If you only eat what birds eat, will you poop bird shit?

They dont have bladders because the cloaca serves relatively the same purpose. The kidneys directly connect to the cloaca as our kidneys link to our bladders.

Bladders can reabsorb water that is stored there (up to 60% in the right conditions) the cloaca does have the ability to reabsorb water but the percentages arent nailed down. That may be due to avians differing digestion system.

Fucking disgusting creatures

That's because the excess calcium is stored in your bones. Milk isnt made in the urinary tract either.