yes our feathered friends have poo issues, as they get bigger you'll need to fence a special area. Im wondering what your gonna do when they are full grown.
http://www.bellaonline.com/articles/art40334.asp -that talks about how to ahve them inside, LOL
Some cats do go after turtles, you can get a screen lid for the tank. Ive never had a problem but a friend of mine has had her cats dive in her large aquarium and carry off baby turtles