Growing shiny feathers

I watched a family of crows with two young a few days ago. One of the youngsters appeared to be having a 'nap' on the ground. I have only seen feral pigeons do this before, never in crows, so I took a shot. The crow immediately became nervous and started moving away, following another one. When checking the photo, I noticed that a few brand new, glossy black primary feathers can be told apart from the worn, dark brow, immature ones.