Iridescent colors, such as those found on the throats of many hummingbirds, are very bright and change with the angle formed by the observer's eye, the reflecting surface (the iridescent throat patch), and the light source (in this case the sun). As the angle of view changes, light waves contacting the hummingbird's throat feathers interfere with each other in different ways: at each angle, some wavelengths of light are brightened and others are cancelled out before they reach the observer's eye. At each position the observer only sees the brightened colors. The hummingbird's throat appears to flash on and off because his movements change the angle of view, and hence which colors the observer can perceive.

Ruby-throated Hummingbird and Feather Iridescence

Go back to QUIZ page