I'm a very light sleeper, so I have blackout stickers on my bedroom window. (They're vinyl sheets that stick to the inside of the window with water.) I've used these most of my life with no issue. Well, I moved from the city and my new place is in a wooded area. I'm hearing birds and squirrels bonk into the window because they think it's a little cave or something. With the heatwave it's now multiple times a DAY. I opened my window today and there's actually a small pile of dead bodies on the ground. I feel awful.
Is there anything I could do to help these animals understand my window is a black wall and not a cave?
Put something like this outside your window or stick this onto the outside of your window.
The reflectiveness of your window over a dark background makes it appear like a mirror so birds think the can fly through this „opening“. The sticker with the silhouette of a bird of prey will scare them away.
It's not necessarily the predator thing that scares them away. The most important part is breaking up the reflection on the outside. The anit-collision stickers will work well for this. Look on amazon or at a local hardware store, they come in many patterns and shapes, just pick one that you like. You can also hang a couple old CD's in front of your windows from fishing line. People do that where I'm at to scare off woodpeckers from their house and it should work for other birds too.
Second this - if you google anti-collision stickers this should do the trick. Alternatively you could also use some scotch tape (non-transparent) and tape a line across the outside of the window every 3-4 inches for a DIY fix.
How well do they work though? I’ve read that in order to be effective you basically need lines every 50-75 mm, and a few stickers aren’t that effective
That's true, so closely spaced markings are recommended. I had the same problem and this dotted tape solved it completely. Personally, I didn't want clip art graphics on my windows, and I like the fact that the dotted tape minimizes interference with my view outside. You can find more information on other strategies here though (like drawing deterrent patterns with bar soap).
*Two inch spacing worked for me, but you might need to make it denser depending on the species you're accidentally luring
you could put some other foil on the outside that is cut to the silhouette of a bird of prey. and there exist bird models that work as scarcrows that you could setup somewhere close to the window. i saw them in standing and hanging variations
Putting up some kind of reflective or high contrast pattern of bars or spots works quite well. The St. Louis Zoo has an entire exhibit about making your home windows "bird safe".
Unfortunately, the only online mention I can find of it is on Twitter, and I'm not going to link them.
You could switch from the Vinyl to a combination of blackout blinds and black out curtains. At least these can be opened in the day time which is when you'll get the majority of your problem presumably? Blackout blinds are also not usually black on the outer surface; they're better white to help reflect light so wouldn't look like a cave?
Basically what everyone suggested. Reduce the reflectivity of your windows since birds see it as sky or trees. Different window treatments have different efficacy. Gotta shop around for what fits your budget and what is effective for your window.