I raise one breed, all black and hatching 100 or more a year, it is impossible to tell them apart. I track them from egg collection till they die. Egg weight, egg hue, date of lay, date set, sire, hen # if I know it. I tried zip ties at first but there weren't sufficient colors to differentiate birds and forgetting to change a tie on a bird is traumatic. I went to numbered colored bandettes.
Each year was a different color so I could tell the age of a bird from afar. I did that for a few years but they kept losing the bandettes which screwed up the whole program.
Now I only wing band. That is the only way to do serious breeding and progeny tracking for line breeding. I usually band them at about a week of age and they are with them for life.