Less than an hour outside Miami lies the largest subtropical wetland in the United States and the most extensive wilderness east of the Mississippi. Originally called Pa-hay-okee or “grassy waters” by the indigenous Seminole, the Everglades is more than the famed national park. Covering 18,000 square miles from Lake Okeechobee to Florida Bay, the Everglades comprises nine distinct habitats, including the largest contiguous stand of protected mangroves in the Western Hemisphere. Deserving of its superlatives, the Everglades is one of America's most unparalleled and treasured landscapes. Unfortunately, it is also one of our most threatened and fractured, sitting at ground zero for climate change and facing a laundry list of anthropogenically driven threats.
Despite these challenges, the Everglades remains home to endangered or threatened species such as the American Crocodile, West Indian Manatee, Florida Panther, and hosts as many as 400 species of birds throughout the year. It is also the most significant breeding ground for wading birds in North America, with numerous species of herons, egrets, and ibis relying on this system's health for their survival. Using tracking devices to study the movements of Wood Storks and Roseate Spoonbills within the Everglades, researchers believe the data collected from tracking devices placed on these birds give us the information we may need to save the Everglades.
One such researcher is Dr. Jerry Lorenz, director of research for Audubon Florida. Working in this system for over a quarter of a century, Lorenz has primarily focused his research on water management practices within Florida Bay and their effect on the Roseate Spoonbill and its food webs. Since he first started working within the Everglades, Lorenz has witnessed many changes within both the Everglades and Roseate Spoonbills, which he calls a Goldilocks species for their ability to indicate when conditions are “just right.”
According to Lorenz, when he first started working for Audubon in 1989, 90 percent of Roseate Spoonbills in Florida nested in Florida Bay, with only a few nests located in Tampa Bay in Central Florida. However, that all changed shortly after Lorenz’s arrival. From 1990 to 2005 the Tampa Bay population exploded, while the Florida Bay population declined, largely as a result of poor water management practices. When restoration and water management efforts improved hydrology in Florida Bay, nesting began to increase. Unfortunately, sea level rise began impacting the Florida Bay populations as early as 2010, and is now a driving force in their movement. “The spoonbills are now abandoning Florida Bay for the Everglades and points north!” exclaims Lorenz. “They were no longer foraging there due to sea-level rise; the water is too deep.”
Lorenz says some of the most significant factors that caused the mass exodus of spoonbills out of Florida Bay were the anthropogenic impacts on Taylor Slough over the years. Unfortunately, between 1982 and 1984, humans deeply impacted the hydrology of Taylor Slough, which is the primary source of overland freshwater to Florida Bay, helping to balance water levels and salinity. As a result, the 1250 nesting pairs of spoonbills in Florida Bay in 1979 dropped precipitously to 600 nesting pairs by 1989. These numbers bumped up slightly in the early 1990s but eventually declined to an abysmal 400 nesting pairs by 1994. By 2010, less than 100 nesting pairs of this emblematic species occurred in Florida Bay.
To look at these declines on a more granular level, on Tern Key, located in Florida Bay, 660 nesting pairs of Roseate Spoonbills were documented in 1978. The number of nesting pairs dropped to 200 in 1994 and by 2010, the island was completely abandoned. No Roseate Spoonbills have nested on the island since. According to Lorenz, these declines, both on Tern Key and within Florida Bay, are directly attributed to the deterioration of the Everglades.
When asked what is happening, Lorenz relays, “Spoonbill prey are going away; the system isn't as productive as it would be previously.” In addition, he adds, “The salt content of Florida Bay is much higher than it has ever been historically, damaging an already vulnerable prey base.” As a result, Roseate Spoonbills were not getting enough food, which caused them to go elsewhere, including Tampa Bay.
But it wasn't just the lack of spoonbill presence that worried Lorenz; it was also about the decline of productivity. In the 1950s and 1960s, the research of Bob Allen, Audubon's first director of research, noted that Florida Bay spoonbills produced two chicks on average. However, when the canals were first built in the 1960s, this number dropped to 1.2 chicks per nest. These numbers represented a sizeable decline but kept the population stable through 1980. Fast forward to the end of the last century, and the monitored success rate between 1994 and 2000 was 0.6 chicks on average per nest in Florida Bay. As Lorenz had noted, “The food base deteriorated, but that didn't stop the birds from tending to go back to where they were hatched.” As a result, mortality exceeded recruitment, a stark contrast to the excelling Tampa Bay population.
In 2000, Congress passed the Everglades Restoration Plan. Five years later, positive impacts started to happen within the system, and since 2005, spoonbills in Florida Bay yielded about 1.2 chicks per nest, which was a welcomed improvement. But, as Lorenz notes, Roseate Spoonbills in Florida Bay were still struggling. “By 2000, I thought I had the scenario locked down. Roseate Spoonbill numbers stabilized as far as production was concerned, but the number of birds continued to decline.” It was at this time that Lorenz smartly turned to the hydrology of the system, for which spoonbill success is ultimately tied. “We looked at water level data at a dozen locations throughout Florida Bay and noticed that the water levels were not going down, which is what concentrates prey for spoonbills, which are tactile foragers.” For Lorenz, sea-level rise had finally impacted the wetlands where spoonbills forage. “They didn't have access to food.”
Historically, the water level of the Everglades would drop to less than five inches in depth between 100-150 days a year. These low water levels during the dry season were critical for spoonbills to find food for their young. Unfortunately, due to a five-inch rise in sea level, the number of days the water dropped below five inches plummeted to only 13 or 14 days in 2019. Roseate Spoonbills and other wading birds went from having nearly half the year where water conditions concentrated prey to just two weeks.
