From what I observed a few years back when a pair of crows built a nest in an old gumtree opposite my house, as the baby crows developed proper feathers and grew bigger, they progressively left the nest, but remained in the home tree, stretching their wings and exploring its upper branches for several days. By the time they were ready to take flight, they looked pretty much like their parents, just a little bit smaller. Unless you were looking closely, you probably wouldn't realise they were the new kids on the block.