Nesting declines for some species of wading birds shows the long-term damage suffered by Florida's Everglades, and targets set for higher numbers of nests may become unattainable if conditions in the unique wetlands do not improve soon, state officials said.
The gains seen for some species last year suggest that conditions in some parts of the Everglades have become more favorable for birds, possibly because of changes in the way water flows through the wetlands, a reduction in mercury levels and cyclical weather patterns, according to an annual report on wading bird nesting released Thursday by the South Florida Water Management District, the state agency that oversees Everglades restoration.
But steep declines or a lack of improvement for other birds show that conditions still don't compare to water levels in the Everglades before officials sought to drain the wetlands half a century ago to make way for development and farming.
"Ecological deterioration is occurring across all parts of the ecosystem, and this increases the probability of irreversible ecosystem changes that limit our ability to recover the essential defining characteristics of the historical Everglades," Mark Cook, lead scientist for the district's Everglades systems assessment section, wrote in the report.
Last year was a below-average nesting season, with a total of 34,714 nests, down from 48,291 the year before. The best year on record for nesting since the 1940s was 2009, when officials counted 87,564 nests.
The number of wading bird nests counted each year is a barometer for the health of the Everglades. Historically, large flocks of birds thrived throughout South Florida, but their populations declined as canals and flood-control structures drained the wetlands.
One of the main goals of Everglades restoration is to restore natural water flows that would sustain healthy wading bird populations, but the success of those projects may depend on how soon they start working, Cook said.
Nesting by little blue herons, tricolored herons and snowy egrets declined significantly last year, according to the report.
In the mid-2000s, over a thousand nests would be counted each year for each of those species. In 2014, a total of 133 nests were counted for those three species, and most of those belonged to snowy egrets, according to the report.
The number of nests for roseate spoonbills, great egrets and the white ibis also declined.
The only species that showed improvement was the wood stork, which produced 2,799 nests and returned to nesting sites in the Corkscrew Swamp Sanctuary that the birds had abandoned years ago, officials said.
Everglades restoration has long been stalled by funding challenges, and environmental advocates say the decline in nesting highlights the urgency in securing resources for those projects.
Wading bird nesting has improved the most in the Kissimmee River Valley, where Everglades restoration efforts are nearly complete, said Tabitha Cale, Everglades policy associate at Audubon Florida.
Restoration projects that would direct more water south through Everglades National Park are in the works, which would increase the amount of habitat available for nesting, she said.
"We know the sooner we get them going, the sooner we'll see improvements for the birds," Cale said.