With the arrival of nesting season comes displays of love and territorial behavior. Some birds are notorious for defending their territory from all intruders that they will even attack their own image. Robins, Cardinals, Bluebirds and an Indigo Bunting are some that have attack their reflection in house and car windows. The male birds will literally launch themselves at the glass; repeatedly. What the birds is seeing is their reflection and they feel its another male in their territory. The image the bird sees is the outside glass surface that act like a mirror. In order to discourage this abnormal behavior you must do something to the outside surface. Pulling the curtains or shining a light towards the outside will do nothing to alter what the bird is seeing. You can mix up a solution of dish washing soap and water and wash the window. Do not wipe it off allow the solution to dry as is. The film will diffuse the perfect image the bird is seeing and hopefully they will go elsewhere. You can cover the glass with a screen as this will also shield the image from the bird. Sometimes the bird is doing it as their nest is nearby. Unfortunately even if you do something to one window there's nothing to say the bird won't got to the next one and attack it too. If they attack the side mirrors of your car you can cover them with plastic bags. These solutions are usually temporary. Once nesting season is over the birds go elsewhere.
The other type of bird strike is more harmful to a bird. It happens when you hear a heart wrenching thud against a window. It happens because a bird sees the perfect image of earth and sky in a window reflection and feels they can fly right through it. Sometimes it's the time of year, weather pattern, immature bird or Hawk attack that precipitates a window collision. For this type of glass strike you can apply decals to the outside of the window so that the bird sees a distortion in the mirror, that is wrong.