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Protecting Nanjemoy Creek's Great Blue Herons

Story by Michelle Brosco Christian
Photography by George Jett

On an undisturbed chunk of wooded land in Charles County, nature is slowly taking its course.

At one time, the Nanjemoy Creek Great Blue Heron Preserve's rookery was one of the largest on the East Coast with upwards of 2,000 pairs of nesting birds. Over time, however, it has lost favor to rookeries across the Potomac River in Virginia, said Dr. Deborah Landau, an ecologist with The Nature Conservancy.

"The great blue heron rookery has been there a really long time; it's close to 100 years old," said Landau, who monitors the site. She said the rookery now consists of about 12 pairs of birds. "Their droppings eventually kill the trees they are on; it's a natural cycle."

The trees the great blue herons prefer, said Landau, are Virginia pines. For the large number of birds to return, she said the "trees that have died would have to regenerate. …After Hurricane Isabel we lost a lot of these mature pines."

Landau pointed out it will be about 20 to 30 more years before the trees regenerate. That may sound like a long time, she said, but on nature's timeline, it's a mere second in time.

Nanjemoy Creek is said to be "the green thumb" of the Potomac River by The Nature Conservancy because it remains about 80 percent forested and is protected from human disturbance by the conservancy.

To date, more than 3,000 acres surrounding Nanjemoy Creek have been under the watchful eye of the conservancy, which established this rare block of contiguous forest - the Nanjemoy Creek Preserve - in 1978.

The preserve was initially protected due to the great blue heron rookery, or nesting ground. While great blue herons are not threatened, said Landau, "they're just gorgeous native birds." The preserve also protects 48 tree species, 86 wildflowers and numerous other species including the rare dwarf wedge mussel found in only 20 sites worldwide.

While not endangered, the great blue heron is facing challenges such as loss of nesting sites and deterioration of water quality and wetland habitat, according to information from the U.S. Fish and Wildlife Service's Chesapeake Bay Field Office.

Great blue herons are "very sensitive during nesting season," said Landau, which happens each February when the birds come back to the same large stick nests. "They rebuild their nests each year and the nests get bigger and bigger," she said, with some nests growing as large as truck tires.

Landau said the preserve, which is only open by permission for researchers, is totally closed off when the birds "are on the eggs and hatchlings are new." She said they've had problems in the past with all-terrain vehicle (ATV) riders. "Just a few could really devastate a nesting season," she said.

Local birding expert and photographer George Jett has watched and captured on film the great blue heron over the years and has visited the Nanjemoy site through group trips The Nature Conservancy used to coordinate.

Jett has observed great blue herons eating very large objects, such as catfish or even a small muskrat. "They take a long time to get something down," said Jett. "They'll stay here all winter if the water doesn't freeze; if they can get food they won't migrate."

Much of a bird's life is precarious, said Jett. "Migration is a risky business. The mortality rate of birds is around 80 to 90 percent," he said.

While the great blue heron is present across the United States and Canada, more than half of the Atlantic coast's breeding population nest in the Chesapeake Bay's wetlands. The East Coast's largest wading bird, often standing four feet tall, has a wing span of up to six feet.

Observation of the great blue heron is usually only accomplished from a fair distance. The birds are often spotted standing stick-still in shallow water, their S-shaped neck often stretched out and their tall, dignified body reeks of a stiff British butler standing at attention.

"You have to be respectful of nature and be careful," said Jett. "The great blue heron is a big bird, but it still sees a bigger object (a human) coming at it. Those in Nanjemoy are not accustomed to humans."

To learn more about the Nanjemoy Creek Preserve, call 301-897-8570 or visit www.nature.org/wherewework/northamerica/states/maryland/preserves/art4812.html.

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