European Robin (Erithacus rubecula)

European robin (Erithacus rubecula), is a small insectivorous passerine bird -- a chat that is now considered to be an Old World flycatcher. It is found across Europe, east to Western Siberia and south to North Africa. British robins are usually resident but a few, usually females, migrate to southern Europe during winter as far as Spain, while Scandinavian and Russian robins migrate to Britain and western Europe. These migrants can be recognised by the greyer tone of the upper parts of their bodies and duller orange breast. In autumn and winter, robins add to their usual diet of terrestrial invertebrates, such as spiders, worms and insects, berries, fruits or seeds. Despite their cute look, male robins show highly aggressive territorial behaviour not only attacking other males that stray into their territories, but also other small birds without apparent provocation.

While humanity is generally bedazzled by space exploration perceived as pushing new boundaries, I believe this planet contains the most inextricable mysteries of the Universe (unless there are more planets like earth), the great bulk of which is still beyond our ken -- after all Universe is a dark cold and deadly empty place. This tiny bird is one of such marvels -- like many other birds robins have the ability to sense the magnetic field of the earth for navigation which is affected by the light entering the bird's eye.
The physical mechanism of the robin's magnetic sense is not fully understood, some scientists even throw in theories like quantum entanglement of electron spins. There exist two main hypotheses to explain the phenomenon of magnetoreception in animals. One hypotheses holds that, cryptochrome, when exposed to blue light, becomes activated to form a pair of two radicals (molecules with a single unpaired electron) where the spins of the two unpaired electrons are correlated. The surrounding magnetic field affects the kind of this correlation (parallel or anti-parallel), and this in turn affects the length of time cryptochrome stays in its activated state. Activation of cryptochrome (a class of blue light-sensitive flavoproteins found in plants and animals. Cryptochromes are involved in the circadian rhythms of plants and animals, and in the sensing of magnetic fields in a number of species) may affect the light-sensitivity of retinal neurons, with the overall result that the bird can "see" the magnetic field. The Earth's magnetic field is only 0.5 Gauss and so it is difficult to conceive of a mechanism by which such a field could lead to any chemical changes other than those affecting the weak magnetic fields between radical pairs. (Cryptochromes are thought to be essential for the light-dependent ability of the fruit fly Drosophila melanogaster to sense magnetic fields.) According to another model, Fe3O4, also referred to as iron (II, III) oxide or magnetite, a natural oxide with strong magnetism remains permanently magnetized when its length is larger than 50 nm and becomes magnetized when exposed to a magnetic field if its length is less than 50 nm. In both cases the Earth's magnetic field produces a transducible signal via a physical effect on this magnetically sensitive oxide.

European robin (Erithacus rubecula). (by-nc-nd)