Abstract

Birds have been bred in captivity since the dawn of civilization. In the nineteenth century, breeding rare and exotic animals for the menageries of royalty and aristocrats transitioned to the formation of public zoological gardens and natural history museums. With industrialization and human population expansion, some bird species became rare or disappeared entirely. Once the magnitude of the destructive forces of humans became evident, concerted efforts were initiated to restore depleted bird populations by using, among other techniques, captive breeding. In this article, I explore the evolution of avian conservation breeding programs and evaluate how this historical review informs our outlook for addressing the current extinction crisis.

The charm of history and its enigmatic lesson consist in the fact that, from age to age, nothing changes and yet everything is completely different. Huxley (1952) 

Menageries and Zoological Gardens

Birds have been bred in captivity since the dawn of civilization, as a source of food, for entertainment and sport, and as status symbols, spiritual totems, or personal companions. Breeding rare and exotic birds in captivity originated in elaborate royal menageries, first in China around 3,000 B.C. and later in ancient Egypt, Rome, and Greece (Jennison 1937; Schafer 1968; Lamberton and Rotroff 1985; Cooper 1995; Graham 1998; Benson 1997; Birkhead and van Balen 2008), and by the early medieval period, an extensive trade in birds had been established throughout the known world (Graham 1998). In the thirteenth century, Marco Polo marveled at the menagerie of Kublai Khan, the fifth Great Khan of the Mongolian Empire and grandson of Genghis Khan, who was accompanied by “ten thousand falconers … and five hundred gerfalcons [sic] [Falco rusticolus], and peregrine falcons [Falco peregrinus] and saker falcons [Falco cherrug] and other kinds of birds in very great abundance” (Bergreen 2008). Other aristocrats and noblemen of that time such as Holy Roman emperor Frederick II of Hohenstaufen, author of the falconer's bible De arte venandi cum avibus (The Art of Hunting with Birds) also maintained extensive menageries and engaged in trading birds and other animals (Bergreen 2008). Social evolution in Europe during the nineteenth century resulted in a shift from these elaborate private menageries of monarchs to public institutions (Hoage and Deiss 1996). Concurrent with this shift, a scientific approach to explaining and organizing life was emerging from Enlightenment thinkers, and by the nineteenth century, natural history studies were in vogue in Europe, leading to the expansion of public natural history museums and zoological gardens (Farber 2000).

Zoological gardens provided a dimension to natural history studies that could not be gained by looking at study skins in natural history museums. They opened up the possibility of studying behavior, comparative physiology, and evolutionary relationships of exotic animals, some of which were from opposite ends of the Earth, but which could now be viewed, living and breathing, side by side (Burkhardt 1999, 2001). Following his adventures on the H.M.S. Beagle, Charles Darwin studied the breeding habits and hybridization of birds in the London Zoo and relied on private breeders and zoological institutions to obtain pigeons (Columbidae) for breeding experiments (Darwin 1868; Stauffer 1975; Steinheimer 2004). His study of pigeons later helped form the basis for his opening salvo in On the Origin of Species (1859) as a model of how variation and selection could give rise to new species (Secord 1981; Burkhardt 1999; Montgomerie 2009). Italian scholars also were using specimens in zoological gardens to conduct studies on living animals in the 1800s, and, when the animals died, they would turn the specimens over to natural history museums for further study and archiving (Gippoliti and Kitchener 2007), something that was also done in Paris (Burkhardt 2001) and presumably elsewhere. English aviculturists with private collections in the late nineteenth and early twentieth centuries also were donating specimens to natural history museums, as evidenced by records in museum catalogs.

Despite advances in scientific knowledge facilitated by captive animals, the menageries and zoological gardens of the late nineteenth and early twentieth centuries were consumers of wildlife (Frankham et al. 2002). Some birds certainly bred in these institutions, but many birds were not kept under conditions that would have facilitated breeding, and as early as the 1830s, some were arguing how improved captive conditions might improve a bird's ability to breed. For example, in 1838, Swainson wrote the following:

Such species, again, as show the least disposition to breed, (and many, we have no doubt, would do this, if their habitations were constructed on the principle we are now advocating,) should be more particularly supplied by natural shelter; that is, the shelter of leaves and branches: dwarf trees or shrubs, having foliage, should be put in their inclosures, within which the nests may be constructed among the branches, and the females screened from observation. The parrots, nearly all of which build in hollow trees, might have such retreats provided for incubation. The present mode of putting boxes and pigeon-holes into all aviaries, without regard to the different nature of the birds, is but a rude and inadequate substitute for more appropriate contrivances. In short, we consider that the art of preserving and rearing foreign birds in this country, is quite in its infancy; and our only surprise is, that, with the inadequate means that are employed, any species are kept alive more than a few months after their being consigned to such comfortless habitations (Swainson 1838, p. 154).

It is interesting to note that two decades after Swainson's writings, Darwin was at a loss to explain why some species bred readily in captivity, but others did not (Stauffer 1975):

Considering all the facts which I have been able to collect, most of which I have given, it seems impossible to come [to] any more definite conclusion, than that captivity has an especially injurious influence on the reproductive system; & more injurious in some orders than in others, but with many exceptions in every case …. We can attribute this deficient action [i.e., inability to breed in captivity] only to general constitutional derangement (C. Darwin, as cited in Stauffer 1975, pp. 80–81).

As the natural history field evolved in the early 1800s, those in charge of collections assembled catalogs of captive animals, including descriptions of morphology and behavior, sometimes indicating whether the animal would breed in captivity. The first of these catalogs was prepared by Frédéric Cuvier (the younger brother of Georges Cuvier) in the early 1800s (Burkhardt 2001) followed by a publication of the London Zoological Park in 1835 (Bennett 1835), which set the standard for the larger zoos around the world (e.g., Anderson 1883; Brown 1892; Sanyal 1892; Stephan 1900; Hornaday 1911).

In the early catalogs, it was apparent that a wide variety of bird species were, at least occasionally, breeding in captivity, including parakeets (Psittacidae), doves and pigeons (Columbidae), weaver-birds Hyphantornis spp., bluebirds Sialia spp., black kites Milvus migrans, sunbitterns Eurypyga helias, cranes (Gruidae), emus Dromaius novaehollandiae, red-wing tinamous Rhynchotus rufescens, common rheas Rhea americana, white-eyebrowed wood-swallows Artamus superciliosus, Australian brush-turkeys Alectura lathami, black-tailed native-hens Gallinula ventralis, cassowaries Casuarius spp., pheasants and junglefowl (Phasianidae), gulls (Laridae), and waterfowl (Anatidae; Bennett 1835; Mitchell 1852; Sclater 1870, 1877). In some instances, where species were especially prolific, there was a need to dispose of individuals. Sclater (1870, p. 19) noted “A certain number of the young of the various species of Pheasants bred in the Gardens are disposed of every year in the month of November. Priced lists of these birds may be obtained on application at the Society's Office.”

In the mid-1800s, zoological parks were trading breeding birds (Sclater 1877), but these efforts were opportunistic and their purpose was to promote the interest of the zoo and not the species. Manchurian cranes Grus japonensis, which would have been a great rarity outside of the Orient, were noted breeding in captivity in Paris and attempting to breed in London, but failure to maintain a captive population only resulted in requests for more birds to display:

The birds which were imported by M. de Montigny, on his return from China in 1854, not only flourished at Paris in the most perfect health, but for three successive seasons made a nest and hatched out their young. The pair in possession of the [London Zoological] Society in 1860 nested twice but did not succeed in hatching their eggs. The following year, however, they were more successful, and a young bird was hatched on the 24th of June, 1861, to which they devoted unceasing care and attention for many months. The Manchurian Crane is a favourite bird among the Chinese, and it has been stated that a considerable number of them are always in captivity at Pekin[g] …. It is much to be regretted that only one individual of this fine Crane is now left in the Society's collection. No more valuable present could be made by the Society's correspondents in China than additional specimens of this species (Sclater 1870, p. 8).

By the mid- to late 1800s, zoological gardens were becoming increasingly popular in Europe (Farber 2000), and the template of these institutions was starting to be copied in the United States, first in Philadelphia, Pennsylvania, and then in Cincinnati, Ohio. When the New York Zoological Society opened its park in 1899 (later called the Bronx Zoo), it was the largest zoo in the world (approximately 4 times larger than the Berlin Garden, 5 times larger than the Paris Garden, and 9 times larger than the London Garden), and there was a conscious effort to adapt lessons learned from other zoological parks (The New York Times 1897). As the first director of the Society, William Temple Hornaday, stated in an interview with The New York Times in 1896:

We have a splendid opportunity to make here in New York the finest zoological gardens in the world. We can borrow from the accumulated treasures of knowledge acquired by the Zoological Society of London and by the managers of Jardin de Plantes in Paris, and we can avoid the mistakes necessarily made by these and other large owners of wild animals in the process of finding out the best way to keep them in captivity (The New York Times 1896, p. 8).

Hornaday was already a towering figure in the zoological community when he took the helm of the society (The New York Times 1896). He had traveled extensively throughout Europe, studying their natural history museums, and he participated in expeditions to Cuba, South America, Egypt, and Southeast Asia, collecting and studying animals. Later, he was instrumental in establishing the National Zoological Park in Washington, D.C., under the control of the Smithsonian Institution, and was superintendent of that park in 1890 (The New York Times 1896). He would go on to help prevent the extinction of the American bison Bison bison, to successfully lobby state legislatures to pass bills banning trade in wild game, and he would successfully lobby Congress to pass the Migratory Bird Treaty Act and prohibit the importation of skins and plumage of birds intended for the millinery industry (Hornaday 1931).

