Rabbits ...

They communicate like u & me! You can look up a behavior guide if u r curious.

http://rabbit.org/behavior/body-language.html

My bunny makes funny oinking noises when he is running around playing, & purring noises when I pet him.

I was kind of shocked when I first got him because I thought rabbits were silent, haha. Far from it.

P.S.

I would still feed him his normal veggies, & just discard what he does not want. He will still need all those vitamins afterall! (Plus, do not forget he needs unlimited hay 24 hours a day)

There r different noises for different reasons. Honking & circling is a content rabbit that wants to mate. Light teeth grinding is contentness though this must not be confused with pain grinding.
Grunting is signs of anger & fear.
Some rabbits that feel snared will scream. It is an awful sound.
Rabbit should be fed a mixture of veg in the evening on a daily basis as this is where they get their nutrients. Grass does not give everything that they need. See my website for a guide.
More so if they r exercise right as they use up that energy.
In the wild rabbits feed late in the evening & early morning. The same with domesticated rabbits.

for the noises, that is normal, people say that rabbits do not make noise but they really do. and that is the noise. normally their body language will tell you what it means because it is hard to tell sometimes.

if you always let them out then no, but i would say get some rabbit food for extra vitamins and other good stuff.

hope that helped :)