Chickens don’t fly obviously. So they don’t use their wings which are controlled by their “breast” muscles. This is why chicken breast meat is white. They do use their legs though which is why the legs and thighs are dark meat. This is also why duck meat is all dark (they fly), and also probably part of the reason people say duck meat is “greasier” than chicken meat. Because dark meat is fattier and the duck meat we get access to was probably used more than the chicken meat most people eat (wild vs sitting getting tube fed) Most significantly for you to know is that dark meat contains significantly more nutrients than white meat because the muscles were used you can imagine all the things this causes - all the additional blood flow to muscles that are used, and all the additional nutrients needed by those muscles for the whole lifetime of the chicken. This is also a good reason to believe that pastured chicken meat would be more nutritious because they are so much more free to move and use those muscles, not to mention their improved diet because they walk around eating bugs and things which is their natural diet and those nutrients go into their muscles and eggs. I thought you all night find this interesting and useful. It’s something I had never heard before being told by a crazy nutritionist I saw for awhile.