might be some sort of bug? I have to kill off the rollie pollies, they like to snack on mine... cant tell you for sure tho.

Your fern's leaves look a lot like feathers. My guess is that birds are snipping them off to use for nesting material. They often do this. If it were bugs, they would not snap them off where the leaf meets the stem (mostly), they would do haphazard munching leaving scallops and holes in the leaves. It does not look like bugs to me. Your ferns look healthy and they can surely survive losing a few little frondlets. I wouldn't worry unless it got much worse.

In the meantime if you think there may be bugs, spray the ferns with some homemade cayenne pepper spray.

Lainey