Diving Duck Identification: Divers, Scaup and Mergansers

A diving duck goes completely under to feed, sits low in the water with its tail flat toward the surface, and runs across the water to take off. A dabbling duck tips forward with its rump up, sits higher with the tail held up, and springs straight off the surface.

Shape follows from that. Ducks Unlimited describes divers as having shorter, more compact bodies and stouter necks, flying straight and fast with much faster wingbeats than dabblers; the larger divers such as Canvasback and Redhead have longer, more pointed wings built for covering open water. Divers also show a lot of black and white, which is part of why a distant raft of them looks so different from a marsh full of brown dabblers.

Habitat separates them too. Divers use deeper open water: large lakes, reservoirs, rivers, coastal bays and the Great Lakes.

Four species cause most of the confusion, and the head is the way through.

• [Canvasback](/lookup/ducks-and-raptors/canvasback): chestnut-red head, a long straight neck, a sloping forehead running into a long black bill, red eyes, and a white back with fine grey markings. Males average 21 in and 2.7 lb.
• [Redhead](/lookup/ducks-and-raptors/redhead): chestnut-red head with a steep forehead, a blue-grey bill with a white saddle near the tip, and yellow-gold eyes. Males average 20 in and 2.4 lb.
• [Ring-necked Duck](/lookup/ducks-and-raptors/ring-necked-duck): a peaked purplish-black head, black back, a white crescent between the dark breast and the pale sides, and a blue-grey bill with a white band at the base and a black tip. The named neck ring is usually invisible.
• Scaup: black head with blue, purple or green gloss depending on the light, pale blue bill, yellow eyes, pale back.

The cinnamon collar of a Ring-necked Duck is a poor field mark; the white band on the bill is a good one.

This is the hardest common pair on open water, and Ducks Unlimited gives a mark that works when the bird flies: both show a bold white stripe along the secondaries, but on Greater Scaup the white continues into the primaries, and on Lesser Scaup it stops at the secondaries.

On the water, Greater Scaup has a rounder, larger head and a wider bill; Lesser Scaup often shows a peaked crown, though Ducks Unlimited itself notes this can be inconsistent. Size overlaps: Greater males average 18.6 in and 2.32 lb, Lesser males 17 in and 1.76 lb, which is not enough of a gap to judge at distance.

Head gloss is usually quoted as green for Greater and purple for Lesser, but both species show blue, purple or green depending on the angle of the light, so treat it as a hint and not a decision.

Range helps a little. Greater Scaup breeds on Arctic tundra wetlands and winters on very large waters including the Great Lakes, coastal bays and nearshore marine waters.

• [Bufflehead](/lookup/ducks-and-raptors/bufflehead): the smallest North American diving duck, males about 15 in and 1.1 lb. The male has a large white patch running from the eye to the back of the head; the female has a small white patch below and behind the eye.
• [Common Goldeneye](/lookup/ducks-and-raptors/common-goldeneye): black head with green iridescence and a round or oval white spot between bill and eye; fast wingbeats produce a whistling sound. Females have a chestnut head and a black bill that shows a yellow tip from February to May.
• [Hooded Merganser](/lookup/ducks-and-raptors/hooded-merganser): the smallest of the three mergansers; the male raises a white fan-shaped crest on a black head and has two black bars down white sides.
• [Common Merganser](/lookup/ducks-and-raptors/common-merganser): 22-27 in; the male is white with a black back and green head, the female grey with a bright rusty head and a sharp white throat.
• [Ruddy Duck](/lookup/ducks-and-raptors/ruddy-duck): about 15 in, compact; the breeding male is reddish brown with a bright pale blue bill, the female dusky grey-brown with a dark stripe below the eye on a pale cheek.

Divers are usually farther out than dabblers, so the head shape is often all you get. Shoot side-on and level with the water rather than down from a bank, and take a burst as a raft lifts off: the wing stripe that separates the two scaup is only visible in flight.

Be patient about the dive. A bird that vanishes for twenty seconds and comes up sixty feet away is worth waiting for; the frame where it surfaces facing you, with the bill visible, is usually the frame that settles the identification. Photograph it and the app identifies it, then check the head profile and the bill markings on this page.