I have a big cage on wheels and a smaller cage that I can carry. I put the birds outside on my back porch with a rug over half the top to give them shade and then I used to leave them out there for as long as a few hours (weather permitting). I always wheel the big one out to clean it because hay flies everywhere. Like
Casper said, it gives me a chance to sweep and mop really good in their corner. It also gives them some sunshine and fresh air and a chance to listen to the outside birds. I've never left the house with them out there and I always have an eye on them out the window.
But yeah, once a mourning dove landed on the cage and I freaked out and sprayed the cage with mite spray. And then I saw a few snakes, not by the cage, but around my apartment in the grass, they were small enough that they could slip into the gaps of my big cage and it just made me nervous. And now I don't leave them alone anymore!!! But they really like going outside. They cock their heads to the side and listen to the birds and call back.
)