Mine catch frogs occasionally too. I've never seen one eat them, but I'm sure they do. Usually, I just see a hen parading around with one while they others chase her trying to get a taste. I saw one with a big lizard a few days ago. Sometimes they catch mice too. Frogs seem to be their favorite though. We have an abundance of them in our yard.
I tried to rescue the first one! That just made them run faster with it making the others give chase and pull it apart! I have mostly open grass yard and rarely see one myself so I don't even know how they find them!
mine dont free range so when i catch bugs or lizards i take it over and drop it in the pen. and like someone said they play chase/keepaway with it for awhile till it gets torn apart and eaten. i havent done frogs, i dont know which frogs are poison