One of the more barbaric practices of bird-catchers in the olden times was to split the tongue of songbirds to make them better singers.
Not sure of the details of this, but apparently some birds' tongues are inflexible and the process of splitting them loosens them up and makes the song more fluid.
We were told this by members of a family of English bird-catchers known as the 'Gilly-Gooley" Smiths, who specialised in catching songbirds and selling them; 'tongue-splitting' was still practiced by them up to the middle of the 20th century.
Jim Carroll