Hummingbirds have amazing colors on their beautiful throats. The throat area is called the gorget. Interestingly, the feathers on the gorget are specialized and only the outer third of each feather is iridescent. This part of the feather contains layers of minute structures called platelets that are filled with tiny air bubbles. These structures partially reflect back light, causing the brilliant shining colors of reds, purples and blues seen on hummingbirds. The iridescent parts of the feathers of the gorget are flat, and so reflect light in just one direction. So for you to see the full iridescent color of the gorget, the sun must be striking the feathers head on. If not, the feathers will look dusky or even black.
You can see this on this male Ruby-throated Hummingbird at our feeder, who had his head turned away from the sun. The feathers on the side of his gorget have more of the sun reflecting off them and look ruby; the feathers on the front of his gorget look dusky or even black.
When male hummimngbirds display to female hummingbirds, they face the sun, which reflects the full beautiful color of their gorgets. We saw this male yesterday displaying to a female and flying back and forth in front of her in a deep arc flight path, his brilliant red gorget gleaming. We're sure she was impressed!
Photo © Lillian Stokes, 2006