Under Hornaday's leadership, the New York Zoological Garden stood out from its European counterparts, not only because of its size but also because it adopted the approach of displaying animals in more natural settings (Farber 2000), something that Hornaday had brought to natural history museums a few years earlier. Perhaps most importantly, he implemented a conservation-oriented charter that was revolutionary. Specifically, the New York Zoological Society had established three primary objectives when it was founded in 1895 under a special charter granted by the legislature of the state of New York: 1) development of a public zoological park, 2) preservation of native animals, and 3) promotion of zoological education (Hornaday 1911). This charter, along with Hornaday's leadership and advocacy for wildlife conservation, would set the stage for later efforts to establish international endangered species lists (see Scott et al. 1987) and to redefine the role of zoos as organizations committed to species preservation.

Despite Hornaday's belief that zoos had an integral role to play in conserving native species (some of which were in serious decline at the time he was appointed director of the New York Zoological Society), he did not believe that captive breeding and restocking game decimated by hunters would produce any meaningful results in the United States, unless strict regulations were put into place and enforced. He noted the following:

The game owners and game-keepers of England, Scotland, Germany and Austria have not saved their game and their sport for 300 years by investigations, restocking, doctoring or breeding game in coops and pens. They have provided shelter, food, water and protection from enemies. But greater than any or all of those has been the protection afforded by savage regulations against exterminatory slaughter with guns! (Hornaday 1931, pp. 60–61).

Hornaday clearly understood one of the key limitations of captive breeding for conservation purposes: without removing the threats in the wild, breeding species in captivity for restocking populations would be fruitless.

Bird Population Declines and Extinctions

In addition to fueling the spread of zoological gardens, expansion of natural history as a new academic pursuit in the 1800s had some unintended consequences. One was the desire to fill newly constructed natural history museums with exotic specimens from around the world. Specimens brought back from faraway lands were a status symbol in scientific circles—the rarer, the better.

The story of the extinction of the great auk Pinguinus impennis serves as a sad example of this mentality (Fuller 1987, 1999, 2003; Gaskell 2000). By 1854, there was a growing sentiment that the great auk was already extinct, collectors having taken >40 specimens from the single island where they were known to breed in 1830 and 1831, and a dozen or more in 1833 (Gaskell 2000). However, in 1854, an article was published in The Edinburgh New Philosophical Journal entitled The Great Auk Still Found in Iceland, and English ornithologists John Wolley and Alfred Newton, fully aware of the extreme rarity of the bird, quickly set out for the island … to procure specimens! (Gaskell 2000). They did, and that is the last time anyone ever saw a great auk alive. Apparently, the naturalists of the time were far more concerned with solidifying their reputations by acquiring rare specimens for natural history museums than in preserving birds in nature for future generations.

The extinction of the great auk did little to curb the collectors' appetite for specimens, perhaps because society, as a whole, saw little economic value in this bird, or because some did not actually believe it was completely gone from its remote haunts. Thus, other bird species continued to be stalked by skin and egg collectors in the late 1800s and early 1900s, including the California condor Gymnogyps californianus (Wilbur 1978), imperial woodpecker Campephilus imperialis (Nelson 1898), and ivory-billed woodpecker Campephilus principalis (Hasbrouke 1891a; Snyder 2007). Slaughter of birds for museum specimens is evidenced by the fact that in 1872 there were approximately 30,000 stuffed birds and bird skins at the British Museum and by 1909 there were 500,000 (Allen 1909). Egg collecting for personal collections and natural history museums was also at its zenith around this time (Kiff 2005). Rarity only increased the collector's appetite. When, at the turn of the century, there were thought to be only approximately 50 heath hens Tympanuchus cupido cupido remaining, all on Martha's Vineyard, an island off of Massachusetts, collectors were offering US$25–30 apiece for specimens, because, as The New York Times pointed out, “the ornithological collector who does not get a Heath Hen for his collection at once will not get one at all” (The New York Times 1900).

The tide of public opinion toward bird conservation only started to turn when large numbers of economically valuable and otherwise “useful” bird species started to show vulnerability around 1870, with the invention of breech-loading shotguns (Forbush 1913; Hartley 1922). Pump-action and semiautomatic shotguns soon followed (both were in production by 1900). These advances in gun technology lead to drastic declines in gamebirds throughout most of the civilized world (Hartley 1922; Hornaday 1931).

By the late 1800s, bird extinctions due to human activities were readily acknowledged by some in the ornithological community (e.g., Meyer 1889). However, solutions to the extinction crisis were either not contemplated or not readily offered. There seems to be a sense of fatalism in the writings of early naturalists who were torn between an untamed world teeming with wildlife and a world that had to sacrifice nature to accommodate the juggernaut of expanding civilization after the industrial revolution and the growing railroad empire. Elliot Coues, one of the founders of the American Ornithologists' Union (AOU), perhaps best epitomized this malaise when he noted the sheer number of bird deaths from telegraph wires in 1876 during a horseback trip from Denver, Colorado, to Cheyenne, Wyoming (Coues 1876). He came to the following rather dismal conclusion:

Usually a remedy has been or may be provided for any unnecessary or undesirable destruction of birds; but there seems to be none in this instance. Since we cannot conveniently abolish the telegraph, we must be content with fewer birds. The only moral I can discern is that larks must not fly against telegraph wires (Coues 1876, p. 736).

Development of the railroads, along with perfection of cold storage facilities for shipping game to market, drastically increased the number of birds killed for food in America each year in the late 1800s (Palmer 1900). The invention and spread of personal automobiles in the early 1900s only made matters worse, as hunters fanned out across the countryside in search of dwindling game. As it became more and more evident that hunting was taking a serious toll on game populations and the millinery industry was wreaking havoc on birds around the globe for their prized feathers, public sentiment began to shift from the malaise of the late 1800s toward a call to action, followed by a full-blown movement to save the birds.

Direct proof of the ability of humans to destroy a once common bird species was finally put on full display with the extinction of the passenger pigeon Ectopistes migratorius in 1914 (Schorger 1955; Fuller 1987). Stories of passenger pigeons once blackening the sky are now legendary. John James Audubon experienced the following firsthand:

The air was literally filled with pigeons; the light of noonday was obscured as by an eclipse; the dung fell in spots, not unlike melting flakes of snow; and the continued buzz of wings had a tendency to lull my senses to repose (Audubon 1832, p. 321).

Loss of a bird species that once numbered in the billions and ranged throughout the central and entire eastern half of North America put things into perspective for many. The strength of our destructive abilities was now evident, and the need to combat those who attempted to maintain the status quo was equally evident to conservation minded individuals. Thus, in 1900 the United States passed its first federal wildlife protection law, The Lacey Act. This act prohibited the transportation of illegally captured or prohibited animals across state lines. Hartley (1922, p. 5) described the impetus for the law as follows:

Passenger pigeons were gone, the Heath Hen was gone, prairie chickens [Tympanuchus cupido] were going, turkeys [Meleagris gallopavo] were disappearing, the quail [Colinus virginianus] had been entirely eliminated from some States. Soon all game birds would be distant memories of the past. Non-game birds also were suffering from the depredations of plumage hunters, and they too would soon be effaced.

Although last ditch efforts were made to breed the few remaining passenger pigeons by Professor Charles O. Whitman at the University of Chicago and by the Cincinnati Zoo, breeding efforts (including cross-fostering passenger pigeon eggs with a rock dove Columba livia) were insufficient to sustain the small captive population (Deane 1908, Herman 1948). Similarly, last ditch efforts to breed a few remaining Carolina parakeets Conuropsis carolinensis would fail (Snyder 2004). Despite the knowledge that populations were being decimated and their range had drastically contracted since the early 1800s (Hasbrouke 1891b), aviculturists breeding Carolina parakeets in Europe and America (including the Philadelphia Zoo, Hanover Zoo, and Frankfurt Zoo) since the mid-1800s (Nowotny 1898; McKinley 1978) did not contemplate a coordinated effort to save the species from extinction. As Cokinos (2000, p. 48) explained,

… no one could yet see the larger context in which captive breeding could take place: through a widespread, well-managed program in which private owners and zoos shared birds for breeding. Such a program might have prevented the extinction of the Carolina Parakeet …. Instead, aviculturists and zoos competed against each other for prized individuals, knowing that the species kept inching closer to extinction.

On the back of these extinctions and drastic waterfowl declines in the United States, which were about to get worse with the draining of wetlands and the continental drought of the 1930s (Perry 2008), people were beginning to wonder if once wide-ranging and numerous species could be killed off, what was to stop bird species that were considered more valuable, such as geese, ducks, heath hens, and turkeys (at the time all in severe decline), from going extinct?

A Call for Bird Conservation

In the late 1800s, a small group of mostly self-taught ornithologists organized to form the AOU and generated a movement to change the status of wild birds in America (Orr 1992). At the AOU's second meeting in 1884, William Brewster (a founding member of AOU and curator of birds and mammals for the Boston Society of Natural History) expressed concern over the slaughter of birds for the millinery industry. Apparently, the statistics he presented “startled” some members, and he moved for appointment of a committee for the protection of North American Birds (Orr 1992). Brewster's motion passed unanimously, and he was named committee chair. The committee announced its formation, offered a draft state bird protection law, and suggested law enforcement tactics in an article published in Forest and Stream, January 21, 1886. The article also included a proposal to form, “an association for the protection of wild birds and their eggs, which shall be called the Audubon Society” (Orr 1992).

