Migration Dynamics of the Whooping Crane

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TABLE 2 -4 CHARACTERISTICS OF ROOST SITES IN STANDING AND FLOWING WATER USED BY MIGRATING WHOOPING CRANES Habitat Characteristic Standing Water (a) Flowing Water (b) Size less than 1 acre to several thousand relatively wide (60 -75 yards to acres; sufficient shallow water to over 400 yards); slow flowing (1 -4 allow birds to roost 20 -30 feet from mph) shoreline or from dense emergent vegetation Water depth less than 16 inches (3 -8 inches all sites less than 12 inches, optimum) usually 2 to 6 inches; main channel may be considerably deeper Emergent or floating vegetation little or none in immediate none vicinity of roost Submergent vegetation absent or only those that form mats none (e. g. , Myriophyl l um) Bottan composition finely divided substrate; e.g., fine substrate, usually sand sand, mud, or clay Topographic relief Variable ranging f ran 0 to over 30 all roosts had sandbars nearby char - feet within 150 yards of roost acterized by gradual slope (often (actual slopes into water rarely (often less than 1 -20), little topo- e)ceed 4 -50); probably will not graphic relief (often less than 1 use deep basins foot), no banks over a few inches high, and little or no vegetation Horizontal visi bil ity 50 feet minimum in all directions; usually unobstructed from riverbank often 100 yards or more in most to riverbank and at least several directions hundred yards up and downstream Overhead visibil ity unobstructed; no tall trees, thick same, though river roosts are shrubbery or high banks im immed- usually isolated from developments late vicinity of roosts by tall trees and /or high banks located at a distance which allows suitable horizontal and overhead visibil ity Distance to feeding site almost always within 12 -15 miles, usually less than 1 mile or in often within 1 mile or in immed- immediate vicinity of roost; in late vicinity of roost Platte River Valley, feeding sites have been documented within 3 miles of the river Distance from human development 300 to 400 yards (minimum) fran roost is usually at least 1/4 mile and /or disturbance moderately used roads or other from human developments; e. g. , developments; 400 to 600 yards roads, houses, and railroad tracks (minimum) from unconcealed humans (a) Source: Johnson and Temple (1980, pp. 39 -42), based on an evaluation of 57 standing water roost sites. (b) Sources: Johnson and Temple (1980, pp. 42 -43), based on an evaluation of 7 riverine roost sites; and Johnson (1981, p. 40), based on an evaluation of 10 riverine roost sites. 2 -15