Figure 1.

Sexual selection accounts for the occurrence of elaborate displays such as the bright plumage color of the male hooded warbler Wilsonia citrina (Upper). The intensity of sexual selection is apparently much weaker in species such as the Canada goose Branta canadensis (Lower), where the sexes have similar plumage colors. In this issue of PNAS, Doherty et al. (1) demonstrate that sexual selection can have dramatic effects on the structure and dynamics of North American bird communities: sexually dichromatic species experience much higher local extinction and turnover rates than monochromatic ones. (Photograph taken by Paul Doherty.)