Having a bird hit a house window is an unfortunate consequence that can happen at anytime of year. However, during bird migrations in spring and fall, the incidence of bird collisions increases as birds are traveling to their new summer or winter homes. This white-eyed vireo slammed into my neighbor's window, and with a little TLC, it survived, despite being knocked completely unconscious! This leads to the question, "What can I do for a bird that hits my window?" The answer to that depends on the situation. Audubon suggests calling a wildlife rehabber, and that would certainly be the best approach. Unfortunately, many of us don't have a rehabber nearby, and the task of aiding in the bird's recovery falls on us.
Sometimes, birds are only lightly stunned post-collision. Their eyes are open and they are looking around, but show no interest in flying. If it's fairly warm outdoors, and the bird is not at risk of hypothermia, I fashion a makeshift nest out of a clean cotton hand towel, and place the bird in the "nest" and leave it alone. From a distance, I do keep an eye on the recovering bird to see how it responds, and to make sure it stays safe from predators. There's a good chance the bird will fly off within a few minutes; although, I have seen it take as much as 20-30 minutes.
If a bird is laying on the ground and appears lifeless, GENTLYtry to move its legs. If the legs are stiff and don't move, the bird is likely deceased, and nothing more can be done. However, if you can move the legs, the bird is unconscious and there are some steps you can take to aid in its recovery. Line a small box with a clean cotton or paper towel, and gently place the bird in the box. Bring the box indoors and place it in a dark or dimly lit area of your home that is away from noise and pets. At this point, it's a waiting game. It can take as much as an hour for a bird to regain consciousness and clear its head. When you hear it scratching around the box, it's on the road to recovery! At this point, I take the box outdoors and wait for it to fly out of the box.
What if the bird does not recover, and it dies? It's sad, and not the outcome that any of us want, but the unfortunate truth is that this sometimes happens. It's very likely that the bird sustained extreme head trauma, and/or there were other injuries that were not visually apparent.
In the case of our white-eyed vireo, the time from collision to full recovery was about an hour. It regained consciousness within a few minutes, but sat perched on the shrub and looking around for what seemed to be an alarming amount of time. Fortunately, it eventually flew away, continuing its migration south to its winter home.