Herodotus [c. 484 – c. 425 BCE] (Histories, Book 2.75-76) [Book 2,.75] Winged serpents are said to fly at the beginning of spring, from Arabia, making for Egypt; but the ibis birds encounter the invaders in this pass and kill them. The Arabians say that the ibis is greatly honored by the Egyptians for this service, and the Egyptians give the same reason for honoring these birds. [Book 2.76] Now this is the appearance of the ibis. It is all deep black, with legs like a crane's, and a beak strongly hooked; this size is that of a land rail. Such is the outward form of the ibis which fights with the serpents. Those that most consort with men (for the ibis is of two kinds) all the head and neck bare of feathers; their plumage is white, save the head and neck and the tips of wings and tail (these being deep black); the legs and beak of the bird are like those of the other ibis. - [Godley translation]

Pliny the Elder [1st century CE] (Natural History, Book 8, 41; 10, 40; 10, 45): [Book 8, 41] A somewhat similar display has also been other species made in the same country of Egypt by the bird called the ibis, which makes use of the curve of its beak to purge itself through the part by which it is most conducive to health for the heavy residue of foodstuffs to be excreted. [Book 10, 40] Also the people of Egypt invoke their ibis to guard against the arrival of snakes... [Book 10, 45] The ibis is black only in the neighborhood of Pelusium, being white in all other places. - [Rackham translation]

Aelianus [170-230 CE] (On the Characteristics of Animals, Book 1, 38): ... the Egyptians maintain that all snakes dread the feathers of the ibis. [Book 2, chapter 38] Here is another story relating to the Egyptian Ibis which I have heard. The bird is sacred to the moon. At any rate it hatches its eggs in the same number of days that the goddess takes to wax and to wane, and never leaves Egypt. The reason for this is that Egypt is the moistest of all countries and the moon is believed to be the moistest of all planets. Of its own free will the Ibis would never quit Egypt, and should some man lay hands upon it and forcibly export it, it will defend itself against its assailant and bring all his labor to nothing, for it will starve itself to death and render its captor's exertions vain. It walks quietly like a maiden, and one would never see it moving at anything faster than a foot's pace. The Black Ibis does not permit the winged serpents from Arabia to cross into Egypt, but fights to protect the land it loves, while the other kind encounters the serpents that come down the Nile when in flood and destroys them. Otherwise there would have been nothing to prevent the Egyptians from being killed by their coming. - [Scholfield translation]

Gaius Julius Solinus [3rd century CE] (De mirabilibus mundi / Polyhistor, Chapter 32.32-33): [Chapter 32.32] The ibis bird frequents the same banks. It plunders serpents’ eggs, and carries off the choicest of them as food to their own nests. Thus the success of noxious broods is prevented. [Chapter 32.33] These birds are not useful only within Aegyptian borders. The swamps of Arabia send forth swarms of winged serpents, whose venom is so quick-acting, that, after a bite, death follows more quickly than pain. The ibis, from an innate wisdom, go out aroused and in readiness for battle and devastate this foreign evil before it reaches the borders of their land. Mobbing the pestilential horde in the air, they devour all of it. For which reason, ibis are deservedly held to be holy, and no-one may injure them. They lay eggs with their mouths. Only Pelusium produces black ibis; all other places breed white ones. - [Arwen Apps translation, 2011]

Isidore of Seville [7th century CE] (Etymologies, Book 12, 7:33): The ibis [ibis] is a bird of the Nile river that purges itself by spurting water into its anus with its beak. This bird feeds on snake eggs, carrying the most pleasing food that it takes from them back to its nestlings. - [Barney, Lewis, et. al. translation]

Alexander Neckam [1157-1217 CE] (De naturis rerum, Book 1.55): The ibis devours the eggs of the serpent, and carries this most agreeable food to its nests, so that harmful broods of snakes are rare. And yet these birds are useful not only within the borders of Egypt. For all the marshes of Arabia send forth swarms of winged serpents, whose venom is so quick, that death rather than pain follows the bite. With an innate wisdom the birds are able to do this, so they go all in readiness, and before external evil ravages the borders of their country, they meet the pestilential groups in the air; there the flock devours them all. For which reason they are sacred, and are never harmed. Only the ibis near Pelusius are the black, the rest are white. - [Wright/Badke]

Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Birds 5.63): The ibis is a bird, as Solinus says, that lives by the banks of the river Nile. It destroys the eggs of serpents, and brings these as the best food to its chicks: thus the offspring of the noxious creatures are rare. And yet these birds are not only useful around the borders of Egypt, for when the feathered serpents want to fly to Arabia, and before they could overstep their bounds, the ibis-birds go into readiness everywhere, and in the air meet the pestilential multitudes, and there devour the serpents. The venom of these snakes is so swift that death follows the bite before pain. This bird gives birth with its mouth. If anyone eats its eggs, he dies. Isidore: Some say that this bird is a stork; but if this is true, it is a wonder why the authors have distinguished between storks and birds of prey. They are plainly lying who say that ibises are the same as storks, unless perhaps they say that it is a species of stork not commonly seen in our world in Europe, because Pliny says of ibises that they have a hooked beak, which is certainly false of storks, which have a long, straight beak and a sharp point at the tip, and they do not have a hook. This bird cleans itself with its beak, pouring water on its rear. .But when the ibis is constipated from eating too much food, as Pliny and Solinus say, resting on the Nile it draws down with its beak indigestible food from the secretions of nature. And by this is meant detractors, who are always ready to spread rumors about their neighbors and interpret doubts in a bad way. Around the shores of the sea or of the river or of the ponds this bird walks night and day, feeding on either dead fish or of some corpse which has already been thrown out by the waters, rotten or withered. However, it never enters the water, but delights only in cast-off corpses. Pelusius has black birds, while the rest are white. It is found in the Histories of Josephus that Moses, while still a young man, directed against the Ethiopians by the king of Egypt, took ibis birds and caused them to precede the army through an inaccessible desert, so that the serpents might flee for fear of them. But the Ethiopians could in no way have suspected the passage of Moses through the desert because of the serpents. Hence it happened that Moses found Ethiopia undefended on the side of the desert, and unexpectedly attacked the nation and subjected the whole country to slavery and took their queen as his wife. - [Badke translation/paraphrase]

Guillaume le Clerc [ca. 1210 CE] (Bestiaire, Chapter 16): There is a bird—never was one like it— / Which in latin has the name ibis. / Its name in romance I know not, / But it lives a very evil life. / None is more dirty or more bad. / This bird ever dwells / On the shore of pond or sea / To look if it can find / Either carrion or putrid fish, / For on such food it lives. / The carrion which the sea throws up, / Man or beast, shell or other fish, / This bird seizes and consumes / When it is cast upon the shore. / Into the water it dares not go, / For it knows not how to swim, / Nor does it wish to trouble / Or take pains to learn it. / On the shore it stays hungry, / So bad and lazy it is, / That into clear water it will not go, / Nor will it eat the good fish there; / But always feeds on rotten stuff, / And never cares for what is clean. - [Druce translation]