Clinton Jeske kills the motor on the United States Geological Survey's 5.5-metre Whaler boat and noses it into the moss-covered mud that surrounds this stretch of Louisiana's southern marshlands.
Ahead, the horizon disappears behind a shallow sea of green. Grasses wave in the breeze, rocking a million dragonflies, each perched on its own stalk. In the water, a blue crab scuttles about, a small swarm of baitfish swims past and a needlefish flits by.
For all the fecundity on display, however, this marsh is a shadow of what it will become in a few months, when it will suddenly become home to millions of birds. Today, most of those birds are in Canada, where their summer homes in Ontario, the northern Prairies and the Arctic have been safe from the effects of the oil despoiling the Gulf of Mexico.
Some of those birds, however, are nearly ready to begin flying back south. They come to the Gulf to feed on those baitfish, needlefish and crabs - a smorgasbord of food that is as rich a draw for fowl as it is for the area's restaurants.
What environment they will return to has become a matter of great scientific concern, as researchers struggle to assess what damage - if any - the oil-spill environmental catastrophe could have on one of the world's great annual wildlife movements. Oil remains about 10 kilometres from this stretch of marsh, for example. If the spill is stopped and winds continue to keep crude from shore, the risk could be low.
But even a relatively small tropical storm could bring a large enough storm surge to inundate parts of the marsh, coating the grasses with oil that could prove impossible to clean up.
"A lot of people have the initial reaction that it's going to be bad," Dr. Jeske said. "But it's really difficult to say. It could have a devastating impact or it could have no impact."
Dr. Jeske is a top ornithologist in the state, who is leading the Lafayette-based National Wetlands Research Center's efforts to assess the impact the Deepwater Horizon oil spill could have on birds.
He points to the marsh shore. As many as 70,000 snow geese could descend on this very shore, he said. A few minutes later, as he guided the boat through the waterways that puzzle through the marsh, he glanced at a communications tower. In the past he has seen as many as 5,000 purple martens on the tower's support wires alone. Those birds will soon leave their Canadian summer grounds.
Every fall, some four million ducks, one million geese and four million to five million shorebirds touch down on the Gulf of Mexico. Almost all of the geese and roughly 75 per cent of the ducks come from Canada. Pelicans fly here from Fort Smith, NWT; snow geese from Coral Harbour, Nunavut; lesser scaup, a small diving duck, from Northern Ontario and Manitoba. Shearwaters winter here, as do albatrosses, northern gannets, common loons and black terns.
They are thousands of kilometres apart, but from a wildlife perspective, Canada and the Gulf are intimately linked. That makes the spill an issue of serious concern to hunters, conservation groups and scientists who study birds on both ends of the hemisphere.
"I would draw a parallel between the Mackenzie Delta and the Mississippi Delta. One's a world-class breeding bird delta and the other is a world-class wintering bird habitat," said Fred Roetker, a biologist with the U.S. Fish and Wildlife Service.
Birds fly north to nest their young and evade some of the predators in the south. The Gulf, however, is critical habitat for all of them. They arrive here in the fall weakened from the flight, ready to replenish their bodies. Some birds, such as the blue-winged teal and ducks won't be back until late August and September. Others, shorebirds such as terns, will return in a month.
Birds landing in areas with oil could find their flotation and insulation compromised and be subject to longer-term issues with nervous systems, kidneys, livers and reproductive systems. Those effects could eventually hurt bird populations, said Marty Haulena, a veterinarian at the Vancouver aquarium, who has with extensive experience in responding to wildlife affected by oil spills.
That hangs a sizeable question mark over the spill's environmental impact, and on BP's liabilities. U.S. environmental law deals in equivalencies, so every dead bird will have to be replaced with either enough habitat to sustain another of that species, or a bird of a different species that fulfills a similar environmental role.
For now, the Louisiana marsh remains an area of substantial uncertainty. Will the birds return to a dangerously sullied home? Or will it be preserved? Neither Dr. Jeske nor any other scientist can know.
"It's something, I think, to be cautiously hopeful about," he said. "Not optimistic, but hopeful. Hope for the best but be real cautious that the worst could occur."
One thing is clear, however: This is vital habitat, and any impact to it will likely reverberate broadly.