Worst-case scenario: Oil continues to flow from BP's deepwater well off the coast of Louisiana, and tropical storms and perhaps hurricanes this summer and/or early fall would push the crude not only into barrier saltwater and brackish marshes, but also farther inland, into freshwater marshes and ponds. This would kill not only ducks and other birds, but despoil crucial habitats, perhaps for generations. Worse, it's possible that oil flowing from the well won't be staunched for many months. Or even, as was the case in Mexico in 1979, for up to a year. If so, thousands - perhaps hundreds of thousands, or even more - of ducks, geese and other migrants, including shorebirds, could be killed this fall.