Cockney Rhyming Slang - Bird

Bird has become commonly known in certain circles as slang for prison or jail.

It was often used in TV programmes such as Porridge and Minder. In the former the inmates were already doing bird in the latter Arthur Daley was constantly trying to not end up doing bird.

Arthur Daley - at large and definitely not doing bird.

So where does 'bird' come from? Here's a clue

Birdlime

'Birdlime' is a substance of varying ingredients that is used as a glue to capture birds on trees, not the most pleasant item.
It's possible that it was also used by criminals on their hands and where the expression 'sticky fingers' came from. The slang meaning however is rhyming lime with time,

birdlime=time

'Time' is a slang description of a prison sentence, so there you have it.