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<br />. .{~"'. <br /> <br />10 <br /> <br />(Carex aauatilis). musk-grass (Chara ~,). and other aquatic plants are common (Allen <br />1956. Novakowski 1965. 1966. Kuyt 1976l!. 1976!!. 1981l!). <br /> <br />Nest sites are being located in the rushes or sedges of marshes. sloughs. or along lake <br />margins (Bent 1926), Allen (1956) found an abundance of invertebrates. primarily mollusks. <br />crustaceans. and aquatic insects. in the ponds occupied by nesting pairs. He also <br />encountered several species of minnows. frogs. and garter snakes (Thamnoohis ~.). and <br />believed that mollusks and frogs must be important items in the diet of breeding adults and <br />their offspring. <br /> <br />Lightning-caused fires have burned large portions of the nesting area during drought (e.g.. <br />1981). but losses of eggs. chicks. or adults have not been confirmed. Molting adults or <br />flightless young would be vulnerable to fire. Wildfire may be beneficial to cranes due to <br />removal of dense or tall vegetation thus making the area more accessible for whooping <br />crane use and recycling nutrients. <br /> <br />Although the quality of the nesting habitat can be debated. there is no evidence that growth <br />of the AWP is limited by habitat. Hatching success is high in most years (Kuyt 1976,g, <br />1981l!. 1981!!) and the area is remote from human activities. Thousands of hectares of <br />unoccupied. apparently similar habitat are available in the area. Some new pairs pioneer <br />unoccupied nesting habitat as the population increases (Kuyt 1978!!). A project of Parks <br />Canada is underway to identify the suitable unoccupied nesting habitat within WBNP. <br /> <br />Whooping cranes use a variety of habitats during migration (Howe 1987, 1989. Lingle <br />1987, Lingle g! lll, 1991). Twenty-seven cranes were monitored for one or more seasons. <br />including nine radio-marked birds and others that associated with them (Howe 1987, 1989). <br />They fed primarily in a variety of croplands and roosted in palustrine (marshy) wetlands. A <br />majority of the roosting wetlands were less than 4 ha (75 percent) and within 1 km of a <br />suitable feeding site. More than 40 percent of the roosting wetlands were smaller than 0.5 <br />ha, Although heavily vegetated wetlands were generally not used, family groups appeared <br />to select more heavily vegetated wetlands than non-families (Howe 1987,1989). Cropland <br />accounted for 70 percent of the feeding sites of non-families. but wetlands accounted for <br />67 percent of the feeding sites of families. <br /> <br />Whooping cranes also roost in riverine habitat. most notably the Platte River, Middle Loup <br />River. and Niobrara River in Nebraska; Cimarron River in Oklahoma; and the Red River in <br />Texas (U,S. Fish and Wildlife Service confirmed sighting records). Cranes roost on <br />submerged sandbars in wide unobstructed channels that are isolated from human <br />disturbance (Armbruster 1990). Large palustrine wetlands are used for roosting and feeding <br />during migration, Included in this category are those at Quivira NWR in Kansas (68 <br />confirmed sightings). Salt Plains NWR in Oklahoma (61 sightings confirmed). Cheyenne <br />Bottoms State Wildlife Area (34 sightings confirmed), and large reservoir margins in the <br />Dakotas. <br /> <br />About 9.000 ha of salt flats on Aransas NWR and adjacent islands comprise the principal <br />wintering grounds (Fig, 3). Marshes are dominated by salt grass (Distichlis soicata). <br />saltwort (Batis maritima), smooth cordgrass (Soartina alterniflora). glasswort (Salicornia ~.), <br />and sea ox-eye (Borrichia frutescens). Inland margins of the flats are dominated by Gulf <br />cordgrass (Soartina soartinae). Interior portions of the refuge are gently rolling and sandy <br />