You should find the information you need here:


The problem is that the bird is quite able to see glass, BUT, it focused not on the glass, but on the reflection.  This is analogous to looking into a mirror out of doors and focusing on the reflection of the sky in the background.  You can’t focus on two widely separated plains at the same time, so if you can clearly see the sky, distant trees and so on in the mirror, you cannot possibly see the surface of the mirror, and vice versa.


So the trick is to place objects on the surface that, when the bird in motion focuses on, gives him or her a chance to see the glass surface.  That is why, when you approach an all glass door or wall, you usually see, at eye level, little stickers or imbedded material, that forces you to focus as you approach, on the same plain (or focus to the same distance) that the glass is, and you see the glass and don’t walk through it (in this case you may not be focused on the reflection so much as where you want to go beyond the glass…but it’s the same optical principle.


There has been a lot of research to show that to work effectively the decals (and WHAT they are does not matter) must be placed pretty close together.  I am pretty sure that website has the information.





Barry Kent MacKay

Bird Artist, Illustrator

Studio: (905)-472-9731
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From: SciArt-L Discussion List-for Natural Science Illustration- [mailto:[log in to unmask]] On Behalf Of Chris Gralapp
Sent: March-03-14 11:54 AM
To: [log in to unmask]
Subject: [SCIART] TAN: Hummingbird problem


I have a most distressing problem--I just installed a big, brand new bay window, and have had three hummingbirds hit it.  I think it reflects the sky and the mountains, and the mirror effect deceives the little guys to fly into it.  I moved my feeder about ten feet away, to keep them on the other side of the yard, if possible, but they still hit the window.  It's just heartbreaking. 

I know there are decals for deterring bird strikes--any suggestions for the most effective?



Chris Gralapp, MA, CMI

Medical/Scientific Illustration


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