Okay so I had to do some research based on my hypothesis and it turns out that the circulatory system in the legs of ducks (or any other temperate bird) and chickens (or any other tropical bird) does not greatly differ. The reason ducks are more comfortable at lower temperatures has more to do to do with everything above the leg.
Anyway, the complex circulatory network in bird legs (called the “rete mirabile”) doesn’t actually keep legs “warm.” While the arteries being close to the veins does warm the blood returning to the heat, the cooler blood in the veins, in turn, decrease the temperature of the arteries. By having the blood traveling to the extremities pre-chilled, it minimizes the total loss of heat. It also facilitates heat loss from the arteries which helps cool the bird in hot weather and actually helps prevent overheating of well insulated animals in cold conditions. So, really the fact is that chickens, or any other birds, feet aren’t warmed per se, but rather kept cool so that they don’t lose heat.