Usually a fox will snatch and stash and snatch again and will not leave much sign. They will then carry back to the den.. The one found in the field sounds like a bird of prey kill, Falcon, Hawk, Owl etc.
So all the meat was eaten from the breast?
It sounds like it could be a hawk. Were they out where a hawk could get to them and or do you know if they were taken at night or during the day?
Welcome to BYC ! From West Tn ! Sorry your first post has to be of this nature, first thing I would do is secure the birds so that nothing can get to them. Locked up tight at a drum at night. Then try to determine if it is the dog that is doing the damages, if you have seen them in the...