We have also lost chickens and duck to a loose spaniel ( 2 separate occassions, once it got loose from it's house, second time it slipped it's lead as it was being walked past our property). The same dog has killed chickens eslewhere in the village and a pet rabbit ( trashed the rabbit house to get at the rabbit). A couple of hens were damaged, but survived the first time, along with the dead one, second time my OH saw it happening and gave chase, but duck dead by the time he got there ( in all cases the dead bird was warm and floppy...)
We informed the local PCO the second time it happened and the owner/owners daughter no longer walks dog past our property. PCO was not aware of the other 'deaths'. We have not been offered compensation for any loses, although I think that the rabbit hutch was replaced. We have been told that no charges will be brought unless a higher value animal was/is killed.
Our own dog has escaped on a couple of occassions, so we understand that these things can happen (fortunately our retriever is not interested in large chooks/ducks, having been trained that these are off limits - although I do not trust him around chicks and quail!). BUT an apology would be have been nice and/or an offer of payment to replace missing birds

. And if it happens more than once with the same dog then I think that the owner certainly needs to put into place stricter controls/avoidance measures.
HTH
Jo
Jo
Jo