Well, I've just looked through 'Ree Ny Marrey' (Songs of the Isle of Man) - 'Manx Ballads And Music' - and listened to the Manx selection on Jill Rogoff's CD 'The Celtic Cradle' and still haven't come up with anything resembling the words that you quote. Bobby Bob is the man who might have the answer but he's in Belfast at the moment, I'll ask him when he gets back. The chorus as given doesn't suggest 'Ushag Veg Ruy' (Little Red Bird).