QUOTE (Gizmo #1 @ Jun 26 2007, 12:41 PM)

See like a quaker and a cockatiel i couldnt see one killing the other cause there the same strength.
They aren't the same strength though. Quakers are much tougher birds than tiels are. While the birds themselves are approximately the same size, a Quaker is much heavier (stocky) and their beak is more than twice the size of a Cockatiel's. It is very possible for a Quaker to kill a tiel. And it has happened before.
Greys and Amazons can get along, but it really depends on the birds themselves. Some birds can be very aggressive towards another, no matter what size they are and no matter what size the bird is. You kinda have to try it out. If you do, make sure you are right there and watch *very* carefully for body language that suggests aggressive.
Something else to think about with having another bird in your house that doesn't live there full-time, is that you are opening your existing bird up to disease. While the Grey may appear healthy, that doesn't mean he/she isn't a carrier for something else. So use caution with that.