Of all the birds in the animal kingdom, only hummingbirds can fly in multiple directions.
A day like any, nir sapir He was on the balcony of his house when he observed something that caught his attention. She noticed that hummingbirds that go to a feeder fly in various directions, including reverse, and that they do so at great speed.
Sapir is a evolutionary biologist and researcher of the University of Haifa and after several months observing the hummingbirds in his house, he decided to properly study this flight mechanism. So he met Robert Dudley of the University of California to do research together.
However, when Sapir explored the scientific literature on the matter, he found that there were virtually no studies on reverse flight.
“This surprised me a lot considering that they fly backwards all the time, so I decided to study how they do it and what consequences this type of flight has on their metabolism,” said Sapir.
Dudley and Sapir used high-speed cameras to observe the flight of 5 captive hummingbirds. they placed a flower shaped syringe with sucrose inside a wind tunnel and right to one side, the camera. Then they manipulated the breeze to make the birds fly in different directions.
back flight
The hummingbirds chosen for the study are of the species calypte anna, whose most conspicuous feature is its bright red head. In America there are about 350 species hummingbird, and it is one of the smallest birds in the world. They measure between 10 and 13 centimeters and his weight is between 4 and 6 grams.
According to Sapir, these small birds visit flowers to feed every two minutes. This is due to their fast metabolism, since they need a lot of food since they consume a lot of energy.
The five hummingbirds in the study entered the wind tunnel one by one to feed from the sugar syringe. The scientists then activated air currents that altered the position of the syringe to force the birds to use different flight strategies. Then, high-speed cameras (220 fps) captured the movement of the hummingbirds.
They observed the body posture of the bird, the tilt of their wings when it flew forwards, backwards or stayed in the same place. In addition, the scientists measured the oxygen consumption well they wanted quantify flight efficiency regarding the oxygen the bird needed while feeding and changing its flight strategies.
unique ability
The study was published in the journal Journal of Experimental Biology and the most important result has to do with energy consumption.
They first noticed that hummingbirds have the ability to fly in all directions: up, down, forward and reverse; they can even stay in one place. This factor was decisive because they were able to measure the energy consumption with respect to each type of flight.
The most impressive discovery is that reverse flight consumes a similar amount of energy as normal flight.
Also, according to Sapir, flying backwards is even more efficient to stay at the same point. Another detail is that these birds keep their bodies much straighter when they fly backwards. Scientists also found that hummingbirds fly backwards. when they move away from the flower from which they have just fed.
“The results of the experiment surprised us, because we expected that reverse flight would have a much higher metabolic cost,” Sapir said.
They also noted that air resistance in backward flight is slightly older with respect to forward flight. This is because the speed decreases when the hummingbirds they fly backwards.