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 Nanoparticle Exposure Can Awaken Dormant Viruses in the Lungs
16.01.2017 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt

nachricht Cholera bacteria infect more effectively with a simple twist of shape
13.01.2017 | Princeton University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

Im Focus: Bacterial Pac Man molecule snaps at sugar

Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.

The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

Satellite-based Laser Measurement Technology against Climate Change

17.01.2017 | Machine Engineering

Studying fundamental particles in materials

17.01.2017 | Physics and Astronomy

Multiregional brain on a chip

16.01.2017 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>