ὑποπτέρους is perh. meant here to suggest ‘shy’ (and therefore hard to shoot); for the word often implies ‘taking wing’: cp. Helen. 1236 “μεθίημι ϝεῖκος τὸ σόν, ἴτω δ᾽ ὑπόπτερον”: id. fr. 420. 4 “ὑπόπτερος δ᾽ ὁ πλοῦτος.” So Ai. 139“πέφόβημαι”, | “πτηνῆς ὡς ὄμμα πελείας”.