Plato, Laws 789b

ναί. θαυμαστὸν δʼ οὐδέν ἐστιν ἀγνοεῖν ὑμᾶς τὴν τῶν τηλικούτων γυμναστικήν, ἣν βουλοίμην ἂν ὑμῖν καίπερ ἄτοπον οὖσαν δηλῶσαι. πάνυ μὲν οὖν. ἔστι τοίνυν παρʼ ἡμῖν μᾶλλον τὸ τοιοῦτον κατανοεῖν διὰ τὸ τὰς παιδιὰς αὐτόθι μειζόνως τινὰς παίζειν ἢ δεῖ· τρέφουσι γὰρ δὴ παρʼ ἡμῖν οὐ μόνον παῖδες ἀλλὰ καὶ πρεσβύτεροί τινες ὀρνίθων θρέμματα, ἐπὶ τὰς μάχας τὰς πρὸς ἄλληλα. ἀσκοῦντας τὰ τοιαῦτα τῶν θηρίων πολλοῦ

It is. Still it is by no means surprising that you know nothing of this pre-natal gymnastic; but, strange though it is, I should like to explain it to you. By all means do so. In our country it is easier to understand a practice of this kind, because there are people there who carry their sports to excess. At Athens we find not only boys but sometimes old men rearing birds and training such creatures to fight one another.