Two days later, I decide to walk in Central Park, and find it full of newer migrants that arrived here at night and stayed to rest and feed. A black-and-white warbler tacking along a slanted tree trunk deep in the Ramble, a yellow-rumped warbler sallying forth into the bright spring air to grab flies, a black-throated blue warbler so neat and spry he looks like a folded pocket handkerchief. These songbirds are familiar creatures with familiar meanings. It’s hard to reconcile them with the remote lights I witnessed in the sky.
Living in a high-rise building bars you from certain ways of interacting with the natural world. You can’t put out feeders to watch robins and chickadees in your garden. But you are set in another part of their habitual world, a nocturne of ice crystals and cloud and wind and darkness. High-rise buildings, symbols of mastery over nature, can work as bridges towards a more complete understanding of the natural world – stitching the sky to the ground, nature to the city. For days afterwards, my dreams are full of songbirds, the familiar ones from woods and backyards, but also points of moving light, little astronauts, travellers using the stars to navigate, having fallen to Earth for a little while before picking themselves up and moving on.
Under heavy rain the lakes have turned to phosphorescent steel. Pygmy cormorants hunch on dead trees. Twelve of us stand on the shore. Some have set out spotting scopes on tripods on the grass, others carry binoculars. Silently we stand in wait for the Hungarian dusk. As the sun slips behind the expanse of water the air grows colder. We strain our ears until – there it is – we hear a faint noise like baying hounds or discordant bugles, at first hardly discernible through the wind rattling the reeds before it grows into an unearthly clamour. ‘Here they come!’ someone whispers. Overhead, a long, wavering chevron of beating wings is inked across the darkening sky. Behind it flow others, and there are others behind them, all passing overhead in ever-increasing waves, filling the air with a barrage of noise and beauty.
The birds above us are long-necked, graceful Eurasian cranes. Every autumn more than a hundred thousand of them stop off on their southward migration from Russia and Northern Europe to spend a few weeks in the Hortobágy region of north-eastern Hungary, feeding on maize left in the fields after harvest. Every night they fly to roost in huge numbers in the safety of shallow fish-farm lakes, attracting wildlife tourists who come here to witness the spectacle of their evening flights. Similarly impressive congregations can be seen in other places. In Nebraska, more than half a million sandhill cranes fatten up in cornfields before continuing their spring migration; in Quebec, watchers are awed by blizzards of snow geese blotting out the sky as they rise from the Saint-François River. In Britain, clouds of wintering starlings flying to their roosts draw crowds of all ages.
Standing close to vast masses of birds affects everyone differently: some people laugh, some cry, others shake their heads or utter profanities. Language fails in the face of immense flocks of beating wings. But our brains are built to wrest familiar meaning from the confusions of the world, and watching the cranes at dusk I see them first turn into strings of musical notation, then mathematical patterns. The snaking lines synchronise so that each bird raises its wings a fraction before the one behind it, each moving flock resolving itself into a filmstrip showing a single bird stretched through time. It is an astonishing illusion that makes me blink in surprise. But then, part of the allure of flocking birds is their ability to create bewildering optical effects. I remember my amazement as a child watching thousands of wading birds, knots, flying against a cool grey sky, vanish and reappear in an instant as the birds turned their counter-shaded bodies in the air. Perhaps the best-known example is the hosts of European starlings that assemble in the sky before they roost. We call them murmurations, but the Danish term, sort sol, is better: black sun. It captures their almost celestial strangeness. Standing on the Suffolk coast a few years ago, I saw a far-flung mist of starlings turn in a split second into an ominous sphere like a dark planet hanging over the marshes. Everyone around me gasped audibly before it exploded in a maelstrom of wings.
Though the rapid dynamism of flocking birds is a large part of their beauty, news sites and magazines often publish still photographs of murmurations that look like other things: sharks, mushrooms, dinosaurs. In 2015, an image of one flock over New York City shifting into the shape of Vladimir Putin’s face went viral, though it may have been fake. It’s not difficult, when presented with such a strange phenomenon, to believe in signs and wonders. The changing shape of starling flocks comes from each bird copying the motions of the six or seven others around it with extreme rapidity; their reaction time is less than a tenth of a second. Turns can propagate through a cloud of birds at speeds approaching ninety miles per hour, making murmurations look from a distance like a single pulsing, living organism. In a 1799 notebook entry, Samuel Taylor Coleridge wrote of a murmuration that shaped itself into various forms and moved ‘like a body unindued with voluntary power’. Sometimes they seem uncannily like an alien, groping entity, living sand or smoke moving through a suite of topological changes. Murmurations are thrilling, but they can also provoke an emotion akin to fear.
And fear is in large part why many of these flocks exist. Cranes, for example, roost in shallow water because it is safer than sleeping on the ground; and the sheer profusion of beating wings makes it hard for predators to focus on any single starling in a murmuration. No starling wants to be on the edge of the flock, or among the first to land. Anne Goodenough, who runs the Royal Society of Biology and University of Gloucestershire international starling survey, speculates that murmurations may act as signposts to invite other starlings to join a specific roost and increase its size – in cold weather, large roosts keep birds warm. But in the air, fear is the factor shaping the flocks, pressing and contorting them as they fly. A dark, shivering wave running through a mass of starlings is often a response to a raptor diving into the flock in search of a meal.
It is nearly dark now at the Hortobágy fishponds, and my ears ring with the cacophony of calling cranes. There is boiling confusion over the lake as flocks come from all directions to join the mass on the water that now looks like stippled, particulate fog. White-fronted geese are pouring in, too, tumbling and sideslipping from the sky through swathes of other wings. Suddenly it is almost too much to bear. I feel uncomfortably disoriented. Big flocks of birds can do this. Birders have described the experience of watching flocks of rooks at nightfall as so confusing and noisy that it produces in the viewer something close to motion sickness.
In search of something solid, I peer through a spotting scope focused on the far side of the lake. In the circle of the viewfinder, the confusion resolves into individual birds. It’s so dark that their colour has leached away. I am watching stately groups of cranes in greyscale, landing, drinking, shaking their loose feathers, greeting one another and getting on with the business of finding a place to sleep. The switch in recognition is eerie: I go from seeing rushing patterns in the sky to the realisation that they are made of thousands of beating hearts and eyes and fragile frames of feather and bone. I watch the cranes scratching their beaks with their toes and think of how the starling flocks that pour into reed beds like grain turn all of a sudden into birds perching on bowed stems, bright-eyed, their feathers spangled with white spots that glow like small stars. I marvel at how confusion can be resolved by focusing on the things from which it is made. The magic of the flocks is this simple switch between geometry and family.
As I stand there watching the cranes, my mind turns to human matters. The village we’d stayed in the previous night had felt so much like my home in the fens. It had the same damp, underwater air, chickens roaming around backyards, poplars, piles of winter firewood. Before I came here I’d asked a few British friends who’d spent time in Hungary what it was like, and several said that the strangest thing about it was how much it felt