Sources : Aeriophylon

Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Birds 5.16): Aeriophylon is a bird, commonly called aelion, which seems to have its name from this fact: it is a Latin and Greek name, derived from 'air' and 'phylos' (which is love), as if 'lover of air'. For this bird is the noblest of birds. It takes chickens and goat and of these, with a lashing of its claws, the eyes are first taken, and thus the brain is drilled until life is extinguished. Its feathers are ruffed, its tail long, its claws, beak, and legs very large. The eagle is a little larger, with powerful flight and swift wings. It dwells in the calm air, and this to such an extent that he hardly ever dwells or rests on the earth. Often flying above the clouds, it catches a fish in the air, and this is the manner of birds of prey; as it cannot be seen by man, it cannot be taken. For the aeriophylon flies so high that it can seldom be seen by man; and especially when his vision is blocked by a cloud. However, when the air is calm it is sometimes seen, and this by those who have keen sight. When it is still a chick, before it knows itself, it is captured by people who want to tame it, and so it is trained to be a hunter. And its nature is so changed by the estrangement of the forest, that it thinks of no other condition than that of living with men in the houses where it was brought up. Hence it happens that, contrary to the custom of other noble birds, it remains in perches and houses without any ties. They fly socially in pairs and the two divide the captured prey. - [Badke translation/paraphrase]