I'm a native speaker of Hebrew and this is a point about English, but I'll try. In English you say "I eat a peach" but "I eat bread", since peaches are countable and bread is not. In Hebrew there is no "a", so no distinction (אני אוכל אפרסק, אני אוכל לחם). Regarding chicken, I think in most contexts of people eating, "chicken" behaves like a non-countable noun - like bread and not like peaches. One typically doesn't eat one whole bird, but pieces that might come from different individual birds.