UF/IFAS scientists learn ‘threatened’ wood storks are showing flexible traits
DAVIE, Fla. – On the heels of World Migratory Bird Day, the international May 9th celebration drawing attention to the phenomenon of bird migrations and connecting people to technologies used to track birds and promote conservation, comes good news for wood storks.
A recently published study analyzing migratory patterns in wood storks by UF/IFAS scientists at Fort Lauderdale Research and Education Center found that the species is not only showing signs of flexibility in the face of environmental changes, but are also demonstrating a variety of migratory patterns, as well as showing changes in their food foraging strategies.
“The biggest take-home message I want people to receive is that wood storks are highly adapted to an environment that is unpredictable (the Florida Everglades) and one that continues to become even more unpredictable because of human-driven impacts on how and where their food is available,” said Simona Picardi, a doctoral candidate in the Department of Wildlife Ecology and Conservation at UF/IFAS Fort Lauderdale Research and Education Center at the time of the study.
The study utilized a long-term GPS-tracking dataset collected between 2004-2018 of 133 wood storks that analyzed migratory patterns and food foraging behaviors. The wood storks were captured in the field by a team of scientists and graduate students at the Frederick’s Lab of the UF/IFAS Wildlife Ecology and Conservation Department located in Gainesville. The team fitted the wood storks with solar-powered GPS tags which allowed them to obtain hourly location data.
Mathieu Basille, assistant professor of landscape ecology at the Fort Lauderdale Research and Education Center, explains that the typical life cycle of wood storks is to migrate south to the Everglades to nest in the winter, and then to spread in the landscape for the rest of the year, normally further north in Florida and neighboring states such as Georgia and South Carolina.
By comparison, what the UF/IFAS scientists at Fort Lauderdale learned from the study is that:
- Some individuals migrate as we typically expect (59% of the population); but others are year-round residents and don’t show migration (28% of the population).
- Some individuals do not migrate consistently every year (13%), sometimes they do, sometimes they do not; these are known as facultative migrants.
- Those wood storks who are residents tend to stay near urban areas.
“My findings suggest that behavioral differences among individuals are helping the wood stork population cope with challenges posed by environmental change,” said Picardi. “If other findings corroborate this idea, this might mean that wood storks will be able to persist in the future in the southeastern U.S. despite drastic urbanization and alteration of their environment.”
The wood stork is one of Florida’s wading birds that was historically a common species throughout the southeastern United States. Canals, irrigation, and other water control projects have long affected the flow and path of the water channeling into the Everglades, the stronghold of this species in Florida. Steep declines in stork populations occurred during the first half of the 1900s because of the stork’s specialized foraging behavior dependent on the diminishing wetlands especially during south Florida’s era of increased development.
In 1988, wood storks were listed as “Endangered” by the U.S. Fish and Wildlife Service (FWS). In 2004, the Florida Fish and Wildlife Conservation Commission (FWC) declassified the word stork from “Endangered” to “Threatened” as the wood stork experienced a slight upward trend in its population. Florida holds the largest nesting population of Wood Storks in the United States.
Picardi noted how the wood stork plays an important role as an indicator of ecosystem health in the Everglades.
“If their population thrives then that’s a symptom that the ecosystem, as a whole, is functioning well. If wood storks were to become more urban and their population dynamics were to be de-coupled from natural availability of food sources in the Everglades, this would make them a not-so-reliable indicator of the health of the natural ecosystem,” she said.
Additionally, wading birds also play an important role in the nutrient cycling of the Everglades, added Basille. In other words, if wood storks were to go extinct or be displaced from the Everglades, there would be consequences in terms of nutrient content in the water, with impacts on plants and other animal species.