Something that comes in handy when you have many chickens, from different parents and generations, are Chicken Leg Bands. These are usually pretty cheap, and can be easily placed on the legs of a chicken.
I use different coloured bands to mark chickens from different generations, so I know the ages of my chickens and who was their father. I have read that some people will mark the bands with a number, so they know each chicken’s history… yet I am not that fastidious with my documentation.
After I accidentaly killed a chick while moving my Chicken tractor the other day, I decided I needed to band my chicks so that they can soon be released from the pen and spend time in the garden. It wasn’t easy as, for some reason, they didn’t want me to grab them and shove a plastic band around their leg. Despite this, I still proceeded to band them all.
With this done, I will release them into the garden to free range. I will only release the females… I want to keep the males seperate so I can cull them when they are large enough to make it worth the effort. It will probably be around the time they start to crow.
If you intend to get more than a few chickens, I would recommend using a system like mine. If you only have a few chickens (rather than the 21 I own) you could place a different coloured band on each chicken, so you can tell them apart.