This year's spring migration, as noted in Bird Flu Revue has caused some panic about the spread of the H5N1 avian flu. It's a process that takes place outside mankind's jurisdiction, which is one of the scariest things about nature.

Migrating birds can appear “virtually anywhere and come from virtually anywhere. That’s just the nature of birds and bird migration,” Ken Rosenberg, director of conservation science at the Cornell Lab of Ornithology, said in this AP Article from early March, when Homeland Security Secretary Michael Chertoff announced that the virus could hit our shores in the next couple of months.

A recent National Geographic article reports a study showing that certain kinds of wild ducks may be especially prone to spreading the virus. Led by Björn Olsen of Umeå University in Sweden, the study found that flu viruses, "generally passed via bird feces" can stay infectious in lake water for up to 30 days. Certain species of ducks, including mallards, teal, pintails (apparently known as "dabbling ducks") feed near the water surface, where the virus is most likely to be spread.

Perhaps as a result, dabblers have the highest known rates of avian influenza infection, the study says. For instance, nearly 13 percent of mallards tested positive for bird flu. Other species tested include the American black duck (18.1 percent), blue-winged teal (11.5 percent), and northern pintail (11.2 percent).

Swans are also particularly vulnerable to the strain, but tend to get lazy and die of the disease before they can spread it around. Here's an excellent quote to that effect: "Swans apparently drop dead quite easily, but they are unlikely to be the vector because they are not going to fly very far if they are dead," said Ron Fouchier, a virologist at the Erasmus Medical Center in Rotterdamsaid. Certainly not very far.

But ducks are not only dirty, they're unstoppable! Or rather, the form of the virus they contract tends to be in a low-pathogenic form, which means they usually won't get sick enough to die from it. Which leaves them free to fly around infecting other birds.

So, the question it always comes down to when man faces beast: do we just shoot them all? Now this might seem like a completely crazy proposition, as it did to me, but since the headline on the National Geographic article is "Flu Spread Is No Reason to Kill Wild Birds, Study Says," I guess some people have seriously considered it. But the experts' answer, fortunately, is no. "Blaming avian flu on bird migrations is misleading. And a 'quick fix' of culling migratory birds is certainly not the solution," says Shafqat Kakakhel of the United Nations Environment Programme Kakakhel.