Robins (again)

I know - I've become obsessed since I found a Robins nest in my shed, but I really have been spending a lot of time checking the babies are ok, keeping my cats out and the adult Robins in.

One of the checks has jumped out and is now walking around on the floor.
I'm worried a fox or something may break in through the small gap I have left but I suppose my only comfort is they are safer in here than if they had fallen to the ground from a nest in the garden.