In the earliest part of spring, when it may not feel too spring-like at all, you might step outside one night and hear it—a faint, mournful hooting, far overhead. If you look up then, and the skies are clear, you might be lucky enough to catch a glimpse of this spring phenomenon: a wavering white line of birds moving across the night sky, glinting in the moonlight. These are whistling swans, headed from their winter home on the East coast to their nesting grounds in the arctic.
Whistling swans (a type of tundra swan) are even more amazing close up. Snow white with a black bill, they typically measure at least five feet from wingtip to wingtip, and mature males can weigh over twenty pounds. You would not want to challenge one when they are nesting. Though usually whistling swans fly at night, this spring I heard the first ones in the morning, flying high above the overcast, invisible from below. I could barely hear their faint woo-woo above the Sunday morning roar of jets heading off to Cancun and Miami, and cars going by too fast on 31st Street.
According to National Geographic, when migrating, these birds can fly as high as 27,000 feet, so high that, when they pass over Corcoran neighborhood, they may find themselves looking down on outbound planes, which haven’t yet reached cruising altitude, or inbound ones descending to land. On my last winter flight that had a data display in the cabin, the temperature was shown as -52 degrees F at 35,000 feet (only 8,000 feet above the swans), and that was considerably south of the Twin Cities. This is what gives goose (and swan) down its reputation for lightweight warmth!
I’ve read that young birds of various types will fly in the right direction on their first migration, even without guidance, but they don’t know how far they need to go, or the exact route. That information seems to be learned. Young whistling swans stay with their parents a full year, to learn the route to their wintering grounds and back again. After that short course of instruction, presumably they’re qualified to guide the next generation. It is a distance of several thousand miles, with many things to watch out for.
Following their parents, the young swans not only learn what dangers to avoid, but construct memory “maps” of the route. This is based partly on recall of landmarks, partly on sensitivity to the earth’s magnetic field at various latitudes, and partly on celestial navigation. Birds are known to get their bearings from the sun, moon and stars, but must adjust for the position of these bodies at certain latitudes and times of the year. This ability appears to be hard-wired into their brains. There is also a theory that birds can recognize familiar areas by their smell. Sea birds are one of the few types that have a well-developed sense of smell. Can they smell the ocean from land, or vice versa?
Some birds migrate considerably farther than the swans. Some shearwaters (a type of albatross) migrate from their nesting ground in the Falkland Islands (off of Argentina) to the North Atlantic coast near Norway, a distance of about 8,700 miles each way. Another type of shearwater does the same migration in reverse, and one of these, which had been banded when young, was caught several times, and documented to be still in good health at the age of 25. Ornithologists estimated that this bird had flown about five million miles in its lifetime, about the same distance as two round trips to the moon.
It is hard to imagine nature overcoming such challenges, or how such an ancient ritual as migration continues in our dangerous, dirty world. Once birds crossed miles of pristine wilderness on their migrations, with many lakes and miles of woodland to choose from when they needed rest or food. Now they’re flying higher to clear skyscrapers and must dodge planes and weather helicopters. Their night flights take them over huge cities that sparkle like diamonds below—sometimes FAR below!–but are filled with dangers at close range. What do the birds think of it all? And how, in spite of it, do they still find their way home?
Scientists have proved that birds learn from experience. For example, a young bird may eat a toxic monarch butterfly, but once it does, and gets sick, it won’t eat another one. Nor will birds who have learned about monarchs eat the look-alike Viceroy, which has a bitter taste but isn’t poisonous.
However, (because so much isn’t known about animal communication) it pleases me to think that adult whistling swans teach their young more than just the migration routes.
“Do NOT go near those big silver things, that look a bit like swans from a distance, but roar loudly close up,” I imagine adult swan telling the young ones. “They move fast and they will kill you. And those long, thin things stretching from pole to pole will kill you too.” Refineries, cell phone towers, smokestacks, wind generators, and toxic sump pits from mines, all must be avoided. Yet the swans don’t really know what any of these things ARE, or why there are so many of them now. They just know that some swans got near one of the big silver things once—or landed in a green sump pool—and didn’t survive.
Given all this, I love it that the swans still migrate in spite of everything, because it is so unbelievable. That’s why, in the spring, I make sure to get outside on clear evenings, and try hard to listen, in spite of all the racket of the city. When I hear their faint calls, I squint and peer at the sky, hoping for a glimpse of that white, wavering line. For all that swans don’t understand about the world, they know one thing. Spring is here, and they’re on their way home!