Wednesday, May 6, 2009

FLORIDA BAY -- Relying heavily on the normal wet/dry seasonal cycle of the Everglades in order to thrive, the roseate spoonbill has long been considered an indicator species on the health of Florida Bay.

But despite nesting in numbers this year that were nearly as low as has been seen in three decades, the future of the bay's spoonbill population could be looking positively rosy. And that rosiness, says the bay's preeminent spoonbill biologist, is in large part due to the South Florida Water Management District, an agency that hasn't always won praise from the environmental community.

"[T]he actions of the SFWMD in considering spoonbills in water management decisions may have prevented this iconic species of Florida Bay from becoming locally extirpated," Jerry Lorenz, who heads Aububon's Tavernier Science Center, wrote in a paper completed last week summarizing spoonbill nesting patterns from 2006 through 2008. The paper has yet to be published.

Audubon scientists counted just 316 spoonbill nests in all of 850-square-mile Florida Bay during this winter's nesting season, said Lorenz. The nesting season typically lasts from November through March.

The figure is just two more than last year's total of 314 nests, which was the lowest count since the late 1960s, when the spoonbill had in part recovered from decades of plume hunting early last century.

That's the bad news.

The good news is that while the number of nests remained dismal this year, the production from those nests was not. If during a given nesting season each spoonbill nest hatches an average of one chick or more, scientists consider it a successful year. This year the baywide average surged above two fledglings per nest, Audubon samples indicated. It's the fourth straight successful nesting season, a stark contrast to the 19 years that preceded 2005-06. During those years, there were just seven successful nesting seasons, Lorenz said.

Since spoonbills take approximately four years to mature, Lorenz believes that the increased number of chicks per nest should begin to show up in the number of nests soon.

"We'll start seeing those ones from 2005 come back next year," he said.

The surge in nest productivity for the spoonbill can be attributed to a more consistent wet/dry cycle -- partially the result of plain, old good weather, and partially controlled by water managers at the SFWMD.

During a typical summer, heavy rains in South Florida raise water levels in the Everglades, expanding the range of the minnows that serve as the main food for spoonbills and other foraging birds. More rain means low concentrations of salt in the water as well, another boon for the fish.

Winter's dry season forces minnows to retreat into the far less vast areas that remain underwater, where they are easy targets for spoonbills, other wading birds and the prize gamefish, snook, which shares the spoonbill's diet.

But starting in the early 1980s, when the massive C-111 canal -- cutting a swath through the Glades all the way from southern Miami-Dade County to Barnes Sound -- went online, the bay's health began to decline.

Water managers, charged with protecting cities and farms from flooding, responded to heavy rains by releasing large pulses of water through the canal and out to the bay throughout the year, disrupting the wet/dry cycle. Spoonbills, robbed of their captive minnows, declined in response.

Beginning in 2005, however, water managers began taking the spoonbill into consideration before releasing water, consulting when necessary with Lorenz.

In general, they have released excess water slowly, rather than in big pulses, allowing for the natural winter drying cycle to run something close to its natural course. Behind the effort has been Paul Linton, director of the division's water controls section.

In an interview last week, Linton demurred any suggestion that he has saved the Florida Bay spoonbill population, as Lorenz wrote.

More significant than anything the district has done, he said, has been the weather over the past four years, featuring dry winters and wet summers -- just what the spoonbill doctors ordered.

If there were to be a wet winter, he said, water managers would have little choice but to release larger volumes into the bay.

"[Lorenz] may give us too much credit," Linton said. "Neither he nor anybody can overcome a bad year. We can tweak the system a little bit."

Linton also explained that new water storage systems in south Miami-Dade, one of which just began operating this year, have freed water managers' hand a bit.

"It's about 80 percent Mother Nature and 20 percent us," he said. "It used to be maybe 2 percent us."

rsilk@keysnews.com