I have had birds come back lots of times both ducks and geese. In my experience early season ducks will come back if kicked up without gunfire, there seems to be a dead zone in between the weekend after opening day untill the first big groups of migrators where ducks once spooked won't come back. As the season goes on into the winter and migrators are pouring in they seems to always come back when kicked off. As far as geese, they seem less likely to come back in the original numbers, I have had it happen once for sure when I kicked up about 50 Canada's and one was callord, a flock of about 10 came back including the collard goose about 2 hours later, I have seen eagles and coyotes scare up flocks of birds, once the eagle or coyote left the birds would start coming back about a half hour later whether it was over water or in a field. I have also seen mallards fly about a mile off make a big circle and come right back after being kicked off in the afternoon. I think a lot of it has to do with how many birds are in your area, what kind of landscape your area has and how far north you are, the weather has also played a large role in birds coming back in my experience, they seem more likely to come back if the weather is nasty because they want to get back to where the were out of the weather. There is so many variables to this subject it's next to impossible to answer but only be able to offer my past experience. I hope some of what I said may be able to help you in some way.