Even the frantic preparations to protect the most vulnerable coastlines likely will not prevent devastating harm to key species as the Gulf of Mexico oil spill hits shore at the worst possible time for migration and breeding.
While no one can yet predict the full extent of the damage, experts say more than 400 species in the estuaries are at risk from the slick headed their way.
"It could be very devastating, unfortunately," said David Ringer of Audubon's Mississippi River Initiative. "The timing is pretty disastrous."
Wildlife officials are particularly worried about brown pelicans, which were recently removed from the endangered species list and are currently nesting on barrier islands off the southeast coast of Louisiana.
Breton National Wildlife Refuge, home to about 34,000 birds, is the top priority among the key nesting Gulf Coast areas being recommended by the Fish and Wildlife Service to be protected by booms, said Tom MacKenzie, the spokesman for the service's Southeast Region. In 2005, Breton was hit by an oil spill that killed more than 800 nesting ground pelicans, he said.
"It's those nesting pelicans that we're trying to defend right now," he said.
While four national wildlife refuges are in the immediate danger zone, another 15 along the coast of Mississippi, Alabama and Florida could be hit by the oil, he said.
Over the past few days, berms have been placed at Breton consisting of a series of booms designed to deflect and absorb oil. "They're done in a series of rings almost like a defensive ring if you were going to set up against an invading army," MacKenzie said.
While the booms will help protect nests, little can be done for shorebirds that wade or land in the water, because the oil is already in the ocean, he said.
Several federal agencies are flying over the affected areas to monitor wildlife that could be affected by the oil, such as large flocks of birds, and FWS spotters saw whales swimming in the oil, he said. The first oiled brown pelican was sighted Wednesday on an oil platform near the source of the release.
Other species in particular danger include sea turtles, which will begin nesting "any time now"; gulf sturgeon, which are listed under the Endangered Species Act and migrating upstream to spawn; manatees, which are beginning to spread out along their full range of summer habitat in the Gulf; and numerous species of birds that forage for fish, MacKenzie said.
"This looks like an extremely extensive oil spill that has the potential to impact a lot of resources," he said.
Two whale species may be in the area of the spill, Bryde's whales and endangered sperm whales, according to the National Oceanic and Atmospheric Administration. The greatest threat is if whales get oil in the filtering structure in their mouths, which could lead to starvation and death.
A total of 21 whale and dolphin species that routinely inhabit the northern Gulf are protected under the Marine Mammal Protection Act. There also are five species of threatened or endangered turtles in the Gulf, and one of the only foraging grounds for the endangered Kemp's ridley turtle -- which is in its peak nesting season -- is in the area of the oil spill, NOAA said.
BP PLC, which by law is responsible for the cleanup costs, has hired Delaware-based Tri-State Bird Rescue and Research, a private nonprofit wildlife rehabilitation organization, to clean oil-coated birds and wildlife.
Five staging areas have been set up to protect sensitive shorelines in Biloxi and Pascagoula, Miss.; Pensacola, Fla.; Venice, La.; and Theodore, Ala. More than 217,000 feet of boom has been placed, with an additional 305,760 feet available.
While government officials and BP are handling all the frontline response currently, they will be looking to conservation groups with local presences to mobilize volunteers, said Audubon's Ringer.
"From our vantage point ... everything that can and should be being done, is being done," Ringer said. "Unfortunately, given the magnitude of what's happening, it's probably not going to be enough to prevent some environmental impact."
Audubon has been fielding calls from across the country from people wanting to help and is organizing volunteers. But the affected areas can only be reached by boat, and only those who have certified training in handling both wildlife and hazardous materials will be able to clean oil-soaked birds, he said. Brown pelicans are large birds with strong bills and will be frightened, he noted.
"It's not something someone off the street can just volunteer to do," he said.
Declaring a state of emergency, Louisiana Gov. Bobby Jindal (R) announced that BP had agreed to allow local fishermen to assist in the expected cleanup and that the state was also training prison inmates to help clean up wildlife harmed by oil slicks moving toward shore, AP reported.
If birds are significantly affected by the oil, it could disrupt the breeding efforts of entire colonies this season, Ringer said. Terns, plovers and egrets have not started nesting yet but are congregating and soon will, he noted. It's also the peak of spring migration for birds that spend the winter in South and Central America.
Some small, colorful songbirds, including warblers, orioles and hummingbirds, fly across the Gulf from Mexico's Yucatan Peninsula. The birds could be disoriented by smoke from controlled burning of the oil, he said, and depend on a healthy ecosystem to refuel after the long flight.
Other birds, such as sandpipers and plovers, winter in South America and migrate to the Arctic tundra to breed and use the Gulf Coast wetlands for stopovers and face a "tremendously dangerous situation" if they land on oiled beaches, he said.
"The last week of April and first week of May are the two weeks of the entire year that the highest migration takes place," he said. "We're just very concerned for a number of different bird groups and species based on the timing and the potential scope of the impact."
The delta estuary also is the breeding ground for a lot of fish, shellfish and crabs, noted LuAnn White, director of Tulane University's Center for Applied Environmental Public Health.
"All of those are at risk for being damaged," she said. "That estuary area is responsible for the breeding for about 40 percent of the aquatic life that's in the Gulf, [so] you could be affected not only the wildlife that lives in that area, but the whole Gulf."
The spill also could worsen ongoing coastal erosion problems, because oil could kill the grasses and plants that grow in marshy areas, she added.
"They're putting booms up now, but there's not enough booms in the whole country to protect the miles of coastal wetlands," she said.
Even without being toxic, the oil can smother oyster beds and coat birds' feathers, she noted.
"It affects how they're able to cope with the environment and interrupt some of the breeding patterns," she said. "It's a physical effect more than a chemical toxic effect. It's devastating, nonetheless, and it can kill many of those species, particularly those that are in there breeding."
After Hurricane Katrina caused minor oil spills, officials used controlled burns in some wetlands and found that those recovered much faster than areas where the oil was left to break down on its own, White said. That same technique may be used to help remediate the area once the spill stops leaking, she suggested.