Arctic Terns: Long-haul Migrators

The sky was filled with around fifty Arctic Terns, fluttering their wings as they hovered over their nests in a field not quite an acre. It looked like someone had tossed a stack of papers into the breeze. These white delicate birds were flying and swooping and screaming Kriiaaah! making it clear to anyone who was around that they weren’t about to let anyone compromise their nests.

Our van was stopped in the middle of the narrow road. (There really wasn’t a shoulder to pull out on and there weren’t any cars around.) Birds from this colony began dive-bombing our van, sending the message to keep back. We were careful not to disturb them or get too close, so we stayed in the van and just opened the sliding door to take some pictures. It was dizzying trying to snap a photo of anything in the sky, so I focused on the field, which looked like high-density housing with nests made of little mounds of straw a few feet from each other. These terns have come a long way to get here, and they were nesting in Iceland and nearby Greenland.

Arctic Tern on nest

Just before this trip, I’d been reading the book, A World on the Wing: The Global Odyssey of Migratory Birds, by Scott Weidensaul and in the early part of the book he writes about the impressive migration of Arctic Terns. For years, Arctic Terns were assumed to travel 22,000 – 25,000 miles, which is roughly the round-trip distance between the highest latitudes of the Northern Hemisphere (where they would nest) and the southern oceans between Africa, South America, and Antarctica (where they spend their non-breeding period).

Once technology for geolocators became small enough to put on Arctic Terns, scientists discovered that the terns didn’t actually migrate in a straight shot from, say, Iceland toward Antartica. They actually took detours east and west, in a figure-eight pattern, before reaching Antartica. And they did the same thing when they returned. What the geolocators revealed was that in some cases, the terns traveled up to a staggering 57,000 miles in one year.

“Any seabird biologist will admit, especially after a beer or two, that no one really has a clue what the true limits of tern migration might be.”

Scott Widensaul
Arctic Tern making it known to bystanders to stay away.

Most arctic shorebirds migrate to the southern tip of Africa or South America, chasing the summer season from pole to pole for its long days of sunlight. They do this for the ability to eat all day, but it’s also because the very long days full of sunlight speeds up photosynthetic productivity at sea, resulting in plankton blooms. This all leads to an abundance of food source for Arctic Terns as well as other seabirds. Yet, what I find most remarkable is the variance of bird migration distance. For instance, the gorgeous Painted Buntings that visit our backyard feeders in the summer only migrate back and forth between Texas and Central America. It’s a miniscule journey when compared to the Arctic Tern. Yet it’s all about what’s on the plate. For the Arctic Terns, their meal-of-choice includes krill, capelin and herring, as well as crustaceans such as shrimp.

Arctic Tern

Most casual observers of birds don’t typically make the connection of unique food sources for birds. Humans, for the most part, don’t migrate or move around because of our food sources. (Though, I might argue that when it comes to Texas barbecue.) We live in a world where, for the most part, our food is gathered, processed and then sent to us. I don’t have to go more than a mile to find food on shelves. It’s all readily available. If I want naan, I don’t have to go to India–it’s right at the grocery store down the road. Salmon from Alaska? Well, I just have to go to the grocery store butcher department where it was flown in and they’ll wrap it up nicely for me.

We didn’t spend very long at the colony’s nesting site, so not to bother or create any stress for them. We snapped our photos, pulled the sliding door closed and made our way to the place where we would stay for the next couple of nights. As we drove away I looked back at the colony one more time and saw not just delicate fluttering creatures, but determined birds with an extreme lifestyle, reminding me that I have it easy.

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POST SCRIPT: I highly recommend the book, A World on the Wing: The Global Odyssey of Migratory Birds, by Scott Weidensaul. It ranks among some of the best science writing out there. Weidensaul is a great story teller and breaks down complicated scientific material in a very understandable way. I did not grow up with a fascination for science, but Weidensaul makes me wish I had.

Here’s a video of the Arctic Tern colony.