Research pair uncover secret of hummingbirds' ability to fly in the rain (w/ Video)

Jul 19, 2012 by Bob Yirka weblog
Green Violetear at a flower. Image: Wikipedia.

(Phys.org) -- Hummingbirds are an interesting creatures. They dart around and fly like insects yet because they are warm blooded and cute, they inspire smiles in most who watch them. What’s not so cute is watching an Anna hummingbird (Calypte anna) try to feed on the nectar in a flower during a heavy rain. Because the birds are so small, big rain drops, typical in the South American rain forest in the eastern Andes where they live, tend to look like liquid boulders dropping from the sky. Worse still is the additional weight the birds must carry as the raindrops make them wet. Still, the birds manage to work it out due to necessity.

Because of their small size and rapid wing beating, they have a very high metabolism rate that requires very frequent meals. To find out how they manage to fly in the rain, Victor Manuel Ortega-Jimenez and Robert Dudley from the University of California, working with the Smithsonian Tropical Research Institute, set the tiny birds in a clear plastic box, doused them with varying degrees of simulated rain and filmed the whole thing with a high speed video camera. They found, as they report in their paper published in the Proceedings of the Royal Society B, that the birds cope, mostly by changing their posture and working harder.

This video is not supported by your browser at this time.
This video shows 'light-to moderate' and 'heavy' drop impacting a wing. This research was published in the journal Proceedings of the Royal Society B in the paper: Flying in the rain: hovering performance of Anna's hummingbirds under varied precipitation by Victor Manuel Ortega-Jimenez and Robert Dudley.

The two researchers filmed the birds undergoing simulated rain showers of various degree: light, moderate and heavy, and also with no rain at all to compare against. They found that under light or moderate rain conditions, the birds seemed to hardly notice the rain at all and flew much the same way as when conditions were dry. But when they turned up the tap, producing a lot of rain, the birds were forced to change tactics. They picked up the number of wing beats per second and adjusted their bodies into a more horizontal stance. They also raised and lowered their wings less.

At first the researchers were confused by the birds’ actions, as a horizontal posture would mean more body area being bashed by the drops. But then, after watching the video over and over, they noted that in a more horizontal position, the birds were better able to adjust the angle of attack of their wings, and doing so also tended to reduce the amount of that actually struck their wings. Changing position then, appears to give the more power while still expending as little as nine percent more energy. The end result is a tiny bird that is able to fly and feed in all but the most torrential downpours.

Explore further: Rare Sri Lankan leopards born in French zoo

More information: Flying in the rain: hovering performance of Anna's hummingbirds under varied precipitation, Proceedings of the Royal Society B, Published online before print July 18, 2012, doi: 10.1098/rspb.2012.1285

Abstract
Flight in rain represents a greater challenge for smaller animals because the relative effects of water loading and drop impact are greater at reduced scales given the increased ratios of surface area to mass. Nevertheless, it is well known that small volant taxa such as hummingbirds can continue foraging even in extreme precipitation. Here, we evaluated the effect of four rain intensities (i.e. zero, light, moderate and heavy) on the hovering performance of Anna's hummingbirds (Calypte anna) under laboratory conditions. Light-to-moderate rain had only a marginal effect on flight kinematics; wingbeat frequency of individuals in moderate rain was reduced by 7 per cent relative to control conditions. By contrast, birds hovering in heavy rain adopted more horizontal body and tail positions, and also increased wingbeat frequency substantially, while reducing stroke amplitude when compared with control conditions. The ratio between peak forces produced by single drops on a wing and on a solid surface suggests that feathers can absorb associated impact forces by up to approximately 50 per cent. Remarkably, hummingbirds hovered well even under heavy precipitation (i.e. 270 mm h−1) with no apparent loss of control, although mechanical power output assuming perfect and zero storage of elastic energy was estimated to be about 9 and 57 per cent higher, respectively, compared with normal hovering.

Related Stories

Why does rain keep bats grounded?

May 05, 2011

(PhysOrg.com) -- In a new study published in Biology Letters, researcher Christian Voigt from the Leibniz Institute for Zoo and Wildlife Research in Germany details their findings on Sowell’s short-tailed bats a ...

Are some rainforests too rainy?

Apr 08, 2010

(PhysOrg.com) -- Tropical birds migrate to escape the weather While some bird species migrate thousands of miles annually, others follow a much shorter migratory route - specifically, up and down tropical Costa Rican mountains.

Bird rest stops to be tracked by NASA rain radar

Jun 08, 2012

(Phys.org) -- At sunset on a spring night, tree-dwelling songbirds take off in a flurry of wings from the lower Delmarva Peninsula near Oyster, Va. The peninsula is a temporary home to hundreds of species ...

Birds: Soaring is better than flapping

Dec 08, 2010

Large birds, such as storks, save energy on the flight to their wintering grounds by soaring through the air on thermal currents. Until now, however, we knew nothing about the flight patterns of small migrating ...

China has its worst spell of acid rain

Sep 22, 2006

China had its worst spell of acid rain in August with Beijing among the hardest hit, the China Meteorological Administration said Friday.

Recommended for you

'Killer sperm' prevents mating between worm species

11 hours ago

The classic definition of a biological species is the ability to breed within its group, and the inability to breed outside it. For instance, breeding a horse and a donkey may result in a live mule offspring, ...

Rare Sri Lankan leopards born in French zoo

14 hours ago

Two rare Sri Lankan leopard cubs have been born in a zoo in northern France, a boost for a sub-species that numbers only about 700 in the wild, the head of the facility said Tuesday.

Researcher reveals how amphibians crossed continents

16 hours ago

There are more than 7,000 known species of amphibians that can be found in nearly every type of ecosystem on six continents. But there have been few attempts to understand exactly when and how frogs, toads, ...

User comments : 0