To further complicate matters, the introduced Mayan Cichlid made things worse for struggling parent spoonbills. “These are tough, territorial cichlids from Central America that do well in both freshwater and marine conditions,” says Lorenz. “Because of increased water depth, the young cichlids, which would normally be prey items for spoonbills and other wading birds, are now surviving to adulthood.” The result of this is thousands of seven to eight-inch, half-pound fish that are too large for spoonbills to eat, which go on to consume all the smaller prey items themselves. During some of Lorenz’s surveys on forage fish, cichlids comprise some 95 to 100 percent of what is detected. For Lorenz, the message is clear, “Spoonbills will not return to Florida Bay unless we stop sea-level rise.”
Some of these findings are coming thanks to banding and tracking programs coming out of Lorenz’s office; efforts that according to him helped explain why these birds historically did not recover after plume hunting and why they are no longer in Florida Bay. “If we had not done the banding and tracking program, I would have continued to believe that spoonbills were moving around the state.” But, as Lorenz sadly notes, “We as humans have burned their house, and thanks to banding and tracking efforts, we know spoonbills are now going inland and north.” Lorenz adds, “They've moved upslope to the mainland Everglades. Furthermore, the numbers in Tampa Bay are now plummeting also as birds are choosing new nesting locations inland, further and further from the coast.”
As subadults and adults, Roseate Spoonbills exhibit extreme levels of natal colony fidelity, returning to the area, sometimes even the island from where they were born to nest. For example, one spoonbill, named "Enrico," was captured as an adult on Tern Key by Lorenz and his team, already banded by other researchers who came before. Looking into the records, Lorenz discovered that the spoonbill was rediscovered nesting back at nearly the exact location from which it was hatched. Despite this level of homing, spoonbills are known to wander. During their first year, like many other species of wading birds in North America, Roseate Spoonbills disperse much farther than during any other point in their life. This is why many of the vagrant spoonbills discovered in other parts of the country outside of their normal range are often young individuals, as has been well documented in 2018 and 2021.
Lorenz is quick to note that spoonbills are also moving because of global warming. “We now have them nesting in Georgia, South Carolina, and Arkansas. As the world gets warmer, their habitat is getting bigger.” He adds, “the bird itself is doing great across this expanding range, but spoonbills are telling us the Everglades has a serious threat in sea level rise as much as they do in over drainage.” According to Lorenz, “Those two things are compounding to mess things up. You need to fix flow and rehydrate.”
To determine the movements of these birds throughout their full annual cycle, Lorenz outfitted 20 adult Roseate Spoonbills with satellite telemetry tags between 2006 and 2009. The resulting movement data, the first of their kind, helped Lorenz and his team discover the timing of their migration, migration routes, stopover sites, and nonbreeding grounds. Because these data have been archived on Movebank and contributed to Audubon’s Migratory Bird Initiative, they are not just helping Lorenz understand more about Roseate Spoonbill movements, they are helping anyone who wants to look.
Out of the 20 birds from Florida Bay tracked by Lorenz and his team, all but three never left the Everglades. “They were always found between Lake Okeechobee and Florida Bay. Seventeen birds stayed in a drainage basin, which was certainly not what we expected,” says Lorenz. But, as Lorenz noted, these birds would have essentially vanished from the landscape if not for the satellite tags. One of the birds that left the Everglades migrated to Andros Island in the Bahamas but the other two went either to Tampa Bay on the Gulf Coast and Merritt Island on the Atlantic Coast, all locations within their pre-plume era nesting range. But Lorenz is not one to rest on his laurels. Lorenz is currently redoing the study from the mid-2000s, using modern cellular technologies to better track his beloved spoonbills and understand where they are going to feed, which is critical to better knowing how to restore the Everglades. However, the birds continued to be full of surprises! Unlike the earlier study, three of the eight birds tracked during the non-breeding season of 2021 went well outside the historic nesting range, spending time in northeast Florida from just south of St. Augustine to the St. Mary’s River, which acts as the Florida-Georgia border.
As he reflected further on the importance of Everglades restoration, Lorenz added that all birds would benefit, not just spoonbills. Such species include Wood Stork, Snail Kite, and the Cape Sable Seaside Sparrow,a subspecies of Seaside Sparrow that is currently threatened with extinction. For Lorenz, he sees the Everglades as more than just a place for spoonbills and other wading birds. “The Everglades are critically important for raptors too.” he says. “These include Bald Eagle, Osprey, and the Peregrine Falcon, which annually sees its largest migration in North America through the Florida Keys.” Lorenz also adds that despite the Everglades being an expansive wetland, it is critically important to our songbirds as well. “The tree islands in the Everglades are where warblers and other passerines rest and feed before crossing to Cuba and points south.” It is also worth noting that restoration efforts in the Everglades help more than just the birds; the region's people would also benefit in a number of ways.
As Lorenz sees it, when it comes to Everglades restoration, “We have got a long way to go.” But, to him and others, there are signs of improvement, including the C-111 Spreader Canal Western Project, which positively impacts the region as it helps keep freshwater flowing into Taylor Slough and ultimately Florida Bay. Along with improved bridges along the Tamiami Trail (U.S. Highway 41), water is finally moving downstream to Everglades National Park.
When asked how the Audubon network can help, Lorenz noted, “Hold our leaders’ feet to the fire! We must protect our wetlands. We need to make sure our leaders understand the importance of our wetlands to all wildlife. Not just birds or spoonbills. What the birds do, so do the alligators and the fish.” He also urged everyone to protect their local wetlands through similar means, which he urged as being just as valuable to our migratory birds as the Everglades.