Sun Sentinel Palm Beach Edition
S. Florida wading bird nesting level low
The number of nesting wading birds in South Florida, a key measure of Everglades health, sunk to a decadelong low last year, according to a South Florida Water Management District report released last week, the latest in a 22-year tally.
Just over 26,000 nesting birds were counted across the Everglades and in Lake Okeechobee last year, well below the 10-year annual average of about 42,000. Last year’s El Niño-driven weather, which triggered a late start to the wet season followed by a record wet winter, played a big part in a drop in the amount of fish that birds eat, and influenced their nesting. But the rain can’t explain the ongoing trend, biologists said.
“The system isn’t really geared for wading birds at this point,” said district biologist Mark Cook, who co-edited the report. “It is when we have this perfect storm of conditions, but until we get more water in the system, we’re not really going to have the good nesting bird seasons we had in the 1940s.”
Biologists track five different wading birds that historically nested in such vast numbers that John Audubon famously claimed they blocked the sun when they took to the air. While some — white ibises, wood storks and great egrets — show long-term increases, their colonies remain far below what they once were. Where and when the birds nested also changed, indicating just how severe ongoing disruptions to water flows in and around their wetland homes have become.
“They’re telling a story. And when a decline as dramatic as this occurs, we really need to take that seriously,” said Julie Hill-Gabriel, Audubon Florida’s director of Everglades policy.
Overall, nesting among white ibises, the Everglades’ most common bird, dropped 45 percent last year. Wood storks fell 38 percent, and great egrets were down 7 percent. The steepest drops were in little blue herons, which fell 61 percent, and snowy egrets, which dropped by 51 percent.
Because freshwater that once flowed from Lake Okeechobee across marshes to Florida Bay has been cut off, some nesting colonies over the last 50 years have also shifted. That pattern is no more stark than with roseate spoonbills, the scarlet-colored birds that once nested among the small mangrove keys in Florida Bay. Over the past five years, the birds have moved to a pond near the park’s main road and a coastal hammock. Cook said colonies are also appearing in conservation areas far to the north. The reason is not certain, but may be caused by the disappearance of pockets of freshwater as sea levels inch up. Pythons may also be staking out the islands.
“It is clear in my mind, clear as day, that these birds are already responding to sea rise,” said Jerry Lorenz, Audubon’s state research director. “The things that really are telling us that this is their response is critical data shows increased water levels on traditional foraging grounds. They are moving further inland to get shallower and fresher waters.”
Spoonbills and wood storks have also begun nesting later, which makes food harder to find and puts young chicks at risk, Cook said.
Typically a wet summer spreads water across the marshes, leading to more fish. When the dry season arrives, marshes begin drying out and channel the water through the Everglades ridges and sloughs to concentrate fish in ponds where birds nest. But last year’s unusual wet and dry seasons meant fewer fish were even less concentrated because the marshes never dried out.
“We literally almost had the reverse hydrologic conditions,” Cook said. “Instead of water levels coming down, they actually went up.”