I heard a Royal Engineers warrant officer sing this to the tune of 'The Old Hundredth' in 1949:

Three big black crows sat on a tree
They were as black as black could be;
One big black crow said to the other:
'You're blacker than me, you dirty black bugger'.

They flew across a lofty plain
And found a horse just newly slain;
They setteld on the poor brute's head
And pecked his eyes out, one by one.

As I was walking through the wood
I shit myself just where I stood;
I called for help, but no help came
And so I shit myself again.

Yes, I am aware that I've lowered the tone with this horrible lyric, but I did collect it with my own bare hands.