Lewis & Short

1. anser, ĕris, usu. m. [Sanscr. hasas; Gr. χήν; Germ. Gans; Engl. Gander; Erse, goss = goose] (f., Varr. R. R. 3, 10, 3; Col. 8, 14, 4; cf. Schneid. Gram. II. p. 7; Bentl. ad Hor. S. 2, 8, 88; Neue, Formenl. I. p. 612 sq.), a goose; sacred to Juno, and which preserved the Capitol in the Gallic war. Hence held in high honor by the Romans, Liv. 5, 47; Cic. Rosc. Am. 20; Plin. 10, 22, 26, § 81 al.
Anser Amyclaeus, the swan, into which Jupiter changed himself at Amyclœ, Verg. Cir. 488.