Figure 1

Photographs of red-necked nightjar plumage showing differences in perception of porphyrin-based coloration under natural and ultraviolet light. (a) Details of the wooden structure used to take standardized ventral photographs of nightjar plumage under a 395 nm light source. (b) Male red-necked nightjar during a courtship flight showing clearly visible white patches on wings and tail. Note that porphyrin-based coloration is not perceptible to the human eye under natural light. (c) Example of the under-side of a nightjar wing under ultraviolet-light irradiation, showing fluorescent sections along the rachis of exposed primaries and secondaries. The yellow line denotes the length of pink fluorescence (L_p) for an individual feather (the second innermost primary, P2) and also serves to illustrate the differences in L_p among closely adjacent feathers (e.g. between S1 and P1). Photographs by Carlos Camacho.