In 1954, concerned citizens in Southwest Florida rallied together to protect the old-growth cypress forests of Corkscrew Swamp from logging. These trees, now more than 500 years old, supported the renowned Corkscrew wading bird colony that seasonally hosted thousands of nests and fledged tens of thousands of Wood Stork chicks. The establishment of Audubon’s Corkscrew Swamp Sanctuary provided much-needed protection of the colony site, but Wood Storks remained vulnerable to ecological changes throughout the region, as their core foraging area includes all wetlands within 18.6 miles of the colony.
Since the 1960s, Wood Stork nest numbers at the Corkscrew colony have declined steadily, concurrent with development. In recent years, Wood Storks have opted to not nest at the Corkscrew colony site more often than they’ve chosen to nest — a clear sign that food resources in our area are inadequate. Years that Wood Storks choose to nest at the Sanctuary, particularly when they’re able to successfully fledge chicks, give scientists hope that there is still time to improve regional conditions and restore annual nesting.
Wood Storks incubate their eggs for 30 days, and fledge their young about two months after hatching. The chicks are fast-growing and have large food requirements: their primary food being small fish and crayfish. Loss of wetlands and a decline in the quality of many existing wetlands have reduced the ecosystem’s capacity to produce enough aquatic prey to support a large Wood Stork colony in the Corkscrew area. To make matters worse, over-drying of the Sanctuary during the dry season (as we’ve seen in recent decades) makes nests vulnerable to mammalian predators. For the second consecutive year, unusual winter rainfall patterns delayed Wood Stork nesting, which in turn reduced annual nest productivity. In 2020, while regional nesting began in March, Wood Storks chose not to nest at the Sanctuary at all. This trend is troubling for storks, as predictions of global climate change call for increased variablility in annual rainfall patterns.
In 2021, the first nests were observed in the Corkscrew colony during the first week of March. While over 60 storks were in the colony, they were attending to only 16 active nests — a fraction of the nests seen historically at this colony. This mixed colony also contained over 140 Great Egret and a few Roseate Spoonbill nests. By June 1, we observed 13 successful Wood Stork nests, with 25 fledgling chicks. Two other Southwest colonies were active this year, Lenore Island (on the Caloosahatchee River) and BC-29 (along SR-29), both producing significantly more nests and fledged chicks than the Corkscrew colony.
While Wood Stork numbers have declined precipitously in the Western Everglades, Wood Stork nesting has increased modestly in the Greater Everglades in recent years, and increased dramatically in Georgia and South Carolina. The decline in Wood Stork nesting in Southwest Florida is a clear indicator of the loss and degradation of our region’s wetlands, but the storks’ annual return to the Sanctuary offers hope. Audubon will continue to work with our federal and state partners to conserve and restore wetland hydrology, while improving foraging conditions in and around the Sanctuary in hopes of seeing our Wood Stork population rebound.