There are a few websites with recordings of bird sounds. But this one is pretty cool. They have a world map and you can narrow down your region on the map, then listen to sounds recorded in that region. Check it out.

https://www.xeno-canto.org/explore/region

Your story sort of reminds me of a family bird story. When I was around 12, we had moved to a larger ranch in the mountains. Every evening around dusk we would hear this strange roaring noise. For months we tried to figure out what it was, speculating that it was some sort of animal. One night, my sister and brother and I decided we were going to find out once and for all. We set out into the woods to wait for the noise. Not a sound. Then suddenly, there it was. The sound came and it was only feet from my face. It was a bird! Once we knew it was a bird, we looked through the bird book (this was before the internet) until we were able to find all about it. It was a nighthawk. Fascinating creature. They tend to be present at dusk. The males circle making a very distinct call, then they close their wings and free-fall at a high rate of speed. At the bottom of their fall, they open their wings. The wings hit the air and make this loud roaring sound. It's really amazing. We named our ranch Roaring Feathers ranch.

I suggest that you consider toad or tree frog calls.

I checked their calls online and they don't sound the same. Thank you though! I really appreciate any suggestions.

The most similar sound I've been able to find is guinea pigs wheeking.

Perhaps a killdeer. They sometime call at night.

https://www.allaboutbirds.org/guide/Killdeer/sounds

Thank you so much gyr_falcon. I checked it out and it's not similar to the sound I hear. The one hear sounds guttural.

Perhaps something like a raccoon or a groundhog is making your noises?

Check out fox sounds at night.

tj

Check out skunk sounds. Good luck!

Bats?

Thanks everyone. I've checked racoon, fox, skunk and bat sounds. No luck : ( I am wondering if it's a guinea pig that escaped. Although I don't know why it would make the sound once and stop instead of doing it continuously like the guinea pigs in the online videos.

Also, I don't hear it every night like I used to, more like once a week 😥

Guinea pigs are diurnal, so even if there were an escaped guinea pig nearby, it would not likely be the source of a nighttime noise.

Porcupines are nocturnal ... maybe compare them next?

I already checked porcupine noises and that's not it either. Good to know about the guinea pigs being diurnal. Thank you!

Check out Pika sounds; not sure if they would be in your neighborhood, but they do live in CA.

Ok so I live in Indiana. A few years ago I heard something outside my bedroom window. It sounded like a giant guinea pig. I grabbed my flashlight. Ran outside. Looked all around and nothing. But I had heard it walking past in the leaves. I looked all over. I too thought perhaps one had escaped, except for the fact it was so large. Well sounded like it was large. Too big a sound for a small guinea pig. I too searched possible animals. Nothing. I am thinking we have heard the same thing. Karen

Did you ever find out what the sound is? I've been going crazy trying to figure out a sound I heard one night at a campground in Santa Paula, CA. It sounded like it was coming from a tree nearby, but I can't be sure. I did record it - you'll probably have to turn your volume way up, but it sounds much like you described.

Anyone compared to a northern saw-whet owl? or maybe a short-eared owl?

I live in the hills of San Clemente, CA, & for a year, I've been hearing the exact same noise, PFCMCL! Haven't heard it in a few months, but heard it late last night, August 29, 2021. I actually incorporated a dream of guinea pigs as I was waking up--our neighbors had guinea pigs so I know the "wheeking" noise

Possum