Passage 8.22.5
αὗται τοῖς ἐπὶ ἄγραν αὐτῶν ἀφικνουμένοις ἐπιπέτανται, καὶ τιτρώσκουσί τε τοῖς ῥάμφεσι καὶ ἀποκτείνουσιν. ὅσα μὲν δὴ χαλκοῦ καὶ σιδήρου φοροῦσιν ἄνθρωποι, διατρυπῶσιν αἱ ὄρνιθες· ἢν δὲ ἐσθῆτα φλοΐνην παχεῖαν πλέξωνται, τὰ ῥάμφη τῶν Στυμφαλίδων ὑπὸ τῆς ἐσθῆτος ἔχεται τῆς φλοΐνης, καθὰ καὶ πτέρυγες ὀρνίθων τῶν μικρῶν προσέχονται τῷ ἰξῷ. αὗται μέγεθος μὲν κατὰ γέρανόν εἰσιν αἱ ὄρνιθες, ἐοίκασι δὲ ἴβεσι, ῥάμφη δὲ ἀλκιμώτερα φέρουσι καὶ οὐ σκολιὰ ὥσπερ αἱ ἴβεις.
These birds attack those who approach to hunt them; they wound and kill men with their beaks. Indeed, anything worn by humans made of bronze or iron is pierced through by the birds. But if men weave thick garments of bark fibre, the beaks of the Stymphalian birds become caught in the bark clothing, just as the wings of small birds are caught by bird-lime. These birds are about the size of a crane, resemble ibises in appearance, but have stronger beaks that are not curved like those of ibises.