The Hooded merganser (Lophodytes cucullatus) is a fish-eating duck from North America. It is the second smallest species of merganser, with only the smew of Europe and Asia being smaller, and it also is the only merganser whose native habitat is restricted to North America.
The Hooded merganser is a sexually dimorphic species. The adult female has a greyish-brown body, with a narrow white patch over the lower breast and belly. She has a light reddish-brown crest extending from the back of the head. During the nonbreeding season, the male looks similar to the female, except that his eyes are yellow and the female's eyes are brown. In breeding plumage the dorsal areas and the head, neck, and breast of the mature male are mainly black with white markings; there are large white patches on either side of the crest, and they are particularly conspicuous when he raises his crest during courtship. His lower flanks are a rich reddish-brown or chestnut in color, and the breast and undersides are more or less white, extending into white stripes across the crop and breast. In both sexes there are narrow white stripes along the tertial wing feathers; when the bird is in repose they have the appearance of longitudinal white stripes along the bird's lower back, if they are visible. First-winter birds differ from adult females in appearance in that they have a grey-brown neck and upper parts; the upper parts of adult females are much darker - nearly black. Furthermore, the young birds have narrower white edges to their tertial feathers than adults do. Females of all ages are dark-eyed, whereas in males the eyes become pale during their first winter.
Hooded mergansers are native to North America. These birds are short-distance migrants, and they winter in the United States. They have two major year-round ranges. One is in the Eastern United States from the southern Canada-US border along the Atlantic Coast to the Gulf Coast in the region of the Mississippi Delta. A smaller year-round range extends from Washington state and southern British Columbia to northern Idaho. They also breed in regions from Missouri to southern Canada and from Nova Scotia to eastern North Dakota and Saskatchewan, migrating when necessary to avoid winter conditions. Hooded mergansers live on small bodies of water such as ponds and small estuaries where there is ample emergent aquatic vegetation, but they also inhabit larger wetlands, impoundments, flooded timber, and rivers. They prefer fresh water but do occur on brackish water bodies as well.
Hooded mergansers are secretive and diurnal birds. They are usually seen in pairs or in small groups and outside of the breeding season, they may gather in large groups to roost at night. Hooded mergansers are diving predators that largely hunt by sight while underwater. They are generally quiet but in order to communicate with each other will emit low grunting or croaking sounds.
Hooded mergansers are carnivores (piscivores) and their diet consists mainly of fishes. However, these birds will also feed on aquatic insects and other aquatic invertebrates such as crabs and crayfish.
Hooded mergansers form monogamous pairs and they remain together until the female has selected a nesting cavity and completed laying her clutch. After that, the male leaves the female to incubate and care for the brood. Females will actively seek out cavities in dead trees or artificial nest boxes such as those provided for nesting wood ducks. They prefer cavities 4-15 feet (1-4 meters) off the ground. Breeding occurs anytime between the end of February and the end of June, depending on the region. The female will lay a clutch of 7-15 eggs and incubate them for around a month. Like most waterfowl, Hooded merganser hatchlings are precocial and usually leave the nest within 24 hours after they hatch. Once they leave the nest, the young are capable of diving and foraging but remain with the female for warmth and protection. They start flying at around 70 days of age and become reproductively mature in 2 years.
The main threat to Hooded mergansers is habitat loss due to deforestation, and agricultural expansion as these birds are cavity nesters and require mature trees with suitable nesting sites. Because of their high reliance on aquatic prey, Hooded mergansers are also very susceptible to harm from many types of pollution; some of these are poisons that accumulate in the food organisms, directly poisoning predators high in the food chain, and some of which simply reduce the populations of their prey.
According to the What Bird resource, the total population size of the Hooded mergansers is around 270,000 to 390,000 individuals. Currently, this species is classified as Least Concern (LC) on the IUCN Red List, and its numbers today are increasing.