Keep a NERF Super Soaker filled and ready to use. You’ll probably only use it once. After that the cat will run off when it sees you.
Spray the fence and edges of yard with bear urine or other predator pee. It’s sold online.
See if you can find an old Wham-O Air Blaster:
Air Blaster from Wham-O (1963) (youtube.com)
Sorry for the wild tangent but this reminds me of a scene from Star Trek: The Next Generation.
I got one similar to the Orbiter that MindsEye_Watering posted about (but cheaper, 'cause I’m a cheapskate).
I got it because my wife was tired of the squirrels coming right up to her huge office window (not quite a sliding glass door, because the bottom sill is 8" above the floor) and leaping onto the screen to look inside and scrape their little claws on the screen, thereby causing my wife’s chihuahuas to go nuts* and start barking and leaping at the window. I also got it to deter the racoons from coming in at night to fish in our in-ground pool.
The pipe for filling the pool is on the house and there’s a spigot that got added to it for attaching a hose or shower or whatever. So I attached the motion-sensing sprinkler to it and strapped it in place (because the pool deck is cement and I wasn’t going to drive the sprinkler spike through it) and adjusted the limits of its turn angles and distance- and sensitivity- settings.
It did a great job of deterring the squirrels. They stopped coming close to the house after a couple weeks.
The racoons, on the other hand, were more stubborn. In less than a week they learned exactly how far the sprinkler stream could reach and they adjusted their habits to stay just outside that circle. That meant they would walk to the two corners of the pool that were farthest from the sprinkler and do their drinking and fishing there. I originally thought they were just sloppy drinkers, drooling and dribbling water as they walked away from whichever safe corner they used, but I happened to see them one night and watched in fascination as they took turns walking up to the pool, scooping their little paws into the water as if trying to snatch a fish, and then taking a few sips before wandering away. They were smart enough to stay out of sensor range, but not smart enough to realize they were at a swimming pool rather than a pond.
After seeing that a couple times, I found a way to mount the special sprinkler on a little stand. Moving it a couple feet one way or the other each day put the sensor closer to one pool-corner or the other, and the racoons finally stopped visiting.
It seems to me you could put such a device out in the back yard (connected to a garden spigot, of course) so that it ‘watches’ the space below the bird feeder. Welcome birds would learn to approach from above, any cats that want to hunt below the bird feeder are large enough for the sensor to detect, and you could adjust the sensitivity so ground-feeding birds are not noticed (though that might leave some vermin undetected as well).
–G!
*It was very clear the squirrels were being sadistic.
That is just what the neighbor’s cats did with our first round of motion sensing sprinklers. One of them would react to the click of the relay by walking behind the sprinkler to get back to his bird watching spot. Assholes one and all. It was thingy that let me turn water on and off with my phone that made all of the difference.
And yeah…squirrels are assholes too.
I hope nobody sends Governor Noem a link to this thread.
I think that is a good solution to keep cats away from the feeders.