A red-billed streamertail from Jamaica. The elongated tail feathers are the next-to-outermost pair. In most other long-tailed birds, the outer pair are elongated.
An Anna's hummingbird outfitted with two long feathers from the Jamaican red-billed streamertail, a hummingbird that naturally sports two 19-cm long tail feathers. (Christopher Clark/UC Berkeley) BERKELEY — The long tails sported by many male birds in the tropics look like they're a drag to carry around and a distinct disadvantage when fleeing predators, but experiments by University of California, Berkeley, biologists shows that they exact only a minimal cost in speed or energy – at least in hummingbirds. "We estimate that having a long tail increases a bird's daily metabolic costs by 1 to 3 percent, which means the bird has to visit 1 to 3 percent more flowers in its territory," said Christopher J. Clark, a graduate student in UC Berkeley's Department of Integrative Biology. "Is that a lot? It's hard to say, but we argue that it's not, especially when compared to the costs of things like molting and migration." Clark and Robert Dudley, UC Berkeley professor of integrative biology, report the results of their study in the March issue of the journal Proceedings of the Royal Society B, which appeared online this week. Male birds of numerous species have evolved elaborate colors and decorations to attract females, many of them involving tail feathers. The peacock's eye-popping display, the broad, gauzy tail of the male lyre bird and the two-foot-long, iridescent green tail of the quetzal are but three examples. Some biologists have made computer models of elongated tails, like those of the Jamaican red-billed streamertail hummingbird, the scissor-tail hummingbird or the marvelous spatuletail hummingbird, and have predicted as much as a 50 percent greater energy cost when flying with a long tail.
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