Hi Dawn,
I only have five hybrids (totally free ranging in a grassed garden with plenty of worms/grubs etc), and am beginning to get the impression that they will eat anything and as much as you can put in front of them. I only have to walk out of the back door and they run up to the patio looking as if they haven't been fed for days. My wife says I am starving them, but I say that if they have layers pellets left over (and they always have plenty in their feeder) then they are not starving, but just keen to get their beaks into something a bit more tasty, such as corn, veggies, pasta, mashed potato etc etc. I agree with you that they see you coming and know there is going to be something a bit more tasty to eat than pellets - simple as that.
Kev