By Jennifer Roof
Geographic Range
The Hooded Merganser breeds throughout the Pacific Northwest of the United States, across southern Canada, and east of the Mississippi. It is largely concentrated in forested regions around the Great Lakes. Wintering ranges include an area along the Pacific Coast of California, and a second area of coastal habitats from Delaware through Texas. ()
Habitat
The Hooded Merganser nests in forested wetlands throughout its range. Some records show nesting in man-made boxes on grasslands and in nonforested wetlands. The kind of forest used for nesting varies from spruce/fur to cottonwood/elder and oak/cypress/tupelo, depending on the geographic location. In the winter they seek out shallow, freshwater and brackish bays, estuaries, and tidal creeks and ponds. ()
These animals are found in the following types of habitat:
temperate 
; terrestrial ; freshwater .
Terrestrial Biomes:
forest .
Aquatic Biomes:
lakes and ponds; rivers and streams.
Other:
riparian .
Physical Description
(19.01 to 23.94 oz)
(15.75 to 19.29 in)
At 40-49 cm, the Hooded Merganser is the smallest North American merganser. Exact weights have not been documented. Like all mergansers, it has a long, narrow, serrated bill. It has a brownish-black back and wings, with a white underside. The male has a black head with a white, fan-shaped crest, which is bordered in black. The males iris is bright yellow, while the iris of females and immature males is duller brown. ()
Some key physical features:
endothermic ; homoiothermic; bilateral symmetry .
Sexual dimorphism: sexes colored or patterned differently, male more colorful.
Reproduction
Hooded mergansers have one brood each year.
Hooded mergansers breed from late February into June, depending on latitude. Although most breeding occurs in March and April.
Pair formation has been observed from November through January. Only monogamous pairs have been documented. ()
Mating systems:
monogamous .
Females select the nest site, which is usually a cavity in a dead or live tree. Nest boxes, along with already built and abandoned nest sites, are preferred. Cavities are usually 4-15 feet off the ground. Between 7 and 15 eggs are laid shortly after the nest is completed, from late February through early June, depending on latitude, although most breeding occurs in March and April. Incubation begins after all the eggs have been laid. The male abandons the female shortly after this point. The female incubates for nearly one month, during which time she loses 8-16% of her body weight. After the ducklings hatch they usually leave the nest within about 24 hours. ()
Key reproductive features:
iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous .
Females brood eggs in the nest and care for young after hatching. Males leave the female soon after egg incubation begins. Young hooded mergansers leave their nest within 24 hours of hatching and are able to feed and dive immediately upon emergence from the nest. There is little information on parental care after hatching. One female abandoned her brood 5 weeks after hatching. ()
Parental investment:
precocial ; pre-fertilization (provisioning, protecting: female); pre-hatching/birth (provisioning: female, protecting: female).
Behavior
Although the Hooded Merganser is mostly aquatic and awkward on land, females lead their ducklings up to 1.2 km across land from inland nests in order to reach water. Hooded Mergansers are clumsy, but quick, flyers. They take off by running on water, and they have a ceaseless and rapid wingbeat during flight. They land at high speeds and are often seen 'skiing' across the water to come to a stop. They dive well, holding their wings in close to their body and propelling themselves underwater with their feet. They have been seen gathering at roost sites in large groups during the nonbreeding season. Little is known about their territoriality during the breeding season. ()
Food Habits
Hooded Mergansers feed in clear aquatic habitats, such as forested ponds, rivers, streams, and flooded forests. Their primary foods include aquatic insects, fish, and crustaceans. ()
Primary Diet:
carnivore (piscivore , insectivore , eats non-insect arthropods).
Animal Foods:
fish; insects; aquatic crustaceans.
Economic Importance for Humans: Negative
There are no known adverse effects of hooded mergansers on humans.
Economic Importance for Humans: Positive
Hooded Mergansers are still hunted occasionally for sport. Aprooximately 18, 000 are harvested annually in the U.S. and Canada combined. They are also used for various scientific studies in the wild, because they will nest in artifical nestboxes. ()
Ways that people benefit from these animals:
body parts are source of valuable material; research and education.
Conservation Status
IUCN Red List: [link]:
Least Concern.
US Migratory Bird Act: [link]:
Protected.
US Federal List: [link]:
No special status.
CITES: [link]:
No special status.
State of Michigan List: [link]:
No special status.
At the turn of the century, Hooded Mergansers were largely overhunted. Today, however, they are not a prized sport species. Habitat degradation is now a more pressing concern for their conservation. River channalization, deforestation, and agricultural practices have caused an increase in loose sediment and turbidity, reducing the available habitat for the Hooded Merganser. Also, acid rain has the potential to harm the species, because a low pH can cause a significant reduction in aquatic invertebrates. A diminished food supply would reduce the growth of young ducklings. There is no informaton on the exact population size, and the Hooded Merganser has no special conservation status. In the future, care must be taken to preserve the cavity producing trees and forests which these birds depend on. ()
Other Comments
The eggs of the Hooded Merganser are almost spherical and have a disproportionately thick shell. ()
Contributors
Jennifer Roof (author), University of Michigan.
