Port Manatee bird sanctuary may be model for dredge disposal

mjohnson@bradenton.comMarch 21, 2014 

PORT MANATEE -- Within the next couple weeks, up to 100 pairs of seagoing birds will begin building nests a few hundred yards offshore from the largest industrial complex in Manatee County.

Port Manatee is home to one of the most productive, most pristine bird sanctuaries in Florida. Every year, hundreds of birds fly to a manmade island on the edge of the port's deep-water navigation channel to brood and hatch their young. The avian visitors include the threatened Reddish Egret, American Oystercatcher and Least Turn.

The island is the jewel in the port's nascent environmental crown, an out-of-place backdrop for hundreds of thousands of tons of concrete berths, metal warehouses and ocean-going freighters.

It may also be the key to the port's future growth, and to the survival of bird species that are running out of room on the coast's human-occupied islands.

Created from dredge material dug out of the bottom of Tampa Bay when the port was built in the 1960s, the 60-acre island is almost accidental habitat. Birds started roosting and nesting there immediately, but gradually shunned the island when it became overgrown. In 2002 and 2003, Gulfstream Natural Gas partnered with the port and the Audubon Society to clear, contour and replant the island with native vegetation. The birds came back, and with the help of a loquatious Manatee County elementary school student, the island was named Manbirtee Key.

Now, Manatee County Port Authority commissioners must decide whether Manbirtee will be the site of or the model for how the port deals with future dredge material. Pending approval of $100,000 federal funding, the port will study deepening its main navigational channel from 40 to 45 feet to accommodate larger ships. Dredging to deepen the channel wouldn't start for at least a decade, but when it does, potentially millions of cubic yards of rock, mud and sand pulled of the bottom of the bay will need a place to go.

One option may be to add onto Manbirtee Key. The port is so short on dry-land storage for dredge material, it could need another disposal location as early as 2018 for its regular maintenance dredging. During a visit this week to Manbirtee, Audubon regional coordinator Ann Paul said increasing the size of this "beautiful, excellent habitat" may benefit the birds.

"It's possible that it might be a good idea," Paul said.

A safe place for birds

As it is, the island offers several types of bird habitat. Its rocky beaches attract birds that nest near the water, while the mangroves and evergreens growing on the short bluffs and in a cove on the south end of the island form coastal hammock that is irresistible for herons and other roosting species.

For birds that dig their nests into the earth, Audubon harrows the island's uplands annually and cuts tall vegetation to open a huge patch of sandy ground with few places for predatory raptors to perch. Contractors also use herbicides to control invasive plants, and pesticides to reduce the island's fire ant population. That work is taking place this week.

Mark Rachal, a sanctuary manager responsible for 25 properties Audubon owns or leases, said more than 140 bird species have been spotted roosting, foraging or wintering on the island. His job in the spring includes supervising the harrowing operation and monitoring the white pelicans that use Manbirtee as a full-time residence.

"The older ones and younger ones that aren't necessarily going to be breeding just hang out here," Rachal said.

The island gives birds a near-contiguous habitat between the Rock Ponds wetlands area around Piney Point Creek and the Terra Ceia Preserve State Park. It also helps make up for habitat lost as the port has expanded its shipping berths. The port recently finished building its 1,600-foot Berth 12 and Berth 14 facility.

Manbirtee is off limits to humans, except those approved by the Audubon Society or the port. The society holds a 20-year maintenance lease on the island that started in 2002. Anyone who gets too close is likely to get a visit from the Coast Guard. Local fishing charters and other volunteers -- as well as a daily Manatee County Sheriff's Office helicopter flyover -- monitor the island to make sure unauthorized visitors don't get close to the birds.

Manbirtee is unique. Paul, whose late husband Rich designed the 2002 Manbirtee project, said that while other ports - including Port Tampa Bay - have dredge spoil islands, none has converted them into permanent, protected habitat.

"This is an aberration that might not be allowed today," she said.

Project is all business

Manbirtee wouldn't exist but for the convergence of business interests. Its original construction came out of a need for a convenient place to put dredge spoils. Its transformation into a sanctuary was environmental payback.

When Gulfstream needed a landfall for its natural gas pipeline entering southwestern Florida, it got permission from the port to use Manbirtee in return for spending a reported $7 million on the 2002 habitat project.

The pipeline was trenched into the ground, and the island was used as a staging ground to drill the pipeline 80 feet under the port's navigation channel. The company paid to clear the island's non-native vegetation at the time and replace it with indigenous plants.

The port spends about $8,000 a year to fund maintenance on Manbirtee, but makes the most of the investment. The project won a regional environmental award in 2004, an award that shows up in the port's public relations and environmental policy.

By this summer, the port authority board must decide where to store future dredge spoils. Port planning director George Isiminger said it's unlikely the port can make room at its 93-acre dry land facility by selling or giving the stuff away, based on current demand.

Adding onto the island, Paul and Rachal said, likely wouldn't damage its demand among birds, since dredging work cannot be done during migratory bird nesting season. An enlarged island or a new island may even draw more birds. In 2009 and 2010, fresh, soft dredge spoils at the dry land facility attracted nesting Wilson's Plovers and Least Turns who normally hatch their young on Manbirtee.

Carol Whitmore, chairwoman of the port authority, visited Manbirtee this week to get some clarity on the upcoming decision. All seven members of the authority are expected to visit the island prior to the start of the spring nesting season.

Whitmore now she knows Manbirtee's worth as habitat.

"It just solidifies it, seeing it," Whitmore said.

Matt M. Johnson, Herald business reporter, can be reached at 941-745-7027, or on Twitter @MattAtBradenton.

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