I hope you get something that will work for you.I really appreciate the information and advice but it would be very difficult to safeguard my birds with line of sight or infrared sensors. If you saw my setup, you'd understand.
The coons have been proven to be able to get into the buildings from all sides. There are at least 6 buildings most of the time surrounded by vegetation. There aren't many line of sight paths on any side of any building with trees, berries and gardens surrounding them. Sometimes, I've seen the raccoons climb down from the trees right onto the roofs.
As an industrial electrician and automation engineer, I'm well versed in all the motion/proximity sensors yet to be invented. If I were able to put some on the perimeter of the whole property (which isn't possible) with deer, rabbits, etc. I'd be getting false alarms all night. I think I need something that works on sound.