Sorry for the silly answer; yes they are and we've had chickens for the past few years and never had problems with rats; did have some mice but sorted them relatively quickly and easily by having a good clear out of chicken run and shed where we kept the food.
No rats, except if you leave food about and there are the old type of timber sheds which cann attract them (they live underneath)
Buy an Eglu if you can .. Easy to clean, safety from predators, move around, empty, etc. One standard perfectly adequate for 3-5 hens.
Think carefully before having a cockerell .. these can really pi$$ off the neighbours : )
Probably depends on how many, a few backyard hens is fine but I'm guessing the local council would have something to say if I decided to increase my "flock" to a commercial size!
Unless there is a covenant on their property which prevents the keeping of any livestock or foul, it is absolutely fine. I've got three. I've not seen any evidence of rats being present (but I do have 4 cats).
Thankyou everyone for your kind answers,we live in a private estate with small back gardens,and my wife said in the deeds that you can't keep chickens,but that was over thirty years ago.
I don't know about now????