"A Corbie Sits At The Top O' Yon Tree"

"An' he's looking doon wi' his black, black eye,
An' he's crying oot wi' his caw caw caw,
If ye try tae sclim up,
ye're share tae fa'

Ma fether says it'll no be lang,
Afore I'm big an' souple an' strang.
An' I'll sclim up,
An' I'll nae fa'
An' we'll see if yon corbie cries caw caw caw!"

This is a poem that I learnt at school, but I can't remember the author, anyoune help?