Migration Dynamics of the Whooping Crane

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2.0 MIGRATION DYNAMICS In addition to the maintenance of suitable habitat conditions on the nesting and wintering grounds, effective management of the whooping crane requires a thorough understanding of the species' needs during migration. To facilitate such understanding, the following sections summarize current information on the whooping crane's migration dynamics, including delineation of the migration corridor and detail regarding the chronology of migration, migratory flock size, flight distances, travel time, stopover duration, habitat requirements and habitat selection strategy. 2.1 MIGRATION CORRIDOR In their study of the ecology of migrating whooping cranes, Johnson and Temple (1980, pp. 17 -20) delineated the width of the approximately 2,400 mile long migration corridor between Aransas NWR in Texas and Wood Buffalo National Park in westcentral Canada by evaluating the number of sightings, number of birds, and number of use -days recorded at various locations al ong the flyway over the 30 -year period 1950 -1979. The primary migration corridor cent off al l ined that portion of the flyway which included approximately 95 percent vari abl es. Based on their evaluation, the primary migration corridor (Figure 2 -1) was described as an 80 to 120 mile wide path which trends approximately 15 degrees west of north through most of the United States until reaching the Missouri River in central South Dakota. The corridor then follows the Missouri River into North Dakota bending sl ightly to the west as it 1 eaves the river near Garrison, North Dakota. From Garrison it follows a basically straight- line course, 30 degrees west of north, broadening in the Canadian portion of the flyway as it approaches Wood Buffalo National Park. The Service's summary of the results of the Cooperative Whooping noted Tracks ng falj e t from al l 1975 through spring 1982 (FWS 1982a, p. corridor appears to be a narrower and more definitive path than the spring corridor. That is, most of the fringe si ghti ngs in Colorado, Wyoming, and Manitoba have occurred during the spring migration. Johnson (1981, p. 37) stated that in Nebraska the whooping crane's primary migration corridor is 100 to 120 miles wide and angles through the state in a direction approximately 15 degrees west of north (Figure 1 -1) . The eastern and western edges of the corridor intersect the northern border of the state at 98045' and 101000' longitude, respectively, whereas the southern border is intersected at 98015' and 100030' longitude. Major phy si ographi c features within these confines include the Niobrara River from portion 5mi es west e saof Valen- tine l to its confluence with the Keya Paha River; a region to the south; substantial portions of the Cal amus, North Loup, Middle Loup, and South Loup rivers; a stretch of the Platte River frcm North Platte to Grand Island; the Rainwater Basin area south of Kearney; and part noted, 82 Republican River (FWS 1981a, p. 40) . As Johnson (1981, p. percent of all confirmed sightings in Nebraska from 1950 -1979 were made within this primary corridor; remaining sightings occurred predominantly to the west. 2 -1