An annual survey found nearly 55,000 nests in the Everglades and surrounding nature areas this season -- the second time in four years breeding has reached levels approaching the 1940s, when flocks of white ibis, snowy egret and other birds could fill a marsh sky.

And that's a ''conservative estimate,'' said Mark Cook, a senior environmental scientist with the South Florida Water Management District, which compiles the South Florida Wading Bird Report that was released this week.

''This could have been one of the best years we've had,'' he said.

There may have been as many as 70,000 nests of nine wading species, if the estimates were adjusted for new survey methods, Cook said.

That would match a 2002 total that stunned biologists and documented a gargantuan gathering unseen in decades -- a rare ''super colony'' of tens of thousands of birds in a willow stand just west of Broward County suburbs.

That cackling colony just north of Alligator Alley remained the center of the bird boom this year, smaller but still home to a staggering 31 percent of all nests south of Lake Okeechobee.

Perhaps a more important trend was the third consecutive increase of nesting in the coastal estuaries of southern Everglades National Park, once-thriving rookeries that had been largely lifeless for decades.

Scientists aren't ready to pronounce South Florida's wading populations recovered, but consider the trends encouraging -- for some birds more than others.

Still, ''it's giving us some reason to be optimistic,'' said Dale Gawlik, an assistant professor of biology at Florida Atlantic University.

Cook credits a near-perfect rainfall pattern for this year's surge.

Birds begin breeding as water levels fall, fattening up as drying marshes concentrate fish and other prey in small pools. Although hurricanes Katrina and Wilma wiped out some nesting areas late last year, they didn't drop enough rain to force a mass abandonment of nests.

Because nesting is closely tied to water levels, wild year-to-year swings have always been common in the Everglades. Nesting this year rose 71 percent from 2005, when hurricanes and late-season rains drowned out fledglings and foraging habitat.

But with numbers leveling off at a increased levels and two gang-buster years, the data suggest more than a weather-driven statistical blip.

NUMBERS WAY UP
Since 2000, the average nesting numbers of five key birds -- white ibis, snowy egret, great egret, wood stork and tricolored heron -- have quadrupled or more from lows in the 1980's and '90s.

''This is a system that is so dynamic, you need a long set of information to factor out the natural cycles,'' said Gawlik, who edited the report for years and still participates in the survey.

It wasn't nature that sent the birds of Everglades into decline.

They were nearly blasted into oblivion in the 1900s by plume hunters supplying a craze for feathered hats. After a public outcry brought a crackdown on hunting, breeding rebounded in the 1930s and '40s, ranging from 35,000 to more than 200,000 nests.

But populations spiraled down again as drainage canals, flood-control levees and rampant development reduced the historic Everglades and nesting grounds by half. Poor water management helped drive nesting to a low of just 5,000 in 1983 and 1985.

WISER DECISIONS
Scientists don't fully understand everything driving the recent surge -- happening without any of the promised benefits of the $11 billion Everglades restoration plan.

But most credit the South Florida Water Management District for making wiser decisions on when water levels are raised and lowered in South Florida.

Biologists now regularly sit in on meetings to discuss potential impacts on foraging and nesting, Cook said.

''One thing we have done a much better job of in the past 10 years is having scientists communicate much more effectively with water managers,'' he said.

While wading birds are considered ''indicator species'' or barometers for the broader Everglades, one thing scientists stress is that the bird boom doesn't mean the struggling River of Grass is healthy again.

There are still serious concerns about some birds species as well.

Nesting totals for tricolor heron, in a slide since 2001, were off 44 percent. Roseate spoonbill numbers also fell below average again -- particularly in Florida Bay.

And wood storks, an endangered species particularly sensitive to water levels, seem to yo-yo in nesting and their overall numbers remain low.

But in the last few years, scientists have been repeatedly surprised and pleased by birds' resilience.

GREAT EGRETS
This year, for example, great egrets on the Southwest coast somehow managed to nest atop broken and rotting piles of mangroves left behind by Hurricane Wilma.

''These birds are more adaptable than we give them credit for,'' Gawlik said.