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The majority of the avifauna inhabiting the Everglades region is wading birds, with a few species of diving birds, song birds, and raptor present. Those colonial wading birds utilize the region as both feeding and breeding habitat. The types of secondly fluctuation water levels exhibited by the natural Everglades hydrologic cycle provide perfect habitat for the wading birds. During the rainy season, when water levels are high, fish and invertebrate prey species re populate the newly flooded marsh and begin to increase in abundance. As water levels recede during the dry season, the density of these prey species increases as they concentrate in remnant pods and along the edge of the drying marsh. This high concentration of prey species provides an excellent source of food for wading birds and has been shown to be a major factor in the initiation of nesting for most wading bird species.
Wading Bird Rookeries
Most wading birds nest in large colonies typically in trees on small islands, such as, mangrove islands in Florida Bay or tree islands in the Everglades. The social nesting aggregations are called rookeries and usually contain a mixture of species. Rookeries commonly contain anhingas, cormorants, and brown pelicans in addition to wading birds. Outside of the breeding season, most of these species and other wading birds disperse, using shifting sites for roosting.
Most rookeries of the Everglades were formerly located in the southern part of the ecosystem, in Everglades National Park. Rookery Branch, located at the head of the Shark River and once home to the largest of the region’s rookeries, is now abandoned. In the 1930’s, it harbored as many as 200,000 birds. Reduced productivity of the estuarine area is due in part from the altered hydroperiod in both the rocky glades of the southern Everglades as well as in the lower Shark River Slough. Compartmentalization of the ecosystem resulting from altered hydroperiod has contributed to the demise of the southern Everglades rookeries.
