Our youngsters are getting ready for their first flight in about a week’s time by tearing about the box, flapping their wings and crearing a snowstorm in the process. At this age, even if one was to fall out of the box during their play activities, it should be able to glide safely to the ground where the parents will feed it until it’s ready to fly up again. If I can find it, I will put up into a tree where it will safe from cats and foxes.
A good example here of ‘wingersizing’ https://youtu.be/AuAixs-Cdww