Photobleaching of pink photoluminescence in owl and frogmouth feathers

Pink photoluminescence is activated in the feathers of owls (Strigiformes) and frogmouths (Podargiformes) when exposed to ultraviolet-violet light. This phenomenon has been reported from Western Australia and worldwide, but has not been investigated in tropical north-eastern Australia. The gradual degradation of porphyrin luminophores is used to age owls, but incidental light exposure presents an unquantified variable when examining both live animals and museum specimens for pink-red photoluminescence. I examined roadkill specimens of two species of owl and two species of frogmouth from the Australian Wet Tropics for photoluminescence, and tested the photobleaching effects of timed exposure to direct sunlight and indoor laboratory lighting. All specimens examined displayed orange-pink feather photoluminescence to varying degrees. Porphyrin pink photoluminescence of feathers became noticeably diminished within one to two minutes of exposure to direct sunlight, or several hours of indoor laboratory lighting. Photobleaching is thus highlighted as a confounding factor when examining specimens with an unknown light exposure history.