Sources : Porphirio

Aristotle [ca. 350 BCE] (De animalibus Book 8, chapter 8.1): Some birds draw in the water, but those which have long necks imbibe it at intervals, lifting up their heads; the porphyrion alone gulps it down. - [Cresswell translation, 1887]

Pliny the Elder [1st century CE] (Natural History, Book 8, 44; 10, 63): [Book 10, 44] The Balearic Islands send the porphyrio, an even more splendid bird than the one mentioned above. [Book 10, 63] Only the porphyrio drinks by beakfuls; it also eats in a peculiar way of its own, continually dipping all its food in water and then using its foot as a hand with which to bring it to its beak. - [Rackham translation]

Thomas of Cantimpré [circa 1200-1272 CE] Liber de natura rerum, Birds 5.99): Porphyrio, as John the Philosopher says, is a bird that differs from the custom and manner of other birds. For it has one foot wide for swimming, and the other is cleft for walking. And in this it is noted that it uses both in the proper element, swimming in the water like ducks and walking on the ground like partridges. It has one foot like an eagle, the other like a goose. Looking for a fish in the water, it lifts itself up above the clouds and descends with one foot, snatches the fish from the depth of the water, and swimming with the other foot brings the fish to the desired place. This bird is the larger than the eagle and the smaller than the swan. Porphyrio, as some people say, is the same as pelican; but it is disputed by the opinion of many. It is a bird from a foreign country. Pliny tells about this: contrary to the custom of all birds except for the parrot, the porfirio, taking water with its foot like a hand, brings it to its beak and drinks and feeds itself in a human manner; and this nature seems to have been given to it as a punishment, because it must drink with every meal and with every bite; for the power of the appetite is naturally weak in attracting and incorporating fish. It is like a bird who gorges himself, who wants to drink at every bite. The most praised of the Porphyrios are those that have a large beak and long legs. - [Badke translation/paraphrase]