That is part of my problem too. I have a hard time figuring out who is still laying and who is well past her prime. I have tried leg bands and zip ties, but both ended up disastrous! I tried different colored zip ties to keep track of male/female and age, but, even though I tried to put them on loosely, I had at least 1 have a serious problem when it grew too big for the circumference of the zip tie!!
Then I tried the leg bands that are made for chickens. I bought the size recommended for my breeds of chicken. These were the leg bands that look like split key rings and were made out of plastic. Again, I had birds that grew too big for them and they were cutting into the birds leg.
I've also had both type come off because they were too big initially for the birds. I even had one bird get its toe stuck up in the band while it was wearing it on it's leg!!
I know that you are supposed to be able to feel their keel bone or something and look at their vent and be able to tell if they are still laying or not. But apparently, I haven't figured that out yet.
I also read one post where the person used different colors of food dye and put drops on the vents of different chickens and the eggs came out with some of that color food dye on them and that was how they figured out who was laying and who wasn't.
I am pretty sure that some of my girls are 3+ years old and they go all the way down to less than a year old! So many of them look the same, (black hens, Rhode Island red looking hens, Americanas/Easter eggers, barred rocks), so basically black, brown, red, and black & white striped chickens!!
from my main coop 2 from silky but I broke one 
