I know where there's a blackbirds nest
I know where 'e be
'e be in yon wurzel bush
An' I be arter 'e

'e spies I, I spies 'e
'E calls I a bugger and a liar
If I gets 'old of that blackbirds nest
I'll catch the bugger on fire

Down on the farm for four and twenty years
'e's tried to take the rise out of I
There baint no bird on this yere farm
Can 'ide it's nesy from I

I wish I was back 'ome in Dorset
Where the birds they fly so high
I claps my 'ands and I laughs like buggery
Just to see they blackbirds fly

That's an approximation of the vernacular, as best as I can do it. I've been singing this song for years and as far as I know that's all there is. I learned it in Wiltshire from a local singer who'd been singing it since he was a kid.