How to prevent birds from hitting windows
Every year, somewhere between 100 million and a billion birds die from crashing into clear glass windows. Buildings and windows that reflect the sky and trees, in addition to natural landscapes, trick birds into flying toward objects. Though most bird deaths are caused by giant glass skyscrapers or reflective condominiums, many birds mistakenly crash into windows or houses. Here is some advice on how to make your windows bird-friendly and prevent bird deaths.
Get a screen or hang mesh over the window
An easy solution to this problem is buying a screen or mesh webbing that fits over the window. The screen will take away the reflective properties of the windows, but if birds still accidentally fly into it, they will simply bounce off. This also has the added benefit of keeping out insects when the window is opened. There are commercial flaps available from companies that make glass visible to birds. For example, there is one called the CollidEscape that still allows natural light into the room, but appears different on the outside.
Adding art and designs to your window
If you'd like to spice up the appearance of your window at the same time you make it bird-friendly, painting pictures or adding decals to the glass provide the house with added decoration. Consider painting the windows with interesting designs or sticking large decals on the glass. For something more low key than visible art, there are many decals that don't stand out to the human eye, but are clearly noticeable to birds.
Move the birdhouse or bird feeder away from the house
Sometimes simply moving the birdhouse or bird feeder is enough to reduce a bird's risk of crashing into a window. According to an article at Susan's Bird Gardens, birds are much more likely to be killed if they fly into a window at full speed, so it's a good idea to place birdhouses or feeders close to the house. This will help birds fly away from your home more frequently, but if they mistakenly fly toward a window, the speed will not be enough to seriously injure the bird. At worst, they will be dazed for a moment before taking off again.
Place some sort of marker on the window
If birds can clearly see something is on the window, they will usually avoid flying into it. Placing painter's tape across the outside of the window or affixing strings and ribbons in front of it will typically avert birds. The movement of the ribbons and strings will scare off birds, while the tape will illustrate the boundaries of the glass. Though these additions sometimes take the aesthetic appeal away from a clear window, they are an easy alternative to adding something completely new to your window.