Sora rail Credit: Michael “Mike” L. Baird/Creative Commons Attribution 2.0 Generic

Its wings are raised, as if before flight, but from the way the bird’s straining, it’s clear—even in the photograph—that the oil is weighing them down. The pelican’s mouth is open, and there’s a little glob of syrupy liquid dangling from the bottom of its beak. The bird is half-submerged in what looks like spoiled pudding.

The toll the Deepwater Horizon oil spill has already taken on wildlife has been astounding. As of October 12 the U.S. Fish and Wildlife Service had reported that of 6,359 birds it has collected, 4,955 were dead.

But the environmental impact of the oil spill, the largest in the industry’s history, may stretch well beyond the gulf. This fall millions of birds are leaving Illinois and heading for their wintering grounds there. For some, the gulf is an oasis on their annual migration to South or Central America. For others, it’s where they’ll wait out another bitter Chicago winter. What will happen to them when they get there is still a matter of speculation. But the possibility that these birds could be flying into harm’s way is distinct.

In early August Carol Browner, the White House coordinator for energy and climate change, claimed that more than three-quarters of the approximately five million barrels’ worth of oil that spilled was “gone,” having evaporated, dissolved, or been collected. But a report issued on October 6 by the National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling sharply criticizes the administration for repeatedly underestimating the amount of oil flowing into the gulf and cites the work of independent researchers who have determined that as much as half of the oil remains in the water, in the seafloor, and in coastal sludge.

This endangers birds in various ways. They may get soaked in oil as they glide above the water or dive down in it to get food. Their feathers may become less water repellent. The food they eat may be contaminated. They may ingest or inhale oil as they groom themselves.The effects may not manifest immediately; they may present as long-term lung, liver, or kidney damage.

In July the National Audubon Society instructed readers of its newsletter to feed birds throughout the summer and fall to increase their body weight, hoping the added energy would allow the birds headed down to South and Central America to bypass the gulf altogether.

That same month, the U.S. Fish and Wildlife Service started building temporary habitats, flooding farm fields, planting feed crops in safe areas, and using fireworks to divert birds away from areas harmful to them.

Annette Prince, director of the Chicago Bird Collision Monitors and a board member of the Chicago Audubon Society, hopes these tactics will work, but is skeptical that they will.

“Birds are very hard-wired to travel particular migratory routes and go to particular areas,” Prince says. “They’re not going to make the judgment call, ‘Oh, that area is destroyed and damaged, I’m going to go over here instead.'”

She also doesn’t think feeding them more will make much difference. “A bird can only fly so far,” she says. “Birds follow routines, they don’t choose.”

Birds from Chicago travel the Mississippi Flyway, a prominent migratory route that covers an area roughly the shape of a funnel.From the west, it comes down through Canada, running diagonally through the Dakotas and along the Mississippi River. To the east, it crosses over Lake Huron and cuts across the northeastern tip of Ohio into Indiana, straddling the Illinois-Kentucky border until it merges along the Mississippi. Blackbirds, sparrows, rails, and warblers are among the species that will follow this route from Illinois to Missouri to Arkansas before ending up in the Gulf of Mexico. Whooping cranes, which pass through Illinois on their way to Florida, are already endangered.

In her work with the CBCM, Prince rescues birds that have crashed into Chicago skyscrapers. She says she has found the same type of bird striking the same building one year apart to the day.

“That just shows the stability of migratory routes,” Prince says.

And when it comes to redirecting birds, she says a lot of those who have been rescued down in the gulf and moved to safer areas have flown back to the dangerous areas—the ones they’re hard-wired to fly to.

“I think you’ve got to do whatever you can,” Prince says. “The unfortunate and scary part to think about is that [the birds] may not have an option; even if provided, they may not take it.”

Down in the gulf, the well is dead. About a 1,000 miles away, a sparrow flying south for the winter collides with a Chicago high-rise.

Prince will rescue and release it. But as she does, it will be with a sense of anxiety. “I often feel we release them to go someplace to safety,” she says, “but now I feel that we’re going to be releasing these birds and setting them off to even greater peril.”