Excellent question. I have totally different breeds so it's a no brainer for my flock but have a friend I got 4 RIR's for. I look for subtle things, ok this one has what looks like a droopy eyelid. That one has a little tear in her waddle, this one has a bare spot there type stuff. Yes it can change from time to time but so far it's worked pretty well for me. Personalities can help too, however I have seen,just like with people, those especially in RIR's, they ALL can get moody!
I breed mutts (EExWyandottexMaran mixes) so all of my ladies look very different from one another. I did buy some Sapphire Gems from Atwoods and expected a homogenous look from them like most other breeds, but one is a really deep blue color that has various shades in her feathers and the other is a solid, lighter blue with black specks on her feathers. I do have issues telling who came from what chick though because their colors are very different from hatch to adulthood.
Hi! Little bit late but I use zip ties with different colors for my girls, you put them on loosely, only one of my chickens pulled at hers the first night but otherwise they were never acknowledged. They were more upset that I was picking them up to put them on! And we have had no problems with them! Your chickens will eventually stop pecking with them, assuming they aren't too tight
Yeah, I can recognize most of them, tho many multiple(6-8)siblings from my specific crosses can be impossible, but my birds aren't just a few pets for pleasure.
And when you need to keep track of birds year after year, and take notes on many for specific issues, nothing works as well as zipties and good notes.