Skunk!

Since our chickens range free, we can only encourage them to lay in the nests we provide. Some of them like to find their own nests. These include a horse stall, between some hay bales, and in a patch of briars behind the chicken coop. The patch of briars is the problem spot. Not because we can't get to the eggs - because the skunk gets to them first.
I haven't seen the skunk. I'm assuming skunk because I see the hen laying, then come back for an egg that isn't there, and encounter a light perfume of Eau de Skunk. Now maybe I'm maligning the poor skunk, who passed through just once some time ago and has been followed by something else. After all, Eau de Skunk tends to - linger.
Whatever it is, it's snitching eggs in broad daylight, which probably narrows the list of likely suspects. Skunks do go after eggs during the day, as my poor Aunt can testify.
My Aunt M and my mother had the job of collecting eggs as kids. Before my grandfather bought the farm they kept a hen in the garage, and she had a nest there. They would wait to hear her cackle, then race to get the egg.
One morning when my Aunt climbed on the box she used to reach the nest, she encountered a faster harvester in a nice black and white suit.
She got out without being sprayed, and called my grandfather, who dispensed the usual farm justice. She wrote about her experience in an essay for school. The teacher sent her work home with the note "Not a true story!"
My husband offered to bait a trap, but there's a little problem with that. The traps are on loan from a friend, and I'm not confident in my ability to remove Eau de Skunk from it. And I guarantee there will be lots of Eau de Skunk. Plus there is likely another skunk just waiting to move in.
What we really need to do is build a coop big enough to house the nest boxes, which would likely make them more attractive to the hens. Only that requires time and money, two things Tumble Rock Farm is fresh out of just now.

-P