Navigation of Migratory Birds:

I still remember that day I visited New York for the first time in my life. My friend helped me with clear directions to the nearby bus-stop in the morning but, I lost my way back home from the bus-stop that night.

I'm sure we all have such experience losing directions in not so familiar routes which are quite normal. Surprisingly, birds, intellectually inferior to humans, realize when winter approaches and understand the fact that they may not get food during such adverse conditions and migrate to more habitable places during winters.

Such birds move from South pole to North pole and vice versa for thousands of miles for survival, these are referred to as Migratory Birds. You could find abundant sightings of such birds in the Bird Sanctuary, the most interesting fact about these birds is every time they migrate they arrive at the same place after travelling thousands of miles and fly back home after few months, they follow almost the same path during every migration, there is something even more surprising... even the first-timers, rookies or amateurs migrate from South to North pole and vice versa without any special assistance!

Scientists have conducted extensive research to study these birds' ability to find directions, as an outcome of their research, they concluded these birds may possess some kind of built-in navigation system in their eyes. You will be surprised to know what powers this built-in navigation system... Quantum mechanics !!!

Do birds have their own built-in GPS system:

It is essential to recall a key concept related to Magnetism using a simple experiment before we try to understand the working of this navigation system.


   Take a magnet and place a piece of white paper over it. After sprinkling tiny iron particles over it... you will be able to see the particles arranged in concentric circles from the North pole of the magnet to its South pole, these lines are called Magnetic field lines, these Magnetic field lines are present in all magnets but not visible to human eyes, there is another concept in magnetism that tells Earth is a huge magnet by itself and that is the reason the needle of a Magnetic compass always points to the North pole, in that case, the Earth, being a huge magnet, must have Magnetic field lines too, what if these Magnetic lines were visible to our naked eyes?! we could travel from North to South pole and vice versa at ease following these lines without help from GPS (Global Positioning System).

Now getting back to Migratory birds, scientists suspect these Magnetic lines may be visible to their eyes How?! let's try understanding this using a simple illustration,

   Imagine a Helium atom. we know it has 2 electrons and we have been taught that these 2 electrons revolve around the Nucleus in a fixed orbit. However, in reality, it isn't exactly accurate. This model was proposed for us to comprehend the idea easily. To be more precise, the electrons in real are around the Nucleus like a cloud formation therefore, from a Quantum mechanics point of view, these electrons share the orbit rather than revolving around it.

A well-known fact about electrons is they are negatively charged particles but a less known fact is they possess a magnetic moment called "Spin", for a Helium atom to possess 2 electrons, these electrons must satisfy a basic rule stated in the Pauli Exclusion Principle. According to this principle, both these electrons must possess their spin directions opposite to each other, to be more clear, if electron 1 spins up then electron 2 is supposed to spin down, technically, the electrons must be in an entangled state. To summarize, electrons sharing an orbit must be in an entangled state.


Suppose, we manage to separate these electrons and make their spins parallel to each other, then these 2 electrons will never be able to share an orbit according to the Pauli Exclusion Principle. Let's see how this principle is related to bird navigation.

Scientists have discovered a complicated molecule in the retina of migratory birds which is connected to the bird's optical nerve system, we know molecules are made up of atoms and also electrons share orbits inside atoms. Assume this pair of electrons shares an orbit inside the atom, when a stream of light or Photon comes in contact with this pair, these electrons could separate due to the energy in the Photon. After the separation, there are possibilities for their spin direction to change due to the influence of the Earth's Magnetic Field. Let's say their spin directions do not get affected by the Earth's Magnetic Field then, these electrons will again be able to get paired up and share the orbit as per the Pauli Exclusion Principle. After pairing up, the energy they gained from photon will be released which stimulates the bird's optical nerve. On the other hand, if the spin directions of the separated electrons become parallel to each other due to the Earth's Magnetic Field, that is, if they lose their entangled state then they can never pair up again eventually giving no stimulus to the bird's optical nerve.

So, based on the influence of the Magnetic field in the direction the birds fly determines whether or not they receive the optical stimulus. It is based on this concept scientists have proposed the idea that birds navigate using Earth's magnetic lines from South to North pole and vice versa.

As of today, this idea stands just like the best possible explanation and hasn't been scientifically proved yet. Also, Electromagnetic noise or Electromagnetic interference coming out of mobile phone towers can affect bird's navigation system, this Electromagnetic noise is a primary reason for the significant decline in sparrows population in urban areas.

Want to know the science behind birds flying in a 'V' formation in groups? I will be doing a separate post to explain this phenomenon, so please follow us.

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