Zip ties aka, cable ties. Using these modern thingies are kinda great and kinda dangerous too. Be really careful. Yes, I've used them too, but to use them is to really put pressure on you to check them regularly. These birds have growth spurts and suddenly that loose, sloppy zip tie is now crippling the bird, digging into the skin and making it's removal very difficult.
Just putting that warning out there. Toe punching for permanent ID is something worth doing.
Even more standardized numbered leg bands can be dangerous. I've seen a lot of birds needing to have those cut off too. So, practice good husbandry. Do the right thing and keep your eyes open when you study your birds. The more you have the more important it is to practice methods that you can ACTUALLY be faithful in doing. Have a great weekend everyone and stay safe.