Habitat

Breeding Range

Closely tied to forested wetland systems throughout range, although nests in man-made boxes have been recorded in grassland areas in Minnesota (Zicus and Hennes 1988) and non-forested wetlands associated with riparian corridors in N. Dakota (Doty et al. 1984). Species uses a wide range of forest types, ranging from spruce/fir in Washington (Beall 1990) to mixed pine/hardwood in Minnesota and Ontario (McNicol et al. 1987b, Zicus 1990), cottonwood/elder riparian corridors in N. Dakota (Doty et al. 1984), and oak/cypress/tupelo in the southeast (LHF). Most specifics about habitat relate to broods.

Brood Habitat

Broods occupy a wide range of habitats throughout their range including emergent marshes, small lakes, ponds, beaver wetlands, forested creeks and rivers, and swamps (Beard 1964, Kitchen and Hunt 1969, Renouf 1972, McNicol et al. 1987a, b, LHF). Although few data available, brood habitat is generally shallow (25 and 67 cm; Beard 1964, McGilvrey 1966) with exposed areas such as rocks, logs, or unvegetated bars that can serve as loafing sites (Beard 1964). Surveys in Ontario indicate that, unlike Common Mergansers (Mergus merganser) which prefer large lakes with irregular shorelines, female Hoodeds with broods prefer small, oligotrophic, fishless, headwater ponds, with neutral acidity (McNicol et al. 1987b). Such ponds, composing < 15% of all wetland habitat in the Ontario study, have low buffering capacity and so are sensitive to acid precipitation. On lakes with fish, broods tend to prefer lakes with minnow/stickleback communities more than lakes with yellow perch/sucker communities (McNicol and Wayland 1992). In New Brunswick, broods prefer active to nonactive beaver (Castor canadensis) ponds (Renouf 1972).

In Wisconsin (Kitchen and Hunt 1969), 75% of recorded broods occurred on a wide (20 m), shallow (33–66 cm), swift flowing (0.3 m/sec), forested river with 90% cobbled bottoms. Such habitat averaged 1.3 broods/km and contained the highest densities of fish and crayfish within the study area. Broods occurred on only 1 of 40 lakes sampled. Twenty-two of 30 observations of foraging broods were in waters over rocky substrate, which also supported the highest fish and invertebrate densities.

Habitat requirements in southern breeding areas are largely unquantified, although in Missouri nest boxes placed along slow moving, heavily forested rivers and lakes, and in dense buttonbush (Cephalanthus occidentalis)/cypress (Taxodium distichum) swamps seem to be preferred (KMD, LHF).

Spring And Fall Migration

Found in a wider range of habitats including the open waters of rivers and lakes, brackish coastal bays, tidal creeks, seasonally-flooded forest, dead timber, and shrub/scrub.

Winter Range

Differs from that of Common Mergansers, which prefer large, open freshwater lakes, and that of Red-breasted Mergansers, which occupy coastal saltwater habitats. Along both coasts, Hooded Mergansers occupy shallow, freshwater and brackish bays, estuaries, and tidal creeks and ponds, where they often concentrate along the edge of ice (e.g., Veit and Petersen 1993, Sibley 1993). In the Mississippi Alluvial Delta, they differ from sympatric Wood Ducks in preferring deeper, more permanently flooded sloughs, backwaters, scrub/shrub, and overcup oak (Quercus sp.) habitats (Fredrickson and Heitmeyer 1987). Elsewhere found in a wide range of freshwater habitats including emergent marsh (BDD), small ponds, rivers, and creeks.