SPECIES DESCRIPTION AND NATURAL HISTORY

The hyacinth macaw (Anodorhynchus hyacinthinus [Latham]) is the largest of the world's 340 parrot species. The bird measures approximately 36 to 39 inches (93 to 100 centimeters) from its bill to the tip of its 21-inch tail (55 centimeters) and weighs approximately 3.3 pounds (1.5 kilograms) (Sick 1984, Forshaw 1981 ). Its cobalt-blue plumage is offset only with small, bare patches of bright yellow skin at the base of the lower mandible and around the dark eye. The hyacinth macaw's black bill is exceptionally large and hooked, dwarfing the bills of other large macaws such as the red-and-green (Ara chloroptera), scarlet (A. macao), and blue-and-yellow (A. ararauna). Like all parrots, the hyacinth macaw is equipped with short, sturdy legs and feet, which enable it to hang sideways or upside-down while plucking palm nuts from fruit clusters in trees. The species nests in tree cavities or cliffs and, like all parrots, regurgitates chopped-up palm nuts to feed its young.

The hyacinth macaw's impressive vocalizations include a variety of very loud, harsh, guttural squawks that can be heard over a kilometer or more in the wild. Due in part to the bird's massive size, its calls are much lower in frequency than the calls of other macaws.

Taxonomy and Distribution

The term "macaw" refers to 18 species of large, long-tailed New World parrots. Taxonomists classify the macaws in three genera: Ara, Anodorhynchus, and Cyanopsitta. The three species of Anodorhynchus -the hyacinth macaw, the extinct glaucous macaw (A. glaucus) and the nearly extinct Lear's macaw (A. leari)-share the same basic appearance, although the latter two species are 25 to 30 percent smaller and not as intensely cobalt blue as the hyacinth. The third macaw genus, Cyanopsitta, includes only one species-the small, blue-gray Spix's macaw (C. spixii). The last three individuals of this species surviving in the wild were illegally caught by bird traders in 1988. While there are 50 or more in captivity; no Spix's macaws are known to remain in the wild (Thomsen and Munn 1988 ).

The hyacinth macaw is not a species of wet Amazonian forest, but rather a species of the seasonally drier forests of the eastern Amazon and the river drainages south and east of the Amazon basin-the Paraguay, Parnaíba, and Preto rivers, among others. There is evidence that hyacinths lived originally in all Amazonian and central Brazilian dry forests with high densities of palms and sufficient nesting cavities. The three or more separate populations of hyacinths that survive today inhabit those portions of the species' original range that experienced the least pressure from bird catchers, meat and feather hunters, and agricultural developers.

The hyacinth macaw's ability to harvest different palm nuts in each part of its range allows it to survive in habitats with extraordinarily different topography, vegetation, and climate. In Pará, for example, the hyacinth lives in seasonally moist eastern Amazonian forest, which is characterized by a broken canopy of Brazil nut trees and an understory of low trees and bamboo (Ridgely 1982 ); in northeastern Brazil (the intersection of Goiás, Piauí, Maranhão, and Bahia), the species occupies dry, open forest in rocky valleys and plateaus (Ridgely 1982, Munn et al.); in Mato Grosso and Mato Grosso do Sul (Ridgely 1982, Munn et al. 1987), and in the eastern parts of the Bolivian state of Santa Cruz (Remsen and Ridgely 1980), the hyacinth macaw lives in moist palm groves interspersed with grassy marshes and gallery forests in the Pantanal marshlands of the upper drainage of the Paraguay River, the world's largest freshwater wetland. The climate in all three of these regions features a pronounced dry season that prevents the growth of extensive, tall, closed-canopy tropical forest (see Figure 1 ).

Diet

Although most other macaw species appear to eat a large variety of seeds, nuts, fruit pulp, nectar, flowers, and leaves (Forshaw 1981, Munn 1988 ), the hyacinth macaw relies almost entirely on the nutritious, fat-rich meat of very hard palm nuts. Only Sick (1969) and Roth (unpubl.) report that the species occasionally eats other food, such as small seeds, palm sprouts, and snails; palm nuts are by far the species' major food source.

