The USDA recommends cooking duck to an internal temperature of 165°F, same as chicken. However, many restaurants serve duck breast medium rare, which is what I prefer. I try to cook my duck breast to an internal temp of 145°F, but it's important that you do what's comfortable for you. I will say that my last whole duck reached temperatures above 165°F and it was still juicy and absolutely amazing. I credit that to the moist cooking environment of steaming first.