Brahmā
Deva who is the creator of the Universe. He is identified as Chaturmukha Brahmā or the one who has four faces.
Haṃsa
Brahmaa’s vaahana – Hamsa symbolizes moksha, the release from the cycle of birth, death, and reincarnation – samsara.
Story
Lord Brahma, the creator among the trinity of Gods, blessed Hamsa, the white swan with a special power. It can separate milk from water even though both are mixed and absorb milk leaving behind water only. Here milk and water are symbolic for knowledge and ignorance respectively. As the swan absorbs all the knowledge leaving behind ignorance.
Lord Brahma considers this quality of utmost importance as he is the creator and needs this awareness to differentiate gnyana from agnyana. Therefore he made the Hamsa as his vehicle and mount.