Birds and windows are not a great combination. Whilst they will avoid windows if they can not see straight through them, i.e. they can see the inside of the building, if you have windows on both sides that allow for a straight view through they will often think they can take a shortcut.
This is often the case when it comes to office buildings as they tend to have windows that are symmetrical to both sides of the building and also a large number of them to allow for the most amount of natural to penetrate the building as possible. One other problem that can occur with office windows is heat from the sun. This is where one item – the Brise Soleil that you can get from companies like aluminium systems can help with both. They are fixed to the outside of the building and not only help to change the angle of light and reduce heat build up, but they also prevent birds from flying straight into your windows.
Other ways you can prevent birds hitting your windows is to use net curtains, plants located on the inside of your building near the windows to cause a distraction to the birds flight path and also to have decorative items on your window. All of these things will cause the bird to be distracted in its sight and will then avoid the window completely.