Every few weeks each winter and spring, Roseate Spoonbills nesting in a southern Florida lagoon receive an odd set of visitors: Audubon scientists, who paddle and trek through the brackish water among small mangrove islands to spy on the birds, their nests, and, later, their chicks.
Nests counts are among the most reliable ways to monitor bird species: No nests means no fledglings, which means fewer adult birds in the future. So in southern Florida, which was once home to 2.5 million wading birds, scientists have spent 22 years counting nests of 18 species in the Everglades and surrounding areas. Five of those are considered indicator species—Wood Storks, Great Egrets, White Ibises, Snowy Egrets, and Tricolored Herons—and their nests’ successes and failures have come to represent the health of the entire ecosystem.
The results of these counts are published each year in an annual report, spearheaded by the South Florida Water Management District, that also takes into account nesting data collected by state agencies, protected areas, and universities. In addition to the Audubon team’s regular visits to spoonbill nests, most other surveyors tally nests by photographing them from helicopters and boats.
The latest South Florida Wading Bird Report, which was published last week, offers signs of trouble for the birds and the places they live. During this nesting season, which ran from December 2015 to July 2016, surveyors were disappointed to find 26,676 nests total. That’s just one-third the number of nests tallied during 2009, one of the best nesting years in decades, and the lowest nest census since the 2007-2008 season. Of the indicator species, only two (Great Egrets and White Ibises) met their nest recovery goals. The only bird to show an above-average nesting season last year was the Roseate Spoonbill.
The disappointing results aren’t a total surprise. In south Florida, wetland ecosystems are driven by water levels, which vary widely depending on an interplay of rainfall, sea level, and water moving through the landscape. Over the course of last year, different parts of the region saw both unusually high and unusually low water levels in patterns that don’t make life easy for birds. More worrisome, however, is that the poor results and their contributing factors are part of a longer-term negative nesting trend—one that speaks to the complexity of these habitats and the severity of the changes they are experiencing, whether from warmer climates, human activity, or some other cause.
“You can blame [the 2016 results] on the weather,” says Julie Hill-Gabriel, who leads Audubon Florida’s Everglades team. According to Hill-Gabriel, in a healthy ecosystem, the occasional bust year would be balanced by the occasional boom year, but those simply aren’t happening these days. “We haven’t seen that above-average [nesting] to balance out when you have a bad year,” she says.
Wood Storks are typical in their response to rainfall patterns. They’re happiest with wet summers, when fish flourish, and dry winters, which cram fish into smaller pools and make for easy fishing, a necessity for feeding their chicks. Last year’s weather—a dry summer and a wet El Niño winter—meant hungry storks missed their nesting targets. All together, Wood Storks produced 1,457 nests, a decrease of 38 percent from the 10-year average.
There’s a chance that number could improve for next year’s report. Thanks to just the right amount of rain this year, the current breeding season shows an increase in nesting activity from Wood Storks, particularly at Corkscrew Swamp, where the birds have bred only twice in the past decade. Audubon monitors at Corkscrew are optimistic, but they remain concerned that nesting is shifting to later in the year.
According to the report, Snowy Egrets, Little Blue Herons, and Tricolored Herons all continued their “sharp declines in nest numbers over the past decade.” Snowy Egrets and Little Blue Herons produced about half as many nests as their 10-year average, and Tricolored Heron nests were down 16 percent. Also noted in the report is that the declines for all three birds have “been particularly acute in the Everglades and are cause for concern,” but it’s still unclear why exactly the drop-offs have been so severe.
One silver lining in the report is that Great Egret nesting numbers didn’t decrease as sharply as with other species, showing only a 7 percent decline from their 10-year average. This was in part because the birds were able to continue nesting at Lake Okeechobee, Florida’s largest freshwater lake. Many wading birds had trouble navigating the lake this year because of unusually high water levels due to excessive rainfall; Great Egrets did better thanks to their long, stilt-like legs.
But this year may be just the beginning of the high-water problems at Okeechobee. Before humans settled the region, lake water would have flowed south through the Everglades wetlands and into Florida Bay, but without that natural flow, water managers are sometimes forced to send water east and west, where it doesn’t belong. One of the most controversial bills on the state legislature’s calendar this spring seeks to reinforce the edges of the lake so managers can store more water. That would reduce the amount of water redistributed east and west of the lake, and it would also keep Okeechobee’s marshlands flooded through the breeding season.
The loss of that southward freshwater flow also has consequences for Florida Bay and its 850 square miles of shallow water that hosts mangrove islands, coral reefs, seagrass meadows—and the lagoon of Roseate Spoonbills. Last year, the bay water grew so salty that seagrass, a cornerstone of the bay’s ecosystem, died off in swaths. That saltiness could be having an impact on the Roseate Spoonbills. In recent years, they have moved inland away from the lagoon, and while this year’s nest count was above average, their nesting in Florida Bay seems to have plateaued overall.
Despite the report being mostly bad news, Hill-Gabriel hopes it will add momentum to the push for projects to restore the Everglades and the region’s natural southward water flow. “We know the birds are telling us that the system is broken,” she says. But between projects that have been recently completed and those that are in the works, “there’s a lot of good news on the restoration front.” That includes one project 30 years in the making, which would elevate a major east-west road so water can flow under it. Another restoration project, which would give a failed subdivision development back to nature, should be complete within about two years.
Other projects in the works or on the table could add to that list. And to find out if they are helping, Audubon scientists will continue their annual spoonbill nest counts in the lagoon. The birds, sensitive indicators as they are, will tell them if they’re moving fast enough to restore and save the critical habitat.