In the animal kingdom, much like in the world of humans, there are many techniques that animals will use in order to attract mates. Parrots, for example, have glowing heads.
Some birds in the parrot family have feathers on their heads that fluoresce. That means these special feathers take in energy from the sun in the form of ultraviolet light and then re-emit that energy. The energy is re-emitted in longer wavelengths that parrots and humans can see.
As mentioned before, certain kinds of parrots use their fluorescing feathers to attract mates. While at the University of Glasgow in Scottland, Kathryn Arnold covered the glowing feathers on some parrots with a jelly that blocks UV-light. Others parrots got a jelly that was transparent. The parrots with glowing heads seemed more sexually attractive to the other parrots.