Re; The Gaelic text: JIFSS and Songs of the Irish. Some spellings are slightly different, but I suspect that's simply due to moderniization of Gaelic spelling. JIFSS starts "'S ar" rather than "Ar" and 4th line starts "'Agus" rather than "'Gus". I see now that JIFSS version lacks the 4th verse of that in songs of the Irish.
Translation: JIFSS version is labeled 'Translation', is not Sigerson's, and I see now that it's not rhymed, so it is stricktly a translation, and not a song. It commences:
When I rose in the morning,
And the summer sun was shining,
I heard the huntsman's horn
And the sweet song of birds;
It also has only 3 verses.