Organizing for Endangered and Threatened Species Habitat

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tuberculosis brought in by snow geese poses a threat to the health of many birds and most particularly both species of cranes. Crowding contributes to disease transmission. As wetlands have been drained and woodlands grown up along the banks, quality crane habitat has shrunk to less than 70 river miles in the Kearney--Grand Island area. Here cranes and other birds crowd dangerously close in the few good habitat reaches that remain (Currier, Lingle, and Walker 1985: 18). Caloric requirements for migration used to be met by starchy tubers from a variety of aquatic plants, worms, snails, snail shells and insects in the floodplain. Now, within 8 miles of the river, 96°l0 of the sandhill cranes' diet is found in waste corn. The remaining 4% is the critical invertebrate cornponent which provides protein and calcium for egg production. Too few whooping cranes have survived during the last century to permit the kinds of studies that would yield comparable nutritional analyses for these rare birds. What central Platte habitat is left for spring and autumn stopovers is as important as the summer and winter destinations themselves and not only for whooping cranes, but also for sandhill cranes, snow geese, mergansers, mallards, teal, pintail ducks, and bald eagles. The interior least tern (sterra antillarum) is the smallest of the tern species approximately nine inches in body and twenty inches in wingspan. Adults are recognized by a white patch on the forehead contrasting sharply with a black crown, a bright yellow bill with a black tip, grey back, white underbody, and orange-yellow feet (Forbush and May 1955, p. 235-6). In recent decades, this species has been found on only a fraction of its former habitat that, early in the twentieth century, had stretched from Texas to Montana and from the front range of eastem Colorado and New Mexico to Indiana. The species was listed as endangered in 1985 and recent estimates place its population at about 4,800 (U.S. Fish & Wildlife Service 1997a). ? Interior least terns nest in colonies amongst sparse beach vegetation, in shallow ? inconspicuous depressions in open sandy areas, in the blinding glare of the sun. Their protection ? is their camouflage of egg and young bird so closely resembling the color tone of sandy beaches - and scattered pebbles that eggs can escape the eye even of the hawk. Tiny young squat so flat they • hardly cast a shadow. Two or three eggs are laid in the May-July months, incubation lasts about 22-23 days, and the hatched chicks remain near the nest as a brood for a week or so and they are ? able to fly within about three weeks. Unlike the piping plover, interior least terns include small ? fish in their diet which adults hunt from the air by diving for minnows near the water's surface. In • Nebraska, they are found on sandbars of the Missouri, the Loup, the Niobrara, and the Platte . rivers, on the beaches of Lake McConaughy, and on shores of sandpits created by human extraction of gravel. Least tern habitat on the Platte has been reduced and fragmented by encroaching trees and other woody vegetation. Traditionally, least terns would await the decline of spring peak flows and then scrape out their nests. With the coming of human manipulation of river flows all sununer long for purposes of irrigation, power production, and municipal use, Platte river flows have become much less predictable (at least from the bird's perspective) and high flow periods are common long into nesting season. The birds are winerable to being flooded out and also to high water that continues long past the time they can wait to nest. One obvious adaptation to sustained 13