On Tuesday morning I heard a thump and realized that a female cardinal went into my sliding window. I do keep bird savers on the sliders.
According to the web, the first thing is to keep the bird safe. If the bird appears just to be stunned, put it in a safe, sheltered place. If possible, leave the bird in the area where the collision occurred, but if the area is not safe from predators or other hazards, put the bird in a small box or paper bag.
I picked the bird up and made sure she was ok. Put the bird on a chair with some seeds. She eventually seemed to come out of the stunning feeling. She then looked at me and flew away.