Kicking an egg out of the nest.

Hi

I have two girls who are very close and lay at the same time.  This am they were both happy in the nest box, when we went out.  When we got back Princess Snow White was still in the nest box and Chuckles had come out.  When PSW finally did emerge (started to think she'd gone broody again!) I went to collect the eggs.  One was in the nest box (a highsided cat litter tray  :oops: ) the other was in their sleeping compartment - rather dirty.

I assumed one had decided to lay in an odd place (as I'd read in a previous post) but I deduced (due to how dirty it was) that it had been rolled out of the nest box deliberately.

They've always laid in the same place - why would PSW take offence to Chuckles egg!?!  Does this happen with your chooks?  

Any help gratefully received.

Ness