Fledgling Magpie in garden

We've had a fledgling magpie in our garden for 3 days now. The parents are observing it and the fledgling seems to find food itself. It is getting stronger and hops around and jumps on branches. How long do they stay on the ground. It isn't showing any signs of trying to fly. We've got a dog so have had to keep her in so are keen for the fledgling to fly. It is very active in the evening and likes to peep through our patio window.