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

From winter 1950 through spring 2011, 6,364 whooping cranes (Grus americana) overwintered at Aransas National Wildlife Refuge, or rarely, elsewhere. Documented winter losses amounted to 105 birds dead or disappeared. About 20% of total losses occurred in the wintering area, where birds spend 5 to 6 months of the year including a few birds that over-summer. Losses of white-plumaged whooping cranes on the summering area in Canada appear to be low with only 3 instances documented. The most significant losses seem to occur in migration and may comprise over 80% of the annual mortality. Migration involves only 17-20% of the annual cycle but is a period when losses are high because birds are exposed to new hazards as they travel through mostly unfamiliar environments. This paper updates a similar account by Lewis et al. (1992) by adding mortality records of the Aransas/Wood Buffalo population (AWBP) from 1987 through 2010 with information on 50 recovered carcasses