You're all wrong - it's a Gloucestershire song! Here's how they used to sing it round here:

I know where there's a blackbird's nest
I know where 'e be
'E be up yon wurzel tree
And I be after 'e
'E spies i and I spies 'e.
He calls me a bugger and liar
When I reach that blackbird's nest,
I'll set the bugger on fire.
Working on the farm, four and twenty years
You can't take a rise out of I
But there yent no birds on this yere farm
Can hide their nests from I.
I wish I was back home in Gloucester
Where all they birds do flock round I
I'd clap my hands and laugh like buggery
Just to see they blackbirds fly.
Be I Gloucestershire, be I buggery
I comes up from Wareham
My old girl has fourteen kids
And she knows how to rare 'em
And they calls I Buttercup Joe.

Check that out!