It is very scary letting them out after keeping them safe for so long! We trained ours to come for treats by always making the same call and shaking the container every time we throw them millet. They are not the brightest, but we think they have made the connection, and take notice when we call or shake the millet container. You might try letting out only a few the first few times. They will stay very close, wanting to be back with their pack. We thought they seemed pretty desperate and did not enjoy the experience. You can increase the number you let out each time until you are ready to release the group (it doesn't matter if it is the same birds or not... can't really tell mine apart). But the first time we let the whole pack out, we didn't supervise them and they wandered too far. I would suggest supervising the first time, calling them to you frequently and offering treats, and keeping the outing short to limit their exploring. Our birds seem to stay close if they are only out for a couple of hours, but roam much farther when they have 4+ hours.