Disclaimer: None of the images used in this article belong to me. All of them were found on the internet.
Many times, I find myself glancing up at the sky only to find a group of birds soaring up above me. They are no more than tiny black specks against the azure sky, flying in a perfect “V” formation. I’d marvel at their perfect arrangement and wish them good luck on their journey.
Now I know these birds are migrating due to the change of season. They travel across the globe to escape bad weather, find better feeding grounds and nest. But how do they do this? And how did we figure this out?
In ancient times, people would wonder where all the birds went during certain times of the year. They’d look out their windows and find that birds, which are at times s plentiful, suddenly disappear, leaving no clue as to where they went.
Many theories sprang up to account for these disappearances. Some suggested that birds transformed into other species, like other birds or even plants, animals and human beings. Others said that birds retreated to lakes, saying they hibernated at the bottom. Few even believed that they had travelled to the moon.
One of the first clues about bird migration came when Count Christian Ludwig Von Bothmer shot down a stork over his castle grounds in Germany. He found that the bird he shot down was impaled by a spear, which a local professor determined to be of African origin. The animal was speared in Africa, somehow survived, and flew all the way to Germany before being gunned down (watch this video).
Bird Ringing and Tagging
To get to the bottom of the migration riddle, Professor Johannes Thienemann began attaching metal rings to the legs of 2000 storks. Each ring contained a serial number. Then, Professor Thienemann spread the word across, hoping that if any of the tagged birds were recaptured or killed, the location and other details would be mailed to him. This way, he plotted the first migration route discovered.
Now bird ringing is conducted to this day, with researchers collaborating from all over the globe. This monumental effort gave them unique insight into this otherwise hazy area of bird ecology.
I travelled to Point Calimere in Tamil Nadu, India, to witness the ringing of shore birds by Dr S. Balachandran. I observed how he and his team captured, measured and tagged scores of shore birds. I even assisted them in securing the birds and recording the data. Each bird was fitted with an aluminium ring, a serial number engraved, and a plastic-coloured flag. The flag could be seen from quite a distance away, allowing the researchers to know whether the animal in sight had been tagged or not.
Each individual bird’s measurements were taken, and its data was recorded with its corresponding serial number. So if the bird is recaptured, the scientists can compare its health status across the years.
But while rings give us the end locations of a bird’s migratory path, they tell us nothing about its journey. To address this, scientists have started fitting birds with transmitters that broadcast the birds’ location to nearby satellites.
But the problem with transmitters is that they are big and heavy. Small songbirds cannot be studied using this method.
Luckily, scientists have found a way around this problem as well. They realised that they needn’t use satellite tracking altogether. They merely needed to fit birds with a light recorder, a clock and a memory chip, an apparatus that weighed less than a raison. This would record the light levels at periodic intervals in the day. So then, when the birds were recaptured, scientists could use ancient navigational technology to figure out the bird’s location during the day. (watch this video)
When looking at static locations on a map, many assume that birds fly linearly between them “as the crow flies”. But the reality is that they zigzag along their path, travelling much more than need be. The reason they do this is to harness the earth’s wind currents. Migration is quite taxing; thus, they utilise the wind to its maximum.
Prior to these journeys, birds are known to consume excessively, to put on as much weight as possible. They lose weight tremendously during their trip. Pictures and data of birds before and after migrations show a dramatic loss in weight.
How do Birds Migrate?
Different species use different means of figuring out how to reach their desired destination. Some navigate using the stars, while others use daylight. Scientists even suspect that birds use the earth’s magnetic field. With the tiny amounts of iron in their eyes and beaks, they detect the earth’s magnetic force and use it to guide their trajectory(watch this video).
While flying, many assume a “V” formation. When a bird flies through the air, the movement of its wings creates vortex’s in the air. So by flying diagonally behind a bird, its fellow avians save on their energy reserves. The vortex created by the first bird’s wing movement gives all the bird’s behind it some extra lift.
But how do birds know when to migrate?
By sensing changes in the weather, temperature and food availability, birds determine when to begin their migratory odysseys.
But climate change is upending all of that.
Trouble in Migration Patterns
As the world heats up due to global warming, we are noticing a change in migration patterns worldwide. Birds are moving around a lot earlier than usual. Months where the air would typically be devoid of certain birdcalls now ring with them. This is indicative of how the world’s climatic conditions are being altered.
With increased industrialisation, birds are finding their migrations all the more arduous. Many birds often use rest stops during their journeys. Locations that were forests or grasslands only a year ago are now covered by sprawls of buildings and farmland. Lakes are more polluted than before, forcing birds to continue on their expeditions instead of taking a break.
Structure collision is a growing issue for migratory birds. High-rise buildings pose a direct blockade in the path of migratory birds. Since many of them are small and can’t fly at high altitudes, they must weave through thousands of buildings. Many of them collide with these edifices and die. (watch this video). Light pollution and landscape alteration also affect the bird’s ability to navigate correctly.
Birds undergo these daunting quests every year. These tiny animals don’t get enough of the credit they deserve. Just imagine traversing entire continents by yourself in the span of a few days. They are a wonder of nature, and I can only hope they can continue to do so in our ever-changing world.
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2 thoughts on “Bird Ringing and Tagging – Studying Migratory Birds”
I also had the opportunity to meet and see Dr. Balachandran at work in Point Calimere. What a coincidence!
Oh wow! Well then you and I both know what an inspiration he is!