Hooded mergansers are a fascinating species of small diving ducks found predominantly in North America. They have many unique features and behaviors that make them stand out from other waterfowl.
Appearance and Size
Hooded mergansers are relatively small ducks, with the males measuring about 18 inches long and weighing around 1.4 pounds. Females are slightly smaller at around 16 inches long and weighing just over 1 pound.
The most distinctive feature of hooded mergansers is the large, fan-shaped crest on the back of the males’ heads. This striking black and white crest can be raised or lowered, and is used for courtship displays. When raised, the crest makes the male’s head look almost comically large compared to its body.
In addition to the crest, male hooded mergansers have bold black and white markings over most of their bodies. Their backs and flanks are black, while their undersides are white. Females have similar color patterns but they are gray and reddish-brown instead of black and white.
Both sexes have narrow, serrated bills that are specialized for catching fish. Their slender bodies and long tails make them very agile swimmers as they dive underwater to hunt.
Range and Habitat
Hooded mergansers are found primarily across North America. Their breeding range extends from southeastern Canada, throughout the eastern United States, and along the Pacific coast. During winter they migrate south and can be found from the southern U.S. into Mexico.
These birds inhabit freshwater wetlands and riparian areas. They are most often found on small ponds, streams, wooded swamps, and rivers, particularly those lined with trees. They avoid large open lakes and tend to prefer shallow, calm waters where they can easily see and catch small fish.
Nesting and Reproduction
Hooded mergansers begin pairing up in late winter to early spring as they migrate back to their breeding grounds. They are monogamous throughout the breeding season.
Females make nests in tree cavities, often in dead or hollowed out trees. Occasionally they will nest in man-made boxes as well. The nests are lined with available materials like leaves, twigs, or even feathers plucked from the female’s own breast.
Clutch size is typically around 10-12 eggs. Only the female incubates the eggs, for about 28-32 days. The nestlings hatch throughout early summer.
Male hooded mergansers do not help care for the young. The female alone will brood and guard the chicks once they hatch. Within a day, she leads them out of the nest tree to nearby water. The ducklings fledge at around 70 days old.
Diet and Hunting
Hooded mergansers have a largely piscivorous diet, meaning they eat mainly fish. Their serrated bills allow them to effectively grasp slippery prey.
They dive underwater to hunt for small fish like minnows, sticklebacks, and perch. Dives generally last around 30 seconds as they swim down and capture fish with their bills. Their eyes are specially adapted to seeing underwater.
In addition to fish, they may occasionally eat aquatic insects, crayfish, frogs, salamanders, and other small aquatic creatures. They forage mainly by diving, either in shallow shorelines or in open water.
Behavior and Threat Displays
Male hooded mergansers perform elaborate courtship displays, especially during the breeding season. Their crest is used to full effect, being fanned, inflated, and otherwise moved to attract females.
Aggressive displays between competing males may include crest erection, bill pointing, wing flapping, and rushing across the water towards each other. However, they rarely engage in actual fights.
Females may perform a broken-wing display if a predator approaches the ducklings. She acts injured to draw the predator’s attention away from the young.
Both sexes make a distinctive rolling frog-like croak as a warning or alarm call, especially when detecting predators. It is one of the most unique waterfowl vocalizations.
Conservation Status
Hooded mergansers have a large population estimated at 460,000 birds. Their numbers increased throughout the 1900s as they recovered from historical overhunting and adapted well to nesting boxes provided in many areas.
They are protected under the Migratory Bird Treaty Act and their current conservation status is Least Concern. Their habitat needs of forested wetlands make them vulnerable in areas of heavy development and deforestation. Overall however, they remain common and widespread.
Fun Facts
- The hooded merganser got its name from the thin, retractable crest that drapes down the back of the male’s head like a hood.
- The merganser family that hooded mergansers belong to is called “sawbills” because of their serrated bill edges that help them grip slippery fish.
- Hooded merganser ducklings can dive underwater almost immediately after hatching, an unusual ability in small baby birds.
- Females have the highest incubation temperature of any bird at over 100°F. This helps speed up embryonic development.
- The hooded merganser’s breeding habitat needs make it a good indicator species for the health of eastern North American forests.
- Their courtship displays are referred to as aquatic “dances” since the males fan their crests, extend their necks, and bob their heads.
- The female’s broken-wing display to lure predators away from ducklings is so convincing that it may have given rise to the myth that mother birds fake injury to protect their young.
- Hooded mergansers can swallow small fish underwater, an unusual ability as most birds swallow only when on the surface.
- Males lose their striking plumage after breeding and molt into a duller “eclipse” plumage more similar to females until regrowing their ornamental feathers.
- They get their frog-like croak from inflatable air sacs in the esophagus that resonate when expelled.
Conclusion
In summary, hooded mergansers are fascinating ducks with many unique adaptations for their fish-hunting lifestyle. Their intricate courtship rituals, remarkable diving abilities, important role as an indicator species, and iconic avian features like the hood-like crest make them appealing birds to birders and nature enthusiasts alike. With stable populations, interesting behaviors, and key connections to forest ecosystem health, hooded mergansers are a cool duck species worth learning more about.
