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f- <br />1 <br />A <br />1 <br />1 <br />r~I <br />S <br />f <br />1 <br />f <br />ti <br />S <br />1 <br />1 <br />S <br />ti <br />S <br />S <br /> <br />HABITAT FOR THREATENED OR ENDANGERED WILDLIFE IN COLORADO <br />S ecies: Whooping Crane (Grus americana) <br />Status: (Endangered Federally) <br />Habitat Requirements and Limiting Factors: These birds nest in an isolated, <br />marshy part of-Wood Buffalo National Park (Canada). They winter <br />on the Aransas National Wildlife Refuge near the Texas Coast. <br />An experiment is in progress whereby Greater Sandhill Crane <br />foster parents are raising Whooping Crane chicks at Gray's Lake, <br />Idaho (a large, shallow marsh). These experimental birds winter <br />on and near the Bosque del Apache Refuge in southern New Mexico. <br />Limiting factors include: (1) the need for extreme isolation <br />on the nesting area, (2) an extremely low reproductive rate <br />(lay two eggs; rarely raise more than one chick). <br />Geographic Description of Habitat <br />Historic Range: Whooping Cranes have historically only occur- <br />red in eastern Colorado as accidental migrants - the main <br />migration path is to the east of Colorado. The most recent <br />documented sighting of migrants was on November 3, 1973 in the <br />Greeley, Weld Co., area. <br />Occupied Range: The experimental birds from Idaho pass through <br />northwestern Colorado and make a major rest stop each spring <br />and fall at the Monte Vista National Wildlife Refuge, Rio <br />Grande County. In May, 1976, one of these migrating birds was <br />sighted in the Piceance basin (see map). <br />Essential Habitat Description: Since the wild population only migrates <br />through Colorado on an unpredictable and sporadic basis, no <br />part of Colorado can be listed as essential for them. Regarding <br />the experimental flock, no area in Colorado should be considered <br />essential at this time. Perhaps at a later time this experimental <br />flock will be firmly established and settle into a predictable <br />land-use pattern. If so, certain areas may eventually be listed <br />as essential. <br />Ma.lor References: <br />Allen, R. P. 1952. The Whooping Crane. Res. Rept. No. 3, <br />Natl. Aud. Soc. 246 pp. <br />Bent, A. C. 1927. Life histories of North American marsh birds. <br />Smithsonian Inst. U.S. Natl. Mus. Bull. No. 135. <br />Drewien, R. 1976. personal communication. <br />McNulty, F. 1966. The Whooping Crane - The bird that defies ex- <br />tinction. E. P. Dutton & Co., N.Y. 190 pp. <br />Miller, R. S., D. B. Botkin and R. Mundelssohn. 1974. The <br />Whooping Crane (Grus americana) population of North <br />America. Biol. Conserv. 6 2 :106-111. <br />Novakowski, N. S. 1966. Whooping Crane population dynamics <br />on the nesting grounds, Wood Buffalo Park, Northwest <br />-57- <br />