MORTALITY IN FLEDGED WHOOPING CRANES OF THE ARANSAS/WOOD BUFFALO POPULATION

A total of 1,893 whooping cranes (Grus americana) overwintered at Aransas National Wildlife Refuge from 1950 through spring 1987. Winter losses (dead and disappeared) amounted to only 1.3% of the population, but 3.7% of the juveniles. About 19% of the annual losses occurred in the wintering area where birds spend 5 to 6 months of the year. Eighty-one percent of the losses occurred from April to November. Losses on the summering area appear to be low. The most significant losses seem to occur during migration and may comprise between 60 and 80% of the annual losses. Migration involves only 17-20% of the birds\u27 year, but a period when losses are high because they are exposed to new hazards as they travel through unfamiliar environments