Birdsong is an important sexually selected trait, and its acoustic features are socially transmitted in the process of song learning. Though a great deal of research has been conducted to shed light on the mechanisms and functions of song learning, we still do not have clear answers as to why for some species, including Estrildid finches and humans, the ability of “social” vocal learning has evolved. Therefore, this paper addresses social factors responsible for song learning, especially focusing on tutor choice in Estrildid finches, with the aim of elucidating what is already clear about how the social environment shapes songs and what is needed in future studies.