The piping plovers already are flying toward peril. The endangered birds are among the first of millions that will migrate this fall to the Gulf of Mexico — and the oil leak that could kill them. Some birds, including the common loon and lesser scaup, spend winters along the Gulf Coast. Others, such as the blue-winged teal, use the Gulf as a staging area where they stock up on food before flying to Latin America. "There are millions of birds at risk," says Ken Rosenberg, conservation science director at the Cornell Lab of Ornithology. "It's safe to say thousands will die." He fears the BP oil spill, which began April 20, "could erupt into a much bigger disaster as oil continues to come to the surface." Hundreds of birds have died, and some drawn to the Gulf by migratory instincts will be affected starting this month, says Paul Schmidt, assistant director for migratory birds at the U.S. Fish and Wildlife Service. He says the agency's "biggest concern is the long-term degradation of the habitat." Oil can kill plants and other food sources on beaches and in tidal and marshy areas, making them inhospitable for years, Schmidt says. Migrating birds, like those that live year-round near the Gulf of Mexico, can introduce oil into their systems by preening oil-soaked feathers, says Greg Butcher, bird conservation director for the National Audubon Society. "If they get oil on their feathers, they lose their ability to regulate their temperature. If they swallow oil, they're going to get sick." Some birds that ingest oil might lose their ability to reproduce. Scientists say hundreds of species could be affected by the spill: • The sparrow-size piping plover, an endangered species, will show up on Gulf Coast beaches this month. They breed on the Atlantic Coast, the Northern Great Plains and the Great Lakes, and they winter in the Gulf of Mexico, Cuba and the Bahamas. • Water birds such as terns and black skimmers are affected, and more will arrive this fall. They feed in open water, putting them at risk of eating fish contaminated with oil. • Blue-winged teal, gadwall, northern pintails and other "dabbling" ducks will arrive in September and October. Most use marshes as habitats, so there are untouched areas for them — unless a hurricane stirs up the oil and pushes it into those areas. • Diving ducks such as redheads eat submerged vegetation that might be inundated with oil, and scaup eat surf clams that are easily contaminated with oil. • Shorebirds such as red knot — an endangered species candidate — live on beaches and will be affected by oil washing ashore. Other species that feed on tidal flats, including the short-billed dowitcher, could be harmed if oil moves inland. • Songbirds, including the Baltimore oriole, might gather in oiled vegetation along the coast. It's almost impossible to steer migrating birds away from instinctive destinations. "Birds are pretty hard-wired to their habitat," Schmidt says. If there's a lot of human activity in their traditional locations — boats, helicopters or airplanes — they will seek quieter areas nearby, he says, but oiled water or vegetation won't prevent them from landing. Scaring birds away with loud noises and using tarp to prevent them from landing in oily areas wouldn't be effective because the spill affects such a large swath of the coast, Schmidt says. Even so, conservationists are doing what they can to save birds. The Natural Resources Conservation Service, part of the U.S. Department of Agriculture, is paying landowners in eight states $20 million to idle farmland and restore wetland to create habitats for migrating birds. Butcher says talks underway about creating barrier islands and marshes are key to restoring bird populations. The Aubudon Society is training volunteers to monitor bird populations and habitat conditions. Its Christmas bird count will provide an early warning about what species are in trouble because of the spill. The most effective way to protect birds is to clean affected beaches, Butcher says. "They're putting out a tremendous effort, but you can't keep all the beaches clean all the time." Tom Moorman, director of conservation planning for Ducks Unlimited's southern region, says 9.2 million ducks and geese winter in Louisiana. Most settle in marshes where salt and fresh water merge, and those areas are protected from oil for now by beaches and salt water, he says. He's worried about the fates of shorebirds that use beach habitats, and he's concerned about what might happen next. If the leak isn't shut off, Moorman says, 1 million diving ducks in the open waters of the Gulf could get hit by an oil slick, leading to "a pretty big mortality event." If BP doesn't contain the spill soon, Rosenberg says, the outlook for birds could worsen. If the oil moves into the Atlantic Ocean and the Gulf Stream, he says, "a number of other endangered seabirds could be affected." And if oil expands along the Texas coast, he says, whooping cranes that arrive there in late September "could be threatened." Butcher says the spill's effects on birds will be felt for years. It is changing the food supply at the bottom of the Gulf in ways scientists don't understand yet, he says, and could result in smaller bird populations and, eventually, changes in migratory patterns. "Oil and life," he says, "don't mix." 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