In 2019, are we now in a position to answer one of the trickiest questions regarding osprey migration?

The majority of the questions we get asked at the beginning of each season follow a similar theme. The annual migration our ospreys undertake each season is a topic of fascination to everyone, largely due to the mystery surrounding it. How do they know where to go? And when?

We all love a story of unknown lands, resilience against hardship and adversity; the journeys these amazing animals take capture the spirit of this perfectly.

Ceulan wings his way to Senegal in 2012

But evidence from surprising places is beginning to shed some light on these mysteries. The answers are also proving to be far stranger than anyone could have imagined and it stands as an example of how surprisingly relevant seemingly unrelated fields of study often prove to be.

How do Ospreys know when to migrate?

How many eyes does a lizard have? Three. That’s right, three! Well sort of at least.

On most lizard foreheads is a small transparent scale called a Pineal eye which appears to allow light to travel all the way through the skull and reach the brain! Neuroscience has known about the epithalamus (a part of the dorsal forebrain) for many years but it has recently been shown to be light sensitive, and guide lizards to the best basking spots and time of day for basking. The Pineal eye is very common in vertebrates, appearing in fish, sharks, frogs, newts, snakes and lampreys.

Birds lack this third eye, instead developing thin skull cases that allow light through to the epithalamus (this also makes them light for flying). There must be many reasons why Monty always manages to return home consistently in the first week of April.

Living in the natural environment surely means he is more in tune with seasonal changes such as varying wind directions, temperature and precipitation for example. However, it is becoming increasingly more evident that the slight change in daylight hours, even in sub-Saharan Africa, is enough to be sensed by the epithalamus of an osprey, urging the bird to begin its migration.

Monty uses changing day lengths as one way of deciding when to migrate

How do Ospreys know where to go to?

So this is going to get a tiny bit complicated, I’m not even sure if I fully understand this.... I’m just a simple Ecologist who likes to play in the mud! I’m afraid I am going to write briefly about quantum mechanics. But bear with me, we will get through this together.

Quantum entanglement is when subatomic particles like electrons are spookily bonded to one another. Put simply, if one bonded particle is made to wobble, the other particle will instantly wobble too - even if this other particle is taken HUNDREDS of miles away from the other (new experiments show this bond could exist when separated by time).

Please stay with me... it’s worth it!

Certain molecules produce these bonded particles in the eye pigments of migratory birds such as robins, who make short migrations from Scandinavia to the UK every the winter. These bonded particles are affected by movement through the magnetic field, meaning ospreys can likely literally see magnetic North!

This is how a migratory bird likely perceives North (Source here):

It is often said facts like these take something away from the beauty and mystery of nature that makes it so appealing to begin with in the first place. However, I find the fact a bird such as a whooper swan can hack into an invisible global force produced by the earth's molten core and travel 1,000 miles in 12 hours, using quantum mechanics that Nobel Prize winners have failed to truly understand, humbling and enthralling.

Whooper swans in the Glaslyn Valley getting ready for a non-stop flight to Iceland in early April

But there are a lot of questions that remain unanswered. How do so many newly fledged birds make it back to the Dyfi Valley after two or three years abroad? Why do some ospreys reach Spain/Portugal and stay there whereas the vast majority of UK birds continue on to West Africa?

And how do ospreys 'know' where to go at all? Their parents didn't tell them did they? Or did they....

Isn't passing on 73 pairs of chromosones - genetic information - tantamount to "telling them"?

There is always more to know and learn; the answers might appear in the most unlikely fields of study - be it physics, neuroscience or a completely unrelated scientific discipline.

P.S The words Mechanics and Quantum will never be uttered in the same sentence on this site again, I promise.

Ceulan: How a three month-old Dyfi osprey travelled 3,000 miles in 11 days: