Every backyard birder has heard the resounding thud of a bird striking a window, and even with the best preventative measures to help birds see and avoid the glass, impacts are inevitable. But when a bird strikes a window, what can be done to help it recover?

Why Birds Hit Windows

Birds are intelligent about natural predators and obstacles in their environment, but they do not recognize glass as a solid surface and they have no conception that it can be dangerous. Most often, window collisions happen because birds see various reflections in the glass and mistake those reflections for something real – a reflection of branches, for example, can seem like a good place to land, or a reflection of a feeder may seem like a tasty food source. Even reflections of other birds can be confusing, because it will seem as though the area is safe. When birds are panicked or threatened, such as being startled or chased by a hawk or cat, they are even more likely to crash into glass, even if that glass has been treated or made more visible.

When Window Collisions Happen

While there are many ways to prevent bird window collisions, even the most vigilant backyard birder will occasionally have a bird strike a window. When that happens…

Find the bird. If the collision was minor, the bird may be able to fly off right away, or it may move somewhat away from the window. If it was stunned, however, it will likely be underneath the window or very close by.

Observe the bird closely. Before handling the bird, watch it closely to see how it reacts. Many stunned birds will sit quietly without moving as they recover, perhaps with their wings slightly drooped, and if they are in a safe area they do not need to be moved. If the bird is unconscious, however, it may need additional care.

Check for injuries. If the bird is unconscious, gently pick it up or carefully check for visible injuries, including signs of broken bones or cuts. Other indications may be missing feathers or a discharge from the edge of the bill. If the bird is severely hurt, contact a bird rescue organization to ensure the bird gets immediate, appropriate medical care. While handling the bird, it is always wise to wear gloves.

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, put the bird in a small box or paper bag. The box or bag should be large enough that the bird can spread its wings, and it may be lined with newspapers or a rag. Close the box or bag and keep it in a quiet, warm spot as the bird recovers.

Give the bird recovery time. Depending on the severity of the impact, it may take just a few minutes or up to two hours for a bird to recover. During that time it should be stimulated as little as possible – do not open the box or bag to check its condition, and do not poke or prod the bird in an attempt to get a response. Instead, listen for it to begin moving around, which will be the best sign of its recovery. If, after two hours, the bird is showing no signs of recovery, it should be taken to a wildlife rehabilitator even if there are no signs of other injuries.

Release the bird. Once the bird begins to move and show more activity, it is time for it to be returned to its environment. Take the box or bag outdoors, and gently open it in the same area where the collision occurred so the bird can easily get its bearings. It should fly out fairly quickly, but it may not fly far as it adjusts to the surroundings. If it is not safe to release the bird in the same area, take it to the closest location where it will find good food, fresh water and safe shelter.

Not all birds will recover from window collisions. Internal bleeding or injuries may not be obvious but can be fatal, and if the bird dies it should be disposed of properly.

What Not to Do

It is natural to want to help every window collision victim, but there are some steps backyard birders should not take, even with the best intentions.

Do not offer food or water to an injured bird. Birds have very specific diets, and an injured bird needs a quiet, calm environment to recover – it will happily forage on its own after it is released.

Do not give the bird any medications. If the bird has an obvious broken limb or severe bleeding, wrap it snuggly in gauze to limit its movement, and get it to a rehabilitator for proper care immediately.

Do not release the bird indoors. It can be tempting to open a bag or box to check on the bird's progress, but doing so may accidentally startle the bird into a premature escape, causing more panic and stress when it finds itself in unfamiliar surroundings.

Never keep a wild bird as a pet, even if you intend to release it. Doing so is a violation of the Federal Migratory Bird Treaty Act and can be punished with fines or jail time, and it is not in the bird's best interests to get it accustomed to humans in any way.

Never handle raptors, even small ones. Birds of prey have powerful bills and talons, and mishandling these birds can create long-lasting problems for them to resume hunting in the wild. If a raptor collides with your windows, contact a wildlife rehabilitor or bird rescue organization for guidance.

Preventing Future Window Collisions

The best thing to do when a bird hits a window is to take steps to prevent any more collisions. If one window is a consistent problem, examine it carefully for reflections or other specific threats that may be causing birds' confusion, and use multiple techniques to keep birds safe. While it is important for backyard birders to know what to do when a bird collides with a window, it is always best if they never need to use that knowledge.

Source: http://birding.about.com/od/birdconservation/fl/When-Birds-Hit-Windows.htm

Ornithology FAQs at the Natural History Museum