To the Ends of the Earth
Arctic Tern taking a well-deserved break.
Photo Sandy McDermott.
When I arrived in Anchorage in May, one of the first birds I noticed as I began to explore my new surroundings is the Arctic Tern (Sterna paradisaea). A relative of the gulls, this sleek bird was dressed in breeding plumage of white and light gray with a head soaked in black from the forehead, over the crown and nape. Red-orange legs and bill accessorized the bold white dominating the body plumage. This elegant bird was a “lifer” for me! “Lifer” is a term we birders use when observing a new species for the first time. Arctic Terns are an uncomplicated species to identify in the field.
Uncomplicated cannot be said for the Arctic Tern’s annual migration pattern. Arctic Terns have the longest migration of any animal on the planet; the only bird to migrate from the top of the earth to the bottom of the earth, and back again every six months.
Arctic to Antarctic and back every six months.
Did that sink in?
Breeding in the Arctic Circle and as far south as New England on the east coast and Washington state on the west coast, Arctic Terns follow the warm season to the Antarctic Circle where they “winter” in the Antarctic summer. Because they don’t fly a straight path, that sums up to be an annual flight of about 25,000 miles! EVERY YEAR.
An annual migration of 25,000 miles every year.
Did that sink in?
Let’s put this into a human perspective. How far can you walk without stopping? Or run? How long would it take you to walk or run from the Atlantic Coast of North America to the Pacific Coast? And do that eight more times? Let’s give you an assist. If fuel was not an issue, how far can you drive your vehicle before exhaustion sets in? Consider the requirements your body and mind need to accomplish the Arctic Tern’s staggering trek….in just one direction?
That is a bit of an unfair comparison; obviously, humans are not built to do the same thing as birds. Still, it offers a way to start understanding what our avian friends undergo each year. Just imagine living a nomadic life that extreme, undertaken by your own physical and mental capacity. Can you?
Wingspan can average between 25-30”!
Photo: Sandy McDermott
Maybe retiree snowbirds can, summering in a northern home and retreating to the warmth of a southern spot for the winter. The only thing similar, though, is that an act of relocation is taking place. The method and reasons could not be more different.
The method: Birds are totally reliant on the strength and endurance of their own bodies. No planes, trains or automobiles. No campers filled with supplies. No jackets, hats or raingear. Just their own wings, evolved biomechanics, and an internal, genetically-coded navigation system that uses a number of external aids including length of daylight, angle of the sun, the stars, and wind direction and temperature. Facing severe weather events, predators and loss of suitable stop-over habitat for fueling up make this annual journey a serious, life-threatening commute.
The reason: In the animal world, the need to migrate is not rooted in seeking out comfortably accommodating weather. Rather, it’s all about food resources. Birds are following the seasons to access food resources. If the food of choice for a given species remained available year-round, there would not be a need to expend enormous amounts of energy to move somewhere else. Simple as that. True, some species do not migrate at all, or are partial migrants, having adapted to seasonal food sources. The vast majority of species, however, need to follow their food source.
Back to the Arctic Tern. This 3-4oz bird has some of the best aerial displays to watch! The smaller size, sleek body shape, forked tail, and edgy wings give agility to hover, twist and dive. Watching handfuls of them navigate the same overhead space as they hunt for small fish is truly impressive. These design features are critical to support long-distance non-stop flights, gliding on the wind for long distances. They can even sleep and eat while carried by ocean winds.
The Arctic Terns have already left Alaska. My last sighting was about two weeks ago. I sort of wish I could fly with them, to see the world as they see it from on high. Let’s say I am migration-curious. But alas, my humble human body lacks biological fortitude and endurance. I can’t do what they do and it would not be the same in a small aircraft. So I’ll wait here on the ground until they return next May and, meanwhile, continue to imagine what that flight might feel like.
There’s so much more to the phenomenon of bird migration! To learn more about the Arctic Tern here are several links that you might enjoy:
I borrowed the title from this NatGeo article, by the way….there is nothing better fitting the flight of the Arctic Tern.
https://www.nationalgeographic.org/article/ends-earth/
A short and beautiful video highlighting the Arctic tern’s aerial prowess and cute chicks:
https://www.youtube.com/watch?v=LyqmOpVncxI
Two interesting academic accounts of this tern’s migratory behavior:
https://www.pnas.org/content/107/5/2078 & https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0242193
Of course, quick facts and stats from Cornell Lab of Ornithology’s All About Birds: https://www.allaboutbirds.org/guide/Arctic_Tern/overview