The hyacinth macaw's large bill reflects its food preference; it uses its bill to score and then - in steel-cutter fashion - shear the nuts in two. The hyacinth macaw cuts open palm nuts so cleanly that the cut surfaces resemble the work of a metal-cutting saw or laser rather than of a bird or mammal. Red-and-green macaws and scarlet macaws, which also are endowed with impressive bills, occasionally try to cut open similarly large and hard palm nuts, but these smaller-billed species invariably butcher the nuts with crude gashes and hacking cuts that require many minutes of effort (Munn unpubl.). Their awkward beakwork contrasts markedly with the elegant, efficient shearing of the hyacinth macaws. Only one other macaw - the Lear's macaw - is able to sheer palm nuts so adeptly.

Throughout its range, the hyacinth macaw seems to rely on the nuts of one or two palm species, which vary in different parts of the bird's range. The populations of hyacinth macaw living in the Brazilian state of Pará in the eastern Amazon, for example, rely on the nuts of the palms Orbignya phalerata (the famous babaçú) and Atrocaryum sp. (locally named "tucumán"). The birds living in the large region at the intersection of the four states of Goiás, Piauí, Maranhão, and Bahía rely on the nuts of the palms Syagrus coronata (catolé) and Atalea funifera (piaçava); the birds living in the Pantanal region of south Mato Grosso and Mato Grosso do Sul eat principally the nuts of palmsAtalea phalerata (bacurí) and Acrocomia sp. (bocaiuva ). Because the nuts of these six palm species are of different dimensions and presumably different hardnesses, they would seem to be of potential interest to other macaw species; however, in each part of the hyacinth's range, the large macaws of the genus Ara seem to concentrate on a wide variety of other seeds and fruits, leaving the hyacinth's food sources virtually untouched. This avoidance by other macaws may reflect a difference in bill force between the hyacinth and the smaller billed Ara species, but field and laboratory data are required to test this hypothesis.

Breeding

Nest Sites In the Pantanal, the hyacinth macaw apparently nests in cavities in large legume trees(Enterolobium sp. or Sterculia striata), which are the only two trees in the region large enough to provide cavities for the parrots (Yamashita.unpubl., Hart unpubl.).

In the drier, rockier habitats occupied by hyacinth macaws in south Maranhão, southwest Piauí, north Goiás, and northwest Bahía hyacinths nest in cavities of large dead or dying Buriti palms (Mauritia vinifera) in gallery forests of this large palm, and in natural rock crevices in the tall red cliffs, which are approximately 656 to 1,312 feet (200 to 400 meters ) above the flat valleys typical of the region. It appears that trapping has removed the young from so many palms in the region that most of the successful nests are now in the cliffs. Whether the previously palm-nesting pairs have moved to cliff sites or have died out is unknown.

Hyacinth macaws living in the northwestern parts of the their range, such as the Carajas region and the mid-lower Xingu drainage, probably nest in the huge holes that result when large branches fall off the 131 to 164 foot (40 to 50 meter Brazil nut trees (Bertolettia excelsa). These large trees are surprisingly common in those parts of Brazil and, in some sections of the forest north of Carajas, occur in densities of from 0.8 to 4 trees per hectare. Therefore, nest sites should not be a limiting factor for hyacinth macaws in that region. In parts of the rocky valleys of northeast Brazil and the Pantanal, however, nest sites are probably increasingly scarce and a limiting factor in reproductive success.

Nesting Seasonality. For reasons presumably associated with seasonal differences in food availability, hyacinth macaws, like most South American macaws, nest during the wet season, which typically falls between November and April in regions south of the Equator. To our knowledge, no data currently exist on seasonal availability of palm nuts in the species' range.

