CactiGuide.com

I have been growing epiphyllums for 50 years, and for 25 years here in the Bay Area of California, and never until this past month have I had a problem with something eating the flower buds off my plants. No new green growth has been touched. There is no sign of snails or slugs. I have enclosed a picture of one of the half-eaten buds (I broke it off the plant). Any suggestions would be greatly appreciated!

My best guess is birds...

Lots of animals (birds, insects, reptiles, mammals and etc.) eat flowers and flower buds. If snails/slugs, you can see them at night. Looks like also possible a small mammal. You might want to check it during night time. Sometime they can even hiding inside that particular pot/plant.
Once I had mice inside one of the larger cactus pot.
If only one plant, I would isolates that particular plant, if it still happen, then the culprit is in the pot itself.

This has happened to almost every plant I have along the back of my house. Definitely some creature that can gather the buds and then sit and eat them (I found a small pile). I've lost an entire season's worth of flowers, unless the epis all grow new ones.