On the science of iridescence in Hummingbirds, my bogey bird falls at last and the bizarre properties of the Photon
My recent experiences with the hummingbirds of Costa Rica led me to ponder the why and how of the dazzling phenomena of Iridescence. As a recap, look at the two pictures of the Fiery-throated Hummingbird above. From sideways on this Hummingbird appears emerald green but front on it is truly transformed into a veritable artists pallet of colours. To see the Fiery throat you have to be essentially face on, a few degrees either side and the fiery iridescence disappears. You would certainly be forgiven for thinking these were two entirely different birds. I guess it’s fairly obvious that the colouration is not your run of the mill pigment colouration. In fact Hummingbirds are coloured by what’s known as structural colouration. This is a similar effect to how a prism splits light into its constituent colours. The Hummingbirds feathers have specialised pancake microscopic structures called melanosomes. These contain little air bubbles that refract the light...