County hopes to protect rookeries

The number of nests on three spoil islands has declined over the past five years

By WILL ROTHSCHILD will.rothschild@heraldtribune.com

SARASOTA COUNTY -- Erosion is taking a toll on the Bird Colony Islands, and bird watchers fear one of the most successful rookeries in Southwest Florida is disappearing.

Though small in size, the islands have been home to 13 wading bird species over the years and once supported an estimated 1,000 nests. Brown pelicans, snowy egrets, great egrets, great blue herons and double-crested cormorants still nest on the islands.

But in the past five years the number of nests on the Bird Colony Islands has declined by more than 400.

Waves from passing boats are blamed for eroding the shoreline. As the shoreline is worn away, mangroves directly exposed to the water have died. That, in turn, exposes more shoreline to erosion.

Since Sarasota High School marine biology teacher Denise Erb's students first started counting in 2000, the number of nests on the islands has dwindled from 682 to 233.

Sarasota County is responding with plans to spend more than $500,000 to protect the islands, which sit just south of the Siesta Drive bridge outside the Intracoastal Waterway.

The islands were created in the 1960s when the U.S. Army Corps of Engineers dumped the spoil material from the dredging of the waterway on top of existing mangrove-covered shoals.

The mangrove-covered islands are a productive rookery because they sit too far from the mainland for egg-hunting raccoons and cats to reach them during low tide.

"Our concern is as we're losing the islands, if nothing is done we could lose this bird colony altogether," said Ann Paul, a scientist with the Florida Audubon Society, which helps to manage and monitor the rookery.

The county wants to build a 1,200-foot breakwater a few feet off the shoreline to absorb the wake from passing motorboats.

Limestone boulders will be laid on top of a gravel base along the entire side of the islands facing the waterway. The boulders will form a barrier about 5 feet wide where they break the surface.

Fill material will be placed behind the breakwater, providing a base for mangroves to spread.

"The idea is as existing and new mangroves grow together, we will get some tidal channels that will be covered and provide quiet shelter for birds," said Curtis Smith, the county's project manager.

Smith said a similar project is protecting a rookery in Clearwater Pass, in Pinellas County.

The project will cost about $560,000. The county has secured that much hat much in grants from the Southwest Florida Water Management District and the West Coast Inland Navigation District.

The project must be approved by the state Department of Environmental Protection and the Corps of Engineers, a process that could take several months.

On a recent trip to the islands, the problem was obvious as waves bigger than what roll up on Siesta Public Beach most days crashed over the shoreline. Leafless, dead mangroves line the most exposed northern and southern edges of the islands.

Erb's classes asked the county to impose a no-wake zone on this stretch of the waterway years ago but county officials said that was not an option.

Instead, the Audubon Society installed signs asking boaters to slow down as they pass the islands.

But the signs appear to have had little effect.

Other efforts have. Erb's students remove fishing line and other trash from the islands once a year. The number of dead birds tangled up in fishing line has decreased each year, Erb said.

"People might not realize when they throw it out that birds can pick it up and get trapped or strangled by it, but it actually does," said Devon Consul, a senior.

"We all took this class because we like to be in the water. It's part of the job."