The mute swan (Cygnus olor) is the most recognized species among swans. With an average weight of 13 kg, it is one of the biggest birds in the world. The mute swan is recognizable by the black bump on its beak. This bump is a tubercle that is easily spotted on the white background of its plumage. The scientific community puts forward several hypotheses on the social role of this growth. One of these hypotheses is that of a sexual attribute because the tuber tends to grow during the reproductive period.