Reproductive Rate. Estimates and censuses of hyacinth macaws during the nesting season in the Pantanal suggest that only 15 to 30 percent of the adult population attempts to breed each year (Yamashita unpubl., Hart unpubl.). As small or an even smaller percentage of adult hyacinth macaws in the eastern Amazonian and northeast Brazilian populations may attempt to breed in a given year (Yamashita unpubl..). These data and estimates coincide with data on reproductive rates of blue-and-yellow, scarlet, and red-and-green macaws in the 6,950 square mile ( 18,000 square kilometer) Manu Biosphere Reserve in Amazonian Peru, where hunting is not permitted (Munn 1988).

Brazilian observers report that not all hyacinth macaw nests fledge young, and those that do rarely fledge more than one bird. Thus, 100 mated pairs of breeding-age hyacinth macaws may only produce from 7 to 25 young per year-a very low reproductive rate. Although data are required to confirm these estimates, it appears that the species does not have a high enough reproductive rate to withstand any substantial, long-term harvesting for the live animal trade or for hunting for meat and feathers. However, because adults presumably live for decades, a low reproductive rate does not necessarily signify that the species will disappear quickly if nests fail for a few years. Nevertheless, in the absence of good year-to-year data on longevity and reproductive rates, it cannot be assumed that the species will survive in areas where humans frequently destroy nest sites, capture nestlings, or capture or kill adults.

SIGNIFICANCE OF THE SPECIES

The hyacinth macaw's major biological significance is that, as the world's largest and most specialized parrot, it represents an extreme in the avian world. The species's reliance on palm nuts no doubt has influenced the distribution, reproduction, and seed defenses of the many palm species on which the hyacinth macaw depends. It is likely that the hyacinth macaw plays a major role in driving the evolutionary "arms race" between plants and animals, in this case between palms and their seed predators. Presumably, many South American palm species have evolved very hard nut shells to prevent predation by hyacinth macaws. Each time a palm plant produced a harder, better-defended seed, the individual hyacinth macaws with the largest bills probably were disproportionately able to crack the seeds. Hence, they passed their "big bill" genes down to their offspring, leading to larger and larger bills in each generation.

Besides its unique relationship with certain species of palms, the hyacinth macaw may boast a variety of other biological peculiarities, that will make it of great interest to evolutionary biologists. These peculiarities may include an apparent ability to thrive - without dying prematurely of arteriosclerosis-on a very limited variety of palm nuts that are exceeding rich in saturated fats; great intelligence (parrots are one of the families of birds with the largest ratio of brain to body weight); and, the possibility of an elaborate social structure within wild communities of long-lived birds.

Hyacinth macaws are of direct economic value in two ways: ((1) as attractions for the rapidly expanding nature tour industry in the Pantanal of Brazil; and (2) as cage birds for the international live-bird trade. Nature tourism, which is expanding in the Pantanal region, could help conserve the Pantanal habitat of the hyacinth, while, ironically bird trade has proven to be the principal cause of the recent substantial declines in hyacinth macaws in many parts of Brazil, Bolivia, and Paraguay (Munn et al.1987). In contrast to the nature tour industry, which uses the hyacinth macaw in an indirect and virtually harmless manner, the trade in wild-caught hyacinths has rapidly devastated many large populations of the species. Because the species is slow to recover from the extreme pressures of harvest, the hyacinthine macaw, should be considered a non-renewable resource. The trade in hyacinth macaws has not only rapidly destroyed wild populations in certain regions, but the bird catchers who live and work in the forests and savannahs of Brazil, Bolivia and Paraguay earn only $40 to $60 per bird, whereas middlemen and international dealers subsequently sell and resell the same birds for $300, $900, $1,300, and ultimately $7,000 to $10,000 per bird (Thomsen unpubl.). The final buyers of these wild-caught hyacinth macaws continue to ignore the fact that the birds have been captured illegally in Brazil, thus driving the species closer to extinction.

