Small birds have more efficient wing strokes than bats

February 5, 2018, Lund University
House finchnigel. Credit: Wikimedia Commons

Small birds are more energy-efficient than bats when flying. Researchers previously believed this was due to air resistance created by the bats' ears. However, biologists at Lund University in Sweden have now discovered another reason.

When in their most elevated position, the wings of small interact in a completely different way compared to the wings of . As the birds flap their wings downwards, they create a single large air vortex ring behind themselves rather than two small ones.

"This makes the airflow slower and the aerodynamics less energy-demanding. This in turn means that birds are more suitable for flying than bats," says Christoffer Johansson, biologist at Lund University.

According to him, the new results should be incorporated into existing models of how much energy birds consume when they fly. Among other things, these models are used to calculate how far birds can migrate.

The results are based on studies of the European pied flycatcher flying in the Lund University's wind tunnel while the researchers studied the movements of the air behind the bird.

Although the researchers have shown how the interaction of the small birds' wings makes them efficient flyers compared to bats, the birds are far from being perfect little "flying machines." The researchers found that European pied flycatchers (and probably all other small birds as well) tilt their bodies backwards when flying at low speed. The tail is lowered and the head is raised. This leads to increased energy consumption.

"The technique increases the force generated by the wings – as when aeroplanes go in for landing. For birds, which don't have any engines, tilting the body is also about having the resulting force point in the right direction. This results in more body resistance and increased ," says Christoffer Johansson.

Explore further: The pros and cons of large ears for bat species

More information: L. Christoffer Johansson et al. Mechanical power curve measured in the wake of pied flycatchers indicates modulation of parasite power across flight speeds, Journal of The Royal Society Interface (2018). DOI: 10.1098/rsif.2017.0814

Related Stories

Bats' flight technique could lead to better drones

May 4, 2016

Long-eared bats are assisted in flight by their ears and body, according to a study by researchers at Lund University in Sweden. The recent findings improve researchers' understanding of the bats' flying technique and could ...

Winging it: How do bats out-maneuver their prey?

July 5, 2017

Bats catch food 'on the wing' without touching the ground, but how do they do it? A new study by Per Henningsson at Lund University, Sweden is the first of its kind to analyse the aerodynamics of bats performing manoeuvers ...

New study changes view on flying insects

September 29, 2017

For the first time, researchers are able to prove that there is an optimal speed for certain insects when they fly. At this speed, they are the most efficient and consume the least amount of energy. Corresponding phenomena ...

Jackdaws flap their wings to save energy

August 11, 2017

For the first time, researchers have observed that birds that fly actively and flap their wings save energy. Biologists at Lund University in Sweden have now shown that jackdaws minimise their energy consumption when they ...

Recommended for you

A world of parasites

May 25, 2018

Alex Betts, Craig MacLean and Kayla King from the Department of Zoology, shed light on their recent research published in Science, which addressed the impact that parasite communities have on evolutionary change and diversity.

Bumblebees confused by iridescent colors

May 25, 2018

Iridescence is a form of structural colour which uses regular repeating nanostructures to reflect light at slightly different angles, causing a colour-change effect.

A better B1 building block

May 25, 2018

Humans aren't the only earth-bound organisms that need to take their vitamins. Thiamine – commonly known as vitamin B1 – is vital to the survival of most every living thing on earth. But the average bacterium or plant ...

Plant symbioses—fragile partnerships

May 25, 2018

All plants require an adequate supply of inorganic nutrients, such as fixed nitrogen (usually in the form of ammonia or nitrate), for growth. A special group of flowering plants thus depends on close symbiotic relationships ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.