Chickens with magnetic sense

Not only migrant birds are based on the magnetic field of the earth

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Until now it was believed that the ability to orientate itself on the magnetic field of the earth was reserved for migrating birds. But now ornithologists have found out that even domestic chickens have a built-in compass. Apparently the magnetic sense of direction in birds has already developed at an early stage of evolution. The common ancestor of today's birds probably served the earth's magnetic field to better navigate their habitat.

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40 years ago, Wolfgang Wiltschko, a professor at the University of Frankfurt, showed for the first time that robins use the bird's pull to align themselves with the earth's magnetic field. The magnetic sensor gives them the course of the field lines of the Earth's magnetic field. This results in an inclination compass, which responds to the inclination of the earth's magnetic field to the surface of the earth, thus distinguishing between "poleward", the side on which the field lines are down, and "equatorial", where they are inclined upwards.

In addition, the built-in compass is very finely tuned to the field strength of the local Earth's magnetic field, but it can flexibly adjust to other field strengths that migratory birds encounter on their flight. Meanwhile, one has discovered such a compass in more than 20 species of birds, with the vast majority is one of the songbirds that make annual migrations as migratory birds.

Experiment with artificial magnetic field

Now, an international working group under the leadership of the couple Wolfgang and Roswitha Wiltschko has succeeded in proving a magnetic sense of direction in the domestic chicken as well. Newly hatched chicken chicks were coined on a red ball, which they considered from then on as their "mother". The researchers now hid the ball behind one of four umbrellas and taught the chicks through training that the "mother" was always behind the screen in a northerly direction. To prove that the chicken detects this direction with its magnetic sense of direction, the researchers set up an artificial magnetic field in an easterly direction. And indeed, the chicks were looking for their "mother" behind the screen that lay to the east. display

Sensor sits in the eye

Further experiments showed that the magnetic sensor of the chickens works quite similar to that of the robins. It also responds to the inclination and local field strength of the Earth's magnetic field. The magnetic sensor probably has its seat in the eye, because the birds need short-wave light (for example, blue light) in order to be able to orient themselves. In long-wave light beyond the yellows, this ability is lost to all previously studied birds.

The research group concludes from these similarities that magnetic sense of direction could be a common feature of all birds. Since it takes a long time in evolutionary history to find a common ancestor of chickens and robins, this ability must have been established before the birds began to pull. Thus, the magnetic sense of direction has already helped the primitive birds to move quickly in their habitat between their nest, the sleeping place, food and water sources.

(University of Frankfurt (Main), 03.07.2007 - NPO)