Arctic Terns

 

We saw a colony of Arctic terns in southern Iceland. One of these birds attacked me. I guess I got too close to its nest. They are very protective.

One of the most fascinating aspects of birds is their ability, often truly amazing, to migrate, often over amazing distances, and in amazing circumstances.    Why do birds, unlike most animals migrate in the first place?  How do they navigate?  How do they know where to go?   How can they migrate so far, often under very adverse conditions?  In fact, to me the very notion of migration is a vast mystery that I will never understand, no matter how much I learn about it.   Just as one example, among many, some species of shorebirds, a relatively short time after giving birth to their young abandon them to their own devices while they fatten up for the long migration.  Then the adults head south many thousands of miles away, often to South America.  Amazingly, the young, who have never been anywhere in their short lives other than northern Canada, fly south on their own without any guidance from the adults, and turn up at the same place as the adults some weeks behind the adults.  How do they do it?  It is very difficult for us mere humans to fathom such incredible abilities.  It is a profound mystery.

Why does the Arctic Tern migrate literally from one end of the earth to the other, and then later back again?  What drives the bird to do that?  Why do they travel so far to go from one seemingly inhospitable place to another?  I will never understand these things, but will never tire to trying.

Some recent information about Arctic Terns is just downright amazing. The Arctic tern is justifiably famous for its astonishing migration. It is one of the most astonishing stories in a natural world filled with astounding stories. It flies each year from its breeding grounds in the Arctic in the spring and then back again after the summer. The shortest distance between these two points is 19,000 km (12,000 mi). This is the longest migration of any animal in the world! It flies about 2 times farther than scientists earlier believed because its route is not straight. It meanders.

Recently scientists have been able to install very small transmitters onto them so that their track could be monitored. One Arctic tern followed a zig-zag pattern from Greenland to Antarctica and back again each year and in the process racking up 44,000 frequent flyer miles (or 71,000 kilometers), as National Geographicdescribed them.  This is 4,000 miles or 6,440 km more than its nearest competitor the sooty shearwater. The researchers who found out this new information estimated that because the birds often live to be 30 years old over their lifetime they travelled about 1.5 million miles (2.4 million kilometers) which is equal to 3 trips to the moon and back![1]

Until recently scientists could not find a tracker light enough to be carried by a tern. Now they use one that is 1/20thof an ounce or 1.4 grams. The researchers also learned that terns often stop for month in the open Atlantic Ocean possibly to “fuel up” on small fish and crustaceans before continuing their awesome (for once that word really does apply). Even more surprisingly, they don’t take the shortest route. Instead they zig and zag literally across the ocean and back again! Some wondered why they would zigzag so much. For example, the terns from Greenland don’t fly straight up or down the Atlantic. Instead they “hopscotch from Antarctica to Africa to South America to the Arctic.”[2]Even though this is a detour of several thousand kilometers because they zigzag across the Atlantic Ocean, The birds appear to be following huge spiraling wind patterns in the atmosphere, avoiding flying into the wind,” according to Carsten Egevang one of the researchers.[3]

Though scientists are not sure why these amazing birds take such a long journey nearly from pole to pole, they believe it must be that the terns find rich feeding grounds in the waters of the poles. Why else would they do it?

 

 

[1]“World’s Longest Migration Found–2X Longer Than Thought,”National Geographic(Jan 2010)”

 

[2]“World’s Longest Migration Found–2X Longer Than Thought,”National Geographic(Jan 2010)

[3]Carsten Egevang, “World’s Longest Migration Found–2X Longer Than Thought,”National Geographic(Jan 2010)

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