Meeting Abstract
The ability to discriminate between colors is important across taxa and behavioral contexts. In birds, color discrimination is thought to be enhanced by carotenoid-containing oil droplets found inside photoreceptors. We asked whether variation in the ability of female zebra finches (Taeniopygia guttata) to discriminate colors along an orange-red color continuum corresponds to variation in the carotenoid concentration of retinal oil droplets. This color continuum parallels variation in male beak color, a mate assessment signal, and is perceived by both female and male zebra finches in a categorical fashion. We behaviorally tested color discrimination and then used microspectrophotometry to measure cone oil droplet absorbance, a proxy for carotenoid concentration. We found that underlying variation in oil droplet carotenoids corresponds to variation in behaviorally measured color discrimination ability. Oil droplet carotenoid concentration did not affect discrimination ability across the entire orange-red range equally, however. Rather, higher carotenoid concentration was associated only with increased discrimination of colors from different sides of the previously identified color category boundary. These data show that differences in sensory physiology can correlate with individual variation in perception of a signal-relevant color range.
