A second part of the explanation has to do with the rapid and free exchange of information among raptor breeders throughout the world (Cade, 1986a). This exchange has followed the very best tradition of open scientific inquiry, unlike the secretive activities of some aviculturists.
Finally, successful raptor propagation owes much to the application of basic scientific information on avian reproductive physiology and breeding behavior and ecology. One quick example makes the point.
One of the chief bottlenecks hindering the mass production of raptors in captivity has been the frequent failure to achieve fertilization of eggs because of incompatibilities between mates. Thus, breeders must often resort to artificial insemination of egg-laying females. Obtaining usable quantities of semen from male raptors by the standard poultry method of physical massage and forced ejaculation is difficult and yields only small volumes of material over a short time (Weaver and Cade, 1983).
Since the work of the German ethologists Oskar Heinroth and Konrad Lorenz, it has been known that under certain conditions birds reared in isolation from members of their own species will become sexually imprinted on their human keepers and will actually attempt to mate with them. A fascinating body of scientific literature has developed on this subject (Brown, 1975; Immelmann, 1972; Lorenz, 1937). Raptor breeders have capitalized on this information and on their own experiences with hand-reared hawks and falcons raised in isolation to develop human-imprinted raptors into highly effective semen donors for artificial insemination. The birds are usually trained to copulate and ejaculate on a special hat worn by the human companion. Such birds produce copious volumes of high-quality semen for 2 to 3 months and have been great assets in increasing the percentage of fertile eggs laid in raptor breeding projects (Weaver and Cade, 1983).
Other examples of how basic scientific research has provided information useful to propagators involve incubation, photoperiod, hormone physiology, and psychobehavioral factors such as courtship displays, nest-site stimulation, and other factors, which Lack (1937) referred to as “psychological” in nature (Cade, 1980, 1986b).
There have been more than 1,670 attempts to establish avian species in outdoor environments, according to the excellent summary by Long (1981). At least 425 (25%) of these have been successful in establishing breeding populations. For example, in attempts to establish 119 species in North America up to 1980, success was achieved for 39 (37%) species. Comparable figures for Europe are 69 attempted and 27 (31%) established; for the Hawaiian Islands, 162 attempted and 45 (28%) established; for New Zealand, 133 and 38 (29%); and for Australia, 96 and 32 (33%).
Most of these have been introductions of exotic species into a new range. Some of these exotics have caused ecological or economic problems, but others appear to have filled vacant niches without seriously disrupting other species in the ecosystem (Long, 1981). There is much to be learned from careful study of these