3 There are also innumerable kinds of birds. If we review them all, as we have partly done the fish, we shall find that under one name, the creatures which fly differ infinitely in size, form and colour; that in their life, their actions and their manners, they present a variety equally beyond the power of description. Thus some have tried to imagine names for them of which the singularity and the strangeness might, like brands, mark the distinctive character of each kind known.
Some, as eagles, have been called Schizoptera, others Dermoptera, as the bats, others Ptilota, as wasps, others Coleoptera, as beetles and all those insects which brought forth in cases and coverings, break their prison to fly away in liberty. But we have enough words of common usage to characterise each species and to mark the distinction which Scripture sets up between clean and unclean birds. Thus the species of carnivora is of one sort and of one constitution which suits their manner of living, sharp talons, curved beak, swift wings, allowing them to swoop easily upon their prey and to tear it up after having seized it. The constitution of those who pick up seeds is different, and again that of those who live on all they come across.
What a variety in all these creatures! Some are gregarious, except the birds of prey who know no other society than conjugal union; but innumerable kinds, doves, cranes, starlings, jackdaws, like a common life. Among them some live without a chief and in a sort of independence; others, as cranes, do not refuse to submit themselves to a leader. And a fresh difference between them is that some are stationary and non-migratory; others undertake long voyages and the greater part of them migrate at the approach of winter.
Nearly all birds can be tamed and are capable of training, except the weakest, who through fear and timidity cannot bear the constant and annoying contact of the hand. Some like the society of man and inhabit our dwellings; others delight in mountains and in desert places. There is a great difference too in their peculiar notes. Some twitter and chatter, others are silent, some have a melodious and sonorous voice, some are wholly inharmonious and incapable of song; some imitate the voice of man, taught their mimicry either by nature or training; others always give forth the same monotonous cry.
The cock is proud; the peacock is vain of his beauty; doves and fowls are amorous, always seeking each other's society. The partridge is deceitful and jealous, lending perfidious help to the huntsmen to seize their prey.
Source: Nine Homilies of Hexaemeron (New Advent)