The real mystery is why people keep eating quail on the toxic migratory routes
Coturnix quail are pretty adorable little creatures. Tasty, too. Except that sometimes they can poison and kill you. In fact, this problem is so common that it has been given a name: coturnism. I expect it to show up on an episode of "House M.D." any day now.
Coturnism only happens with wild quail, and only those in the Old World. There are several species of Coturnix quail which migrate between Africa and Europe every year. They travel north to Europe in the spring, and south to Africa in the fall. These days their migrations are greatly reduced in numbers, due to habitat loss and overhunting. But hundreds of years ago, the coturnix migration was truly astounding, massive flocks moving past. Who could resist hunting and eating a few of the round, plump little birds?
And therein lies the problem. On some migrations, the coturnix quail becomes poisonous. There are three migration routes between Europe and Africa. On the western flyway, the quail are poisonous during the spring (northward) migration but not during the fall (southward) migration. On the eastern flyway, the reverse is true: the quail are not poisonous while flying north in springtime, but they are poisonous while flying south in fall. And the central flyway across Italy is not poisonous in either direction.
This fact has been known for thousands of years. In fact, coturnism is mentioned in the bible. Numbers 11:31-34 covers the topic of "an incident where the Israelites became ill after having consumed large quantities of quail." Aristotle mentioned coturnism, as did Lucretius and Galen, among other luminaries of the ancient world.
But people kept eating the dang quail. That's the REAL mystery!
Most people assume that the quail become poisonous after having eaten something toxic. This is a common route for toxicity in animals, particularly something as seasonal as what we see with quail. But no one has yet been able to nail down what exactly it is that the birds are eating.
For a long time, people thought that the birds were feeding on poison hemlock during their migration. But first of all, hemlock isn't in seed at the right time for that to happen. Second of all, some pragmatic scientists fed poison hemlock seeds to a batch of quail and… the quail died. The same is true for a species of toxic beetles that had been fingered as the possible culprit.
Coturnism will probably always be with us to a certain extent. Unfortunately we will never run short of people who are as hungry as they are foolhardy. But the rapidly dwindling numbers of wild quail, coupled with the rise of domestic quail farming, mean that we may never really get to the bottom of what causes it.