Status and Recovery of the Wood Stork (Mycteria americana)
The U.S. Fish and Wildlife Service determined in 2007 that the stork had met the criteria for downlisting from “endangered” to “threatened” status. In 2010, it published a positive 90-day finding on a 2009 citizen petition to commence downlisting.
The delisting criteria have not been met, but are expected to be achieved by 2017.
Precipitous declines in the wood stork’s range and population occurred during the mid-1900s . The total population in the southeastern United States declined from an estimated 15,000-20,000 pairs in the 1930s to between 4,500 and 5,700 pairs in most years between 1977 and 1980 . This decline was accompanied by a major shift in breeding abundance from southern Florida (where large colonies numbering between 5,000 and 10,000 nesting pairs were found ) to a much more dispersed distribution northward though peninsular Florida and into coastal Georgia and South Carolina , where colonies formed at artificial water impoundments and nesting frequently occurred in exotic tree species . The decline in wood stork populations was primarily due to loss of suitable feeding habitat . In South Florida in particular, manipulation of water levels through levees, canals and floodgates changed natural water regimes and affected the stork’s habitat .
Wood stork populations are monitored using aerial synoptic surveys to count nests . Although population estimates based on this technique can be biased by changes in colony location and may underestimate population size, it is considered the most effective method for monitoring long term population trends . Aerial surveys were conducted over a 10-year period starting in 1975 and again over two five-year periods starting in 1991 and 2001 . The number of nesting colonies increased from 29 at the time of listing in 1984 to 71 in 2002 . The number of nests increased from 6,245 in 1984 to 11,279 in 2006 , declined to fewer than 6,000 in 2007-08 due to drought in Florida, then rebounded to more than 12,000 in 2009 .
Increases seen starting in the late 1990s in southern Florida may have been in part due to favorable rainfall and drying patterns . Future monitoring will continue to track population trends and will also help to monitor effectiveness of the “Comprehensive Everglades Restoration Plan,” a recent long-term plan intended to restore more natural water regimes to the Everglades .
Wetland preservation and restoration, protection of nesting areas, and management of water flows began with the approval of the wood stork’s first recovery plan in 1986. The plan was revised in 1997 and augmented with a South Florida recovery strategy in 1999 and a Wood Stork Recovery Action Plan in 2009.
The 1997 plan establishes that “Reclassification from endangered to threatened could be accomplished when there are 6,000 nesting pairs and annual regional productivity is greater than 1.5 chicks per nest/year (calculated over a 3-year average).” .
The plan does not estimate when the stork is likely to reach its downlisting criteria, but in 2007, the U.S. Fish and Wildlife determined that the criteria had been attained and the downlisting process could commence . In 2009, the agency developed a Wood Stork Recovery Action Plan designed speed downlisting. On September 21, 2010, the agency formally initiated the downlisting process with the publication of a positive 90-day finding on a May 28, 2009 citizen petition to downlist the stork .
The recovery plan states that “Delisting could be accomplished when there are 10,000 nesting pairs calculated over a 5-year period beginning at the time of reclassification, annual regional productivity greater than 1.5 chicks per nest/year (also calculated over a 5-year average) and a minimum of 500 successful nesting pairs in South Florida.” This threshold has not yet been met. The plan projects that it might occur by 2017.
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