Ducks are animals, and since living a Paleo lifestyle means eating plenty of plants and animals, there’s no reason not to eat duck. When it comes to duck meat, the legs tend to be fattier than the breasts, but ducks have a layer of fat between the skin and the meat to keep them warm when they’re in the water. This means that all duck meat is naturally fattier than chicken, and therefore a better nutritional option.
Muscle vs. Organs
There’s no reason to limit yourself to the breast and legs though. Try incorporating more organ meats into your diet by eating duck liver, heart, or gizzards. You’ll get more nutrients and probably a pretty good deal out of it, too.
Farmed vs. Wild
You might want to be careful where you get your duck. Although duck farms aren’t as bad as some industrial chicken farms, they’re not much better either. They still involve enclosed spaces and nutrient-deficient diets (source). If that’s something you worry about, you can always check the internet for organic farms that provide duck in your area.