Most dogs are not trying to kill your birds. They simply want to chase, but even chasing can be fatal, because chickens often break their necks trying to get away, or die of heart attacks if they have no where safe to escape. In cases where your chickens are neither hurt nor killed by a dog attack, they can still be thrown off laying for days or even several weeks due to the upset. If that is all that occurs, though, consider yourself lucky! And remember, even a very small dog can scare, hurt, or even kill your chickens.
A domestic dog that gets into your coop or run will kill your pets indiscriminately, even accidentally. If dogs are the culprit, you can find one or more chickens--sometimes an entire flock--laying scattered about with broken necks and just an occasional bite mark. Some dogs will simply chase them until they die; some will shake a chicken to death; some will kill with one hard bite and move on to the next... but well fed pet dogs will rarely actually eat a chicken. They chase and kill just for fun. Most wonderful, sweet, calm and gentle dogs--dogs who would never think of hurting a human being--have chasing and killing instincts when it comes to chickens.
Dogs will jump and even climb fences to get to chickens--they will dig under barriers and tear through wire. If your dog kills your chickens, remember that it is not your dog's fault; he is responding to his natural instincts. It is your responsibility to keep your own dog leashed or adequately fenced so that he does not chase your or anyone's pets, get into trouble, get hurt, cause property damage, or kill other animals.
Not all dogs will kill!Far from it, in fact. Some dogs, like livestock guardian dogs (Maremma; Anatolian Shepherd) are bred and trained to live outdoors with your animals and protect them from predation. Others, like our friendly lab, here, let the chickens rule the roost. If you have a dog and you're worried about getting chickens, it's important that you have a good sense of how trainable and docile your pet is first. If you feel they'll go after your flock, you'll need to prepare a very secure chicken run, with buried or apron fencing, using heavy gauge hardware cloth -- not chicken wire. You'll need to make sure the chickens don't free-range while your dog is out. Conversely, if your dog is obedient or very docile, you might not need to worry so much. The bottom line is, nobody can tell you for sure whether your dog will be a threat to your chickens. It's up to you to know your dog, and to prepare to protect your flock.
If a neighbor's dog kills your chickens...In most areas, owners must keep dogs leashed or fenced, and are legally and financially responsible for any damage done by dogs that escape or are not properly confined. Legal consequences vary--check your local laws. Some areas will require that a pet killing dog be put down. In other areas, chickens are considered to be "only livestock" rather than pets... but dogs that kill livestock fare no better. In my rural area, dogs that kill livestock can be shot by the local sheriff, or by you if you catch them in the process and are acting to save your flock. For that reason, if your chickens have been killed by dogs and you can identify the owner, be sure to check your local laws to see what the owner is responsible for. In most cases, they will have to reimburse you for any damage the dogs caused to your coop and run, as well as reimburse you for the loss the pet chickens that were killed.
If you had rare show or heritage breeds, the replacement cost can be substantial, even though baby chicks may only cost $3 to $10 each. We have seen some exceedingly rare imported varieties sell fro as much as $40 PER CHICK. When it comes to estimating the value of adult birds, for example, we wouldn't expect the rarest breeds and varieties like Black Copper Marans juveniles to sell for less than $100 each, if you can can even find a breeder that will sell them. Other heritage breeds that are not quite as rare may sell for half that. Even common breeds kept just for egg laying might be as much as $50 each to replace. Consider that shipping will be involved in most cases, and that you will also have to account for the cost of feeding replacements until they are old enough to begin laying. Further, you may need to erect special quarantine facilities when you buy adult birds, or at the very least you will have to have a special set up so you can introduce your new birds to the rest of your flock in a safe way. If your entire flock was killed, you may not need a special set up... but you will be forced to buy eggs elsewhere until your new birds begin laying, or simply go without.
Be sure to account for all these costs if you have experienced a dog attack and are calculating reimbursement. In some cases it may be helpful to retain a lawyer to ensure you are remunerated fairly according to the laws in your state, and that the owners of the dog are held accountable for the loss of your pets and any damage their animals caused to your property.