I am sitting on the shores of Lake Inari (Lapland Finland) watching a gorgeous sunset reflected in the lake’s glassy waters when a small, white and grey, aerodynamic bird catches my attention. I watch as this little bird floats on the wind currents and then suddenly dives down to the water with incredible accuracy and returns to flight victorious, a small fish clenched in its beak. I glance back towards the setting sun but my attention is again called back to the bird. There are now two of them and they are squawking loudly! I can’t help but wonder what they are saying but it seems there is a disagreement about who has the rights to sit on a particular post. Laura, who is also enjoying the scene, tells me that this bird is called Lapintiira in Finish (otherwise known as the Arctic Tern – Sterna paradisaea).
The Arctic Tern is renowned for making the longest migration on earth, literally traveling from pole to pole each year! The Tern migrates from its breeding grounds in the north (largest colonies located in Greenland and Iceland) to feeding grounds in Antarctica. Despite weighing only around 100 grams this incredible bird travels about 71,000km annually. Considering that Arctic terns can live more than 30 years, scientists have calculated that these birds may travel 2.4 million km in a lifetime. That’s equivalent to about 3 round-trip journeys to the moon! As a result of it’s migratory lifestyle the Arctic Tern probably experiences more sun than any other creature on Earth! Watching the two terns flying over Lake Inrari I wonder where they have been and what they have seen? Have they been to Antarctica recently? Where are they headed?
Lapintiira’s migratory pattern corresponds with global prevailing wind systems. Scientists from the British Antarctic Survey traced the bird’s route, which begins by following the western coast of Europe. Around Cape Verde Islands it was discovered that about half of the birds carried on down the west coast of Africa while others crossed the Atlantic to follow a parallel route off the Coast of South America. The scientists were also surprised to discover that most Terns spend a month at sea feeding in a high productivity zone in the middle of the North Atlantic. The Northbound migration back to breeding grounds tends to be much quicker however, with the terns traveling an average of 520 Km up to 670 km per day.
How does a little bird know where it’s going, I find myself wondering? Like many migratory species Arctic terns navigate using the earth’s magnetic forces as a guide and perceive clues like dropping temperatures to know when it’s time to go. Although migration timing is synchronized (all birds reach the North Atlantic, depart winter grounds and cross equator within a few days of eachother), scientists have not found evidence that the birds travel together in large flocks.
So why would Lapintiira undertake such an arduous task each year? It is obvious that the migration is linked to the Arctic Tern’s breeding season and despite the fact that these birds have chosen to live in the harsh environment of arctic regions, it seems that they still try to avoid the worst weather and follow the sun and resulting productivity.
Sitting by beautiful lake Inari, I have to admit Lapintiira may be onto something, choosing to live in the extremities of the earth where the sun barely sets. Although the sun has almost slipped behind the horizon it is nearly midnight and I decide I should head to bed!