In 1987, long overdue changes in international laws finally resulted in a worldwide ban of trade in wild-caught hyacinth macaws. However, it still will be legal to sell captive-bred birds, both in the United States and abroad. This production in captivity at least should allow aviculturists to obtain the species without further straining wild populations. In 1987, one breeder reportedly produced eight hyacinth macaw fledglings from the eggs laid by one mated pair of captive birds (G. Jennings pers. comm.). As aviculturists further refine captive-breeding techniques, it is possible that by using incubators and by hand-raising, each year a captive pair of hyacinth macaws might produce more healthy fledglings than they could produce throughout their entire lives in the wild.

HISTORICAL PERSPECTIVE

It is impossible to say what the original range and population size of the hyacinth macaw was before the advent of humans to South America approximately 11,000 years ago. Likewise, it is impossible to know the distribution of the species before Europeans arrived in the 1500s. Native Brazilian tribes may have engaged in sizeable trade in hyacinth macaw feathers. It is even possible that hyacinth and other large macaws increased in density throughout South America as European diseases swept across the continent, killing most of the Indians long before Europeans began to penetrate and exploit the resources of the interior (Sweet 1981, Thomsen and Brantigan in press).

It is known, however, that in the early part of the 20th century explorers reported flocks of hundreds of hyacinth macaws at localities in Piauí in northeast Brazil where today the species is totally extirpated (Munn et al. 1987, Roth pers. comm.). In reviewing reports of many collecting expeditions between 1930 and the 1960s and from his own personal observation, Yamashita believes that the species formerly existed in many parts of Goiás, Maranhão, and Mato Grosso where none exists today. It is likely that the species originally ranged from just south of the Amazon in Pará to the drainage of the Parana and Paraguay rivers in Paraguay and southern Brazil. To try to estimate the species' world population size prior to the advent of Indians and then Europeans would be difficult, but there were probably between 100,000 and 3,000,000 birds in all.

A combination of habitat destruction for agriculture, capture the bird trade, and hunting for meat and feathers have brought the world population of hyacinth macaws down to an estimated 3,000 individuals, although the number could range between 2,500 to 5,000 (Munn et al. 1987). It seems likely that the destruction of hyacinth macaw habitat - palms and nest trees - and hunting for meat and feathers were the predominant causes of the species decline until the 1960s or early 1970s. Beginning then and continuing until 1988, it appears that a major increase in the international trade in live macaws may have taken a greater toll on the species than either habitat destruction or hunting.

The evidence implicating the live-bird trade as the recent major threat to the hyacinth macaw comes from field surveys, interviews with people living in former hyacinth macaw strongholds (Munn et al.1987), and from analyses of international trade records of the species (Nilsson and Mack 1980, Inskipp et a1. 1988, Thomsen and Brantgian in press). From these data, scientists have proven that bird catchers systematically and single-handedly harvested entire populations of hyacinth macaws to sell to national and international bird dealers (Munnet al.1987, Roth pers. comm., Yamashita unpubl.).

The records of international trade in hyacinths over the last five years also demonstrate that there has been substantial reported trade. Still, actual trade may significantly exceed reported trade (see Table 1). In particular, data from U.S. Department of Agriculture quarantine stations at ports of entry into the United States suggest that 1,382 hyacinth macaws entered the United States from 1981 through 1984, while the Convention on International Trade in Endangered Species of Fauna and Flora (CITES) data for the same period indicate only 702 hyacinth macaws were imported into the country (see Table 1) (Inskipp et a1.

1988). If this discrepancy in import figures also occurs worldwide, two assumptions can be made: (1) CITES data on the hyacinth macaw trade for other countries may be even less accurate and (2) easily two or three times more birds may have been traded than CITES records indicate.

CURRENT TRENDS

Human activities have driven 2 of the 18 macaw species to extinction within the last 100 years: the Cuban macaw (

Ara tricolor) and the glaucous macaw. Eight of the surviving 16 macaw species are in danger of extinction, while the remaining species, which tend to be the smaller macaws, appear to be declining steadily throughout their range in Central and South America due to habitat destruction, the pet trade, and hunting for meat and feathers.

