If you go to - http://isle-of-man.com/manxnotebook/search.htm - and search for "O What if the Fowler my Blackbird has Taken" you'll get the book 'Manx National Music' where on page 56 there's a four-part arrangement of the tune only.
If you go to 'Manx National Songs' p115 you'll get both words and music - with the words credited to Charles Dalmon.
This is a song better known as 'The Royal Blackbird' (Roud No. 2375 - 242 entries).
James Hogg 'The Ettrick Shepherd' wrote in his 'Jacobite Relics of Scotland' 1819 "one of the street songs of the day."