Abstract
Recognizing the premise that importation of exotic birds will not continue indefinitely, emphasis must be placed upon self-sustaining captive breeding programs. The question that arises, however, is if birds are properly established in a proper breeding environment, won't they successfully rear their own young? The answer involves a basic difference in the dynamics of a wild population as opposed to a captive population. Wild populations rely upon mediocre results on a large scale. Captive populations generally are a "boom or bust". Until the proper breeding requirements are discovered, exotic bird breeding is on a very sporadic and rarely self-sustaining basis. However, once the requirements are outlined, the population virtually explodes, as we have seen with many forms of gallinaceous birds.
Unfortunately, if a breeder is working with a relatively small number of birds, or, as is commonly the case, he is working with a single pair, he may not have a compatible pair, or if compatible, he may not have a breeding pair. Commonly, under the best conditions, he will observe his birds attempting to nest but find they are falling short in terms of hatching the eggs or rearing the young. Even if the adults do rear their young, a bird successfully nests only once or twice a year, and the number of young that will be successfully reared may only amount to one or two. If one of the adults is lost after a few years, the breeder may find himself in big trouble. In short, we generally do not have sufficient space or enough time to rely upon "natural" breeding cycles.
The obvious approach to this problem from a technological point of view is to limit the bird's activities to only what is required to maximize reproductive potential. In this situation, the birds are only needed to lay fertile eggs with the incubation and rearing to be left to an alternative means which may involve handraising or foster parents.
This is a commonly used technique for waterfowl and gallinaceous birds, due to the simple care involved. It has not been applied to non-gallinaceous birds due to the problems involved such as: I) few eggs being laid; 2) difficulty in artificial incubation, and 3) difficulty in handrearing, particularly with altricial birds.
As discussed in previous articles, there are successful methods to increase the number of eggs laid (Watchbird Nov. 76) and to hand-raise the young of altricial birds (Watchbird April 76). These techniques are certainly in an experimental stage and I would prefer to allow the adults to incubate and rear their own young, but feel that the establishment of self-sustaining populations will rely upon the development of these techniques. With the present large collection the Los Angeles Zoo maintains, there are pairs that constantly break their eggs if they are not removed. This provides us with the eggs to work with. Results to date have been mixed, but encouraging. Our Stanley cranes normally lay a single clutch of two eggs each year. Through removing the eggs, the birds continue to lay and at the year's end we collected 16 eggs and successfully reared five chicks. Our Harpy eagles laid several fertile eggs which unfortunately failed to hatch under our standard incubation procedure. What works for chickens also works for cranes but not for Harpy Eagles. In checking with several major zoos and institutions, I found wide variances in settings and procedures for temperature and incubation controls. Numerous changes were proposed it was a haphazard approach.
At this point. when all seemed lost, to my pleasant surprise l learned of three UCLA graduate students who were doing studies into this problem. with very interesting results. Don Hoyt designed and commenced research by charting temperature fluctuations through the use of thermocouplers implanted in infertile eggs, refilled with fluids, and replaced in the nest. Dave and Carol Vlect are presently continuing these studies. Their preliminary results documented several important factors, including the natural incubation temperatures, the frequency of eggs being turned, and through measurements of weight loss and eggshell thickness, the necessary humidity. In addition to the above data, we also discovered, as was to be expected, that birds are individuals. Birds that break their own eggs also break thermocoupled eggs. Birds that eat eggs of other birds will also eat thermocoupled eggs if they are not identical in size, shape, and color to their own. Finally, it was clearly demonstrated that the present state of artificial incubation of exotic bird eggs is in a very primitive stage.
The accompanying summary prepared by Don Hoyt outlines the preliminary findings. The final dissertation will be published in approximately one year. Anyone in the Los Angeles area having birds suitable for this kind of study and wishing to cooperate is invited to correspond. Correspondence should be directed to the Los Angeles Zoo and will be forwarded to UCLA.