Both roadkill and antleraddict are correct.

The shot itself is the same. the animal on the package changes, but thats about it. The main difference is that the turkey loads do have heavier payloads (more shot) and in turn have lower velocity. However, there have been plenty of turkey's killed with waterfowl loads and vice versa around our household. I find that duck loads are cheaper in the spring and turkey loads go on sale in the fall.