Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Small birds' vision: Not so sharp but superfast

21.03.2016

One may expect a creature that darts around its habitat to be capable of perceiving rapid changes as well. Yet birds are famed more for their good visual acuity. Joint research by Uppsala University, Stockholm University and the Swedish University of Agricultural Sciences (SLU) now shows that, in small passerines (perching birds) in the wild, vision is considerably faster than in any other vertebrates -- and more than twice as fast as ours. The new research findings are published today in PLOS ONE.

In behavioural experiments, the scientists have studied the ability to resolve visual detail in time in three small wild passerine species: blue tit, collared flycatcher and pied flycatcher. This ability is the temporal resolution of eyesight, i.e. the number of changes per second an animal is capable of perceiving. It may be compared to spatial resolution (visual acuity), a measure of the number of details per degree in the field of vision.


The video clip visualizes one advantage of the ultra rapid vision discovered in birds. The almost three times faster refreshment rate of visual input in a pied flycatcher than in a human makes it far easier to track and predict the flight paths of two blue bottle flies. This is most likely a crucial ability for a bird that catches its airborne prey on the wing.

Credit: Malin Thyselius

The researchers trained wild-caught birds to receive a food reward by distinguishing between a pair of lamps, one flickering and one shining a constant light. Temporal resolution was then determined by increasing the flicker rate to a threshold at which the birds could no longer tell the lamps apart.

This threshold, known as the CFF (critical flicker fusion rate), averaged between 129 and 137 hertz (Hz). In the pied flycatchers it reached as high as 146 Hz, some 50 Hz above the highest rate encountered for any other vertebrate. For humans, the CFF is usually approximately 60 Hz. For passerines, the world might to be said to be in slow motion compared with how it looks to us.

It has been argued before, but never investigated, that small and agile wild birds should have extremely fast vision. Nevertheless, the blue tits and flycatchers proved to have higher CFF rates than were predicted from their size and metabolic rates. This indicates an evolutionary history of natural selection for fast vision in these species.

The explanation might lie in small airborne birds' need to detect and track objects whose image moves very swiftly across the retina -- for blue tits, for example, to be able to see and avoid all branches when they take cover from predators by flying straight into bushes. Moreover, the three avian species investigated all, to a varying degree, subsist on the insects they catch. Flycatchers, as their name suggests, catch airborne insects. For this ability, aiming straight at the insect is not enough. Forward planning is required: the bird needs high temporal resolution to track the insect's movement and predict its location the next instant.

The new results give some cause for concern about captive birds' welfare. Small passerines are commonly kept in cages, and may be capable of seeing roughly as fast as their wild relatives. With the phase-out of incandescent light bulbs for reasons of energy efficiency, tame birds are increasingly often kept in rooms lit with low-energy light bulbs, fluorescent lamps or LED lighting. Many of these flicker at 100 Hz, which is thus invisible to humans but perhaps not to small birds in captivity. Studies have shown that flickering light can cause stress, behavioural disturbances and various forms of discomfort in humans and birds alike.

Of all the world's animals, the eagle has the sharpest vision. It can discern 143 lines within one degree of the field of vision, while a human with excellent sight manages about 60. The magnitude of this difference is almost exactly the same as between a human's top vision speed and a pied flycatcher's: 60 and 146 Hz respectively. Thus, the flycatcher's vision is faster than human vision to roughly the same extent as an eagle's vision is sharper. So small passerines' rapid vision is an evolutionary adaptation just as impressive as the sharp eyesight of birds of prey.

Anders Ödeen, the lecturer at Uppsala University's Department of Ecology and Genetics who headed the study, puts the research findings in perspective.

'Fast vision may, in fact, be a more typical feature of birds in general than visual acuity. Only birds of prey seem to have the ability to see in extremely sharp focus, while human visual acuity outshines that of all other bird species studied. On the other hand, there are lots of bird species similar to the blue tit, collared flycatcher and pied flycatcher, both ecologically and physiologically, so they probably also share the faculty of superfast vision.'

###

Jannika Boström, Marina Dimitrova, Cindy Canton, Olle Håstad, Anna Qvarnström, Anders Ödeen (2016) Ultra-rapid Vision in Birds, PLOS ONE

Link to manuscript once it goes live: http://dx.plos.org/10.1371/journal.pone.0151099

Media Contact

Anders Ödeen
Anders.Odeen@ebc.uu.se
46-703-015-262

 @UU_University

http://www.uu.se 

Anders Ödeen | EurekAlert!

More articles from Life Sciences:

nachricht Researchers develop eco-friendly, 4-in-1 catalyst
25.04.2017 | Brown University

nachricht Transfecting cells gently – the LZH presents a GNOME prototype at the Labvolution 2017
25.04.2017 | Laser Zentrum Hannover e.V.

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

NASA's Fermi catches gamma-ray flashes from tropical storms

25.04.2017 | Physics and Astronomy

Researchers invent process to make sustainable rubber, plastics

25.04.2017 | Materials Sciences

Transfecting cells gently – the LZH presents a GNOME prototype at the Labvolution 2017

25.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>