As are all the insects and worms that will probably die as a result of the poison spray, too. What's the point of letting your chickens free range on a boring mowed carpet if there's nothing for them to eat there? Chickens can eat grass occasionally, but the main point of free ranging them (and the most attractive to them) in the whole experience isn't the monoculture of cut turf grass, it's the insects, worms, and larva that they find while foraging in a more natural setting.The weeds you kill are probably good for the chickens.