The Cutty Wren
About the Song
"The Cutty Wren" is a traditional English folk song that is generally considered to be about the tradition of hunting and killing of a wren on Boxing Day aka St Stephen's Day in the British Isles.
An alternate interpretation of the song is that it originated in the English Peasants' Revolt of 1381 with the Cutty Wren representing King Richard II who is killed and fed to the poor. Wikipedia's article on the song says that the evidence is that the song was written later & suggests that this idea was derived from an A.L. Lloyd's 1944 book The Singing Englishman.
"Billy Barlow" which was included in Ruth Crawford Seeger's American Folk Songs for Children collection is an American variant of the song where the wren is changed to a rat.