Adrian, what do you consider as 'bad designs'? Thinking of a chicken that can't fly, I don't see it as a bad design. Who says that all birds have to fly? They seem to do pretty well on the ground, not to mention their eggs which we utilise to great effect. It's possible their wings used to be larger and due to mutations they became stunted? They seem to do just fine.
"The eternal mystery of the world is its comprehensibility"
Albert Einstein
Albert Einstein