Scure the prentious name (originally for CB radio when it was illegal and fun) I always played this song in D major.as below.

         D      G         D
Oh that I could hear the birds again
                     G
In the fields of Ardmourn
          D             G          D
Where the Sun Lies over Sllom Vo ....o
       C               D
And the Mist Silent all around

If you fingerpick you can tune the bass E string down one note to a D and occassionally pick that to suit your picking style and get something similar to the CorriesOriginal,