The whooping crane (Grus americana) formerly occurred from the Arctic coast south to central Mexico, and from Utah east to New Jersey, South Carolina, Georgia and Florida . In the 19th and 20th century, the whooping cranes' primary nesting area extended from central Illinois, northwestern Iowa, northwestern Minnesota, and northeastern North Dakota northwesterly through southwestern Manitoba, southern Saskatchewan and into east central Alberta. Wintering grounds and migration routes included much of the United States east of the Rocky Mountains. Currently, whooping cranes nest in the wild at only three locations: 1) Wood Buffalo National Park and adjacent areas in Canada (this population winters in Aransas National Wildlife Refuge, Texas), 2) Central Florida (this is an introduced, non-migratory population), and 3) Wisconsin (this population winters in Florida) . An effort to reintroduce whooping cranes into the Rocky Mountain area by cross-fostering whooping cranes to sandhill crane foster parents was abandoned when the last whooping crane introduced into this population died in 2002 . Captive whooping crane populations are maintained at the Calgary Zoo, International Crane Foundation, Patuxent Wildlife Research Center, San Antonio Zoo, New Orleans Zoo, Lowry Park Zoo, and the Audubon Center for Research on Endangered Species.
Whooping crane populations in 1870 were variously estimated at 1,300-1,400 and 500-700 birds, but then declined precipitously due to hunting and habitat destruction . Conservation efforts were able to maintain an extremely endangered but relatively stable population of 21-44 birds between 1938 and 1966 . When placed on the endangered species list in 1967, just 48 wild and six captive birds remained. In 1978, critical habitat was designated in parts of Idaho, Kansas, Nebraska, Oklahoma, and Texas, primarily on Federal and State wildlife management lands . Due to intensive habitat management, nest area protection, captive breeding and reintroductions, the population rose steadily to 513 (368 wild and 145 captive) birds in 2006. [2, 4]. Estimates as of May 15, 2007 indicate a population decline of 31 birds , due in part to storm which killed 17 of 18 birds being held at the Chassahowitzka National Wildlife Refuge in Florida.
The 2003 draft international recovery plan sets forth two alternate criteria for downlisting the whooping crane to threatened status: 1) The Aransas-Wood Buffalo population must have at least 160 total birds with at least 40 productive pairs, and two additional separate self-sustaining populations must have at least 25 productive pairs and 100 total birds each. All three populations must maintain their status for a decade; or the Aransas-Wood Buffalo population must have 250 reproducing pairs and a total of 1,000 birds . In either scenario, at least 21 productive pairs and 153 total birds must be maintained in captivity. Downlisting is estimated to occur in 2035. Delisting criteria have not yet been established.
Current threats to the species include low genetic diversity, loss and degradation of migration stopover habitat, construction of power lines, degradation of coastal habitat, and in Texas, the threat of chemical spills .
 Canadian Wildlife Service and U.S. Fish and Wildlife Service. 2005. Draft International recovery plan for the whooping crane. Albuquerque, New Mexico. 196pp.
 International Crane Foundation. 2006. Historic whooping crane numbers (www.savingcranes.org/pdf/whooper_table.pdf). Baraboo, WI.
 U.S. Fish and Wildlife Service. 1978. Determination of critical habitat for the whooping crane. 43 FR 20938.
 Stehn, T. 2007. Whooping crane numbers - November 22, 2006. Report provided by Tom Stehn, U.S. Fish and Wildlife Service, on May 16, 2007.
 Stehn, T. 2007. Whooping crane numbers - May 14, 2007. Report provided by Tom Stehn, U.S. Fish and Wildlife Service, on May 16, 2007.
 Dinnage, R.J. 2007. Federal whooping crane relocation program suffers setback. Land Letter, February 2007.