Hooded Merganser

About the hooded merganser

The hooded merganser is a species of fish-eating duck and the only living member of the genus Lophodytes. Its genus name comes from Greek — "lophos" for crest and "dutes" for diver — and its species name, cucullatus, is Latin for "hooded." Both sexes carry a crest they can raise or lower at will, and the male's breeding plumage is sharply patterned and colored. Although it has a sawbill, the hooded merganser is not classified as a typical merganser. It is the second-smallest species of merganser in the world, smaller only than Europe and Asia's smew, and it is the only merganser whose native range is confined to North America.

The species was formally described in 1758 by Carl Linnaeus in the tenth edition of his Systema Naturae, based on an account and illustration by English naturalist Mark Catesby, who called it the "round-crested duck" in his Natural History of Carolina, Florida and the Bahama Islands. Linnaeus placed the type location in America, later restricted to Virginia and Carolina. The genus Lophodytes itself was introduced in 1853 by the German naturalist Ludwig Reichenbach, and the hooded merganser is the only species placed in it; no subspecies are recognized. A fossil merganser from the Late Pleistocene of Vero Beach, Florida, was originally described as Querquedula floridana but on reexamination proved to be a species closely related to the hooded merganser, now named Lophodytes floridanus, though its exact relationship to the modern bird remains unknown. The hooded merganser is sexually dimorphic. The adult female is grayish-brown with a narrow white patch across the lower breast and belly, and a light reddish-brown crest running back from the head. Outside the breeding season, males resemble females except for yellow eyes rather than brown. In breeding plumage, the mature male's back, head, neck, and breast are mainly black marked with white, including large white patches flanking the crest that become especially conspicuous when he raises it during courtship; his lower flanks are rich chestnut, and his breast and underside are largely white with white stripes across the chest. Both sexes show narrow white stripes along the tertial wing feathers, visible along the lower back when the bird is at rest. First-winter birds are grayer-brown across the neck and upper parts than adult females, whose upper parts are nearly black, and young birds have narrower white edges on their tertial feathers.

Behavior and diet

The hooded merganser hunts underwater by sight, diving for its meals rather than dabbling at the surface. Across studies, fish typically dominate the diet, making up 44 to 81 percent of what the bird eats, supplemented by aquatic insects (13 to 20 percent) and other invertebrates such as crabs and crayfish (22 to 50 percent), with the exact mix varying by circumstance.

Pairs are monogamous and stay together only until the female has chosen a nesting cavity and finished laying her clutch, after which the male departs, leaving the female to incubate and raise the brood alone. Females actively seek cavities in dead trees or artificial nest boxes, including those meant for wood ducks, and prefer cavities 4 to 15 feet (1.2 to 4.6 m) off the ground. Breeding runs from late February through late June depending on the region. Eggs measure 4.3 to 6.2 cm (1.7 to 2.4 in) long and 3.9 to 5.4 cm (1.5 to 2.1 in) wide. A female lays 7 to 15 eggs but does not begin incubating until the last egg is laid, so all the chicks hatch at once and in similar size — a strategy that makes parental care more efficient, though it costs the female 8 to 16 percent of her body weight during incubation. Like most waterfowl, hatchlings are precocial and typically leave the nest within 24 hours of hatching, already able to dive and forage for themselves, though they stay near the female for warmth and protection.

Range and habitat

The hooded merganser has two major year-round ranges within its North American distribution: one running from the southern Canada–U.S. border along the Atlantic Coast down to the Gulf Coast near the Mississippi delta, and a smaller one stretching from Washington state and southern British Columbia into northern Idaho. It also breeds to some extent from Missouri to southern Canada and from Nova Scotia to eastern North Dakota and Saskatchewan, migrating as needed to avoid harsh winters. As a short-distance migrant, it winters within the United States wherever temperatures keep ponds, lakes, and rivers ice-free.

The species prefers small bodies of water such as ponds and small estuaries with ample emergent aquatic vegetation, though it also uses larger wetlands, impoundments, flooded timber, and rivers, generally favoring fresh water while also occurring on brackish water.

The hooded merganser is also a common species in captivity in Europe, and most individuals recorded in the wild there are regarded as escapes or feral birds rather than natural arrivals. A small number, however, are considered genuinely wild vagrants — Britain's first accepted record was a bird seen on North Uist in October 2000 — and small numbers are seen regularly around Dublin, though those sightings are presumed to be feral rather than wild.

Conservation status

The hooded merganser is rated Least Concern (LC). From 1966 to 2015 its population grew by more than 1.5 percent annually across its breeding range, and as of 2021 the global population was estimated at 1.1 million mature individuals. Historically, population declines were linked to large-scale deforestation, since the species depends on cavities excavated in mature trees for nesting — though it will also use nest boxes provided by people. Because it relies heavily on aquatic prey, the hooded merganser remains vulnerable to pollution, both from toxins that accumulate in the animals it eats and from contamination that simply reduces the populations of its prey.