Figure 9.18 Long-tailed widowbird. (a) During the breeding season, males have exceptionally long tails. (b) When researchers made male tails shorter, the same length, or longer than typical males, females preferred males with longer tails. Error bars are standard errors.
Photo by FLPA/Dickie Duckett/age fotostock. Data from M. Andersson, Female choice selects for extreme tail length in a widowbird, Nature 299 (1982): 818–820.