• Appearance: sexual dimorphism – males are larger, look like females except during breeding season – red beak and legs, brown head with ragged crest, white chin and chest, gray and white back, large white patches on upper wings (visible in flight)
  • During breeding season males have green heads, mostly white, black stripe down back – these feathers molt during the fall
• Length: 20-28 inches (about 2 feet)
• Wingspan: 34 inches (about 3 feet)
  • Shorter than many other ducks so that it is easier to tuck wings in and deliver bursts of power for diving
• Status: least concern, but declining
  • 65% decline between 1966 and 2014
  • Threatened by pesticides, acid rain, and chemical pollutants in water – degrades habitat, thins eggshells, poisons/kills prey
• Habitat
  • Freshwater rivers, lakes, and ponds
  • In winter, they may use saltwater estuaries
    • Salt water has lower freezing point than freshwater and ocean cools slower than smaller bodies of water in winter
  • Spend most of lives on water: foraging, roosting, sleeping, etc.
  • Found in all but southernmost U.S., also found in Europe and Asia
• Diet
  • Mostly eat fish, but also insects, mollusks, crustaceans, and worms, frogs, small mammals, birds, and plants
  • Forage in clear bodies of water, usually less than 13 feet deep
  • Feet are located closer to tail than non-diving ducks, which helps propel them downward when diving but makes them awkward on land
    • Ability to “run on water” before flight, have trouble taking off because of leg placement so they need
      to build up speed
  • Paddle across surface of water until prey is spotted
  • Dive up to a few feet down into water, catch prey underwater
    • Usually spend 30 seconds under water, can last up to 2 minutes
  • Often forage with other ducks
• Migration
  • Coastal birds migrate locally, inland birds fly long distances
  • In Long Island, mergansers may migrate from freshwater body to estuary
    • Migrants from mainland New York may also inhabit Long Island bays
  • Migratory mergansers usually last to migrate in fall (mid-November) and first to arrive on breeding site in spring (February)
  • Breeding grounds in northernmost United States and Canada
  • Immature young skip migration for 1 year, at 2 years old migrate to breeding site (males also fledge first breeding feathers)
  • Wintering sites all over United States except in southeast corner of country
• Nesting
  • Prefer nesting in natural cavities or woodpecker holes in trees up to 100 feet high and within mile of water
    • Less commonly nest in rock crevices, old sheds, chimneys, lighthouses, holes in the ground, hollow logs, burrows, nest boxes, and on ground
    • Sometimes steal nests of other ducks
  • Female chooses nest site and uses materials in cavity (old nests, woodchips, etc) to form “bowl” – may also add grass
  • One mate per season, may choose different mate each year
  • Average brood is 6-17 creamy white/yellow eggs
  • Male protects nest until eggs hatch, then female is left to care for ducklings
  • Females may form group with 40 or more young
  • Young leave nest about 1 day after hatching, learn to forage for insects
  • After about 12 days, ducklings begin to hunt for fish
  • Fledglings learn to fly about 45-65 weeks after hatching
  • Mother abandons young around time of first flight
  • Average lifespan is 8-12 years, oldest common merganser was 13 years old