King Penguins
Tall in stature and long of beak, king penguins bear striking color patches along their necks, ear regions, and the sides of their beaks. In the visible light spectrum, these beak patches appear orange. Penguins are able to see into the ultraviolet region of the electromagnetic spectrum, however, and can detect additional patches of ultraviolet color along the lower bill that are imperceptible to human eyes. Scientists hypothesize that these beak markings signal sexual maturity and make penguins more attractive to mates. As a king penguin matures, the ultraviolet hue of the beak markings increases. In wild penguin studies, scientists have documented higher ultraviolet reflectance in recently formed male-female pairs.