I have no memory of ever consciously learning this (and I've certainly never sung it) but in Dorset it's:

Be I 'ampshire, be I buggery,
I comes up from Wareham,
I've got a girl with calico drawers
And I knows how to tear 'em.....

Where be yon blackbird to?
I know where 'e be
He be in yon wurzel bush and I be arter 'e.
'E sees I and I sees 'e
And 'e knows I be arter 'e
With a bloody great stick I'll knock 'e down
Blackbird,I'll have 'e.