SOUTH FLORIDA -- The 2012 nesting season was the third straight subpar one for South Florida's wading birds, which count in their ranks some of the most beloved denizens of the Everglades region.
Wading birds built an estimated 26,400 nests in South Florida last year, according to an annual study released Jan. 2 by the South Florida Water Management District. The numbers were almost identical in 2011 and even worse in 2010, when the nest estimate came in at 21,900. Still, the 2012 count was 39 percent below the average of the past decade.
During the banner 2009 year, nest counts for South Florida's wading birds, including white ibis, egrets, herons, the roseate spoonbill and the wood stork, among others, was 77,000 -- more than any year since the 1940s.
Water management district lead scientist Mark Cook, who helped author this year's South Florida Wading Bird Report, blamed the intensive drought of 2010 and 2011 for the low numbers of the past few years.
When drought leaves the Everglades unusually dry during the typically wet months of summer, it leads to less breeding among fish. That, in turn, makes life tougher on wading birds, who have less food to prey upon when the winter nesting season comes along.
"I think that really it's a function of bad luck that they've had from a weather point of view," Cook said.
South Florida scientists keep an especially close eye on the health of wading bird populations for a few reasons. For one, they are a top predator in the Everglades ecosystem and, therefore, can only fare well if species down the food chain are also abundant. As such, they provide a strong indication of the health of the entire system, Cook said.
Nesting birds are also simple to see from the air, making them easier to count than many other species, Cook added.
Finally, species like the roseate spoonbill, the great blue heron and other nesting birds captivate many people's imagination, facilitating the process of getting information about them out to the public.
There were winners and losers in this year's wading bird survey.
One winner was the roseate spoonbill, with scientists counting 348 nests in Florida Bay last year, up from just 69 the previous year. However, the improvement was at least partially cosmetic since the 2012 count included 164 nests in a previously unknown colony that is now believed to have existed in 2010 and 2011.
A loser was the wood stork. Though the species is faring well enough in such areas as north Florida, Georgia and South Carolina for the U.S. Fish Wildlife Service to have announced its intent last month to downlist it from "endangered" to "threatened" status, it is struggling mightily in its historical homeland in the Everglades.
Scientists believe that all 820 wood stork nests that they observed in Everglades National Park this year failed to produce successful fledglings. The culprit was a combination of a late start to their nesting season followed by heavy early rains in April.
Wading birds nest during the winter and early spring because the dry season's dwindling water levels concentrate prey into smaller foraging grounds. Last April's rains, however, allowed that prey to disperse, dooming the Everglades National Park wood stork nests.
Overall, 26 percent of the 26,400 wading bird nests counted in this year's South Florida study were in the park, with the rest occurring in estuaries, on rivers and lakes and in designated water conservations areas from Lake Okeechobee to the southwest coast and numerous points in-between.
In a bullet-point document released in response to the study, Audubon of Florida emphasized that in the 1930s and 1940s, 90 percent of wading bird nests in South Florida was concentrated in Everglades National Park. Though 26 percent is an improvement over recent years, a goal of Everglades restoration is to bring that number up to 50 percent.
"What we'd like to see through nesting efforts is for that improvement to continue," Audubon Everglades policy analyst Megan Tinsley said.
Audubon emphasized that it is important for restoration work to proceed, including an additional 5.5 miles of bridges along Tamiami Trail, so that more water can flow into the park.
Cook noted that any given year of the wading bird study shouldn't be overemphasized, since each year's results are largely dictated by weather idiosyncrasies. But through 20 years of studies, scientists have learned a lot about how the birds respond to various hydrological conditions and which conditions they need to thrive.
"We know that even in the current conditions of the Everglades right now -- what man has done to it -- it can still support good wading bird nesting if we get the water right," Cook said, referencing water management practices. "But it has been degraded and it is continuing to be degraded, so we need to get good restoration the sooner the better."
To view the report, go to http://www.sfwmd.gov/portal/page/portal/xrepository/sfwmd_repository_pdf....