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".