Green-headed Ducks

     One late afternoon in early November, I stopped at a two-acre, human-made pond to see if there were any duck species besides the couple hundred mallards that rest there through much of each
winter.  The mallards were there, and so were a drake green-winged teal and a young male shoveler duck.  While watching those ducks for a few minutes, it occurred to me that the drakes of all three species have at least some green feathering on their heads.  The heads of male mallards and shovelers are totally green.  And I thought, drakes of several other kinds of ducks that are in Lancaster County at least part of each year also have some green on their heads when they are sporting their breeding plumages during winter and into early spring.  Those other ducks species include wood ducks, American wigeons, common mergansers, American goldeneyes and bufflehead ducks.
     Green-winged teal and American wigeon males each have a green stripe on each side of the head.  Common mergansers' heads are completely green.  Wood duck drakes have green on their crests.  And goldeneyes and buffleheads have green sheens on the dark parts of their heads. 
     The iridescent-green feathering on the heads of these ducks in their breeding plumages is caused by the way light is reflected off the ducks' heads.  The green is a sheen visible to view in certain lighting.  Because it is with the breeding colors on each drake, that green sheen is a part of each male's courting of his mate.  It is a flashy color, but still camouflages each drake to some extent.  Probably through trial and error over the eons, other bright colors highlighted the males' existence to predators that killed them.  But iridescent-green expressed the males' readiness to mate with their female partners while not exposing themselves to predation.  Drakes with green on their heads survived.  And partly due to that, so has each species to the present day.
     Nature works in wondrous ways.  Changes that benefit each species help it survive from one generation to the next.  Today's species of life are the result of a long time of changing form and color to fit into a habitat.