bases for the Preservation of the Hawaiian Crow The application of intensive in situ manipulate techniques can often lead to more effective and less-expensive means of augmenting wild populations than captive-breeding programs, although both approaches might be required initially until the number of wild breeders is increased significantly. Many recovery programs have substantially enhanced fecundity or survivorship of wild birds through the judicious application of predator control, supplemental feeding, and multiple clutching. The geographic distributions of several endangered species that had been reduced to single, relict populations have been expanded through deliberate releases into suitable habitat either within or outside their historical ranges. Some species, such as the Mauritius Kestrel, have even been induced to colonize successfully habitats that differ from their original ones. Not surprisingly, many programs have focused their efforts on re-establishing multiple populations (a "metapopulation" structure) (Simberloff, 1988; Murphy et al., 1990) to minimize the possibility of extinction caused by catastophic events. Suitable habitat is necessary for the re-establishment of wild, self-sustaining populations. Indeed, a recent analysis of vertebrate translocations (Griffith et al., 1989) determined that habitat quality is one of the most important predictors of success. Habitat preservation or restoration must have a high priority in every recovery program. This finding serves as a crucial reminder that endangered species represent signals, or "indicators" of systemic degradation in whole habitats or ecosystems. Habitat protection and restoration ultimately are the goals of any meaningful endangered-species recovery program. In summary, on the basis of the successful restoration efforts that have been undertaken with a variety of avian taxa, the committee believes that there is a good chance that an effective program for the 'Alala can still be designed and implemented. Options for programs that manage both wild and captive populations as one unit are discussed in Chapter 6.
Representative terms from entire chapter: