Sexual displays as amplifiers: practical examples with an emphasis on feather decorations

Exact patterns of displays are not easy to explain on a functional basis. However, if displays evolve initially as amplifiers of previously perceived differences in quality, their patterns should correspond with patterns of quality cues that are amplified. Consequently, exact patterns of behavioral, morphological, and structural displays can be explained. I illustrate this with examples of some feather decorations. Furthermore, these examples indicate that, frequently, cues on which female choice is based cannot easily run away, whereas their amplifiers can. Finally, I present specific predictions of the amplifying theory of sexual selection.