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** Archived Article - please check for current information. **

Sept. 21, 2011

Results from 2011 Wood Stork surveys, nest monitoring

The S.C. Department of Natural Resources (DNR) Wading Bird Program counted 2,031 wood stork nests in South Carolina in 2011. Wood stork nests were observed in 23 colonies this year, including 6 colonies where storks were not known to nest in the past. Aerial surveys were used to locate the nesting colonies. Stork nests were counted during ground surveys or, when ground surveys were not possible, from photographs taken during aerial surveys. During 2011, storks nested in the following counties: Beaufort (5 colonies), Charleston (5 colonies), Colleton (3 colonies), Georgetown (2 colonies), Hampton (1 colony), Horry (4 colonies), Jasper (2 colonies), and Williamsburg (1 colony).           

During 2011, DNR monitored individual nests from a distance at two colonies (Donnelley Wildlife Management Area and Dungannon Plantation Heritage Preserve) to determine how many chicks survived to fledging age (mature enough to fly, which is about 8 weeks after hatching) per nest. An average of 1.6 chicks survived to fledging age per nest in 89 monitored nests. At least one chick survived to fledging age in 79.8 percent of the nests. Both of the colonies were successful this year and are managed by DNR to provide good habitat for wood storks, so they are not representative of all of the colonies in the state. DNR hopes to expand the nest monitoring project during the future to include more colonies so the data are more representative. The boardwalk at Dungannon Plantation Heritage Preserve was closed during the nesting season to prevent disturbance to the storks.
           
An aerial survey was conducted in late June to determine if storks reproduced successfully at the colonies where DNR did not monitor nests. The storks appeared to have had a successful season at 15 colonies, failed to fledge a significant number of chicks at 7 colonies and the status of one colony was not determined. The causes of colony failure were not determined, but in some cases it appeared that the water around the vegetation where the nests were built dried up and predators probably were able to disturb and/or depredate the nests. Wood storks typically nest in trees in flooded forests or on small islands surrounded by water. If there is adequate water, alligators below the nests deter predators such as raccoons from swimming to the nesting trees and eating stork eggs and/or chicks. Potential causes of colony failure for wood storks include predation when colonies dry out, inadequate food during the chick rearing period, and disturbance. Overall, 2011 was a decent year for wood storks in South Carolina.
           
Wood storks (Mycteria americana) are a federally endangered species. The United States breeding population of wood storks was listed as endangered after nesting pairs declined from between 15,000 and 20,000 in the 1930's to 2,500 pairs by 1978. Historically, wood storks used South Carolina as a feeding area during the summer and fall after dispersing from nesting colonies in Florida and Georgia. In 1981, the first successful wood stork nests were documented in South Carolina (11 nests). Since 1995, wood storks have built between 800–2,060 nests in South Carolina each year.
           
The wood stork is the only species of stork that nests in the United States. Wood storks are particularly vulnerable to habitat degradation and to unpredictable weather conditions because of their specialized feeding behavior and because their chicks require care for a very long period of time before becoming independent. Wood stork chicks are altricial, which means that they are completely dependent on their parents for temperature regulation and food when they hatch. At least one parent is usually at the nest caring for the chicks during the first three weeks after they hatch. Wood stork chicks require parental care for a long period of time (over two months) before they can depart from their nests and feed themselves.
           
Unlike herons and egrets, which hunt visually, wood storks are tactile feeders, which mean that they hunt by feeling for fish, crustaceans, and other prey. This feeding strategy requires high concentrations of prey in water that is shallow enough for storks to wade through it. When natural and impounded wetlands with abundant fish slowly dry out, excellent feeding conditions are created for the storks. In order for the storks to nest successfully, prey must be abundant and available throughout their nesting season. When adequate food is not available, adult wood storks will abandon their chicks and leave the area to find food.


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