The article focuses on various functions of birds appearing as an indispensable element of the mythological system. First of all, their role is underlined in the cosmogonic and anthropogonic act. The most archaic is the image of the Great Bird, the creator of the world and man (among Mordvinians- Erzians). Mention is made about the role of prophetic birds and their use in the capacity of sacrifice and rituals. Gods and deities presented themselves in im- ages of different birds (duck, eagle, pigeon, swan, swallows etc.). Some compari- sons with other Finno-Ugric ethnoses (Mari, Komi etc.) are given. Images of birds occupy a particular place in the mythology of Mordvinians, and among other peoples. However, the subject matter presented in the article has so far not received the due attention of researchers. Birds appear as an indis- pensable element of the mythological system and perform different functions. First of all, it is essential to describe their cosmogonic and anthropo- gonic functions. The image of the Great Bird (mdM Ine Narmon', mdE Ine Narmun') is the most archaic in Mordvinian mythology where she acts as the creator of the world. Thus, she lays the Great World Egg (mdE Ine Al, mdM Otsiu Al), from which the world appears. The Earth comes from the egg-yolk, while the sky and the underground solidity emerge from the eggshell. A similar motif, the creation of the world from an egg laid by a bird, is typical in the cosmogony of other Finno-Ugric peoples: Finns, Estonians, Saami, Komi (Myths 1994: 564). Likewise, in Mordvinian mythology, the Great Bird is the original mother of some ethnoses and deities. According to a Mordvinian myth, the forefathers of Erzians-Mordvinians, Russians and Chuvashs were born from the three eggs of the Great Bird. Similarly, deities-patronesses of fertility - Norovava (mdE), wind - Varmava (mdM, mdE), woods - Vir'ava (mdM, mdE) were hatched out of three eggs laid by Ine Narmun' (mdE) in the nest on