Why Are So Many Bird Flowers Red?

Why are so many bird fl owers red? PLoS Biol 2(10): e350. and Luis Santamaría. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Open access, freely available online M ost bird-pollinated fl owers are both red and rich in nectar. The traditional explanation for this association is that, since red is inconspicuous to bees, it evolved to prevent bees from depleting the nectar of bird-pollinated fl owers without effecting pollination. But bees can see, and they actually visit red fl owers. So why are most bird-pollinated fl owers red? To help answer this question, we need to consider how the outcomes of foraging decisions are affected by the community in which individuals live, and by the foraging options of other individuals. Plants face a trade-off between attracting pollinators and remaining hidden from fl ower parasites (such as nectar robbers and seed predators). Consequently, there is often strong selection pressure for highly specifi c communication channels that can advertise the presence of their fl owers to effective pollinators but not to other individuals. Many aspects of pollinator syndromes are best understood in these terms (Proctor et al. 1996). For example, fl owers that are pollinated by birds—bird fl owers—produce nectar at much