MY 2-YEAR-OLD GRANDSON has just started playing with fingerpaints. At first, he made discrete blobs of each color that I’d call, say, cardinal red or goldfinch yellow, then discovered that mixing those two creates oriole orange. The pigments in bird feathers are a bit like Walter’s fingerpaints, each producing its own color and, when blended, creating more shades. But feather coloration is far, far more complicated than a toddler’s fingerpaints.
Birds have two entirely different ways of producing non-iridescent colors. The first is via pigments, which, like Walter’s paints, absorb specific wavelengths of light, reflecting the colors not absorbed to our eyes. For