Young blackbird

We have had the pleasure of watching 3 blackbirds fledging for the last couple of weeks, the dad has been so busy feeding them from our garden, two have now flown but one has remained. He can fly but doesn’t seem to want to, he sits in our bird feeder or behind the Passion flower and doesn’t seem at all bothered by us or our dog being in the garden. He sits on the bird feeder for ages, he has even looked asleep on it. Is he ok, should I be worried or doing something for him. His dad is nowhere to be seen now, he is feeding himself and I have food and water out for him, Should we be doing anything else?