As if yesterday's magnets story was not enough, today we find that domestic chickens follow the Earth's magnetic field, much like many other bird species.

The story starts around 40 years ago when Prof. Dr. Wolfgang Wiltschko proved that migrating robins use the Earth’s magnetic field to direct themselves during migration. Their magnetic sensor showed them the course of the field lines of the Earth’s magnetic field, helping them decipher which direction is the pole and which direction is the equator. Since then, a compass of this kind has been found in more than 20 species of birds, the majority of them being those songbirds that undertake annual migration, and now chickens join the roost group.

To show this, newly hatched chicks were imprinted on a red ball which they from then on regarded as their ‘mother’ (I know it sounds cruel but it's not that bad, really). The researchers then hid the ball behind one of four screens, and taught the chickens by intensive training that the mother was always behind the screen that was in the northerly direction. To confuse the chickens, the researchers then set up an artificial magnetic field in an easterly direction (so East became the new North) and the chickens did actually seek their mother behind the screen that lay to the East. Finally, if the researchers used an oscillating magnetic field (i.e., one that comes and goes instead of staying steady), the chickens lose their orientation.

Why is this interesting? There are two key questions. Firstly, when did this evolve? Given the diversity of birds that have been shown to possess magnetic field orientation, the avian magnetic compass may have evolved in the common ancestor of all present-day birds to facilitate orientation within the home range. And since birds are really flying dinosaurs (yes, birds are direct descendants of dinosaurs!), it would be very interesting to figure out just how old this common ancestor is.

The second question is how do birds detect the magnetic field? In the beaks of chickens, iron-rich structures have been found, making them very likely candidates. However, the researchers showed that this area was most likely not involved in magentic orientation. This means that we still have work to do to find out what mechanism is used to detect magnetic fields.

The full paper is available freely, so go have a read. And if you get lost in all the science, it's OK to joke about headless chickens... just this once

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