If the dog-owner were to have to replace the animals, then depending on what breeds they were, it may be very expensive to replace them. For example you may have to pay express-shipping to ship a full-size laying duck/chicken from another area if there are none currently available locally. Just explain that they do not start laying until they are older, so he can't replace w/ babies. I would say a minimum of $30 for each bird (include the number of both ducks and chickens). Another way to explain it to them is to calculate the number of eggs that would be laid over the next 6 months, and how much those eggs would cost you to buy at the store since you don't have the birds any more (use the cost of organic free-range eggs). Then add that to the cost of new baby-birds, timing it such that when the new baby-birds get old enough to lay, the 6 or so months of egg-buying would end. Any way I think about it, it's still a minimum of $30 per bird.... though I'm so sorry for your loss and I know the money would make it any better really, other than teaching the guy a lesson.