In the highly technical, science-driven effort to restore Florida’s Everglades, progress is measured with wings, skinny legs and the South Florida Water Management District’s annual wading bird report.
“There is good and bad news,” said ornithologist Mark Cook, a lead scientist at the district who produced the 2013 South Florida Wading Bird Report, which shows moderate improvement in nesting last year.
Scientists documented an estimated 48,291 wading bird nests throughout South Florida, a 57 percent increase over the last three years, but “the downside is we still have a number of species that are doing poorly,” Cook said.
Smaller herons and egrets continued to see double-digit declines in nesting averages.
Although scientists “do not have a clear picture or reason why,” the smaller species are declining, higher than usual water levels are probably to blame, Cook said. It also could be because some of the smaller species are blue or gray, making them more difficult to monitor than the large, white wood storks, he said.
“When we have rain events during nesting period, it raises water levels and the fish disperse and the birds no longer have concentrated prey,” Cooks said. “We had a number of rain events right in the middle of the breeding season that actually caused a lot of nest abandonment and we lost thousands and thousands of nests unfortunately.”
Wading birds are used as a barometer of progress in Everglades restoration not only because they are large, mostly white and easy to monitor but also because “they respond very quickly and intuitively to changes in water levels,” Cook said.
“They are limited by leg length and beak length so they can only forage in certain water depths,” Cook said. “So they move around very quickly in response to changing hydrologic conditions and hydrology is the key to restoring the Everglades.”
Wading birds monitored for the report include the white ibis, glossy ibis, wood stork, great egret, snowy egret, reddish egret, great blue heron, tricolored heron, little blue heron, black-crowned night heron, yellow-crowned night heron and roseate spoonbill.
After decades of designing projects, buying land and fighting court battles, restoration projects are finally being built and last year’s uptick in nesting reflects that value of those projects, said Tabitha Cale, Audubon Florida’s Everglades Policy Associate.
“In the areas where these restoration projects are coming online, that’s where we’re seeing the most improvement,” Cale said. In particular, the restoration of the Kissimmee River, about 85 percent complete, the C-111 spreader canal project in Miami-Dade County and habitat protection efforts along the shores of Lake Okeechobee are already attracting birds, Cale said.
“It does take time for the fish populations to bounce back and for the birds to return,” Cale said. “It will still probably be a few years before we see really strong results.”
Some notable three-year averages include a 90 percent increase in white ibis nests and a 46 percent increase in great heron nests in South Florida, according to the report.
However, the success of restoration projects will be measured not only by the increase in bird populations but also in birds returning to their natural, native habitat.
For example, wood stork nesting was up 97 percent over a three-year average, but no wood stork nests were found at Audubon’s Corkscrew Swamp Sanctuary in southwest Florida, once home to the largest nesting colony of wood storks in North America.
“Even though wood storks are up overall, they’re not nesting in their historic breeding grounds,” Cale said. “That’s largely due to the loss of wetlands due to development.”
That’s not an uncommon situation, Cook said. Historically, most wading birds nested along the state’s remote, southwestern coast, which is now part of the Everglades National Park. But as the estuaries in the region became more polluted, the birds began migrating north, into the interior of the Everglades, he said.
“One of the first things that rang the alarm bells about the quality of Florida Bay and the southern Everglades degrading by the lack of water supply there was the fact that all these wood storks and white ibises moved elsewhere,” Cook said. “One of the goals of restoration is not only to increase the number of wading birds but to move those wading birds back down to the south where historically they nested.”