State chapters of the Audubon Society were formed, and reports were sent to the AOU for publication in its scientific journal The Auk (AOU 1898). Because the reports were broken out by state, these efforts gave spatial context to what was happening at the national scale in relation to bird declines. That same year, a summary of a report by William Temple Hornaday at the New York Zoological Society was published in The New York Times (The New York Times 1898) with a bar chart illustrating massive bird declines across 30 states. The article concluded that several species were likely to go extinct if measures were not implemented immediately.

Environmental degradation on other continents and the global plumage trade spurred efforts that paralleled those in the United States. In Australia, the Royal Australasian Ornithologists Union was formed in the early twentieth century with the objective of creating reserves and enforcing wildlife laws, and it was soon joined by numerous other local bird clubs, natural history societies, and societies for the preservation of Australian wildlife (Garnett and Crowley 2008). The Dutch Association for Bird Protection (Vereniging tot Bescherming van Vogels), the German Federation for Bird Protection (Deutscher Bund für Vogelschutz), and the Irish Society for Bird Protection were all formed around the turn of the century (Dalton 1993). With the creation of the French League for Bird Protection (Ligue pour la Protection des Oiseaux) in 1912, a national group for bird protection existed in nearly every northern European nation (Dalton 1993).

The British ornithologist Charles Dixon perhaps best summed up the sentiment of conservationists at the time in his book Lost and Vanishing Birds:

… it requires no great strain upon the imagination to picture a time when all the larger wild birds and beasts, all the exceptionally helpless ones of the earth, must perish, or exist as specimens in our museums, or as phantom records in our scientific literature. This will be a serious outlook for the biologist of the future, and the matter has long been sufficiently important to warrant some strong steps being taken to avert as far as possible such a vast calamity. After all, we only hold the fauna of the world in trust, and it is but our bare duty to posterity to hand that fauna down as intact as we found it, or as nearly so as the reasonable exigencies of life will admit (Dixon 1889, pp. 27–28).

Even suppliers of the millinery industry in the late 1800s realized that resources were not boundless. The law of diminishing returns eventually caught up with them, so industrial farms were established for a few species that bred readily in captivity. Dixon (1889) noted the following:

It is gratifying to know that egrets [Egretta spp.] are now being kept in captivity for the sake of their plumes. There is, we believe, an establishment near Tunis [Tunisia, Africa] where these birds are kept and allowed to breed in a large aviary. The plumes are shorn twice in the year, in May and September, each bird furnishing about seven grammes in the year, valued at thirty-five francs, a sum, after deducting all expenses, which leaves a net gain of some twenty-two francs per bird. This shows how easily we can preserve these beautiful birds from extinction and yet gratify the whim of women for wearing ‘aigrette’ [tufted-crest, or head-plumes of the egret, used for adorning a woman's hat] (Dixon 1889, p. 295).

Around the same time (in 1895), Edward Avery McIlhenny, heir to the Tabasco sauce fortune, took a different approach to conserving egrets. Alarmed by the loss of snowy egrets Egretta thula in the southeastern United States due to plume hunters, and having heard stories of an Indian raja who built bamboo cages for captive birds that continued to return to his “flying gardens” long after the raja had died and his cages had rotted away, McIlhenny took eight young birds from two snowy egrets nests and raised them in an aviary he constructed from bamboo and poultry netting near his home on Avery Island in coastal Iberia Parish, Louisiana (McIlhenny 1935; Nickens 2010). In early winter, he set them loose to migrate south. By 1908, there were 10,000 egrets returning to the property and by 1911, the population reached 100,000 egrets and McIlhenny's refuge on Avery Island was affectionately dubbed “Bird City” (McIlhenny 1935; Nickens 2010).

In the late 1800s, ostriches Struthio camelus had also become increasingly difficult to catch in Africa due to overharvesting for the millinery industry (Sales 2009). This led European entrepreneurs in South Africa to begin domesticating ostriches on farms starting in 1867 (Douglass 1881). The model of these farms soon spread, and ostriches were shipped to North Africa, Europe, India, Australia, South America, and the United States where they were raised to produce numerous products (de Mosenthal and Harting 1877; Douglass 1881; Doughty 1973). Although spurred by the notion that wild stocks were running out, breeding served mostly as a cost savings measure to those entrepreneurs who sought to make their living in the millinery industry. It was more profitable to run an ostrich farm than to track down diminishing supplies in the more remote regions of Africa.

In the United States, concerted efforts to breed birds in captivity for the purpose of their conservation began around the turn of the twentieth century in conjunction with the establishment of Audubon societies and the growing public concern for bird resources. Grinnell (1901, pp. 532–533) stated the following:

It is only within a very few years that breeding wild geese and ducks has been attempted. At present, however, a number of persons are very much interested in this pursuit, and there seems to be good reason to believe that after a few more years in experiment, a number of species of our wildfowl will be so far domesticated that they can be depended upon to breed in confinement.

In the early twentieth century, the wood duck Aix sponsa, once a common species in eastern North America, was the rarest duck on the continent and on the verge of extinction (Ripley 1959). Fortunately, this species was being reared in captivity in Belgium, Holland, France, and England at that time (Ripley 1959). In 1918, when the wood duck was thought to be virtually extinct, there were probably more individuals in captivity than in the wild (Ripley 1973). A small breeding program was initiated in Litchfield, Connecticut, by Alain C. White under the direction of Herbert L. Job (Ripley 1973). Job had studied early rearing experiments with North American diving ducks at Cornell University and attempted to emulate them with the wood duck. He found that although it was relatively easy to maintain the birds in captivity, they were hard to rear. In 1922, he sought the assistance of the English gamekeeper Henry Bowden, who helped the program flourish. According to Ripley (1973, p. 56),

The project, in which up to 400 Wood duck[s] were banded and released each year (2579 in all), probably had a seminal effect on the restoration of the species in the wild. Banding returns from the US Banding Laboratory records (pers. comm.) indicated that the Litchfield birds had reached 15 US states and Ontario in Canada, and had formed the nuclei of breeding colonies from South Carolina up to Massachusetts. Like the later success with the Hawaiian goose Branta sandvicensis, it would seem that captive rearing programme for birds could be a positive step towards the conservation of the species.

Another important early waterfowl conservation breeding venture in the early 1900s was the program to breed the giant Canada goose Branta canadensis maxima (Hanson 1965; Lee et al. 1984).

The origins of breeding depleted stocks of gamebirds came at a time when the most of the civilized world was just beginning to come to terms with the idea of resource conservation. In 1910, Gifford Pinchot, the first chief of the U.S. Forest Service (under Theodore Roosevelt), wrote The Fight for Conservation (Pinchot 1910) that called on the American people to adopt a doctrine of wise use as a measure of national security. Around that time, many U.S. states began to establish game farms to help restock the countryside with gamebirds that had undergone massive declines in the late nineteenth century. Birds that were raised included ring-necked pheasants Phasianus colchicus, wood ducks, black ducks Anas superciliosa, mallards Anas platyrhynchos, quail (Odontophoridae), ruffed grouse Bonasa umbellus, and wild turkeys. These operations were initially considered hugely successful, and by 1919, 55,400 pheasant eggs were produced in New York state alone, along with 9,206 half-grown birds to be released later that year (Hartley 1922). Private conservation clubs also were initiated by those interested in buoying gamebird numbers to provide hunting opportunities. However, these programs may only have been successful in boosting local numbers for hunters (Brakhage 1953), with little contribution to the populations that were now allowed to heal due to increased habitat protection and more restricted hunting seasons (Hornaday 1931).

Commissions were formed and meetings were held to develop techniques on breeding game birds, and “game farming” of birds became part of the curriculum at Cornell University (The New York Times 1918), the leading institution in ornithology at the time (Battalio 1998). One of these early meetings (arranged by the American Protective and Propagation Association) included such notable figures as William T. Hornaday, head of the New York Zoological Society, professors at Cornell University, superintendents of the game farms, representatives from the U.S. Department of Agriculture, and the chief of the U.S. Biological Survey (The New York Times 1918).

Another man at the 1918 meeting of these conservation luminaries was W. C. Adams. Adams was the chairman of the Commissioners on Fisheries and Game in Massachusetts, and the man in charge of managing heath hen populations on Martha's Vineyard (The New York Times 1918). Around that time, only a few years after the loss of the passenger pigeon and Carolina parakeet, there was growing concern over the precarious state of the heath hen, once a widespread species in New England and Mid-Atlantic region (The New York Times 1907, 1917; Gross 1923). In 1907, the Massachusetts Game Commission had gathered US$2,000 in private donations for recovery of the bird and was seeking additional money from the state legislature to build firebreaks around breeding grounds and to maintain artificial incubators (The New York Times 1907). Conservation efforts of establishing a preserve for the species in 1908 proved temporarily fruitful, increasing populations to >2,000, but habitat loss due to a wildfire, a series of severe winters, combined with an increase in predators, and disease devastated the single isolated population. By 1924, only 50 birds remained, all on Martha's Vineyard (Gross 1931).

The state of Massachusetts, the Federation of Bird Clubs of New England, and other organizations were involved in the struggle to preserve the heath hen. When the birds were more numerous, they were introduced to Long Island, New York, and the mainland of Massachusetts, but these attempts failed. In addition, attempts were made to breed the birds in captivity, but these attempts also failed (The New York Times 1917; Gross 1931). Despite their best efforts, by 1927, there were only 13 birds left and by winter 1928, only two birds remained. When in 1929 only a single bird remained, requests were made to secure a prairie chicken Tympanuchus spp. or ruffed grouse as a potential mate. These efforts were never realized.

