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46 <br />3. Promoting adoption of captive- reared whooping crane chicks by wild adults <br />established in an area through cross - fostering to sandhill cranes. The adoption process <br />would add to the wild population a group of whooping cranes without the improper <br />imprinting problems. The young birds, hopefully, will learn migratory and survival <br />techniques from their adoptive parents. This approach has been termed the guide bird <br />technique. <br />The Grays Lake cross - fostering experiment successfully produced wild whooping cranes <br />capable of migrating and surviving in a challenging environment. However, because these <br />cranes did not pair, and have experienced excessively high mortality, a technique for <br />reestablishing a self- sustaining migratory population is lacking. A potential solution would <br />be to use cross - fostered whooping cranes as guide birds to introduce young captive - <br />produced whooping crane chicks into the wild. Members of the Canadian Whooping Crane <br />Recovery Team in 1992 suggested the guide bird experiment as an appropriate use of the <br />birds surviving in the RMP. Such an experiment would test one technique which might be <br />used to establish another migratory population in Canada late this century. The young <br />whoopers, reared by adults of their own species, might learn to survive in the wild and <br />follow a predetermined migration route in the Rocky Mountains. Being reared by <br />conspecifics, they would be sexually imprinted on their own species. <br />Ten adult whooping cranes survive in the RMP, including 4 females. Males range in age <br />from 8 to 16 years and females from 8 to 12 years. Six of these whooping cranes winter <br />annually at Bosque del Apache NWR and 2 at state game management areas north of the <br />refuge. Three captive - reared chicks were released into the population in the guide bird <br />experiment in fall 1993 and one survived in the winter of 1993 -1994 in New Mexico. <br />The cross - fostered cranes have exhibited various parental behaviors on summer territories at <br />GL and in a pen nearby. Solitary territorial males have helped neighboring sandhill crane <br />pairs raise young, including protecting, feeding and brooding them. Several males have built <br />nests. One male intermittently incubated an empty nest and a sandhill crane egg placed in <br />this nest. In 1988, 2 male whoopers assisted a sandhill crane foster - parent pair raise a <br />whooping crane chick. Male and female whoopers associated with, fed and temporarily <br />reared sandhill crane chicks in the pen during 1990 -91. These activities and chick <br />adoptions at the United States captive facilities, suggest that some cross- fostered whooping <br />cranes might adopt or bond with and rear a whooping crane chick. Such bonding <br />experiments will occur in pens with wild - captured adults and on the spring territory of free - <br />living wild birds. These experiments began in 1993 and will continue in 1994. Four to six <br />whooping crane chicks are planned for use in this research each year. The completion of <br />the 2 -year project will provide another decision point about future efforts in the Rocky <br />Mountains, and an opportunity for review and recommendations by all interested parties. <br />The other techniques for reintroducing a migratory population should be tested in the Rocky <br />Mountains or at other geographic locations. <br />As part of the guide bird experiment, the Service is proposing to designate the RMP as <br />experimental nonessential. The "experimental" designation increases the flexibility of the <br />Service and other land management agencies to manage reintroduced populations because <br />they can be treated as threatened species rather than endangered. The Service has more <br />discretion in devising management programs for threatened species than for endangered <br />