Drawing the curtains or blinds prevents collisions.
Facts
This isn’t entirely wrong.
Drawing the curtains and blinds can block fly-through effects. That is, it may ensure that birds won’t try to fly through corner or parallel windows.
If the slats of the blinds are open and clearly visible through the glass, that may even help break up reflections on the outside.
But in general, as you can see in the photo below, curtains and blinds do not consistently eliminate dangerous reflections on the outside of the window.
Look at your own windows from outside at different times of the day, under different light conditions, to see what we mean.
Sunshades on the outside will block reflections. However, this is only effective when the shades are closed.
