In The Twelve Days of Christmas obscure avians called "colley birds" are mentioned. This name is so obscure that it has been sometimes changed into "calling birds". In fact, the colley bird, which is first mentioned in a version of the carol written down in 1780, is the European blackbird, also known as the merle or ouzel. It is an English dialect name.
Less easy to explain is the carnal in the carol The Carnal and the Crane. None can say with certainty what this is, although according to guesswork it is a crow. Is it even a bird, though?
At least we all know what a crane is.