Hens Stopped Laying

We all know that egg production falls off in the shorter and darker days of winter but we had a bit of a mystery on our hands. From a dozen eggs a day we found ourselves with quickly falling numbers and finally one day with no eggs at all!

Some of the hens were in moult so you'd expect them to stop laying for a while but it was only three hens moulting which didn't solve the mystery. It was autumn but not the darkest or shortest days by far so that wasn't the answer.

Each morning, we'd hear the hens triumphant shouts as if they'd layed an egg, but the nestboxes were empty. Can you guess what happened?