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34 1990, 12 eggs were transferred from WBNP to ICF, 11 were fertile and 8 fledged. Nine eggs were laid by three captive females in 1991, and one chick was parent - reared (fable 6). In 1992, the same three breeding pairs produced 16 eggs (3 from natural copulation), and 6 were reared. Closed circuit TV proved effective in (a) eliminating egg breaking by a pair that broke eggs in 1991, and (b) in monitoring and supervising the socialization of new pairs. Eleven eggs were received from WBNP, and 7 chicks fledged. One captive - produced chick was parent- reared, 4 were hand - reared, and one (together with 7 chicks from AWP eggs) was costume - reared. Costume- rearing refers to the use of a white crane -like costume worn by animal caretakers whenever they are around the birds. In this manner, cranes are never exposed to the human form and remain fearful of people. From the time of hatching, costume - reared whoopers are exposed to live whooping crane role models in adjacent pens to avoid imprinting problems. Eight of the costume - reared birds were sent to Florida in January 1993 for the reintroduction experiment. In 1993, three females produced 9 eggs and four chicks fledged. ICF also received nine fertile eggs from WBNP, eight hatched and all fledged. Four were sent as chicks to Idaho for use in the guide bird research. In August 1993, ICF held three breeding pairs, three mature females being re- paired to stimulate breeding, five other pairs nearing sexual maturity, a single adult male, four yearlings, and eight juveniles. ICF has the capacity to house 15 breeding pairs of whooping cranes. Research is ongoing to improve reproduction, rearing procedures, behavioral management, health care, and other topics which may directly benefit management and recovery. J. The Cross - Fostering Experiment For any species, the probability of extinction is largely determined by its abundance, fecundity, and distribution. Conventional management procedures for the whooping crane have been aimed primarily at increasing the size of the AWP population. Even though this population has increased substantially since the 1940's, it remains vulnerable due to its relatively restricted breeding and wintering distributions. It was recognized that survival prospects for the whooping crane would be greatly enhanced by establishing additional, disjunct populations. Although several approachesto establishing additional breeding populations had been proposed, the technique which seemed most worthy of consideration was cross- fostering whooping cranes to sandhill crane foster parents. This procedure was initially proposed in the 1950's by Fred Bard, a former Director of the Saskatchewan Museum of Natural History. By this method, whooping crane eggs from the wild or from captive breeders would be placed in sandhill crane nests, and the sandhill cranes would incubate, hatch, rear, and introduce the whooping crane chicks into the wild. Cross- fostering is relatively simple and could be applied in various areas formerly within the whooping cranes breeding range. Furthermore, migration routes, stopover points, and wintering locations could be determined in advance by banding and subsequently observing potential foster - parent pairs. Despite these obvious advantages, the technique raised a number of unanswered questions: Would the food items used by sandhill cranes be nutritionally adequate for whooping cranes? Would altitudinal differences between the source of the eggs and the transport point affect hatchability? Would whooping crane chicks become sexually imprinted upon sandhill cranes, and eventually select a sandhill mate? These and other questions could only be answered by experimentation ( Drewien and Bizeau 1978, Drewien and Kuyt 1979).