One for sorrow

But don't worry, there were 7 others sitting in the tree. My knowledge of the song is based on a misspent youth watching Tommy Boyd, Susan Stranks and some other fella on the 70's childrens TV show 'Magpie'. As far as I remember the credits stopped at '7 for a secret never to be told' so I have no idea what 8 magpies are supposed to represent.
I'm not sure I have seen so many together before.