This is made possible by a special energy storage mechanism in their bodies and the way they choose to move, similar to marathon runners.
Some bird species, including the Arctic Tern, can travel more than 30,000 km each year.
The Arctic Tern is a monogamous bird; after the breeding season, it migrates south to Antarctica. (Photo: Shutterstock).
Botanists have nicknamed this bird the “Champions of Migration.” The Arctic Tern weighs just over 100 grams on average and migrates from one pole to the other each year.
These birds live in pairs, breeding in the summer in the Northern Hemisphere, and when winter arrives in the Arctic, they migrate south to Antarctica in flocks.
To put it simply, these birds fly towards sunlight in a literal sense, aiming to escape the cold of the Antarctic winter. These migrations include a direct flight of over 8,000 km across the Indian Ocean.
Where do birds get energy for their journey?
Most animals primarily metabolize various carbohydrates and glucose to fuel their energy needs.
However, studies reveal that birds metabolize fats, converting lipids into fatty acids as their energy source.
Before migration, birds enter a hyperphagic state, consuming a diet rich in fats. In fact, it has been noted that certain birds can double their body weight before each migration.
Yet, merely eating more cannot solely explain their rapid weight gain. These birds also excel at absorbing nutrients from their food.
The fat they store can account for 50-60% of their body weight. The fat is stored in fat cells located just beneath their skin.
Bird fat cells can store up to 95% of their volume as fatty acids. They can also store fat in non-muscle tissues and in the liver (similar to glycogen storage).
Additionally, birds can store fatty acids in the liver, which are then converted into triglycerides. These triglycerides are transported out of the liver as VLDL (very low-density lipoprotein), which contains cholesterol (10%), triglycerides (70%), proteins (10%), and other fats (10%).
The Albatross glides and flies over water surfaces to conserve energy. (Photo: Shutterstock).
They oxidize fats to provide energy for their wing muscles to enable flight, which is then converted back into fatty acids. The enzyme lipase, produced by the endothelial cells of muscle tissue, mediates this reaction.
How do birds utilize this energy?
Long-distance migratory birds, like marathon runners, prioritize endurance over speed. In fact, this helps minimize their energy expenditure wherever possible.
Many birds take off by flapping their wings quickly, which consumes the most energy during migration. Take-off is an anaerobic activity, and birds utilize stored glycogen (a type of carbohydrate) to initiate flight.
However, during long flights, birds do not flap their wings as much.