As mentioned previously, from field surveys and interviews, an estimated 2,500 to 5,000 hyacinth macaws survive in three different populations in Brazil and part of Bolivia. In Paraguay, the species was represented by only two birds in early 1987 (Munn et a1.1987).

Hyacinth macaws in the Pantanal of Brazil and Bolivia, are currently not hunted for meat or feathers; the birds have plenty of food bird but catchers continue to capture them and farmers continue to cut down their nest trees. Cattle ranchers in the Pantanal continue to convert patches of forest to pasture. However, ranchers tend to leave all the palm trees standing because their cattle eat palm fruits and their horses reportedly eat palm leaves. After the cattle digest the nutritious outer layers of the fruits, they regurgitate the hard inner nut. As a result, in some extremely well-protected locations where ranch-owners actively protect wild hyacinth macaws on their property, the birds forage in cattle pastures and stockyards for the clean palm nuts. Unfortunately, while ranchers leave palms standing, they cut down and burn other large trees, including the only two tree species that grow large enough to provide nest sites for the birds. In addition to suffering from the loss of nest sites, in the last two decades- and continuing today despite international protection - thousands of hyacinth macaws from the Pantanal have been captured and sold by professional bird catchers. Unless this capture is halted, the catchers will surely continue to exploit the birds of the Pantanal.

In northeast Brazil, a well-organized professional bird-trading ring is the most severe threat to the species. This ring must be broken if there is to be any hope for the species in this region. Meat hunting by local people is another threat to hyacinth macaws in northeast Brazil. Animal protein is not nearly as abundant in this bleak region as it is in the cattle-rich Pantanal, so the birds are probably killed for food as well as trade. There seems to be much palm-rich hyacinth macaw habitat in the northeast currently devoid of the birds. Although it is possible that future agricultural expansion may threaten the bird's food supply, the threat seems minor compared to major threats from bird catchers and hunters. The number of nest holes in cliffs probably will remain constant and thus are not a factor in the continued loss of the species in northeast Brazil.

Hyacinth macaw populations in Pará are threatened mostly from subsistence hunting by colonists and perhaps from feather trade by some Indian groups. If there are illegal bird-trading rings operating in the region, they are still not as entrenched as in northeast Brazil and in parts of the Pantanal and, thus, are not yet an obvious problem. Furthermore, the Indians of Pará aggressively defend their land and macaws from any outsiders; this will prevent traders from successfully operating in the region. The species' food sources and nest sites are still reasonably intact in Pará, although the rapid, destructive, and unproductive expansion of cattle ranching (on thin soils that will not withstand this type of extensive clearing and use) may be affecting the huge nest trees and palm resources in ways that are not yet known. The environmental changes now taking place in much of Pará are more rapid and generally more devastating and, irreversible than those in northeast Brazil or the Pantanal. This destructive development should be replaced with sustainable development in order to protect both forest organisms and the economic health of humans colonizing the region.

Capture or hunting of. hyacinth macaws has been illegal for many years in Brazil, Bolivia, and Paraguay, but generally the effectiveness of the governing laws has been minimal. In Brazil, the conservation officials of the state of Mato Grosso do Sul (including the southern half of the Pantanal) have confiscated some illegal shipments of hyacinth macaws, and the federal government of Brazil occasionally captures illegal traffickers. with small numbers of birds. Despite these limited successes, until 1987 it remained too easy to capture, buy, and ship the birds for long distances within Brazil, to adjacent countries, and ultimately the world market. But in 1987 and 1988, Brazil stiffened penalties for wildlife trafficking and currently several bird smugglers are being aggressively prosecuted by the Brazilian government.

