That was a pretty amazing video! Very cute, but I'd be afraid of just letting my parrots fly outside without restrictions though. One never knows about what an animal is thinking. It could fly away at any time, and then you've just lost your friend and investment (parrots aren't cheap!). I wouldn't take any chances like that. And what if a predator caught them? Nope, I wouldn't risk it!
We bought a harnesh & leash for our Eclectus a couple years ago. We tried to get him used to it, but then gave up about midway through the training. We're not dedicated enough to stick with much of anything, I guess! Maybe we'll work on it again this summer and try to get him outside with us. It would be fun to take him to a park or even shopping.
