Cormorant

The common cormorant, or shag,
Lays eggs inside a paper bag.
The reason you can see, no doubt,
It is to keep the lightening out.
But, what these unobservant birds fail to realise is,
That heard of wandering bears will come, with buns,
And steal the bags,
To hold the crumbs.

Anon (probably Christopher Isherwood)