The importance of directionality in these iridescent colors is really well illustrated in the Magnificent Riflebird, where the male has these intensely iridescent feathers along his chin and throat and upper breasts. It can really only be seen from certain perspectives. And the female, in order to see this color at its best, has to be right in front of them. What’s cool is that the male has chosen a display site that’s a thin narrow horizontal vine. Because of the nature of the vine, the female really has no choice but to be in the proper spot to see that intense color so his whole display is really designed to project that incredible color right where the female’s going to be. Maybe the most striking example of this, of the importance of directionality, comes at the end of the riflebird’s display. When the male is pointing his head upwards, he maintains that incredibly iridescent blue color on his chin but then he moves the feathers from his upper breast in a wave of black. It’s this change in that angle of the feathers that causes it to go from this blue color to black as he moves them up. The effect is really quite stunning.