Although attempts to conserve the heath hen failed, they showed that ornithologists had largely broken out of the fatalistic mentality of the late nineteenth century. The fight to save species from extinction was on, and captive breeding was clearly a potential weapon in that fight. According to Gross (1923), in a letter to The Auk, “The response to a questionnaire sent out by Mr. William C. Adams, Director of the Division [of Massachusetts Fisheries and Game] has shown conclusively that public opinion favors saving the Heath Hen at all reasonable costs.” In the April 1923 issue of The Auk's Notes and News section, there was a discussion of Mr. Adam's questionnaire, with the remark that “The saving of the Heath Hen is not a local or State matter but is of interest to the whole country and scientific world” (AOU 1923, p. 379).

After extinction of the heath hen, efforts were already underway to prevent a similar result for the prairie chicken. State game officials in Texas closed down the hunting season of the prairie chicken for 5 y, and captive breeding experiments were attempted by the State Game Department. Although the captive breeding experiments were unsuccessful (Associated Press 1937), there was a growing sentiment that preservation of species had broad public support and was of national interest. Moreover, in 1933, Aldo Leopold, the father of wildlife management, had introduced a novel concept in his paper The Conservation Ethic that would transform the debate of conservation from one of economic expediency and wise use to one of right and wrong (Leopold 1933, 1949). Thus, the stage was set for conserving birds from extinction as an ethical duty, regardless of perceived economic value to society.

Captive Breeding Evolves: Breeding Nongame Birds

Ornithology was growing as a profession in the 1920s and 1930s, but experimental science in ornithology was still in its infancy (Battalio 1998). The model of conservation clubs or state biologists raising game birds to maximize production was still the norm (although see Wood (1926) for a discussion of aviculture in private English aviaries). Furthermore, there were lingering questions regarding some rare species, and whether they were doomed to extinction, thus rendering captive breeding efforts futile.

Loyle Miller (Miller 1942), who was studying New World vulture (Cathartidae) fossil remains at the tar pits of southern California was detecting some interesting trends in the historical abundance of vultures in the fossil record, and opined the following:

Were not teratorns an antiquated group that time had weathered away before we arrived? Is not the California Condor a senile species that is far past its prime? It was widely distributed and numerically abundant in Pleistocene time (Florida, Mexico, New Mexico, Texas, Nevada, California), but now it is restricted to one or two localities and a numberable roster of individuals within the two Californias. Is it not a species with one foot and even one wing in the grave? (Miller 1942, p. 213).

Those who opposed later efforts to take California condors out of the wild for captive breeding would point back to Miller's (1942) paper as an argument against intervening to save the condor. However, Miller's (1942) statement must be put into the context of the time, when the world was at the height of World War II, the techniques for breeding raptors in captivity had not been developed, no one knew the real cause of the recent condor population decline, and expending dollars to conserve rare species would have been toward the bottom of a long list of global priorities.

By the late 1940s, the war was over, science was being reinvigorated both financially and in public opinion, wildlife management was beginning to be seen as a professional endeavor, and the concept of conservation ethics was spreading (Leopold 1933, 1949). In 1948, the International Union for the Preservation of Nature (later to be renamed the International Union for the Conservation of Nature and Natural Resources, or simply the World Conservation Union) was formed by a consortium of governments, national groups, and international organizations at a United Nations Education, Scientific, and Cultural Organization meeting in Paris, with a goal of conserving “the entire world biotic community … on which rests the foundation of human civilization” (Holdgate 1999, p. 33). Fledgling experiments to breed nongame birds in captivity were underway in this era. For example, the AOU Committee on Bird Protection reported attempts to breed whooping cranes Grus americana in captivity in 1949:

Attempts have been made to breed captive birds [Whooping Cranes] in a large enclosure in Texas but the initial clutch proved to be infertile. Another pairing is now being encouraged with a different male bird and the experiment will continue (AOU 1950, pp. 321–322).

Whooping cranes had declined precipitously in the late 1800s and early 1900s, and by 1947, only two birds were known from Louisiana and only 25 from Texas (Hamerstrom 1947). It was clear at this time that extraordinary measures would be necessary to save the species from extinction. By 1957, when it was believed that 27 whooping cranes were left in the world (1 at the San Antonio Zoo, 2 at the New Orleans Zoo, and 24 at the Aransas National Wildlife Refuge on the Texas' Gulf Coast), plans to take several pairs into captivity for a breeding program were considered by the Whooping Crane Advisory Group (consisting of U.S. and Canadian authorities), but not carried out (Time 1957) pending completion of studies on a more common surrogate species.

At the time of the first whooping crane breeding experiments in 1949, the nēnē, or Hawaiian goose Branta sandvicensis, was also on the verge of extinction. Although the nēnē was numerous and well distributed on the main Hawaiian Islands when Captain James Cook landed in 1778, when the Journal of Wildlife Management published Baldwin's (1945) estimate of only approximately 50 birds remaining, all on the Island of Hawaii, the gravity of the situation was apparent. As a result, a breeding program for the nēnē to prevent its extinction began in 1949 by the State Department of Land and Natural Resources Pohakuloa Breeding Facility (Smith 1952; Stone et al. 1983).

Although nēnē had bred at estates and zoological gardens throughout Europe starting in 1823, and in the U.S. mainland (Brown and Canton 1880), they were apparently gone from these collections by the time Germany invaded France in 1940 (Smith 1952). An ill-fated attempt to establish a captive flock and split it up amongst wealthy landowners and menagerie owners on the Hawaiian islands for further breeding was made in the 1920s and 1930s, but those who received the birds lacked the facilities or abilities to raise the birds, and some were simply let loose, whereas a few are thought to have ended up on the dinner table of the farmhands at one of the pineapple Ananas comosus plantations on Lanai (Smith 1952).

At the outset of the breeding program initiated in 1949, it was apparent that unless the causes of decline were addressed, captive breeding would be pointless (Smith 1952). This program also had the foresight to spread the risk to captive birds by establishing two separate flocks—one flock on Hawaii and one flock in England—and to use double clutching (i.e., removing eggs from the nest to induce females to lay a second clutch) and cross-fostering (i.e., having chickens incubate the eggs) to rapidly increase nēnē production (Smith 1952). Captive breeding efforts proved very successful and by 1961, Sir Peter Scott at the Severn Wildlife Trust in England (later renamed the Wildfowl and Wetlands Trust) had a flock of >100 birds and was offering to sell 20 nēnē a year back to the Hawaii at a price of US$22.50 per gosling (AOU 1962).

The early successes of this effort led to captive breeding programs for other Hawaiian waterbirds, including the Hawaiian moorhen Gallinula chloropus sandvicensis, Laysan duck Anas laysanensis, and Hawaiian duck Anas wyvilliana. Captive propagation of Laysan duck was initiated in 1957 at the Honolulu Zoo with the capture of eight ducks and then expanded with the capture of an additional 36 ducks in 1958 that were sent to the Honolulu Zoo for acclimatization and ultimately distributed to eight aviaries in the United States (Honolulu Zoo, Philadelphia Zoological Gardens, San Antonio Zoo, Dr. Jean Delacour, Dr. S. Dillon Ripley, San Diego Zoo, Tracy Aviary, and the Bronx Zoo) and at the Severn Wildlife Trust in England (Ripley 1960; AOU 1962; Warner 1963). This collaboration of breeding amongst multiple institutions, a practice that also was being carried out with the Hawaiian moorhen from 1953 to 1969 (Dibben-Young 2009), represented a new concept in captive breeding, in direct contrast to the provincial and proprietary attitudes of zoological gardens at the time the Carolina parakeet went extinct in captivity in 1916.

Indeed, much had changed over the four decades between the extinction of Carolina parakeets and the captive breeding cooperation being undertaken for Laysan duck. Air transportation was now allowing movement of animals across great distances in a short time, zoos were starting to contemplate their role and responsibilities in endangered species conservation, the field of wildlife management was starting to form into a recognized profession, natural history studies were giving way to experimental research, and the public was starting to accept their ethical duty to conserve species.

However, the focus of avian breeding efforts for endangered species conservation in the 1950s was still heavily rooted in the game farms of the early 1900s and continued to be directed toward those species, or taxa, that were easily bred in captivity or that were valued as a food or hunting resource, primarily ducks, geese, pheasants, and gallinaceous birds (Wildlife Conservation Committee of the Wilson Bulletin 1940; Newman 1945; Sylvester and Lane 1946; Ginn 1947). Although there were a few examples of early efforts to breed nongame birds at this time (e.g., Swedish ornithologists had begun a captive breeding program as early as 1954 to restore eagle owls Bubo bubo, first in Sweden and later in Germany [Wayre 1969, 1975] and a program to breed and reintroduce white storks Ciconia ciconia had been undertaken in Switzerland starting in 1948 [Bloesch 1980; Schaub et al. 2004]), the value of nongame wildlife had not yet been fully realized in most of the world.

But that was about to change. With increasing concern over the impacts of pesticides on wildlife and humans, Rachael Carson's Silent Spring (Carson 1962) hit like an atom bomb in 1962. To Carson, there was an aesthetic value in nature and a connection between the health of nature and our social and physical health. She had made the link between the loss of bird species (i.e., a silent spring) and the concomitant negative effects on society, and the public largely agreed with her argument. Carson's book was an instant best seller that would lead to major changes in environmental laws in the United States as well as overseas. The change in social consciousness associated with Carson's work would spawn a new generation of conservation efforts.

