As far as egg eaters go...sometimes you find evidence in the form of yellow stains.
I let mine free range and I'm surrounded by hundreds of acres woods without any neighbors to speak of.
Most of the time they stay in my small 80 x 100 fenced in yard which is 85% shady most of the day.
When it gets really hot, or in the hours my backyard is in direct sun they take to the woods.
Anyway...there are usually about 40 running around in the yard.
Yesterday someone laid an egg in the dirt, right in front of the front steps.
A roo walked over and pecked it and it was all over for the egg.
He called hens to come eat, and a dozen came running.
They ate everything including the shell. All that was left was a few yellow stains that dried quickly to invisibility.
Egg production is way down which may be because of molt, the heat, or the fact they are laying them in the yard, and in the woods.
I don't eat eggs....I only want eggs for chicks, and for dog food...with some back to the chickens...so I don't really care.
Usually I let them all out of the coop very early...sometimes shortly after daybreak...but if I want to collect eggs...I keep them locked up until they lay.
I've also seen a hen lay an egg in the nest, get up, and peck a hole in it and start to eat it.
They are very well fed birds, so I know it isnt that.