Chickens are the early (cheap) alternative to having cows. Like cotton trees are the early game version to woollies. You should get rid of chickens late game because they are not as efficient. I actually have another plan for chickens. It is super secret though :) LOL not really (I might have posted about it in a dev log), but I do plan on making chickens more useful. It will be one of my side projects to keep me from going mad.