Avian feather research. Researchers Georg Pohland (left) and Peter Mullen (right) holding aloft a museum specimen of a Griffon vulture (Gyps fulvus) as seen in ultraviolet (UV) light. Pohland is also holding a spectrophotometer which measures the UV reflecting properties of the bird's feathers. The plumage of many bird species display markings that are only visible under UV light, which birds can see. This image was taken using a camera adapted to filter through and detect only UV light waves. Surfaces that reflect UV appear lighter than surfaces that absorb UV. Photographed at the Alexander Koenig Research Insitute and Museum of Zoology, Bonn, Germany.