Actually window pecking can be very dangerous to the birds. Basically they see their reflections and think that it is another bird that they are seeing and birds are territorial and because this "other bird" (the reflection) does not go away the bird will continue to peck and peck until the reflection disappears. When they do this they can actually damage their beaks and can even give themselves head trauma. It is recommended that you place something in the window to make it so the bird does not see it's reflection. Do you have a shade that you can pull over the window or close the curtains. You can also put decals or colored paper in the window....anything that will help to loose the reflection that the bird is seeing.