Use 'drake' to identify male ducks, similar to 'rooster' for chickens. See that drake? He's guarding the nest.
Pro Tip 2/3
Bird Watching
Bird enthusiasts often use 'drake' to distinguish the more colorful male ducks. A bright green-headed drake mallard is swimming there.
Pro Tip 3/3
Not For Cooking
Avoid confusing 'drake' with 'duck' when discussing food, as 'drake' is rarely used in culinary context. You won't find 'roast drake' on the menu, but 'roast duck' instead.