The porphirio is found in some medieval encyclopedias. It has different attributes than other birds. It has one foot like that of the goose, suited for swimming in the water, and one foot like that of the partridge, suitable for walking on land (also said of the osprey). It is larger than an eagle but smaller than a swan. To catch fish, it flies high in the air and drops down into the water to grab a fish with its clawed foot, then swims with its webbed foot, taking the fish where it wants it. When it drinks it takes water with its foot, as though it was a hand, and lifts the water to its mouth. It must drink with every meal.

The porphirio is probably some species of rail, possibly the Western Swamphen (Porphyrio porphyrio). The part of the story that says the bird drops from the sky to catch a fish with its foot may have been inspired by the osprey.