I heard a slightly different version by a local group called Double Indemnity:

IF I WERE A BLACKBIRD

I am a young sailor, my story is sad
Oh once I was carefree and a brave sailor lad
I courted a lassie by night and by day
Ah but she's gone and left me here and sailed far away

CHORUS: Oh, if I was a blackbird, could whistle and sing
I'd follow the vessel my true love sails in
And in the top riggin' I will there build my nest
And I'd flutter my wings over her lily-white breast

I sailed o'er the ocean, my fortune to seek
Though I missed her caress and her kiss on my cheek
I returned and I told her my love was still warm
But she turned away lightly, and great was her scorn

Chorus

Or if I was a scholar and could handle a pen
One secret love letter to my true love I'd send
I'd tell of my sorrow, my grief, and my pain
Ah, since she's gone and left me here in yon fern glen

Chorus

My parents they chide me, they will not grieve
Sayin' me and my false love married should never be
Ah, but let them deprive me, let them do what they will
While there's breath in my body, she's the one that I love still

Chorus