Chooks no longer laying in the nesting boxes

We've only got 3 chooks and let them out each day to roam where they choose. A few weeks ago we sensed that something must have spooked them around the laying boxes that are set up in the chook-yard. Since then they now lay their eggs on the 'director's chairs' around the round table under the shade area to the east of the house. Here's a picture of today's effort: