Why do birds fly into windows?

+79 votes
asked May 27, 2015 in Pets & Animals by Mariyam (800 points)
I live in the country and this blue jay keeps crashing into my picture window. He does it several times a day. Why do birds fly into windows anyway? Is their eyesight bad or what?

2 Answers

+15 votes
answered Jun 4, 2015 by salil (1,290 points)
Sometimes a bird will deliberately attack a window. This most often occurs in spring when birds are defending their breeding grounds. If a male bird sees his own reflection in the window glass, he may assume it is another male bird attempting to intrude into his territory and he will attack it, repeatedly pecking at the image trying to drive it away. He may even exhaust himself in the fight before he gives up. Fortunately, this does not normally lead to any fatalities, just some worn-out, frustrated male birds who feel like they are doing something wrong when it comes to home security. Although spring is the most common time this occurs, it may happen in any season. During autumn, male birds frequently get a second burst of testosterone, bringing out their defensive instincts once again. The scientific term for this additional dose of male hormone is called "gonadal recrudescence".
+8 votes
answered Jun 5, 2015 by carolina (700 points)
edited Aug 23, 2015 by Kris
It is believed the most common reason why do birds fly into windows is because they see the reflection of trees, plants, and sky in the glass and do not comprehend that those images are not real. They have no concept that the transparent sheet of glass is there, that it is solid and will stop their flight abruptly. This may happen when a bird is chased by a predator and they are fleeing, looking for a safe escape, and in a hurry to make their getaway. It is an even more common occurrence if there is another window or a mirror across from a large picture window that allows the bird to see what appears to be open countryside. A bird may assume he has a clear flight path ahead and try to fly through the window to get to his destination. Unfortunately, they quickly discover they need to take a detour.
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