Wintering whooping crane behavior and habitat quality at the Aransas National Wildlife Refuge on the Texas Gulf Coast
Tiegs, Lindsey A.
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The Aransas-Wood Buffalo population of Whooping Cranes (Grus americana) exclusively overwinters in coastal saltmarshes of Texas. This study examined how Whooping Crane behavior and habitat quality shift over the course of a winter season, and attempted to discover linkages between their behavior and habitat quality, with the ultimate goal of finding a non-invasive method to infer habitat quality through behavioral observations. Whooping Crane behavioral observations and habitat assessments were conducted at the Aransas National Wildlife Refuge (NWR) and at adjacent urban upland sites January-March of 2016 and 2017. Cranes visiting urban upland sites with game feeders spent significantly less time foraging, and more time resting and in comfort/maintenance activities than cranes observed in their natural saltmarsh territories. On average, birds observed in their saltmarsh territories sequentially spent more time foraging each month during both winters, which correlated to a decrease in the time spent resting each month in 2017. Adult cranes spent significantly more time on alert than juveniles both years. Intra-site variability significantly exceeded inter-site variability in marsh pond salinity, but not in Blue Crab (Callinectes sapidus) or Carolina Wolfberry (Lycium carolinianum) fruit density. Saltmarsh salinity and Blue Crab density dramatically changed throughout the two winters, which were both negatively correlated to mean sea level. Marsh water quality was variable across sites, with some mainland regions and islands possessing similar water quality traits. Whooping Crane time activity budgets were not similar across sites comparable in resource availability, nor did their behavior reflect shifts in pond salinity or Blue Crab density. Whooping Crane behavior also did not consistently correlate to time of day, observation distance, wind speed, air temperature, or mean sea level. To investigate which structural components make one saltmarsh territory more plentiful in Whooping Crane resources than another, future geospatial modeling of the microtopographic variations along the Aransas NWR could be paired with the food density and marsh pond salinity data from this study, to ultimately be applied in future land purchase, protection of existing lands, environmental easement, and restoration decisions.