Humans are not the only fashionistas in the animal kingdom. Titmice can be fashion-victims, too, apparently. A study by Sonja Wild and Lucy Aplin shows that, given the chance, titmice decorate their nests with this season's must-have color.
Dr. Wild and Dr. Aplin were following up the work published in 1934 by Henry Smith Williams, an American naturalist. He noticed that when he put various colored balls of yarn(纱)out in his garden, almost always one and only one became popular that season for incorporation into local birds'nests. But which particular hue(颜色)was favored varied from season to season. This suggested that the color chosen by one of the early birds was spotted and copied by others.
Williams's work was, however, forgotten until Dr. Wild and Dr. Aplin came across it while following up on a different study. This group noted that, during any given breeding season, the blue titmice they were investigating tended to incorporate the same plants into their nests regardless of how abundant those herbs actually were. This, too, suggested fashion-following—and it likewise led Dr. Wild and Dr. Aplin to speculate that birds were studying the nests of others and copying them. They therefore set out to re-run Williams's experiment.
According to the study, of 68 titmice nests built that season in the experimental areas, 26 included wool from a dispenser(分配器). Of these, 18 were constructed after both colors had become available from all dispensers. Even so, 10 of that 18 included only the color of wool first chosen by a nestbuilder. By contrast, all eight wool-bearing nests in the control zone contained a mixture of colors—a statistically significant difference.
Titmice, then, do seem to be "on trend"when it comes to nest-building materials. Why that should happen remains unclear. Dr. Wild and Dr. Aplin suspect the trendsetters are older birds, and that evolution favors younger ones copying their elders since those elders have evidently survived what fortune throws at a titmouse. Williams's onginal work, though, suggested such initial choices were arbitrary(任意的), a bit like those of the leaders of human fashions.