Concurrent with Carson's exposé of the pesticide industry, the Species Survival Commission of the International Union for the Conservation of Nature and Natural Resources (IUCN) was busy generating lists and distribution maps of threatened species throughout the world (later to be formalized in its popular Red Data Books; Scott et al. 1987). These efforts were spawned by several publications highlighting the endangered state of various taxa, including Extinct and Vanishing Birds of the World (Greenway 1958). It was in this context that, in 1966, the Endangered Species Preservation Act (Pub. L. No. 89-669, §§1–3, 80 Stat. 926 [repealed 1973]) was enacted. That act specifically called for the Secretary of the Interior to “carry out a program in the United States of conserving, protecting, restoring and propagating selected species of native fish and wildlife.” Three years later, The Endangered Species Conservation Act of 1969 (Pub. L. No. 91-135, 83 Stat. 275) was enacted, expanding the authorities of the 1966 act and instituting a provision to allow listing of threatened and endangered wildlife worldwide. Although the 1969 act prohibited the importation of foreign wildlife that was endangered, it provided for exemptions in the case of zoological parks or other institutions interested and capable of rearing endangered species in captivity. Despite the lack of regulatory might that would finally come in the form of strict penalties and take prohibitions of the Endangered Species Act (ESA) as amended (ESA 1973, 16 U.S.C. §§1531–1543 [1976 & Supp. V 1981]), the 1966 act was an important milestone as the first national legislation in the world calling for the protection of endangered wildlife. This would soon be followed by the ratification of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (27 U.S.T. 1087, T.I.A.S. No. 8249) in 1975, which aimed to ensure that international trade in specimens of wild animals and plants did not threaten their survival.

Scientific Programs for Breeding Endangered Species

The same year the Endangered Species Preservation Act was passed (1966), the Endangered Wildlife Research Program was established at the Patuxent Wildlife Research Center near Laurel, Maryland, under the direction of the Bureau of Sport Fisheries and Wildlife (an arm of the U.S. Fish and Wildlife Service at the time; Erickson 1975). One of the three divisions of this program was solely dedicated to propagation of endangered wildlife. The other two programs included laboratory science and ecology. Thus, under a single roof, propagation, laboratory science, and ecology were comingling. This was no longer a game farm program to maximize production. Saving endangered species through captive breeding was now a scientific endeavor (an outgrowth of the controlled experiments of the Environmental Contaminants Research Program at Patuxent starting in 1959 when Dr. John L. Buckley became director) that included experimentation on closely related species to work out the best approach for critically imperiled species (Perry 2004).

Such an approach was first used with procuring, incubating, and raising sandhill crane Grus canadensis eggs to provide information that could be eventually be used on endangered whooping cranes starting in 1966 (Erickson 1975, 1980). Erickson's work with whooping cranes eventually led to experiments with artificial insemination and detailed studies of artificial incubation, behavior, and diet (Erickson 1975). In particular, the adoption of artificial insemination techniques, including the use of human imprinted birds to obtain semen, would drastically change the playing field for the captive breeding of endangered avifauna, especially for those species that were not prone to breed on their own when placed together in captivity (Berry 1972; Temple 1972; Grier 1973; Blanco et al. 2009).

In many ways, Erickson's work at Patuxent with whooping cranes—and bald eagles Haliaeetus leucocephalus that were also being bred at Patuxent starting in 1965 (Maestrelli and Wiemeyer 1975; Perry 2004)—changed perceptions about what was possible in captive breeding. As Martin stated in the introduction to the First Conference on the Breeding of Endangered Species in Captivity,

It is noteworthy that the concept of captive breeding, in this instance too [i.e., with Whooping Cranes], initially met with resistance from various quarters, since it was probably felt that conservation in the field can be the only answer. But it is apparent that successful conclusion of the pilot project with Sandhill Cranes will do much to reduce this resistance, whilst at the same time providing a firm factual basis for the main scheme involving Whooping Cranes (Martin 1975, p. xxv).

Many studies at Patuxent followed the whooping crane and bald eagle work, including breeding experiments with the American kestrel Falco sparverius (Porter and Wiemeyer 1970), Aleutian Canada goose Branta hutchinsii leucopareia (renamed Aleutian cackling goose; Springer et al. 1978; Erickson 1980), and peregrine falcon Falco peregrinus (Maestrelli and Wiemeyer 1975). Despite their successes with several species, Patuxent never had any success in propagating peregrine falcons because they used wild-caught migrants, which almost never breed in captivity; something they learned by housing 10 or so pairs for 15–20 y without any breeding success.

The Patuxent group was not the sole faction interested in experimentation with breeding captive birds. In August 1965, Professor J. J. Hickey convened the first international peregrine falcon conference at the University of Wisconsin, where attendees were sobered by the extent and severity of the peregrine falcon population decline (Hickey 1969). Some of the falconers and biologists in attendance were so concerned that at the end of that conference they met to discuss captive breeding as a means of saving the species from extinction (Cade 1986). This rump session, chaired by Donald V. Hunter, Jr, led directly to the formation of The Raptor Research Foundation in 1966, the original purpose of which was to promote the rapid development of captive breeding projects for peregrine falcons and other raptors (Cade 1986, 1988). In its early years, this group played a pivotal role in rapidly disseminating information on husbandry techniques amongst these various groups (Cade 1986, 1988).

At the time The Raptor Research Foundation was formed, most people considered a systematic and reliable raptor breeding program at the scale necessary to recover the peregrine falcon to be unattainable (Cade 1986). Although Renz Waller, a German artist and falconer, had successfully bred peregrine falcons in an old silo near Dusseldorf, Germany, during World War II, attempts to replicate his success in the 1950s in Germany and Britain had failed (Cade 1988). With the magnitude and extent of the peregrine falcon population declines, it was clear that failure was no longer an option.

One of the groups that began experimenting with breeding peregrine falcons after the 1965 University of Wisconsin meeting was The Peregrine Fund, a nonprofit organization led by Tom Cade, a professor at Cornell University and a veteran falconer (Cade 1986). The fund had humble beginnings, starting with unsolicited donations to the Laboratory of Ornithology at Cornell from private citizens hoping to help save the peregrine (Burnham and Whaley 2010). The first donation (of US$2) came from two boys in California that wrote to the Laboratory of Ornithology on October 5, 1970:

Dear Sirs:

Me and my Friend have been studying birds, especially Peregrine Falcon[s]. One day he came over and showed me a newspaper article about you trying to help save Peregrine[s], so we have been going around collecting money to help your project. I hope every thing works out alright. Sincerely Yours, Orin Starn and Jay Hart. Burnham and Whaley (2010, p. 2).

Shortly thereafter, the Massachusetts Audubon Society made a substantial contribution to the laboratory (Burnham and Whaley 2010). With the establishment of the ESA in 1973, numerous additional funding sources were available; and Bob Berry, Frank Bond, Jim Weaver, and Tom Cade officially founded The Peregrine Fund as a nonprofit organization the following year (Burnham and Whaley 2010). Cade took the published knowledge on artificial insemination, artificial incubation, nutrition, hand-rearing, socialization of young, fostering and cross-fostering, and reintroductions, and combined it with his and his colleagues' knowledge of falconry to create the most successful raptor propagation program in the world (Cade et al. 1988; Cade 2000; Cade and Burnham 2003). Cade's research program proved to be a stunning success and The Peregrine Fund raised 434 peregrine falcons, 40 gyrfalcons Falco rusticolus, 50 lanner falcons Falco biarmicus (from a single pair), and 80 prairie falcons Falco mexicanus within 10 y (Cade 1980; Cade et al. 1988). By the turn of the century, >7,000 peregrine falcons had been produced in captivity and released into the wild by The Peregrine Fund, Patuxent, the Canadian Wildlife Service, and other sources (Cade and Burnham 2003). Furthermore, the techniques developed for peregrines proved useful for other species, with conservation breeding and reintroductions having been carried out on Mauritius kestrels Falco punctatus, lesser kestrels Falco naumanni, aplomado falcons Falco vespertinus, orange-breasted falcons Falco deiroleucus, bearded vultures Gypaetus barbatus, griffon vultures Gyps fulvus, bald eagles, white-tailed sea eagles Haliaeetus albicilla, harpy eagles Harpia harpyja, and other raptors (reviewed by Cade 1986, 1988, 1997). What had been considered a pipe dream only a few years earlier by most had been transformed into a reality as The Peregrine Fund and others advanced the field of aviculture through a program that combined the traditional knowledge accumulated over centuries by falconers with modern scientific inquiry.

Lessons learned from the raptor breeding programs at The Peregrine Fund were exported to other avian taxa, including parrots, cranes, and to a lesser extent, passerines. George Archibald, one of Tom Cade's students at Cornell University, embraced the philosophies and techniques developed by The Peregrine Fund and Patuxent and applied and refined these techniques for use on cranes. In 1972, Archibald and Ron Sauey founded the International Crane Foundation, a nonprofit organization dedicated to the study and preservation of the world's crane species (Archibald 1974, 1996/1997). The International Crane Foundation specifically sought to maintain in captivity 15 unrelated breeding pairs of each threatened crane species in captivity as a safeguard against their extinction (Archibald 1974), although the primary interest of the foundation was the welfare of cranes in the wild (Archibald 1996/1997). Through carefully designed manipulative experiments and close attention to pair bonding, territory size, conspecific isolation, species-specific behavior, and the physiological and psychological needs of young, the International Crane Foundation, in coordination with Patuxent, developed a modern scientific approach to breeding cranes (Luthin et al. 1986; Ellis et al. 1996).