Further encouraging trends include the report in Munn et a1. (1987) that some bird dealers were left holding more than 15 birds that had attracted no buyers. The same source reports that ranch-owners in the Pantanal region of. Brazil and Bolivia repeatedly stated that they were unhappy with the decline of the species on their ranches (constituting approximately 57,900 square miles [150,000 square kilometers] of privately owned ranches) many no longer allow bird catchers on or near their land. Munn et al. (1987) also reports similar sentiments from several ranchers in northeast Brazil. Furthermore, all local Brazilian officials and military officers who helped the survey scientists in regions of the Pantanal near the border with Paraguay (one of the areas where the parrot has been hit hardest by bird catchers) were very supportive of the survey efforts and were extremely helpful with information and logistics. Their enthusiasm for scientific studies on the hyacinth macaw seemed to go beyond the usual Brazilian hospitality, extroversion and friendliness and indicated a new environmental awareness and sensitivity among most Brazilians. Local support is indispensable to the survival of the hyacinth macaw in the wild.

Munn et a1. (1987) met a number of dedicated Brazilian, Bolivian and Paraguayan conservation officials and private conservationists who demonstrated the desire and ability to fight for the future of the hyacinth macaw and other endangered species in their countries. Typically working with small budgets and limited support from higher government officials, these people nevertheless are making progress in implementing and enforcing regional and national conservation laws. The question is whether they will be able to act quickly and effectively enough to stabilize the increasingly grim environmental and social situations in their countries.

At the international level, in 1987 the then-96 member countries of CTTES voted to outlaw all international trade in wild-caught hyacinth macaws. But despite CITES protection, more than 700 hyacinth macaws were trapped and traded from August 1987 to November 1988. (Thomsen unpubl.). This alarming amount of trade has led to new sterner measures in Brazil and internationally in an attempt to stem this devastating trade. It is evident: that CITES regulations alone cannot be effective in stopping or regulating the trade in the species.

Recently, several groups recognized the hyacinth macaw' s decline and teamed up to address it. The CITES Secretariat, Wildlife Conservation International of the NewYork Zoological Society, FIC (U.S.A) of the World Wildlife. Fund, and the International Council for Bird Preservation joined forces with the Brazilian government's Forestry Development Institute to launch a hyacinth macaw study that is the basis of this chapter. The Brazilian government's mining company, Companhia Vale do Rio Doce, the Brazilian Foundation for the Conservation of Nature, and numerous Brazilian and Bolivian ranch-owners were especially helpful to the field survey. With their dedication to the protection of the region's natural heritage, these organizations and people will continue to support efforts to conserve the hyacinth macaw.

PROGNOSIS

The hyacinth macaw will survive if the bird trade can be stopped and its food and nest sites protected from future development. Better data on the volume of illegal trade in the next few years will tell whether the trade has slowed or is continuing unabated. If the trade slows or stops, then the species is virtually assured of survival in the Pantanal region for many decades. Even if; the bird trade stops, however, meat hunting and habitat alteration in northeast Brazil remain threats. In Pará, meat hunting, the sale to tourists of feathers in Indian artisan goods, and forest destruction virtually assure the species' continued decline.

The species will almost certainly decline steadily in northeast Brazil and Pará in the coming years, but it is possible that it will stabilize or increase slowly in the Pantanal if people provide nest boxes and keep nest trees from being cut.

RECOMMENDATIONS

The global survival of the hyacinth macaw requires principally: (1) improved enforcement of existing conservation laws in Brazil, Bolivia, and Paraguay; (2) strict international enforcement of the global trade ban on wild birds; and (3) international pressure on countries that permit smugglers operating within their borders- especially Paraguay, Bolivia, and recently Argentina, who by far are the worst offenders- and on those countries that allow the import of the birds.

