Kyla Chamberlaine Physics 11A Mr Jennings Dec 12 th, 2005

How do birds find their way when they migrate? When they migrate, they use a combination of methods. Such as: Visual cues Solar navigation Magnetic fields Star navigation Polarized light There has been much evidence that magnetic fields play an important role in navigation.

Evidence

Wolfgang Wilschko’s study… Wolfgang Wiltschko showed that when European robins were exposed to a magnetic field in a laboratory, they oriented themselves to the artificial field. The homeing pigeon is also believed to have a magnetic sense. In the October 16, 1981 issue of Science, a group of German scientists observed that when homeing pigeons had strong magnets glued to their backs, the pigeons were disoriented and flew off randomly. With this knowledge they decided that the earths magnetic field serves as a primary navigation source.

Besides Wolfgang’s study other research has been done to prove this theory… Robert Beason did a study by: treating migrating bobolinks with magnetic pulses. The pulse reversed the polarity of the magnetite in their bodies and this made them hop northward instead of southeast like they would for fall. The same thing would happen if you did this to a compass.

Vision The other way that birds can detect magnetic fields is by vision. Beason studied the ways that bobolinks respond to lights. For example: Red: they became disoriented Green, blue, white: their sense of direction stayed the same. In these wavelengths the pigments are weak magnets. The light sensitive pigments in the birds eye’s serve as magnetic sensors. Without the blue, green or white light pigment molecules the bird will lose sense of direction.

More info… A lot of animals have the ability to sense geomagnetic fields, and use it as a compass. For example: salamanders and frogs use it to find a way to escape danger. Others migrate via the detection of the Earth’s magnetic field. Such as; sparrows, pigeons, yellow fin tuna, honeybees and bacteria. The three main ways that the animals perceive the geomagnetic field are: 1)Mechanical reception- like in a compass 2)Electric induction- movement in the magnetic field will lead to an induced electric field. 3)Chemical reception- the way they perceive magnetic feilds

Vision-Based Chemical Compass

Twice a year birds migrate thousands of kilometers. Song-birds do this at night. In order to find their way they must process a lot of cues, including the Earths magnetic field. These birds have a cluster of brain regions highly active only at night, it’s called “cluster N’. This may be integration vision mediated magnetic or star compass information for night time navigation. The navigation signals sensed are sensed and processed as the Earth’s magnetic field and or star-light constellations.

A few more facts Migrating birds stay on track because of chemical reactions influenced by the Earth’s magnetic field. These fields have no effect on materials such as magnetite indicating that the birds don’t rely on chunks of metal. There are tiny changes to the magnetically sensitive chemical reactions, probably occurring in the eyes of the birds.