Why do birds fly into windows for no apparent reason?
As stated by a few reflections are often the cause they see what appears to be a continuation of the forest/ sky/ etc. and keep going straight into it. Other times there is what’s known as tunnel syndrome when there are 2 windows on 2 sides of the house that are lined up. In this case the birds think there is a tunnel and they can fly through it only to hit the window. These problems tend to occur a lot more when you have a bird feeder near the house, hence either keep the feeder right beside the window so the birds don’t have momentum when they hit it or 30 + feet to reduce the risk.
