This video from the USA says about itself:
7 September 2016
Its Gray Squirrel Nesting season for 2016 in Florida – Three hours of squirrel kitten watching. One mother squirrel has two kits in the screech owl nest box in this video and another has very small kits in a flycatcher nest box in which I don’t have a camera. The birds are not using the nest boxes right now so this will work out OK – I’ll have the nest boxes secure by December for bird nesting season. These squirrel kittens just opened their eyes for the first time today.