On a clear lake in the Ohio woodlands, hooded mergansers glide by. These small diving ducks with oddly shaped heads will stay until cold temperatures inspire them to fly south to warmer waters.
The length is 16 to 19 inches. This duck's small, thin bill and crested head give it a distinctive profile. Breeding males may have a glossy black head with a neat, rounded crest, and a prominent white head patch starting behind the eye. Rusty flanks are separated from a white breast by two vertical black bars and a black back. Females are dark with a grayish-brown head and a prominent rust-orange crest. The back is dull black, the flanks brownish-gray, and the chin and throat paler.
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Mergansers are the only ducks in North America that specialize in eating fish. Their eyes are well adapted for seeing underwater and they hunt by diving down into the water searching for their prey.
Usually seen in pairs or small parties, these ducks are less sociable than most diving-ducks. Their flocks rarely exceed 15 birds. Pair formation begins in mid-winter. Mergansers feed by diving. They fly rapidly, low over the surface of the water, taking off with some spattering over the surface. They are very agile while flying through the trees. They are migratory, but often remain until force to move by freezing waters.
Females frequently reoccupy the nest site of the previous year if it is still available. They prefer to nest in tree cavities along secluded woodland ponds and streams. When incubation is underway the males desert the females to commence post-breeding molt. Females move their newly-hatched ducklings out of the nest within a day of hatching, and usually go to shallow waters close to timber. The fledging period is about 70 days. It is uncertain how long the female remains with her brood.