By Harold McGee
Ducks and squab are notable for having dark, flavorful breast meat, abundantly endowed with myoglobin-rich red muscle fibers, thanks to their ability to fly hundreds of miles in a day with few stops. The most common breeds of duck in China, much of Europe, and the United States are descendents of the wild green-headed mallard, Anas platyrhynchos, an aquatic migratory bird that puts on as much as a third of its carcass weight in fat for fuel and under-skin insulation. Ducks are eaten at two ages: in the egg as 15–20-day embryos (the Philippine boiled delicacy balut), and at 6 to 16 weeks. The Muscovy duck is an entirely different bird: Cairina moschata, the greater wood duck, which is native to the west coast of Central and northern South America, differs in three important ways from mallard varieties. It lays down about a third less body fat, grows significantly larger, and has a more pronounced flavor.