Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Seeing magnetic fields

23.02.2004


It has long been known that migratory birds can make use of the earth’s magnetic fields to navigate. Birds read the angle that magnetic fields create on the ground and thereby determine how far north or south they are of the magnetic equator and the magnetic pole. But how do they do this? Is there some unknown “magnetic sense”? It seems that birds can actually see magnetic fields-providing the lighting conditions are right. Experiments on redbreasts carried out by a zoo-ecologist at Lund University in Sweden have shown at what light frequencies magnetic force lines appear.



In the early 1990s German scientists demonstrated that in green light birds could find their expected migratory route in relation to the magnetic field. But if the light was yellow or red instead, the birds went astray, taking off in random directions. These German researchers used light-emitting diodes. Rachel Muheim, at the Department of Ecology at Lund, has performed similar experiments but using fiber optics and filters, which yields a narrower and more controlled spectrum.
The classic experimental set-up for such experiments is a funnel-shaped cage where the birds cannot see the sky-birds also use the sun and stars for navigation purposes. Electronic sensors or colors on the walls reveal what route they would like to follow to get out of the cage. Rachel Muheim studied how redbreasts behaved in this situation when they were exposed to green, yellow-green, and red light.

“The birds could navigate in the right direction in low-intensity green light but not in yellow-green light. The frequency difference between green and yellow-green light is very small, which shows how sensitive these perceptions are,” says Rachel Muheim, and continues:



“In low-intensity red light there was a consistent deviation of roughly 60 degrees from the route. We think some of the photo receptors in the eye of the bird are sensitive to magnetism in the green sector of the spectrum. Other photo receptors in the red sector make the bird turn away from the migratory path. When both types of receptors are activated-for instance in yellow-green light-the redbreasts become disoriented.

“Redbreasts migrate during the night. At sunset, when the journey starts, there is low-intensity blue-green light in the parts of the sky that are furthest away from the sun.”

In 1999 Rachel Muheim took part in the Swedish Polar Research Secretariat’s expedition Tundra Northwest in the arctic area of Canada. Her dissertation also presents a study of how two species of North American sparrows behave near the magnetic North Pole. There the magnetic field lines are vertical, and the birds lose their orientation. But when the birds were transported eastward even a tiny degree differential in how the magnet field lines hit the surface of the earth could help the birds navigate. Rachel Muheim and her collaborators found that a differential of as little as 1.3 degrees was sufficient-that’s how sensitive the birds’ magnetic compass is.

Göran Frankel | alfa
Further information:
http://www.lu.se/info/pm/667_pressm.html

More articles from Life Sciences:

nachricht First line of defence against influenza further decoded
21.02.2018 | Helmholtz-Zentrum für Infektionsforschung

nachricht Helping in spite of risk: Ants perform risk-averse sanitary care of infectious nest mates
21.02.2018 | Institute of Science and Technology Austria

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

Im Focus: Hybrid optics bring color imaging using ultrathin metalenses into focus

For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.

But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...

Im Focus: Stem cell divisions in the adult brain seen for the first time

Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.

The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...

Im Focus: Interference as a new method for cooling quantum devices

Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters

Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

World's first solar fuels reactor for night passes test

21.02.2018 | Earth Sciences

Similarities found in cancer initiation in kidney, liver, stomach, pancreas

21.02.2018 | Health and Medicine

First line of defence against influenza further decoded

21.02.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>