From Aeliani de natura animalium libri XVII, X.xxxvi (see also II.xxxii and V.xxxiv). In the translation after Gesner's, from the Jacobs edition of 1832 (p. 154):
XXVI. De cygnis supra etiam dictum est, et quae illic omissa sunt, nunc adjicientur. In mari Africo Aristoteles ait olorum gregem interdum apparere; et cantum, tanquam ex choro quodam consonanti, suavem quidem, at lugubrem, et velut ad misericordiam inclinantem, a praeternavigantibus exaudiri; et ab illa modulatione nonnullos visos extinctos. Fontes, lacus, paludes, aliave loca aquis redundantia incolere solent, ubi earum rerum periti ducunt eos musicas ratioines exercere.
Εἷπον μὲν καὶ ἀνωτέρω περὶ τῶν κύκνων, εἰρήσεται δὲ ἄρα καὶ νῦν ὅσα οὐ πρότερον εἶπον. Ἀριστοτέλης λέγει ἐν τῇ θαλάττῃ τῇ Λιβύων φανῆναί ποτε κύκνων άγέλην, καὶ άκουσθῆναί τι μέλος αὐτῶν ὡς ἐκ χοροῦ τινος ὁμοφωνίας, πάνυ μὲν ἡδύ, γοερόν γε μήν, καὶ οἶον εἰς οἶκτον ἐπικλάσαι τοὺς ἀκούοντας· καί τινας ἐπὶ τᾦ μέλει φησὶ φανῆναι τεθνεῶτας αὐτῶν. Φίλος δὲ ἦν ἄρα ὁ κύκνος πηγαῖς τε καὶ τενάγεσι καὶ λίμναις, καὶ ταῖς ὅσαι πεφύκασιν ὑδάτων ἐπίῤῥοιαί τε καὶ άφθονίαι: ἐνταῦθα γοῦν καὶ τὰς ἑαυτοῦ μούνας αὐτὸν φιλοσοφεῖν οἱ σοφοὶ τούτων φασί.
This page is by James Eason.