The wood stork (Mycteria americana) was once a thriving species in the Florida Everglades, but in recent decades their population has declined dramatically. This iconic wetland bird is now federally listed as threatened under the Endangered Species Act. Understanding why wood storks are struggling is key to protecting them and restoring their habitat.
What are wood storks?
Wood storks are large, long-legged wading birds that stand around 3 feet tall with a 5 foot wingspan. They have white plumage with black accents on the wings and a featherless black head and neck. Their distinctive curved bill is adapted for catching fish and other prey in shallow wetlands.
Wood storks breed in colonies called rookeries, nesting high up in cypress trees or mangroves. Breeding season lasts from December to August, with females laying around 3-5 eggs. Both parents help incubate the eggs for about 30 days until hatching. Wood stork chicks are altricial, meaning they hatch helpless and rely on their parents for food and care while in the nest for 2 months.
These birds feed cooperatively, often in flocks of hundreds, flying between wetland areas and soaring high on thermals to search for food. Their diet consists mainly of fish but also includes frogs, aquatic invertebrates, small reptiles, and baby alligators. Wood storks capture prey by tactilocation – using their sensitive bill tip to probe shallow waters and snap up prey they detect.
Where do wood storks live?
Wood storks historically nested throughout the southeastern coastal plain from South Carolina to Florida and along the Gulf Coast into Texas and Mexico. Since the 20th century, habitat loss has caused major declines in their breeding range. Currently the largest breeding populations are concentrated in Florida, Georgia, and coastal South Carolina.
Wood storks require specific wetland habitats for nesting, foraging, and raising young. Their ideal foraging sites are shallow, open freshwater wetlands like marshes, swamps, lagoons, ponds, flooded forests, and depressions that concentrate fish. Nesting habitat consists of trees or shrubs surrounded by open water, protected from predators.
Why did wood storks thrive in the Everglades?
The Florida Everglades provided ideal habitat conditions that allowed wood storks to thrive for centuries. This expansive subtropical wetland ecosystem historically covered much of south Florida, comprising wide shallow, slow-moving rivers, marshes, swamps, forests, mangroves, and coastal prairies.
Key features that made the Everglades so well suited for wood storks included:
- Abundant food supply – The shallow, fish-filled waters and concentrated dry-season wetlands offered reliable feeding habitat.
- Suitable nesting sites – Islands of tropical hardwood trees like cypress and mangroves provided protected nesting colonies.
- Ideal hydrological conditions – The natural water flows, flooding, and dry-downs promoted healthy fish populations and concentrating of prey.
- Lack of human disturbance – Nesting colonies were relatively safe from human interference and predation.
At one time over 10,000 pairs nested in the Everglades. Huge breeding colonies could be found in protected coastal mangrove forests, inland cypress swamps, and hardwood hammock tree islands throughout south Florida.
How have wood storks declined in the Everglades?
Wood storks have declined drastically in the Everglades region over the past century. Habitat loss, drying of wetlands, human disturbance, and lack of prey have caused their numbers to drop.
Estimates indicate there were between 5,000-10,000 nesting pairs in the 1930s-40s. But by the late 1960s, there were less than 5,000 nesting pairs across all of Florida. The lowest point was in 1978 when only around 1,500 nesting pairs remained statewide.
In South Florida specifically, wood stork nesting colonies virtually disappeared from the southern Everglades between the 1950s-70s. Surveys found no active nesting south of Alligator Alley highway after the early 1970s.
Habitat loss initially drove the decline:
- Draining and development of wetlands for agriculture and urban areas destroyed foraging habitat.
- Hydrological changes disrupted natural water flows.
- Loss of nesting trees to logging, storms, and fire reduced breeding sites.
By the 1980s, the primary threat shifting from habitat destruction to lack of hydrological management to maintain suitable water levels and prey concentrations through the dry season when wood storks nest.
Drying of wetlands
Extensive drainage of the Everglades disrupted the natural variability between wet and dry seasons. Lack of sufficient rainfall and water management practices resulted in prolonged dryouts. Dry-downs are natural and important, but excess drying caused wetlands to shrink and dry up prematurely or completely before wood stork young had fledged.
Loss of prey
Drying water levels and hydrological changes reduced fish populations and ability of wood storks to successfully feed. Fish require shallow, flooded wetlands to spawn and survive dry seasons. But when wetlands dried up too early or too low, fish numbers crashed. Without adequate prey, wood stork colonies could not provision young.
Human disturbance
Increasing human activity and infrastructure like roads, canals, and urban areas allowed predators and disturbance to reach nesting colonies more easily. This may have reduced nest success and colony site use. Drainage canals may have also enabled predators like raccoons to access former wetland breeding grounds.
How hydrological restoration can help wood storks
Scientists recommend a combination of hydrological restoration, maintained water flows, and protected nesting habitat to recover wood storks in the Everglades.
Restoring sheetflow
“Sheetflow” refers to the historic wide, shallow,slow flow of water south through the Everglades. Restoring sheetflow can redistribute surface water to revive dried-out wetlands. Filling canals, removing levees, and using pumps can restore flow.
Providing dry-season water
Managing water levels to prevent excess drying in the winter-spring nesting season can help concentrate prey. Targeted use of canals, pumps, and control structures can achieve this.
Protecting nesting colonies
Fencing, patrols, and declaring sensitive breeding sites off-limits can limit human disturbance of nesting colonies. Maintaining hydrology to hardwood nesting islands is also important.
Habitat protection & restoration
Preserving remaining Everglades wetlands, acquiring land, removing invasive species, preventing fires, and planting native vegetation can all help restore wood stork habitat over the long term.
Outlook for wood storks in the Everglades
Wood storks face an uphill battle, but there are encouraging signs thanks to conservation efforts. Since the 1970s, the U.S. Fish and Wildlife Service and Florida wildlife agencies have made major strides in studying wood stork declines and implementing management strategies like seasonal flooding, constructing wetlands, and protecting colonies.
These efforts have helped halt the downward population trends and even enabled slight increases in recent years. The South Florida Water Management District reported over 3,000 nesting pairs in the Everglades region in 2020 compared to barely 100 pairs in the 1970s.
While wood storks remain endangered in South Florida, ongoing restoration projects provide hope that revived hydrology, sufficient prey, and protected breeding sites can allow these unique birds to once again thrive in the Everglades.
Conclusion
In summary, wood storks were once abundant in the Florida Everglades due to ideal wetland habitat and hydrological conditions. Draining wetlands and disrupting water flows caused declines over the 20th century. Restoring natural sheetflow, maintaining appropriate dry-season water levels, protecting colonies, and ongoing habitat management offer keys to recovering wood stork populations. If conservation efforts continue, wood storks may once again flourish in a revitalized Everglades ecosystem.
