Friday, August 24, 2007

Purple martins' majesty a marvel

MANNS HARBOR - The setting sun dims like a giant footlight and, as if on cue, aerobatic birds wing in from the west over the Croatan Sound bridge near Roanoke Island.

There are a few at first, but soon there are hundreds -- then thousands. The air comes alive with swooping, darting, soaring songbirds.

As night falls, purple martins land shoulder to shoulder on beams and cables beneath the two-lane bridge. An estimated 100,000 come in, creating one of the largest roosts in the state and a midsummer spectacle for bird-watchers.

"It's an incredible show," said Alisa Esposito of the Coastal Carolina Purple Martin Society.

In the morning, with sunrise as their cue, the birds take flight for a day of foraging for insects in wetlands, farm fields and backyards up to 150 miles away.

Though each bird is small, about 7 inches long at most, the flock is large enough to register on Doppler radar when taking off.

The show runs every day from mid-June to September not far from the Waterside Theatre at Manteo, where audiences gather under the stars to watch "The Lost Colony."

Purple martins, migratory birds that spend the winter in Brazil, have been coming to the William B. Umstead Memorial Bridge over Croatan Sound for about 30 years. Esposito said adult birds and fledglings take to the 2.7-mile bridge about 160 miles east of Raleigh because it offers plenty of space and protection from predators.

"They're not nesting here," she said, "they're only spending the night."

Paul and Robin Mann of Manns Harbor watch the birds perch in a tall dead pine tree in their backyard overlooking Croatan Sound.

"They land on the tree until you can't see the branches and then they will all swoop off and go to the bridge," Robin Mann said.

From a distance, the swirling birds look like hordes of insects or bits of wind-blown litter.

Image versus reality

On one recent night, birds covered every available space on steel I-beams and concrete pilings.

For some observers, the gathering may conjure sinister images from the movie "The Birds." But they are surprisingly docile when they line up under the bridge.

The only sound is a low chittering, and they don't attack boaters who come near.

Purple martins rely solely on humans for nesting sites, usually in specially made houses or gourds. They start showing up in the spring, often returning to the same nests year after year. During the roosting period they devour thousands of insects -- mosquitoes and dragonflies are frequent meals -- to build up strength for the 2,600-mile flight to South America.

But roosting on a busy bridge has a downside. Cars and trucks collide with low-flying birds, killing many. A survey in 2005 indicated at least 1,200 birds died on the bridge and more were probably tossed into the water.

The toll prompted Esposito and others to form the local purple martin organization last year to protect the roost and educate the public about the birds. They successfully lobbied to have the state Department of Transportation erect warning signs and lower the speed limit on the western end of the bridge from 55 to 20 mph.

The restrictions apply only around dawn and dusk from June through September.

Dozens of dead birds

Esposito, who lives about 30 miles away in Columbia, didn't know the dead birds littering the pavement were purple martins when she first encountered them after moving to the area in 1999. It was not uncommon to find 20 to 100 birds dead every day.

During a boat tour Thursday night, birds were silhouetted in the headlights of cars and trucks passing through the bird zone on the west side of the bridge.

"Please slow down," Esposito shouted while watching from the boat below.

She later found three dead birds on the bridge.

Esposito said fatalities have declined, partly because of the warnings and also because traffic on the Umstead bridge dropped when a new four-lane bridge between Roanoke Island and the mainland opened a few years ago.

Now she and her family keep watch on 106 purple martin nests at their home, and she occasionally gives presentations about the birds to small groups that gather at the bridge landing. During a recent evening presentation, she pointed out the arriving birds showing up from the west.

"You think, 'Where are the birds?' and then boom, they're everywhere," she said. "Then you think there are no more birds on the planet."

Staff writer Jerry Allegood can be reached in Greenville at (252) 752-8411 or jerry.allegood@newsobserver.com.

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