Wildlife programs in other parts of the world were also starting to experiment with innovative approaches to captive breeding in the 1960s and 1970s, most notably, New Zealand and Australia. In New Zealand, captive breeding efforts were attempted with the critically endangered and flightless kakapo parrot Strigops habroptilus. Although initial attempts failed because the six birds brought into captivity were all males (Clout and Craig 1995), techniques that combined artificial incubation and hand rearing of chicks with translocation to island refugia, supplemental feeding and nest monitoring in the wild, eventually proved fruitful (Elliott et al. 2001). Captive breeding also was attempted with the flightless takahē Porphyrio hochstetteri in the 1960s through the taking of eggs from the wild. As with the kakapo, initial attempts failed, but through a series of experiments, researchers eventually developed a successful captive breeding program (Clout and Craig 1995).

In Australia, the Victorian Government had established a wildlife research station in 1959, known as Serendip Sanctuary outside Melbourne to study, breed, and reintroduce species that had become rare or extinct in Victoria (Ziembicki 2010). One of the species the program began breeding in the mid-1960s was the Australian bustard Ardeotis australis. Researchers at the station recreated the bustard's natural lek mating system in captivity by constructing an elaborate enclosure that allowed females to select the mate of their choice but that prevented the males from direct contact with each other (Ziembicki 2010). Other captive breeding programs in Australia to prevent avifauna extinctions followed, including conservation breeding of orange-bellied parrot Neophema chrysogaster (Orange-Bellied Parrot Recovery Team 1999), helmeted honeyeater Lichenostomus melanops cassidix (Smales et al. 1992), regent honeyeater Xanthomyza phrygia (Menkhorst et al. 1999), and black-eared miners Manorina melanotis (Baker-Gabb 2003).

With government and nonprofit organizations conducting scientific evaluations of captive breeding, by the end of the 1970s many of the modern-day husbandry methods for breeding endangered birds in captivity had been worked out (Erickson 1980), although more sophisticated approaches to demographic and genetic management of captive populations and methods for minimizing behavioral problems in released birds were only beginning.

The Changing Role of Zoos in the 1960s

While Erickson's lab was at work experimenting with breeding endangered species, the public was reacting to Carson's Silent Spring, and Congress was busy putting protections in place for endangered species, zoos were undergoing a sea-change in culture that would be critical to the development of coordinated captive breeding programs.

In 1959, the first zoological park specializing in endangered species conservation, the Jersey Zoological Park, was founded by Gerald Durrell on the small island of Jersey in the English Channel. According to Durrell (1990), all the authorities in the zoological community he consulted on the project told him that his plan to establish a zoo for the conservation of endangered species, which required him to take out a £25,000 loan, was foolish and destined to fail. Durrell (1990, pp. 17–18) was undeterred and reflected on his endeavor:

What I had in mind was an almost completely new concept of the motivation of a zoological garden. Its first major objective should be to act as an adjunct to the whole conservation movement by the setting up of viable breeding colonies of those endangered species whose numbers had dropped so drastically that they could no longer cope with the hazards of life in the wild. This should in no way be misconstrued (as it has been by some conservationists) as an action that merely confined these animals to captivity. The idea was that the captive colonies should be set up merely as a safeguard against extinction, while the most stringent efforts should be made to preserve the wild habitat and wild populations of the species concerned and to release back to the wild captive-bred animals when their habitat had been made sage. This, it seemed to me, was a zoo's major raison d'être.

Durrell drew some of his grand vision from Jean Delacour, a French aviculturist who, after World War I, had the dream of creating a Garden of Eden on Earth (Mayr 1986). According to Ersnt Mayr (1986), Delacour succeeded as closely as is practical by establishing the finest private zoological park in the world at Chateau Clères in Normandy, France, before World War II (Mayr 1986). It was there that he laid the foundations for current aviculture of rare and exotic birds, especially pheasants and waterfowl and was a major influence on the next generation of conservation breeders, including Durrell, who considered Delacour “the most incredible aviculturist and ornithologist” (Botting 1999).

The year after the establishment of Durrell's zoo, volume 1 of The International Zoo Yearbook (hereafter Yearbook) was published by the Zoological Society of London, representing the first authoritative channel for the international exchange of information about zoos (Jarvis 1967; Olney 2003). Information on the latest breeding techniques could now be easily shared with a large number of zoos in short order, meetings could be coordinated, and a network could be formed for sharing breeding stock. Furthermore, the editors of the Yearbook began to solicit and compile information from all known zoos on breeding successes, research, rare animals, and several other subjects (Jarvis 1967). By 1966, Yearbook editors were sending questionnaires to 588 zoos. The reach of the Yearbook was summed up by its editor Caroline Jarvis in 1967:

[The Yearbook] is bought not only by zoos but by zoologists in universities and scientific research institutes from Ulan Bator in Outer Mongolia, to Novosibirsk in Siberia, Anchorage in Alaska and Mount Hagan in Western New Guinea (Jarvis 1967, p. 131).

In the United States, increasing interest in breeding endangered species in zoos resulted from the incorporation of the Wild Animal Propagation Trust (a coalition of 19 U.S. zoos, lead by the Bronx Zoo) under the aegis of the American Association of Zoological Parks and Aquariums in 1963 (Hunt 1964; Conway 1969). This was followed by a series of international symposia and conferences to discuss the role of zoos in wildlife conservation, first in London in 1964 (Fitter 1967) and then in San Diego in 1966 (Durrell 1975). It was out of these conferences that the idea of conserving endangered species in captivity would expand beyond the small island of Jersey in the English Channel and move toward the top of the international agenda for zoos. By that time (in 1963), Durrell had paid back his bank loan and formed the Jersey Wildlife Preservation Trust (later renamed the Durrell Wildlife Conservation Trust; Durrell 1990). His trust still is extremely successful, helping to prevent the extinction of many species through captive breeding. Perhaps the trust's most noteworthy success is the program it established on Mauritius, under the supervision of Carl Jones (Durrell and Durrell 1980; Jones and Hartley 1995). Jones and colleagues, with the assistance of The Peregrine Fund, developed a scientifically based captive breeding program that restored viable populations of several critically endangered birds, including the Mauritius kestrel, Mauritius fody Foudia rubra, pink pigeon Columba mayeri, and echo parakeet Psittacula eques (Jones and Hartley 1995; Jones et al. 1995; Jones 1999, 2008).

At the 1966 conference regarding the role of zoos in wildlife conservation, William Conway, Director of the New York Zoological Society, presented a paper—later published in Oryx (the journal of the Fauna Preservation Society)—entitled The Opportunity for Zoos to Save Vanishing Species (Conway 1967). In this landmark paper, Conway built upon the focus of the San Diego Conference and argued that zoos around the world had an obligation to cooperate in the conservation of endangered species (something that Durrell had been arguing since the 1950s). He calculated that with such cooperation, it would have been possible to save at least 58 extinct birds, including the elephant birds (Aepyornithidae), lesser moas Anomalopteryx spp., dodo Raphus culcullatus, great auk, and Carolina parakeet. He noted that most endangered species in the 1960s were not even being kept in potential breeding groups (Conway 1967) and called for broad changes in how zoos interact with one another. His ideas would get greater readership outside of the zoological community a few years later when he restated his arguments in the journal Science (Conway 1969).

Although there was growing rhetoric regarding the changing role of zoos, the hard work of actually instituting the change would take longer. As Jarvis (1967) noted, “At the moment it is true to say that in the majority of zoos rare animals breed despite the zoos rather than because of them” (Jarvis 1967, p. 134).

Among the problems at the time, were the refusal to cull inferior or aged specimens, the common practice of selling off young zoo-bred stock and keeping too few animals in breeding groups (Jarvis 1967), and the lack of genetic information to help sex birds and discourage inbreeding. Furthermore, few zoos were keeping sufficient records for individual animals (Jarvis 1967; Durrell 1990). For some species, there was little or no incentive to breed them in captivity, especially for those species that were difficult to maintain in breeding groups due to space limitations. As Wayre (1969, p. 47) noted, “It was easier and cheaper to buy freshly-trapped replacements.”

Furthermore, not everyone was sold on the idea of captive breeding as a viable means to prevent extinctions, reminiscent of Loyle Miller's (1942) “one wing in the grave” argument. Vandenberg (1975, p. 85), after discussing some problems with breeding the Congo peacock Afropavo congensis, asked the following:

Should we not then ask ourselves whether some species, which have now become rare, and for the conservation of which cultural and scientific zoological gardens are making the greatest of sacrifices with little marked success, are not doomed to disappear and whether man's interference in these cases is fully justified?

Others were expressing concern about the loss of selective pressures when birds were brought into captivity. Matthews (1973) noted,

There is the distinct risk of a change in the genetic constitution of the population during its time in captivity. Many natural selection pressures, such as predators, food shortage, inclement weather, are removed. An aviculturist would be justly pleased if he raised a complete brood from hatching; yet he will, in fact, be dulling the edge of natural selection …. Few aviculturists are sufficiently ruthless to eliminate even those showing marked defects if the species is very rare. Few are even sufficiently methodical to avoid breeding from such birds (Matthews 1973, p. 9).

