I don’t believe birds transplant fish
When I was a kid I would "help out" ponds by putting fish in them.
I didn’t know any better.
I knew about every pond within 2 square miles of my house it didn’t mater how well it was hidden.
Greens and bullheads are the hardest/ easiest to transplant
I just built a pond and have received several offers to help stock it with everything from bullheads, crappy and even flatheads.
Paybacks a bitch.