I was having what can only be called 'chicken balls' for lunch, when for some reason it occurred to me that you never see a (male) bird's testes. I have noticed that their penises only emerge on certain opportune occasions, but as far as I know we (male) mammals have testes because semen/sperm cannot survive long in the warmth of our (ahem) body cavities. So,since birds are also warm-blooded, how is it that their testicles are not for all the world to see like a mammals?