Zip ties worked fine for me, until they didn't. For whatever reason, the last new birds I got, every time I put a tie on them, they were super tight the next morning. At first I thought they were pulling on the end themselves, so made sure to cut it super close. Still super tight. I don't have time to inspect them every morning and then catch one to cut the tie off, so I went with spiral ones and have not had one migrate yet.
As far as other ways to identify, you can toe punch and nostril notch, but I'm not sure you can (should) do that on adult birds, and some people find it inhumane in any case.