Michael Tiernan told me this.
One time Finn Mac Cool was out in Norway and Finn had a great love for birds and the music of birds.
He knew every bird's music and delighted himself listening to them.
This day in Norway he heard the strange music and at once knew that no Irish bird could whistle so sweet. He had no peace or ease until he got the bird. It was a blackbird and he brought a pair to Allen in Co Kildare and kept them there. This pair lived on and became the parents of all the blackbirds we have.