Wood Storks (Mycteria americana)

Wood Stork colony at Corkscrew

CSS Foraging Storks
Jason Lauritsen
Wood storks foraging

Corkscrew Swamp Sanctuary's old growth bald cypress forest is our nation's most celebrated historic colony.  According to Thomas Gilbert Pearson (in "the Bird Study Book", 1917) it supported an estimated 100,000 storks.  Since 1958, Audubon has monitored nesting at the colony, making it the longest running continuous data set on wood stork nesting in the nation.  Having supported approximately 75,000 nests and fledging an estimated 100,000 chicks since 1958, it is the most productive colony in the nation. 

Storks as indicators of wetland health

Throughout the Greater Everglades of South Florida, wood stork nesting success is a measure of wetland health.  The Greater Everglades is marked by a wet dry cycle defined by an intense four month rainy season followed by eight months of drying conditions.  During the rainy season widespread flooding would connect far-flung wetlands with surface water flowing in sheets across the flat landscape carrying fish and other aquatic fauna to multiply and grow.  Dry season then initiated a slow recession of the surface water, isolating small depressions at the edge of the larger wetland complex.  Over and over again as the recession marched on, from November through May, fish would get trapped and concentrated in these isolated pools. This was ideal for growing wood storks.  These tactile feeders are masters at catching fish when they are highly concentrated in wetlands once they've dropped below 16". 

CSS 2004 Land cover & canals
Jason Lauritsen
2004 Land cover & canal map of CSS wood stork core foraging area
An extensive network of canals, ditches and roads were constructed resulting in widespread drainage and fragmentation of wetlands throughout South Florida.  These impacts coincided with the decline in wood stork breeding effort, and eventually in the population.  Since wood storks are highly adapted to the natural historic "pre-drainage" conditions, conventional wisdom predicts that restoration of the wetlands impacted by development would result in increases in the breeding effort and population of wood storks in the region.

Scattered records of wood stork nesting at Corkscrew date as far back as 1914.  The National Audubon Society has been monitoring the colony since 1958.  Productivity has dropped from an average of 5,450 chicks fledged per year in the first 10 years of monitoring (1958-67) to 540 chicks from 2003-12.  Nesting effort has declined similarly (see figure below).

CSS Wood stork nesting at Corkscrew 1958-2012
Jason Lauritsen
Wood stork nesting at Corkscrew from 1958-2012

Copyright  2015 National Audubon Society, Inc