A villager will just automatically attack a chicken if it paths into it. Absolutely not intended behavior and there's no way to stop it.
Same deal w Cooked Food shooting out of the fire, it autocombines if they group together so you won't be able to split it between villagers.
*edit* Biome just says "like a tree but infinite" but it sure was spitting out enemies over and over and I wasn't given the expectation that I should keep an eye on it.