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37 <br />number of eggs available for transplanting resulted in a relatively small population which <br />peaked at 33 individuals in winter 1985. <br />The sex ratio was equal at fledging age among 22 cranes examined at WBNP and 6 cranes <br />at GL. The data, based on chromosome identification in the blood, suggests that differential <br />mortality rates are the basis for unequal sex ratios among adults in the RMP. <br />In June 1981, a captive, 3- year -old, parent - reared female whooping crane was transferred <br />from PWRC to GL and placed on a wild male's territory (Drewien 1982, Unpubl. Prog. Rept. <br />No. 17, Whooping Crane Transplant Experiment, Idaho Coop. Wildl. Res. Unit, Univ. of <br />Idaho, Moscow: pp. 32 -41). This experimental reintroduction was attempted to determine if <br />it was possible to simultaneously augment the wild cross - fostered population, rectify the <br />male- skewed sex ratio, and hasten the onset of breeding in the wild population. <br />It was assumed that the probability of pair- formation would be relatively high for several <br />reasons, including: (1) released birds are initially subordinate to wild birds following release, <br />a situation favoring male dominance and pairing; (2) the male at GL was sexually mature, <br />and the female was old enough for pairing; and (3) numerous instances have been <br />documented in which wild cranes have successfully paired with tame or captive individuals <br />(Hyde 1968, Longley 1970, Nesbitt 1979). Previous experiments with sandhill cranes <br />demonstrated that the transition period from captivity to the wild involved considerable <br />learning and consequently occurred over a relatively extended period. In this particular <br />release, it was assumed that this transition period would be ameliorated and shortened <br />because if the two paired her mate would introduce her to foods, foraging methods, <br />roosting areas, teach a proper response to potential predators, and ensure proper migration <br />by the female. <br />Although the female rapidly adjusted to the wild and associated periodically with the male, a <br />pair bond was never established. Successful migration by the unattached female seemed <br />unlikely, therefore she was recaptured and returned to PWRC in October (Drewien and Clegg <br />1992). This experiment was repeated the following summer. In 1982, as in 1981, the <br />female readily adapted to the wild environment, and her presence stimulated increased <br />territorial activities by the male (Drewien 1983, Unpubl. Prog. Rept. No. 18, Whooping <br />Crane Transplant Experiment, Idaho Coop. Wildl. Res. Unit, Univ. of Idaho, Moscow: pp. <br />8 -10). Unfortunately, the experiment was terminated early when the male died after <br />becoming entangled in a barbed wire fence on his territory. Again, the female was <br />recaptured and returned to PWRC. <br />The experiment was repeated in 1989, but earlier in the season (May) than the 1981 and <br />1982 attempts (June). A captive six - year -old female from PWRC was placed in a pen on a <br />wild male's territory at GL. The male exhibited much interest in the female and after 1 week <br />she was released from the pen. Considerable pair formation behavior occurred between the <br />two birds including unison calling and copulations. No nesting attempt was made, perhaps <br />because it was somewhat late in the season. The male molted his flight feathers and <br />secluded himself in the marsh. In early June the female abandoned the flightless male but <br />was joined by another wild male. <br />