WSP00190 - Laserfiche WebLink

Home Browse Search

I I I I I I I I I I I I I I I I I I I "y,,~1l0 !.... ~ '.' .J ~, SEellONTHREE Whooping Crane The primary migration corridor of the wild population runs in a narrow band across the United States from extreme northeastern Montana south through North Dakota, South Dakota, Nebraska, Kansas, Oklahoma, and Texas (Figure 3-1). The primary migration corridor of the whooping crane through Nebraska averages 100 to 120 miles wide and angles approximately 15 degrees west of north. The primary migration corridor includes the stretch of the Platte River from the city of North Plane to just east of Grand Island. Johnson (1982) estimated that 82 percent of all confirmed recent sightings had been made within the primary corridor; the remaining sightings have been predominantly to the west. Whooping cranes are diurnal migrants and make regular stops to feed and rest between migration flights. Radio-tracking data indicated migrational flights average about 200 miles per day (Kuyt 1992). However, adverse weather conditions such as strong headwinds or approaching storms can force whooping cranes to shorten flights to as linle as 50 miles and to seek stopover habitats at irregular and frequent intervals. Although whooping cranes will use a variety of habitats for foraging and roosting during these stopovers, they prefer isolated sites away from human activities. This preference for secluded areas and the birds rarity result in few authenticated sightings during ntigration each year. In spring, paired adults have critical nutritional requirements that must be met to ensure that the birds are in good reproductive condition when they arrive at the nesting grounds. Adults need appropriate body fat to sustain them on the breeding grounds (often frozen upon arrival) until food becomes available, and calcium to produce healthy eggs and chicks. Family groups migrating southward in the fall require specific habitats to meet the nutritional and security needs of the young. Howe (1989) found that family groups appeared to select more vegetated wetlands during fall migration than nonfamilies. Vegetated wetlands may provide bener cover for young birds, thus reducing detectability by predators. Vegetated wetlands may also yield higher densities of protein rich invertebrates important to fall juveniles that are not fully grown (Howe 1989). Whooping cranes are generally wary and will not remain near human activity on their breeding grounds, but they will tolerate some human intrusion in wintering areas (FWS 1994). Human presence alone, as opposed to habitat loss, may have been a factor in the reduction of their breeding range. 3.4 IMPORTANCE OF THE PLATTE RIVER Based on a preponderance of sightings along the Plane River in Nebraska during 1820 to 1948, Allen (1952) believed whooping cranes made the Plane River a major stopover. The Aransas- Wood Buffalo population commonly uses the Plane River during both spring and fall ntigrations. Most observations on the Plane River occur during April and October, but sightings outside these months are not uncommon. Not all whooping cranes are observed or reported; the number of reported whooping crane sightings represent only the minimum number of observed stopovers. Confirmed reports of whooping cranes along the Platte River are received more often during the spring migration than during the falL .. SrllilJer ViDIlIIwiInI CJJIfe Fe/IInI SInIaJs 68FOC97286OOfr1.dOc 61211999(9:52 AMyuRSGWCFS/2 3-5