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<br />-..4"" <br /> <br />15 <br /> <br />fall in the water, brooding sites are used only once, and it is unlikely that oocysts <br />accumulate in the wild. Also, the defense of large territories and small brood size ensure <br />low density use of the natal area, and thereby reduce the likelihood of coccidia oocysts <br />being ingested in quantity sufficient to cause disease. However, infected parents can shed <br />oocysts for most of their life and are a constant source of infection. <br /> <br />Although wild whooping cranes are presumably susceptible to a variety of avian diseases, <br />evidence of disea$e-related mortality is only infrequently documented. However, seven wild <br />whooping cranes have had avian tuberculosis, a subadult crane captured in New Mexico <br />was suffering from avian cholera (Snyder et al. 1987), and one died from lead poisoning <br />(Snyder et ai, 1993). The high incidence of avian tuberculosis indicates that whooping <br />cranes may be particularly susceptible to this disease. <br /> <br />Flooding of nests is thought to be rare. Drought is a far greater hazard because the <br />attractiveness of traditional nest sites would be reduced, food supplies would be diminished, <br />and newly-hatched chicks would be forced to travel long distances between wetlands, <br />Drought conditions increase exposure of eggs and chicks to terrestrial predators whose <br />movements are enhanced, Potential predators in the nesting ground include the black bear <br />(Ursus americanus), wolverine @y[Q luscus), gray wolf (Canis ~), red fox (Vuloes ~), <br />lynx ~ canadensis), and raven (Corvus corax), although, with the exception of ravens, <br />these species are uncommon in the nesting area during spring and summer. A number of <br />nests have been destroyed by black bears or other mammals, and prefledged chicks have <br />been killed by wolves (Kuyt 1981,!!, 1981~); however, the overall impact of predation on <br />recruitment remains uncertain. <br /> <br />Whooping cranes are exposed to various natural obstacles and problems during migration. <br />Snow and hail storms, low temperatures, and drought can present navigational handicaps or <br />reduce food avail.bility, Thus, migrating cranes are exposed to a variety of hazards such as <br />collision with obstructions, predators, disease, and illegal shooting, <br /> <br />Hurricanes and drought can create problems on the wintering grounds, Fortunately, the <br />hurricane season usually ends by October 31, before most whooping cranes arrive. A late- <br />season-hurricane could place cranes at risk due to high wind velocities, Drought influences <br />availability and abundance of the natural food supply by altering salinity of tidal basins and <br />estuaries (Blankinship 1976), Bobcats (Lvnx~) prey on young whooping cranes in <br />Texas and Florida. <br /> <br />Man-associated Mortalitv Factors and Disturbance: This subject is treated under three <br />categories: human disturbance, habitat modification, and hunting and specimen collecting. <br />The whooping crane is wary on the breeding grounds and will not remain near human <br />activity. However, as evidenced by the egg transfer and banding programs, whoopers will <br />tolerate human intrusion for short intervals, On the wintering grounds, whoopers will <br />tolerate some human disturbance. This tolerance is evidenced by the little concern they <br />show for barges that travel along the Gulf Intracoastal Waterway (GIWW). Both whooping <br />cranes and sandhill cranes are disturbed by aircraft, particularly helicopters. <br />