@ Illia.. we lock our chickens in the run more often in winter because of coyotes and hawks and sometimes the snow is too deep and they just can't get out.. well, when spring comes I notice a HUGE difference. When they free range in the woods around our house the yolks are dark orange.
I hate keeping them locked up, as they seem so happy outside.. but I know it's risky. Last year, we were out of town and my sister in law watched our house and animals.. and we just had her keep them locked up while we were gone.. and THAT'S when a hawk got two of our birds. It sat up top and undid the wire to get in. Terrible. We now have hawk proof netting... I've seen a goshawk sit there defeated...