It is hard to find a joke today without a dirty word or two in it, but, here is one:

Two tall trees, a birch and a beech, are growing in the woods.  A Small tree begins to grow between them, and the beech says to the birch, 'Is that a son of a beech or a son of a birch?' The birch says he cannot tell.

Just then a woodpecker lands on the sapling.

The birch says, 'Woodpecker, you are a tree expert.  Can you tell if that is a son of a beech or a son of a birch?'

The woodpecker takes a taste of the small tree.  He replies, 'It is neither a son of a beech nor a son of a birch.  It is, however, the best piece of ash I have ever put my pecker in.'