These decals have been bird life savers for me. We have a wildlife area in the back and I feed my birds as well. With all the picture windows on the 3 stories on the west side my house, birds were constantly flying into the windows and often dying. It was so sad to find a dead bird when i was working hard to give them food and shelter.
Since I started using these decals, I have had no instances. The key is to place them according to directions so that the appropriate amount of decals are on the window and replace them as they age (I replace them every 2 years).