07:48 Jul 6, 2009 

First of all, thanks to all answerers.
Before I close this thread, some things I've learned from my own research about the topic: "köy yumurtası" is from chickens that are not grown under systems of intensive agriculture. If they are held in cages or not is not important, so the answer "free-range eggs" is definitely not correct because the criterion is irrelevant; the same is true for "organic egg"; organic eggs can also be produced under conditions of intensive agriculture. Even though the term "village egg" is not colloquial, it is used in scientific contextes (see the links in Selçuk Akyüz' post).