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8 <br />of WBNP. These birds winter along the Gulf of Mexico coast at Aransas NWR and adjacent <br />areas (Fig. 2). The winter habitat extends 48 -56 km along the coast from San Jose Island <br />and Lamar Peninsula on the south to Welder Point and the central portion of Matagorda <br />Island on the north, and consists of estuarine marshes, shallow bays, and tidal flats (Allen <br />1952, Blankinship 1976) (Fig. 3). Some individuals also occur occasionally on nearby <br />rangelands or farmlands. Forty -five AWP pairs nested in 1993. The December 1993 <br />population was 141 birds. <br />Another wild flock consists of eight individuals reared by wild sandhill cranes (termed cross - <br />fostered because they were reared by another species) in an effort to establish a migratory, <br />Rocky Mountains Population (RMP) and one captive - reared bird released in a recent <br />experiment. The project began in 1975 with the transfer of wild whooping crane eggs from <br />nests in WBNP to the nests of greater sandhill cranes Q. Q. i p at Grays Lake NWR in <br />southeastern Idaho. The sandhill cranes became the foster parents to the whooping crane <br />chicks and taught them the migration route which the parents traditionally followed. The <br />RMP birds spend the summer in Idaho, western Wyoming, and southwestern Montana and <br />winter in the middle Rio Grande Valley of New Mexico. <br />The third wild population consists of ten birds remaining from 19 captive - reared whooping <br />cranes released in the Kissimmee Prairie of Florida in February and December of 1993. This <br />flock has been designated experimental nonessential and is the first step in an effort to <br />establish a nonmigratory population in Florida. This population is hereafter called the Florida <br />population (FP). <br />In May 1993, whooping cranes were located at five captive sites. -Two captive flocks are <br />maintained by the U.S. Fish and Wildlife Service, one at Patuxent Wildlife Research Center <br />(PWRC) containing 55 birds and one at International Crane Foundation (ICF) containing 26 <br />birds in December 1993. The Canadian Wildlife Service is starting a population at the <br />Calgary Zoo which now contains 16 birds. Three birds reside at San Antonio Zoological <br />Gardens and a single bird is in captivity at the Rio Grande Zoological Park in Albuquerque, <br />New Mexico, being treated for avian tuberculosis. <br />In the 1970's and early 1980's, the AWP was increasing at an annual rate of 4 percent, <br />double the rate observed prior to the mid 1950's (Binkley and Miller 1983). Subsequent <br />population studies indicate a 10 -year cycle of unknown cause in survivorship (Boyce and <br />Miller 1985, Boyce 1987, Nedelman g1 al. 1987). <br />C. Habitat <br />The current nesting area within WBNP lies between the headwaters of the Nyarling, Sass, <br />Klewi, and Little Buffalo rivers. The area is poorly drained and interspersed with numerous <br />potholes. Wetlands vary considerably in size, shape and depth, and most possess soft marl <br />bottoms. Wetlands are separated by narrow ridges which support an overstory of white <br />spruce 1 ), black spruce (P. Mariana), tamarack L rix I ri in ), and willows Qalix <br />M.), and an understory of dwarf birch (Betula glandulosa), Labrador tea (Ledum <br />aroenlandicum), and bearberry Arctostaohvlos uva- ursi). Bulrush (Scirpus validus) is the <br />dominant emergent in the potholes used for nesting, although cattail (Tvipha _ 12.), sedge <br />