Is the ultraviolet waveband a special communication channel in avian mate choice?

There is growing evidence that ultraviolet (UV) wavelengths play an important role in avian mate choice. One of the first experiments to support this idea showed that female zebra finches (Taeniopygia guttata) prefer UV-reflecting males to males whose ultraviolet reflection has been removed. The effect was very strong despite little or no UV reflection from several plumage areas. However, it is not clear how the importance of the UV waveband compares to other regions of the bird-visible spectrum. We tested whether the response of female zebra finches to the removal of male UV reflection is greater than to the removal of other wavebands. We presented females with a choice of males whose appearance was manipulated using coloured filters. The filters removed single blocks of the avian visible spectrum corresponding closely to the spectral sensitivities of each of the zebra finch's single cone classes. This resulted in males that effectively had no UV (UV-), no short-wave (SW-), no medium-wave (MW-) or no long-wave (LW-) plumage reflection. Females preferred UV- and SW- males. LW- and MW- males were least preferred, suggesting that female zebra finches show the greatest response to the removal of longer wavelengths. Quantal catches of the single cone types viewing body areas of the male zebra finch are presented for each treatment. Our study suggests it is important to consider the role of the UV waveband in avian mate choice in conjunction with the rest of the avian visible spectrum.