Wood Stork (Mycteria americana )
Federal Status: Endangered - U.S. Breeding Population (Federal Register, February 28, 1984)
Description: Wood storks are large, long-legged wading birds, about 45 inches tall, with a wingspan of 60 to 65 inches. The plumage is white except for black primaries and secondaries and a short black tail. The head and neck are largely unfeathered and dark gray in color. The bill is black, thick at the base, and slightly decurved. Immature birds have dingy gray feathers on their head and a yellowish bill.
Habitat: Wood storks use freshwater and estuarine wetlands for nesting, feeding and roosting. They feed in wide variety of tidal and freshwater ecosystems: freshwater marshes, ponds, hardwood and cypress swamps, narrow tidal creeks or shallow tidal pools, and artificial wetlands such as seasonally flooded roadside and agricultural ditches, impoundments and large reservoirs. Particularly attractive feeding sites are depressions in marshes or swamps where fish become concentrated during periods of falling water levels. They nest in patches of medium to tall trees, either in standing water or on islands surrounded by expanses of open water.
Distribution: The current population of adult birds is difficult to estimate, since not all nest each year. Presently, the wood stork breeding population is believed to be greater than 8,000 nesting pairs (16,000 breeding adults). When the wood stork was added to the endangered species list in 1984, nesting was restricted to Florida, Georgia, and South Carolina, however they may have formerly bred in most of the southeastern United States and Texas. Active rookeries were found in North Carolina in 2005. A second distinct, non-endangered population of wood storks breeds from Mexico to northern Argentina.
Storks from both populations move northward after breeding, with birds from the southeastern United States population moving as far north as North Carolina on the Atlantic coast and into Alabama and eastern Mississippi along the Gulf coast, and storks from Mexico moving up into Texas and Louisiana and as far north as Arkansas and Tennessee along the Mississippi River Valley. There have been occasional sightings in all States along and east of the Mississippi River, and sporadic sightings in some States west of the Mississippi and in Ontario.
Threats: The southeast United States breeding population of the wood stork declined from an estimated 20,000 pairs in the 1930's to about 10,000 pairs by 1960, and to a low of approximately 5,000 pairs in the late 1970s. Nesting primarily occurred in the Everglades. The generally accepted explanation for the decline of the wood stork is the reduction in food base (primarly small fish) necessary to support breeding colonies. This reduction is attributed to loss of wetland habitat as well as to changes in water hydroperiods from draining wetlands and changing water regimes by constructing levees, canals, and floodgates to alter water flow in south Florida.
Wood storks have a unique feeding technique and require higher prey concentrations than other wading birds. Optimal water regimes for the wood stork involve periods of flooding, during which prey (fish) populations increase, alternating with dryer periods, during which receding water levels concentrate fish at higher densities coinciding with the stork's nesting season. Loss of nesting habitat (primarily cypress swamps) may be affecting wood storks in central Florida, where nesting in non-native trees and in man-made impoundments has been occurring recently. Less significant factors known to affect nesting success include prolonged drought and flooding, raccoon predation on nests, and human disturbance of rookeries.
Loss, fragmentation, and habitat modification continue to affect wood storks. However, the wood stork has demonstrated an ability to respond to these threats through range expansion, adjusting reproductive timing, and using a variety of wetlands, including man-made wetlands to forage roost and breed. The extent of the wood stork’s breeding range has expanded and shifted northward to include southeastern North Carolina.
Kahl, M.P. 1964. Food Ecology of the Wood Stork (Mycteria americana) in Florida. Ecol. Monogr. 34:97-117.
Ogden, J.C. 1996. Wood Stork (Mycteria americana). Pp. 31-41 in J.A. Rodgers Jr., H.W. Kale II, and H.T. Smith (eds). 1996, Vol. V. Birds, Rare and Endangered Biota of Florida. Univ. Florida Press, Gainesville, FL. 688 pages.
U.S. Fish and Wildlife Service. 1996. Revised Recovery Plan for the U.S. Breeding Population of the Wood Stork. U.S. Fish and Wildlife Service, Atlanta, Georgia. 40 pages.
U.S. Fish and Wildlife Service. 1999. South Florida Multi-Species Recovery Plan for the threatened and endangered species. Vero Beach, Florida.
For More Information on Wood Storks...
- The Birds of North America - online Cornell Lab of Ornithology
John Hammond, Fish and Wildlife Biologist, 919-856-4520 ext. 28
Species profile revised on October 1, 2011.