Mallard Iridescence

Mallard Ducks, an everyday sight in public parks, look like nature exaggerated into artistic fantasy.

The males display a peacock-like iridescence about their heads. Both sexes show iridescent blue wing bars in flight.

Most of the Mallard's colorful effect comes from light reflected directly by feather pigments, as it does in a painting. Special brilliance results from light waves passing through iridescent structures, which are microscopic layers of crystals within the feather barbules. Their interspersion with air forms complex surfaces for refraction which, coupled with underlying pigments, create vibrant sheens on the feather.

Contrasted with the plumage array on its body, its yellow bill and orange feet, the male Mallard's iridescent green head makes a splendid sight in courtship and to casual Park visitors.

A couple of weeks ago as ice was beginning to form on the Halibut Point quarry, these Mallard Ducks swam by with the sunlight at a low oblique angle from the rear. Their apparently dark purple heads momentarily confused recognition. What happened to the lustrous green sheen?

Peter Brown, an art professor friend, supplied the answer. "Green light and violet light are complements. This means that when combined they will create white light. The microscopic structure of certain feathers refracts white light like a prism. At certain angles we see one color and as we shift our vantage point we will see the color’s complement. When one color is being absorbed by the feather, its complement is being reflected to our eyes. With iridescence this process flips back and forth."

This duck seems to be resting peacefully with a blend of green and violet iridescence.