Further study of the species' distribution and biology also would be useful to its conservation. Of particular use would be research on the breeding biology of the birds living in different parts of the Pantanal to determine the possible effect of a shortage of nest sites on reproductive rates. If the data demonstrate a shortage of nest sites, then individuals or organizations should experiment with erecting nest boxes for the birds. Since many palm-forested parts of the Pantanal have lost all their hyacinth macaws to the bird trade, the remaining individuals should have plenty of food to eat and space in which to reproduce. Thus, if food is not limiting, and nest sites are sufficiently abundant, the species most likely could expand its population and reoccupy suitable habitat.

If the bird trade can be discontinued in northeast Brazil and in Pará then the next step would be to improve the nutritional status of the local people so that they do not have to hunt the birds for food. Likewise, Indian tribes should be prohibited from selling hyacinth macaw feathers commercially (the traditional ceremonial use of such feathers may be relatively harmless).

These suggestions will require implementation of plans for sustained development that currently are not welcomed by many local and national policymakers in Brazil. It can only be hoped that the efforts of all people, whether Brazilians or concerned citizens of other nations, will strengthen the environmental movement in Brazil and Latin America and bring an end to the current policies of environmental, social, and economic destruction for one-time gain. Instead, scientifically sound development policies must be sought to provide sustainable growth and a decent quality-of-life for all citizens. Otherwise there will be no way to keep the hyacinth macaws of northeast Brazil and Pará from becoming meat for the stew-pot.

REFERENCES

Forshaw, J.M. 1981. 

Parrots of the World. Second Edition. David and Charles Ltd. Newton Abbot, London.
Inskipp, T., S. Broad, and R. Luxmoore. 1988. "Significant trade in wildlife: A review of selected species in CITES Appendix II," in Volume II: Birds. IUCN and the CITES Secretariat.
Munn, C.A., J.B. Thomsen, and C. Yamashita.1987. Population Survey and Status of the Hyacinth Macaw (Anodorhynchus hyacinthinus) in Brazil, Bolivia, and Paraguay. Report to the Secretariat of the Convention on International Trade in Endangered Species of Wild Fauna and Flora. Lausanne, Switzerland.
----.1988. "Macaw biology in Manu National Park, Peru." Parrotletter 1:18-21. Nilsson, G.1985. Importation of Birds Into the United States,1981-1984. Animal Welfare Institute. Washington, D.C.
---- and D. Mack. 1980. "Macaws: Traded to extinction?" TRAFFIC/U.S.A.) Special Report 2: 1-136.
Remsen, V. and R.S. Ridgely-. 1980. "Additions to the avifauna of Bolivia." Condor 82: 69-75.
Ridgely, R.S.1982. The Distribution, Status, and Conservation of Neotropical Mainland Parrots. Ph.D. dissertation. Yale University.
Sick, H. 1969. "Aves brasileiras ameracadas de extinção e noçoes gerais de conserváção de aves do Brasil." An. Acad. Brasil. Cienc. 41 (supl.):205-229. ----.1984.Omithologia Brasileira, Uma Introdução. Editora Universidade de Brasilia, Brasilia, Brazil.
Sweet D.G. and G.B. Nash.1981. Struggle and Survival in Colonial America. University of California Press. Berkeley, California.
Thomsen, J.B. and C.A. Munn. 1988. "Cyanopsitta spixii: A non-recovery report Parrotletter 1:6-7.
--- and A. Brantigan. In press. "Sustainable utilization of neotropical parrots;', J.G. Robinson and K.H. Redford eds., Neotropical Wildlife Use and Conservation, University of Chicago Press. Chicago, Illinois.

Charles A. Munn is an associate research zoologist for Wildlife Conservation International, a division of the New York Zoological Society. He is a member of the IUBP/SSC Parrot Specialist Group.

Jorgen B. Thomsen is senior program officer at TRAFFIC (U.S.A.), a division of the World Wildlife Fund. He is a member of the IUBP/SSC Parrot Specialist Group and the editor of Parrotletter. 

Carlos Yamashita is a member of the IUBP/SSC Parrot Specialist Group. He has studied birds throughout most of South America since the early 1970s, and is currently finishing a graduate degree at the University of São Paulo.