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Citation:
Woolley, H. W., S. G. Hereford, and J. J. Howard. 2022. Drivers of annual fledging in the Mississippi Sandhill Crane Population 1991-2018. Proceedings of the North American Crane Workshop 15:90-102.
Abstract:
We studied trends in nesting, number of chicks fledged annually, and their environmental and biotic drivers in the
wild population of Mississippi sandhill cranes (Grus canadensis pulla) on Mississippi Sandhill Crane National Wildlife Refuge
during 1991-2018. Population size, number of nests, and number of chicks fledged annually increased slowly but significantly
over the course of the study. Increases in population size were related to both number of wild-reared chicks fledged annually
and number of captive-reared chicks released each year, but wild-reared chicks had significantly higher survivorship than
captive-reared chicks. Hurricanes transiently raised mortality rates but only Hurricane Katrina caused a sustained population
decline among adult birds. Total population size was positively related to precipitation during the nesting season, while number
of chicks fledged annually was negatively related to annual number of extreme heat days and estimates of bobcat (Lynx rufus)
occurrence. Cranes displayed high philopatry to their initial nest location and nested repeatedly in the same general home range
regardless of the time since an area had last been treated by prescribed burning. Number of chicks fledged annually occurred
with approximately equal frequency across management units burned at different times prior to nesting. The results indicate
that both biotic and abiotic factors drive population dynamics on the refuge and suggest that additional attention to prescribed
burns, predator removal, and behavioral conditioning of captive-reared birds prior to release may promote faster population
growth and establishment of a self-sustaining wild population in the future.
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© 2022 North American Crane Working Group
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