WASHINGTON - The long tails sported by male birds in the tropics are often considered a distinct disadvantage because they lead to as much as a 50 percent greater energy loss when flying. Now, however, a new study has shown that they exact only a minimal cost in speed or energy.
University of California, Berkeley biologists have found long tails exact leads to 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,” he added.
During the study, Clark outfitted short-tailed Anna’s hummingbirds (Calypte anna) with long tail feathers from a red-billed streamertail (Trochilus polytmus), giving the hummingbirds two tail feathers that were five times the normal length.
They found that the hummingbirds with enhanced tail feathers suffered only a 3.4 percent drop in their maximum speed. This corresponded to an 11 percent increase in energy needed to fly at high speeds.
For moderate and low speeds - the speeds at which hummingbirds typically flit from flower to flower and hover the long-tailed birds expended considerably less extra energy.
“I think that in most birds with long tails, the long tail is not costly,” said Clark.
“The energetic costs of a long tail are not high, but it remains to be seen if there are any benefits of a long tail, other than the indirect benefit of helping to pass on one’s genes,” he added.
The study is published in Proceedings of the Royal Society.Filed under News, SAP | Tags: California, Washington | Comment Below