A natural history of migration

This is a piece published almost a year ago as the introduction to Issue 2 of Avis Magazine. I shouldn’t re-read my own work, because all I see are its flaws, but the subject of migration and immigrants somehow looms even larger today than it did last winter.

Sandhill cranes in Indiana, on their way south.


A natural history of migration

On the grand scales of space and time, human migration can often be thought of as the liquid flowing of discrete bodies. A liquid will flow from one container into another until there is equilibrium. Balance. Thus it is with humans, as families move away from oppression and conflict and search out new opportunities and a little breathing room. When there are too many people or there is too little peace, humans pour out into new landscapes, establishing settlements, creating diasporas, and always seeking a home and a place for balance. A better life. Today, the word ‘migrant’ is usually followed by the word ‘labor’ or else brings to mind people fleeing calamity, strife, and every one of the four horsemen. But even as soon as humans could walk we started moving, flowing out of eastern Africa and through the Fertile Crescent to every corner of the world, making homes on nearly every scrap of land but Antarctica. Since then, we have flowed back and forth from one continent to another, as circumstance and political geography have evolved. In the deepest sense of the word, we are all migrants and always have been.

The way that animals migrate is different. Their migratory movements tend to follow cyclic paths, as they travel from breeding grounds to feeding grounds and back again. Bats, butterflies, wildebeest, and whales all travel their familiar paths year after year, following maps invisible to us but handed down through countless animal generations. If it moves, it can migrate. Even the humble earthworm makes a migration of its own–moving down deep into the earth to escape the frost line in winter and returning in spring to the soil surface.

But arguably the greatest migrators of all are those descendants of dinosaurs, the members of Aves. Birds have spent eons wandering over parts of the earth that were inaccessible to humans until we too acquired the gift of flight, and the patterns that birds traced annually in the skies have been observed by humans since we first looked up. Romans in the time of Virgil looked for returning white storks to tell them when to plant their grape vines in spring. Glenn Miller made famous the song “When the Swallows Come Back to Capistrano” in 1939. And today scientists track the advancing first arrival dates of migratory bird species as spring encroaches on winter, a result of global warming. So which came first, the peregrine or the peregrination? Were birds migrating back when they were still dinosaurs? It seems like a bit of a chicken-or-egg question.

With all of their wandering and all of ours, it is hardly surprising that our paths have crossed and our stories intertwined. Some birds, though they roam across countless, lonely miles, choose to make their homes with us. The white stork (Ciconia ciconia) is one such bird. When the ancient Romans were planting their vineyards, white storks covered most of the European continent every summer, and they continued to do so through the next two thousand years. Storks are quite at home among humans and will happily build their nests on roofs and chimneys, while pastures and fallow fields make excellent stork foraging grounds. Neighbors are bound to gossip, and Europeans wove all sorts of fabulous stories about storks. With moral natures supposedly as upright as their posture, storks were said to be so dutiful to their elders, so full of filial piety, that adults would carry their aged parents on their backs as they flew. And it is little wonder to think that if a stork adores family so much that it would carry its own elderly, it would be willing to similarly transfer a human infant home from Heaven. But as humans altered the landscape more and more to suit our own purposes–introducing new elements like power lines and pesticides –we made it harder for storks to coexist. By the mid-1900’s, storks were rapidly disappearing from the continent, and it seemed like we were backing out of an inter-species contract negotiated thousands of years ago. But because of their special place in our minds, people took notice and then action, protecting natural areas, curbing pesticide use, and building artificial nest sites. White stork populations immediately rebounded, demonstrating that they are happy to make a home alongside humans as long as humans are willing to leave them the space to do it.

Though most of us these days are disinclined to give much credence to old superstitions, perhaps there are new allegories to be found in the flight of storks. They come to hatch the next generation every European summer, returning to nests they built stick by stick and having crossed the whole of the Sahara and the Mediterranean in order to do so. It is no accident that refugees from Eritrea, Somalia, and Syria follow the same path that white storks travel every year. Just like the storks, they too are searching for home in a changed landscape.

Across the pond in the New World, there are the ruby-throated hummingbirds (Archilochus colubris), sparkling little birds no larger than your thumb, who fly with a buzz like a beetle. But where a flying beetle trundles through the air, ponderous and cumbersome, a hummingbird in flight is pure beauty, all nimbleness and scintillation. They spend their winters in the warm jungles of the Yucatán Peninsula, and then in spring they launch themselves straight across the great Gulf of Mexico to the southern shores of the United States. How is it that a bird that so small that it is vulnerable to spider webs can cross five hundred miles of open water? How does such a tiny creature navigate such a tremendous distance, with no landmarks to guide them and a brain smaller than a pea? Research suggests that they steer by the light of celestial bodies and internal magnetic compasses, just as early human wayfarers learned to do when their feet could take them no further and they first built boats to pursue the horizon. (We are not born with compasses, but must build ours.) But research cannot quantify the evolution of fortitude and daring. Lost to time is the first hummingbird who eschewed the land route over Mexico, who looked out over the shining waters of the Gulf and thought, “Yes, I will go this way.

The champion migrators–those who hardly sit still long enough anywhere to call it home and therefore rightfully lay claim to the all the world as theirs–they are the birds of sea and shore. And the Arctic tern (Sterna paradisea), a diminutive but stylish bird with sleek grey wings, a black crown, and matching red beak and feet, is the standout among standouts. Arctic terns travel 44,000 miles from Greenland to Antarctica and back, hop-scotching from Africa to South America in keeping with the trade winds. These birds have been following trade winds since before we knew what trade winds were, and the appellation “Arctic” seems so inadequate as to be a misnomer for a bird that winters in Antarctica. (Ironically, there is a different species called the Antarctic tern that stays put in the Southern Ocean.) And what is it to winter, anyway, when one travels from pole to pole? Rather, the Arctic tern is a bird who sees only perpetual summer. And for a creature that can live for three decades or more, that means easily more than one million miles in a lifetime. A million miles of summer beaches–it is enough to boggle the mind.

Ancient peoples worshipped birds for their ability to roam on the wing, to disappear into the sky and return as mysteriously and yet as surely as the sun in spring. Our ancestors looked to migrating birds to give them a sense of place and time, to guide them through the world. There is surely much more these natural-born ramblers have to teach us. We must only remain mindful as we trace our own paths.


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