Passage 10.31.6
γένεια μὲν πᾶσίν ἐστιν αὐτοῖς, ἐν δὲ τοῦ Μέμνονος τῇ χλαμύδι καὶ ὄρνιθές εἰσιν ἐπειργασμέναι· Μεμνονίδες ταῖς ὄρνισίν ἐστιν ὄνομα, κατὰ δὲ ἔτος οἱ Ἑλλησπόντιοί φασιν αὐτὰς ἐν εἰρημέναις ἡμέραις ἰέναι τε ἐπὶ τοῦ Μέμνονος τὸν τάφον, καὶ ὁπόσον τοῦ μνήματος δένδρων ἐστὶν ἢ πόας ψιλόν, τοῦτο καὶ σαίρουσιν αἱ ὄρνιθες καὶ ὑγροῖς τοῖς πτεροῖς τοῦ Αἰσήπου τῷ ὕδατι ῥαίνουσι.
All of these figures have beards, but on the cloak of Memnon there are also birds worked in relief; these birds are called Memnonides. The people around the Hellespont say that every year, on certain appointed days, these birds come to Memnon's tomb, and whatever portion of his tomb is bare of trees or grass, the birds sweep clean, and then sprinkle it with water from the river Aesepus, carrying it in their wet wings.