Why the egg song but no eggs

[Wildebeast farm]

Hi, we have a flock of 12 re-homed RIR’s that are about 18 months old.

They keep doing the egg song but when we go out to the coop there are no eggs. What’s going on?
They are laying but not that often, we are based in the south of France, so temps are usually about 30 degrees during the day, are they getting to hot.

 

[Chickeng1rl567]

When do they do this, and where? It could be the predator warning call because they sound similar.

 

[Wildebeast farm]

They are in their large run, and it can happen at anytime. Have noticed that sometimes it is just a short song, so maybe it is a warning call.