Despite these, and other, cautions (e.g., Myers 1979), by the end of the 1970s, captive breeding of endangered species was an accepted method, albeit a last resort, to conserving critically endangered wildlife and many zoos had accepted their role to act responsibly and cooperatively in this endeavor. Moreover, endangered species were now fully protected under the law in the United States, and other countries would soon follow their lead, facilitated by the growing role of the IUCN's Species Survival Commission in organizing international symposia and coordinating the publication of Red Data Books, which detailed species threatened with global extinction (see Scott et al. 1987 for a history of the Red Data Books). However, the methods for deciding which rare individuals to trade between zoos were not yet quantitative or formalized.

It was not until 1979, when Katherine Ralls and Jonathan Ballou, researchers at the National Zoo, in Washington, D.C., found a correlation between inbreeding and juvenile mortality rates for 16 species of captive animals, that the need to keep track of individual pedigrees became apparent (Ralls et al. 1979; Ralls and Ballou 1986). Follow-up studies on 44 species confirmed the results and according to Hancocks (2001, p. 142), “Intensive Population Management became the new catchphrase, and the American Association of Zoological Parks and Aquariums (now known as the AZA) began to strenuously promote the breeding of animals in genetically regulated programs.”

Although studbooks had been kept for a handful of wild species before Ralls and Ballou's work, starting with the American bison in 1932, there were only eight studbooks for wild animals by 1966, when the first studbook list appeared in the Yearbook (all for mammals), but the number increased to 38 in 1979 and to 61 in 1984 (Glatston 1986). The increased number of wild animal studbooks was a clear reflection of the need for pedigrees to help guide the demographic and genetic management of captive breeding programs, especially for imperiled species (Haig and Ballou 2002). By the mid- to late 1970s, there was also recognition that a single body to coordinate management of studbooks and facilitate cooperation amongst zoos was necessary (Martin 1975). Thus, in 1979, the Captive Breeding Specialist Group (later renamed the Conservation Breeding Specialist Group) of the IUCN's Species Survival Commission was formed to promote global partnerships and collaborations in ex situ species conservation programs. Among other things, the Captive Breeding Specialist Group connects all the regional breeding programs, as well as universities and wildlife management institutions in a global network, facilitates assessments of the need for conservation breeding programs, and formulates global breeding strategies (Ebenhard 1995; Byers and Seal 2003).

With the expansion of studbook data, the organization of a central body to coordinate captive breeding efforts, emerging methods to amplify and analyze DNA, and the invention of personal computers, population biologists and geneticists began to develop quantitative models for pairing animals to maximize founder contributions and minimize the risk of inbreeding (Haig et al. 1990; Ebenhard 1995; Frankham 1995). During this time, there was also a growing recognition of the need for behavioral, physiological, and nutritional considerations in pairing and breeding endangered animals in captivity (Dunn 1986; Kear 1986; Wielebnowski 1998); and by the late 1990s, a modern integrated approach to captive management was in place:

Now [in 1998] the need for a broader approach to captive management has been recognized (e.g., Hutchins et al. 1995; Maillinson 1995) and research efforts incorporating behavior, nutrition, disease, physiology, genetics, population biology, and various interdisciplinary studies are seen as necessary to facilitate responsible and successful captive propagation and conservation (Wielebnowski 1998, p. 137).

This modern integrated approach has resulted in consistently successful breeding programs for some bird groups (e.g., gamebirds, waterfowl, cranes, parrots, raptors, Australian finches [Passeridae], and fringillid finches [Fringillidae]); however, some species have proven difficult to breed in captivity. For example, attempts to breed the ‘alalā or Hawaiian crow Corvus hawaiiensis in captivity have been ongoing since 1973 (Duckworth et al. 1992; Banko et al. 2002), but success in breeding and releasing the ‘alalā has, so far, proven elusive, despite the involvement of numerous ornithologists and aviculturists. As the latest recovery plan for the species indicated (U.S. Fish and Wildlife Service 2009, I-16–I-17),

In general, this species does not breed well in captivity: pairs require separate aviaries, many potential mates prove to be incompatible, infertile eggs are common, and males tend to interfere with egg laying and incubation. In addition, inbreeding is apparently affecting fertility and reproductive outcomes (Zoological Society of San Diego, unpublished data).

Currently, the ‘alalā is extinct in the wild and numbers <60 individuals in captivity. It is too soon to tell whether captive breeding will prove successful in saving the ‘alalā from extinction, but, at this point, it is the only hope.

Controversy in Modern Conservation Breeding Programs

Despite the fact that captive breeding programs had grown out of their infancy by the 1980s, most breeding efforts had, until then, involved managing a captive population while at least some individuals of the species persisted in the wild. By 1980, when the California Condor Research Center was founded in a partnership between the National Audubon Society and the U.S. Fish and Wildlife Service, it was obvious that a vigorous captive breeding program would be necessary to save the species (Kiff 1990). Although the intent of the breeding program, which was initiated in 1982, was to leave several birds in the wild to serve as mentors to captive-released birds, between November 1984 and April 1985, 9 of the remaining 15 birds in the wild vanished (i.e., they were probably killed by wanton shooting or lead toxicosis from eating carcasses shot with lead ammunition; Kiff 1990). Notwithstanding internal acrimony and public outcries, the decision was finally made in December 1985 to bring all remaining birds in for a captive breeding program and on April 19, 1987, the last wild condor was captured.

This decision to capture all wild condors fractured relationships between wilderness advocates (also know as preservationists, for which the condor had become an unofficial symbol in California; Phillips and Nash 1981) and scientists (also known as conservationists) who advocated captive breeding as the only remaining hope for the species' survival (Rickleffs 1978). As Alagona (2004, p. 568) stated,

[To preservationists] condors and wilderness existed in a mutually dependent, symbiotic relationship. Condors embodied wild nature and justified the protection of wilderness areas as critical endangered species habitat; in return, wilderness endowed the condor with its symbolic capital. Some took this argument even further, claiming that real condors only lived in the wilderness and that intensive scientific management by definition robbed them of their wild essence. Condors would be better off left alone under any circumstances, even if doing so led to their extinction.

To preservationists, captive condors would be nothing more than “feathered pigs” (Alagona 2004). Despite their rally cries to leave the condors alone in the wilderness to die with dignity, or to stop wasting scarce conservation resources on a bird that was past its time (Pitelka 1981, 1982), the conservationists won out, and an intensive captive breeding program successfully rescued the California condor from the very brink of extinction (Snyder and Snyder 2000). A similar controversy erupted shortly thereafter on the Big Island of Hawaii over capturing wild Hawaiian crows for a captive breeding program (see Walters 2006). As William Conway, Director of the Bronx Zoo, noted in his 1986 paper entitled The practical difficulties and financial implications of endangered species breeding programs (Conway 1986, p. 218),

Thus far, the international conservation community has not seriously faced up to the need to support the acquisition of animals in danger of extinction for captive breeding. Although support has been given to the proposals for the capture of a few animals, the Kouprey Bos sauveli, the Tamarau Bubalus mindorensis, the Arabian oryx Oryx leucoryx, the California condor Gymnogyps californianus and several birds recently rescued from Guam (where seven of its 15 species have become extinct during the past year), in no case has this occurred until the species was nearly extinct, the chances of propagation poor and the opportunity to obtain representative founder stock lost.

Unfortunately, this paradigm has persisted (e.g., puaiohi Myadestes palmeri; Tweed et al. 2006), po'ouli Melamprosops phaeosoma (VanderWerf et al. 2003, 2006), and Maui parrotbill Pseudonestor xanthophrys (Becker et al. 2010). Exceptions are rare and are generally limited to species where there are utilitarian motives. One such exception is the conservation breeding program for the houbara bustard Chlamydotis undulate carried out by the National Avian Research Center, Environmental Research and Wildlife Development Agency of Abu Dhabi and its major satellite operation the Emirates Center for Wildlife Propagation in Missour, Morocco. It is the largest, most expensive, most expansive breeding restoration program for any avian species since the peregrine falcon (the breeding facility in Missour consists of 2,500 individual cages for adult breeders, an incubation building that can incubate up to 40,000 houbara eggs per year, a rearing complex, and a prerelease facility that can hold >2,000 birds; Emirates Center for Wildlife Propagation 2010). The captive breeding effort was initiated in 1986 at Taif, Saudi Arabia, in response to declining populations of houbara bustards, which have significant cultural value in the Middle East, North Africa, and Asia, where they have been the favored quarry of falconers for centuries (Saint Jalme et al. 1996). A program of scientific inquiry into breeding and release techniques has resulted in a remarkable program of artificial insemination, artificial incubation of eggs, imprinting captive breeders to humans, and careful artificial rearing of young destined for release to ensure that they do not imprint on humans (Saint Jalme et al. 1996). Although international guidelines suggest that reintroduction programs should be considered only if the factors that caused the decline are eliminated or sufficiently reduced (IUCN 1987), the apparent success of the houbara captive breeding and reintroduction program demonstrates that with adequate institutional support and funding, it may be possible to produce enough birds to effectively combat the declines caused by falconers, at least at a local scale (Bailey et al. 1998). Some have argued that without bustards to hunt, traditional Arab falconry is finished, and without Arab falconry, the houbara is finished, because no other group in the world has such a passion for conservation of this bird (Bailey et al. 1998). Whether captive breeding efforts will eventually help recover the houbara throughout Asia, where populations are still in decline and threats are increasing (largely from falconry and poaching), remains to be seen (Tourenq et al. 2005; Stone 2008).

