There are some parrots that can learn windows and some parrots that seem to not be able to do this. My Timneh grey Phinney knows windows. When I take her into a new environment, I walk her around to each window and I tap her beak on it so she can see it is a window and knows where it is. I have seen her fly right up to a window and land on the ledge many times. On the flip side, I have another friend with a pionus that tends to fly into the light and will fly into windows.
If a parrot flies into a window with enough force, it can kill itself so this is a serious issue to consider. Windows are most dangerous for new flyers because these birds will not be in good physical shape and/or may not have the skills to avoid. Windows are also most dangerous in unfamiliar environments because the bird will not know where they are.
Flying into a window does not mean that the bird WILL injure or kill itself. I have seen parrots fly into windows many times; however, it must be kept in mind that windows CAN kill a bird if hit with enough force and if hit wrong by the bird.
What do you do to help protect your bird from being harmed by a window?