You can make the duck world easier to understand by starting with how and where ducks feed.
Dabbling ducks
Dabblers usually feed at the surface or tip forward—tail in the air—to reach plants and small animals below. Mallards and gadwalls are familiar examples.
Diving ducks
Divers submerge to find aquatic plants and animals. Their bodies and legs are well suited to underwater swimming, and some need a running start across the surface when taking flight.
Sea ducks
Sea ducks spend much of the nonbreeding season in coastal or marine waters. This varied group includes eiders, scoters, and long-tailed ducks.
For deeper identification help, visit the U.S. Fish & Wildlife Service and Cornell Lab of Ornithology.