While we are all missing our ospreys. I thought I would take the time to learn more about the migration process and try to imagine what ospreys must experience when they are not breeding in Scotland. This got me digging into a treasure trove of migration techniques that probably don’t even scratch the surface on this amazing feat undertaken by birds each year. If we step right back in time, some of the earliest explanations are the most intriguing. People used to believe that barnacle geese came from barnacles as they didn’t see them over winter! We have come a long way since then. With the improvements in technology we have been able to track more birds on migration and even find specific genes that increase our understanding on the elusive subject.
The first thing that has really changed in the past couple years has been a revolutionary discovery on how birds migrate. For a long time there has only ever been theories on what birds are doing. The most obvious ones is that birds are migrating through visual ques from the landscape. As they fly high up on a clear day you can imagine them seeing the Firth of Forth and registering that they are almost home on their way up the A9. This however would not help them on very cloudy days.
It was also theorised that ospreys would be using the stars to align themselves. By checking their star signs, they would be able to know what lies ahead of them in the future. As the north star is always sedentary in the sky, this allows many birds the ability to orientate themselves north and south. This might not help you during the day when all the stars disappear. Some birds prefer flying at night because it is safer to travel away from the eyes of predators. Birds like ospreys however want to take advantage of the thermals on their journey, which are not present during an evening voyage.
The most widely believed theory was that birds were using magnetite present in their beaks that act like a compass. Pigeons have been found to have a large concentration of magnetite in their beaks and are famously great at finding their way home. This has however been shown to only be a small part of the puzzle. The thinking behind the magnetite in beak is that it is used to be able to sense higher concentrations within the magnetic field and could be used for more than just migration. However more recently it has been thought that it might not be their beaks sensing, so much as their eyes seeing.
In 2018 scientist had been looking at a protein that is present in the eyes of birds named CRY4, specifically robins and zebra finches. This protein was shown to increase in the birds leading up to and during migration. This protein is thought to allow birds to see magnetic fields around the earth. It is thought that the CRY4 protein can process the direction of blue light waves into the eye, and in turn, creates a visual compass overlaid on the natural sight of the bird. So even when its cloudy or dark, there is still enough light to navigate.
This amazing discovery is still in its infancy and could only still be a part of the puzzle. Ospreys, like most birds will be able to use a combination of all these techniques on their migration. Every year they make that 4000-mile journey to Africa to escape the cold and feed up for another breeding season. I am sure I am not the only one thinking about eating fresh fish on the Senegalese coast at this time of year. Think I would still struggle to get there even with smart phone navigation though...
Hope you have enjoyed learning this as much as I have. Let me know if you heard of any other strange tales around migration.
Hi Fergus, very interesting indeed, we still have lots to learn.