You eat these pre-historic looking crustaceans by twisting off their heads and exposing their meat. They taste and smell like the sea and they are great with beer.
The English name for percebes, “gooseneck barnacles,” comes from the medieval theory that they are embryonic barnacle geese. This theory conveniently explained why flocks of geese would suddenly appear out of nowhere (the fact that birds migrate was not known in the Middle Ages).
In any case, do not worry. There are no recent reports of percebes flying off the plate to migrate south.