I got rescue ducks that were abandoned on a pond and lived with wild mallards. They looked fine. They actually had infectious bronchitis, probably brought parasites that now live in my soil, and made my original ducks ill. I wish I had taken them to the vet before introducing them to my flock to test for parasites and viruses, instead of after when everyone got sick.
I'm not saying you shouldn't rescue. Rescuing is a wonderful thing. I just rushed things and I wish I hadn't endangered my original birds.
Also, I gave my ducks a stuffy, too. Even a duck stuffy! They don't care. What about an unbreakable mirror?