Wintering River Ducks and Bay Ducks

     One afternoon in January I saw a pair of greater scaup ducks on the Conestoga River in Lancaster County, Pennsylvania.  I was never so close to this kind of bay duck before, and with 16-power binoculars, I could see their every detail and how beautiful they were.  The drake was light-gray with a green sheen on his head feathers.  The hen was rich-brown all over with much white on her face at the base of her beak.  Both birds repeatedly dove under water and swam to the river bottom to eat aquatic plants, snails and smaller crayfish.
     A few days before seeing the scaup, I noticed a mixed group of ducks in a strip of open water among sheets of ice in the middle of the Susquehanna River near Columbia, Pennsylvania.  Ducks there were common goldeneyes and buffleheads, which are related river species, and greater scaups, lesser scaups and red-headed ducks, which are related bay ducks.  All those river and bay ducks took turns diving to the bottom of the Susquehanna for food. 
     Goldeneyes and buffleheads of the genus Bucephala winter mostly on rivers and back waters off estuaries in eastern North America.  Drakes of these two species have similar black and white patterns on top and green sheens to their heads, showing their relatedness.  Their mates have brown plumages that camouflages them when hatching eggs and rearing ducklings.  Goldeneyes' wings whistle when they are in flight.  And both species swim under water with their feet only.  Both species mostly ingest aquatic insects, snails, crustaceans and small fish.  The bigger, stronger goldeneyes overturn underwater stones to get food.
     Five kinds of bay ducks in the genus Aythya winter in "rafts" of their floating, bobbing bodies, often in the hundreds or thousands, far out on estuaries and the mouths of larger rivers, though they overlap the habitats of river ducks at times.  Most of the time one can only spot and identify these ducks with scopes.  Bay ducks include greater and lesser scaups, ring-necked ducks, which also rest and feed on built impoundments, particularly during their spring migration north and west to breeding grounds, red-headed ducks and canvasback ducks.  Females of each of these species are mostly brown, which allows them to blend into their surroundings and have a better chance of escaping predation.  But their mates are more colorful.  Male lesser scaups and ring-necked ducks have purple iridescence to their heads, while the heads of red-heads and canvasbacks are dull red.  But both genders of canvasbacks have sloping foreheads that set that species apart. 
     Bay ducks dive to the bottoms of large bodies of water to get food, swimming under water with their feet only.  The foods of these related species are aquatic plants and water insects.  Canvasbacks also eat shellfish and small fish.  Those slight variances of food choices educe competition for food among these ducks in the same habitat.       
     River ducks and bay ducks winter way out on large bodies of water where there is no shelter for them, except their own dense feathers.  They spend most of their days rocking on the little wavelets or diving to the bottoms of those bodies of water for food or to escape airborne predation such as from bald eagles.  Watch for these attractive and interesting ducks when along rivers or bays in winter.