The Ark Paradigm

Controversy over the efficacy of captive breeding has been debated since its inception as a species conservation tool. However, it was during the 1980s that a few biologists and zoo directors were arguing that governments, zoos, and scientists needed to do much more if they were going to prevent looming mass extinctions. Some of them were starting a new society, The Society for Conservation Biology, to figure out how best to conserve the Earth's biodiversity.

In 1986, Michael Soulé, one of the architects of the Society for Conservation Biology (who earned a Ph.D. under Paul Ehrlich, author of The Population Bomb [1968]), along with William Conway of the New York Zoological Society and others wrote an apocalyptic paper entitled The millennium ark: how long a voyage, how many staterooms, how many passengers? (Soulé et al. 1986). In it, they predicted a coming demographic winter lasting between 500 and 1,500 y in which mass extinctions will occur as human populations expand beyond their resources. They argued that saving species will require that zoos devote most of the space in zoos to the captive breeding of endangered species. However, unlike Noah's Ark, this would entail more than just keeping two of each species; it would require managing populations, which would stretch the resources of zoos (also see Conway 1986). They believed that with advances in technology over the next 200 y, it would be possible to transfer from a “living zoo” to a “suspended zoo” where genetic information from each species is frozen in time until the end of the demographic winter of humans (i.e., after society collapses), and even the possibility of transporting these miniature zoos to the dark side of the moon for cold storage.

Although their ideas were not entirely new—Jarvis (1967) had suggested a “wild animal bank” in 1967, Conway (1967) had talked about the need for someone to play the role of a “stern Noah with little space in his Ark”, and Wayre (1969) had warned of massive habitat destruction in the wake of future population growth and the need to breed more endangered species in captivity—the use of computational tools to estimate the number of animals, the amount of space, and the amount of time needed to conserve endangered species was novel. The concept of miniaturizing zoos was also new.

Following this landmark paper, in September 1987, the IUCN adopted a policy statement on captive breeding that had wide-ranging implications (IUCN 1987; Bennett 1990). With the spread of personal computers and enhanced genetic techniques, quantitative tools for genetic and demographic management became more sophisticated. This new technology coupled with the successes of some breeding programs led the IUCN to suggest that approximately 3,000 species worldwide needed some form of captive breeding program (Ebenhard 1995).

Others would soon co-opt the Ark paradigm to promote increasing the capacity of zoos and increasing the number of captive breeding programs. However, not everyone rallied behind the call for proliferation of breeding programs, because so many had failed (Griffith et al. 1989). In 1996, Noel Snyder, the lead scientist in efforts to save the California condor from extinction in the 1980s, and colleagues published an article in Conservation Biology entitled Limitations of captive breeding in endangered species recovery (Snyder et al. 1996) in which they noted the surge in recovery efforts that were calling for long-term breeding associated with the Ark paradigm. Although they acknowledged the critical role captive breeding played in saving several species from extinction, they expressed concern that not enough care was being given to fully evaluating the limitations of captive breeding, especially for short-lived species that could quickly lose genetic diversity and become domesticated without the forces of natural selection (see Sheppard [1995] for a discussion of space limitations for long-term captive breeding of endangered birds). They also warned of the enormous costs and resources necessary to successfully implement captive breeding programs, which are largely dependent upon economic forces and continued public support for sustenance. Snyder's admonition of Ark paradigm promoters was undoubtedly influenced by his involvement in several conservation breeding efforts that were having difficulty achieving recovery, including efforts for the California condor (Snyder and Snyder 2000), thick-billed parrot Rhynchopsitta pachyrhyncha (Snyder et al. 1994), and the Puerto Rican parrot Amazona vittata (Snyder et al 1987).

Despite this and other critiques (e.g., Balmford et al. 1995), the Ark paradigm is very much alive today (Bowkett 2009). However, even with advances in cryogenics, extracting ancient DNA, artificial insemination, in vitro fertilization, embryo transfer, and cloning technologies, we are not close to realizing the miniaturized millennium ark that Soulé et al. (1986) had envisioned. This is not all bad because there seems to be a consensus among conservation biologists that without concurrently conserving habitats and reducing or eliminating other causal mechanisms responsible for species' declines, the ark might as well be put on the dark side of the moon.

Insights for Addressing the Current Extinction Crisis

The chronicle of captive breeding efforts in avian conservation has only just begun. We are currently faced with pending bird extinctions that rival mass extinctions recorded in the fossil record, with threats from habitat destruction, invasive species, disease, and a changing climate. In particular, the threat of climate change has led some to call for increased attention to captive breeding, in lieu of ecological gambling on novel and untested approaches, such as assisted colonization and assisted migration (Ricciardi and Simberloff 2009). From this brief survey of the history of captive breeding in avian conservation, there are five insights that are applicable to our present situation and the future of all living things.

1) A fatalistic attitude is a sure path to extinction

Inaction will not solve the problems currently facing threatened species. As with the passenger pigeon and Carolina parakeet, deciding to do nothing will simply add more species to the long list of extinct birds (see Fuller 1987 for this list) and will ignore “our bare duty to posterity to hand [a] fauna down as we found it, or as nearly so as the reasonable exigencies of life will admit” (Dixon 1889). Furthermore, no species is “doomed to extinction” unless we decide it is. As Soulé (1987, p. 181) so aptly put it, “There are no hopeless cases, only people without hope and expensive cases.” Believing that species have a destiny to go extinct ignores the all-encompassing impacts that humans have had on our planet. At best it is a form of denial; at worst, obfuscation to promote a competing agenda.

2) Bold action, political fortitude, and conservation leaders required

Preventing the extinction of critically endangered birds by using captive breeding is possible, but it often requires bold action, political fortitude, and strong conservation leadership. The leaders of past generations (AOU founders, Audubon Society founders, William Temple Hornaday, and others) that thought it necessary to stand up against the millinery industry saved tens, maybe hundreds, of bird species from extinction. Gerald Durrell pioneered a new approach to zoological gardens on the small island of Jersey with a bank loan and a dream. Ray Charles Erickson of the Patuxent Endangered Species Research Center, Tom Cade of The Peregrine Fund, and other aviculturists and ornithologists around the world boldly pressed forward with rigorous research agendas to develop the technical means of breeding endangered species, even as others told them it was impossible. Rachel Carson's exposé of the pesticide industry helped catalyze the environmental movement, culminating in a cascade of international environmental protections. Because of these leaders, and those they inspired, we have healthy populations of bald eagles, peregrine falcons, and waterfowl. In addition, many bird species, including nēnē, several crane species, Mauritius kestrels, kakapos, and California condors, are on the path to recovery. However, the war is not won, and many contentious battles remain to be fought if we want to save endangered birds. Recently, much political rhetoric has been expended on the need for partnerships in conservation. Although this need is undoubtedly true, it is either naïve or insincere to believe that we can overcome the pending extinction crisis without significant conflict. Strong conservation leaders will be needed to take bold actions and navigate this conflict to conserve biodiversity, “on which rests the foundation of human civilization” (Holdgate 1999, p. 33).

3) The longer we wait, the greater the risk

Waiting until species are almost gone precludes conservation options and increases costs and extinction risk. As we observed with the last-ditch efforts to save a small population of the heath hen on Martha's Vineyard, unforeseen stochastic events (i.e., fire followed by increased predation and bad weather) can quickly decimate small isolated populations. Even though the public, politicians, and biologists were unanimously agreed that the species must be saved, they had waited too long. The same fate almost befell the nēnē, kakapo, whooping crane, and California condor, which we rescued just in time.

4) Global events matter

Wars, disease outbreaks, famine, and other calamities have affected the prioritization of avian conservation and will probably do so in the future. We must prepare for these events by having redundancy in our conservation network and our breeding programs and by paying careful attention to how global climate change is likely to affect habitats of those species we raise in captivity and release into the wild. Continued international communication and cooperation amongst breeding institutions also are critical to success (Conway 1986).

5) Captive breeding is not a panacea

The fact that birds produce eggs and that some species can be induced to do so in relatively rapid succession makes captive breeding endangered avian taxa an alluring, and sometimes rewarding, proposition (Dixon 1986; Snyder et al. 1996). However, as William Temple Hornaday alluded to in the beginning of the twentieth century, and as many have restated since then, saving a species from extinction requires more than just breeding efforts in a metaphorical ark. Without simultaneous or preemptive efforts to eliminate the threats that caused endangerment in the first place, the ark will never find land. Although there are some species that can be successfully released into human-modified environments (e.g., peregrine falcon and Mauritius kestrel), these species seem to be the exception rather than the rule.

In short, history tells us that captive breeding efforts to save birds from extinction will not be easy, will not come cheap, and will not be without critics. However, when we combine optimism with burgeoning technology, innovation, rigorous scientific inquiry, and conservation leadership, captive breeding programs—in close partnership with in situ conservation efforts—have been, and continue to be, a critical tool in preventing avian extinctions.

Acknowledgments

I thank Susan Haig, Tom Cade, and an anonymous reviewer for sharing their extensive knowledge of avian captive breeding programs and for providing valuable comments on earlier versions of this manuscript. I also thank an anonymous reviewer, the Subject Editor, and the Editor-in-Chief for their helpful comments and suggestions. Last, but not least, I thank Mike Osborne for providing me with the motivation to delve into the history of science.

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Author notes

Jesse D'Elia*

D'Elia J. 2010. Evolution of avian conservation breeding with insights for addressing the current extinction crisis. Journal of Fish and Wildlife Management 1(2):189–210; e1944-687X. doi: 10.3996/062010-JFWM-017