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Avian Invasion

As a battle with foreign invaders continues on the grounds of Greenspring Village in Springfield, Georgia Weatherhead witnesses the struggle between the native bluebirds and the house sparrows, on a daily basis.

"[House sparrows] came over in 1850 from England," Weatherhead said. "They kill the birds and destroy the eggs."

Around the retirement community, Weatherhead and Greenspring's Nature Trail Club built a series of bluebird nests. They put out food and monitor the nests, compile the information and send it to Cornell University's Laboratory of Ornithology, where scientists have a bluebird restoration program. The scientists at Cornell compile the information to study the birds.

"They're the ones collecting the information and dispensing information on birds," Weatherhead said.

Weatherhead is among 13 Greenspring residents that keep track of the 11 bird boxes, several of which contain eggs. In the process, Weatherhead has become an expert on bluebirds. She monitors Boxes 1, 4 and 5, but only one of the boxes has a nest with eggs. The volunteers have a map with all the nest locations numbered.

"They like to be at the edge of the woods, and they like to have a meadow for catching insects," she said.

Carol Snitzer monitors Box 8, which contains four eggs.

"I raised four earlier, and now I got four more," Snitzer said.

INVASIVE SPECIES are nothing new to David Mizejewski, a naturalist with the National Wildlife Federation in Reston. With the transportation abilities of people improving, environmentalists are combating invasive species more and more. Pets and plants can be on another continent in a matter of hours, compared to letting the migration occur naturally, like birds spreading seed, or animals migrating on glaciers. The zebra mussel, hydrilla and kudzu are examples Mizejewski pointed to. The zebra mussels, Mizejewski said, came over in the ballast of ships and are now becoming a problem around Lake Erie, clogging pipes and water-treatment plants.

"It's definitely a real problem," Mizejewski said. "The federal government is spending billions of dollars [on the problem.]"

According to NWF information, the Eurasion ruffe is a fish that's thriving in the Great Lakes, with the financial loss to fisheries in the $119 million range. The European green crab, first spotted in San Francisco Bay in 1989, destroys anything in its path, including shellfish habitats and depleting commercial fisheries. In this area, the snakehead fish has potential to do significant damage, and the West Nile virus is listed as an invasive virus.

House sparrows and European starlings were brought over intentionally before people knew any better.

"A lot of these were introduced before we had a good understanding," Mizejewski said. "Both of these are cavity nesters, like the bluebird. Bluebirds are not anywhere near as aggressive as house sparrows or starlings."

By letting one species dominate, the variety of species suffers, Mizejewski said. A certain species of brown snake on Guam, for instance, caused a few species of birds to become extinct.

"They don't fit into the natural ecology because they didn't evolve here," Mizejewski said.

Beth Smith is a member of the Virginia Native Plant Society. She described how English ivy, purple loosestrife and garlic mustard have taken over gardens.

"[English Ivy] engulfs the whole ground," Smith said. "The native plants can't come through."

At Greenspring, the house sparrows and starlings don't have a big following.

Their nests, Weatherhead noticed, "are made with anything they can get their hands on. They just fill up the whole nest."

"The bluebirds weave the grass very nicely," Weatherhead said.