It's a busy day on the deck with birds frolicking, feeding and bathing - all kinds of activity. Suddenly - chaos, a kerfuffle and a bang. The birds have gone except for a stunned one who doesn't know what happened, lying on the deck.
Sadly, birds are killed in huge numbers each year by crashing into windows due to a surprise, panic or disraction due to strange light and shadows. Usually the bird is stunned, falls to the ground and begins a period of recovery that may take up to an hour. During that recovery period, the bird is vulnerable to hawks, house cats, or weather conditions.
Sometimes hawks are the cause of the commotion in the first place because they have learned a hunting strategy of swooping down on active bird feeders, creating panic and confusion with birds flying in all directions including into windows where they become easy prey.
To help a stunned bird that has hit a window, you should offer it some protection. One way is to place the bird in a safe location, use a small basket and place a light cover in it to keep it warm. When it has recovered sufficiently to fly, it will go on its way.