This video from the USA says about itself:
14 September 2016
Three baby Red Squirrel “kittens” are ready to leave the nest box in the Great Smoky Mountains. I’m the first human they’ve ever seen. It’s been a bumper year for squirrels here and in Florida and a little bit earlier than years past, typically they are not leaving the nest until mid-October. This nest box while built for screech owls is really a squirrel nest box for breeding and winter shelter.