Bird of The Week: Hooded Merganser
SCIENTIFIC NAME: Lophodytes cucullatus
TREND: Stable (Possibly Increasing)
HABITAT: Freshwater and brackish ponds, marshes, swamps.
The Hooded Merganser is the only member of its genus, Lophodytes. This genus name derives from the Greek words lophos meaning crest and dutes meaning diver — an apt description of this small diving duck with the conspicuous fan-shaped crest.
The Hooded Merganser is the smallest of the three North American merganser species (the other two are the Common and Red-breasted Mergansers), and the only one that breeds exclusively in North America. A male “Hoodie” in breeding plumage is a striking sight, with a snow-white, fan-shaped crest bordered in black; black-and-white-striped chest and back; bright yellow eyes; and rust-colored sides. Females and immatures are brown with a tawny hood and dark eyes.
Supreme Underwater Eyesight
Like other diving birds such as the Common Loon and Atlantic Puffin, the Hooded Merganser is a “sight feeder,” detecting and pursuing aquatic prey with eyes specially adapted for keen underwater vision. Recent research on the structure of Hooded Merganser eyes shows how they change shape to correct for light refraction beneath the water’s surface. Powerful eye muscles allow these diving birds to control the curvature of their eyes’ corneas and lenses (in contrast, humans can only control the curvature of their lenses). This allows equally accurate vision both below and above the water. Clear nictitating membranes (third eyelids) also protect the birds’ eyes like a pair of swim goggles would.
North American Native
Like the Wood Duck, the Hooded Merganser is closely associated with forested wetland habitats. In breeding season, this bird is especially common around the Great Lakes, although it is widespread in many other regions as well. Year-round populations occur in two ranges: The first, in the East, extends from Nova Scotia south and west to eastern Oklahoma and northern Louisiana. A second, smaller year-round range includes parts of coastal and southern British Columbia, Washington state, and patches in Oregon and western Montana. The Hooded Merganser is a short-distance migrant, moving south to avoid harsh weathers. The majority winter along the Mississippi Flyway in the south-central U.S.
Unlike the Mallard and American Black Duck, the Hooded Merganser does not quack. Instead, it issues a number of hoarse-sounding calls. In Georgia, this species is sometimes called the “frog duck” because displaying males utter a croaking, growling sound somewhat like the call of a Pickerel Frog.
The Hooded Merganser is an expert fisher-bird, wielding its narrow, serrated bill to grasp slippery quarry. Unlike other mergansers, which primarily eat fish, it augments its diet with aquatic insects, small frogs and tadpoles, plant material, and crustaceans, especially crayfish. This merganser has a particularly strong, thick-walled gizzard, which efficiently grinds up the hard shells of crustaceans.
Displaying, But Not Staying
Several Hooded Merganser males will display to a single female, with ritualized display movements that include showing off the flashy black-and-white crest, vocalizing, and head-tossing, turning, and shaking. In one eye-catching display move, the male rears so far back in the water that his fanned crest touches his back. Once Hooded Mergansers pair off, the male stays with the female until she selects a nesting cavity and finishes laying her eggs. He leaves soon after she begins to incubate her clutch.
The female chooses a tree cavity for her nest location, preferably one above or close to water, about four to 15 feet above ground. (Although some cavities have been recorded over 80 feet up!) She will readily use a Wood Duck nest box if one is available. The only material that the female adds to the nest cavity is down plucked from her belly. She lays a clutch of nine to 11 nearly spherical white eggs. Hooded Merganser hens often lay eggs in each other’s nests, a phenomenon known as brood parasitism that’s often seen in other waterfowl.
The female merganser does not begin incubating until her clutch is complete, which ensures that her young will all hatch at around the same time. This strategy of synchronous hatching makes sense: Shortly after hatching, one after the other, chicks leap out of the cavity, tumbling to the water or ground. The female then leads the ducklings to safety as a group, usually within 24 hours of hatching.
Keeping “Hoodie” Populations Healthy
Acid rain may pose a threat to the Hooded Merganser, as it changes water pH and may reduce the populations of fish and aquatic invertebrates upon which this bird depends. This duck must also contend with habitat loss, particularly of swamplands with suitable nesting cavities.
The conservation and management of wetland forest habitat are vital to maintaining healthy Hooded Merganser numbers, particularly in the Lower Mississippi Valley, where a large percentage of the population winters. ABC is part of the Lower Mississippi Valley Joint Venture (JV), which prioritizes the area’s protection, restoration, and management. This JV’s activities benefit many other migratory bird species, such as the Swallow-tailed Kite, Wood Thrush, and Prothonotary Warbler.
Source: American Bird Conservancy (abcbirds.org)