Bird Brains

At first i thought it was a dragonfly, somehow that far out in the Atlantic. It appeared in the air near the bow of the sailboat where the boards were lashed down, and skimmed for one-one-thousand, two-one-thousand, three-one-thousand, up to seven. Then, it plipped back into the purple Gulf Stream.

Too big to be an insect. Was it a bird?

No, not a bird. Then it appeared again, bursting from the water. The flying fish drew a carving line over the rises in the open-ocean swell with two dips that divided the length of its ride into thirds.

Beside a light-gray cumulonimbus cloud, a frigatebird circled on a thermal. We had been chasing those fronts for wind since we left Florida early in the morning—the same pockets of wind that the frigatebird saw, hit, and cruised. The wind was from the east at 10 knots and we made harbor in the Bahamas by nightfall, our own sort of necessary migration.

Later in the week, after we cleared customs, we sailed to the island I’d been eyeing on Google Earth. The pale sand, 15-feet down through that postcard-clear Caribbean water, was ridged, pulsed, and occasionally broken by brown-and-black clumps of reef. Dark-green seaweed fanned this way and that way. We anchored and took the dinghy ashore with our boards.

A man named Anthony held a plastic five-gallon bucket and dumped purple-red chum into the shallows. A dozen rays and two nurse sharks drew their own distinct lines from the deeper water toward the food. He dropped cuts of meat to lure them close enough for us to touch, dangling the bait in front of their mouths. The rays sliced through the water in tight arcs around our ankles, silently suctioning up the slices of meat. The skin on their wings felt smooth, almost slimy. The nurse sharks drew straight, direct angles through the water. They snapped their jaws when they took the meat, a sound as audible as flip-flops clacking together. Their skin was as coarse as 80-grit sandpaper. A school of bonefish commuted along the perimeter of the shallows where the sand met seaweed. A solitary houndfish interloped, its blue head vivid against the white-sand bottom.

We gathered our boards and walked up the point. Iguanas skittered into the brush. An American redstart flipped its tail at us, highlighted by two vibrant-yellow spots, before it flitted off. We paddled out and I felt distinctly outnumbered: humans to fish, to birds, to lizards, to insects, to trees, to rocks. A line of pelicans dropped and trimmed along the surge of airflow across the unbroken face of a wave. A set came through and we each caught one. Small and crumbled by a light cross-shore.

Back in the lineup, I studied the horizon, rolled my shoulders, and tilted my head. Above us, seabirds wheeled and dove—laughing gulls, a few sooty terns.

The top half of the sooty tern’s foot-long body was jet-black, its forehead and underside white, with a white edge around its forked, swallow-like tail. I closely watched the line that it drew, visualizing its wake. It flap-flapped up, then held its wings still, banking slightly left. It gave one flap and straightened into a steady glide. Suddenly, it pulled its wings in and leaned left, pushing its widened tail down and to the left. Wings tight to its torso, it banked at the water in a smooth carve. It did not dive into the water but pulled up and away, hitting the little cushion of compressed air between its wings and the surface. 

This pocket of air is called the “ground effect.” It’s what causes the upward jolt moments before your plane lands. As the tern pulled away, its black wings were stark against the white sand of the beach. It flap-flapped again and cruised, its white underside contrasting with the clear sky as it climbed to altitude. Then it repeated the flight pattern.

There are many parallels between the carving that seabirds do through the air and the lines that surfers draw across the water. Immediately obvious is that birds and surfers share the forked swallow-tail, and use them similarly. The sooty tern spreads its tail and pushes it into the air to change its angle of attack at lower velocities, just like you stomp on the tail of a surfboard to initiate a carve.

But we have more in common with birds than just the swallow-tail. We’ve all watched pelicans glide along the cresting lip of a breaking wave and thought, It’s surfing, right? In short, yes. And I believe seabirds see and read different pockets of wind like we read different waves and different sections of a wave.

Hot and cold air feels different to birds while they’re flying. Thermals, which are columns of hot, rising air that form over empty spaces like farmland, parking lots, and marshes, provide a burst of extra lift. Like a fast, steep section. Conversely, it takes more energy for a bird to fly through cold air—the equivalent of when the wave shoulders.

Just watch them. Over land, barn swallows zip along steep, fast sections, avoiding certain pockets of air as if they were closeouts. Vultures glide and stretch out across thermals in what must be their equivalent to a perfect, unspooling pointbreak. Pigeons and doves—surely the boogie boarders of the avian world—zip and jab here and there.

A bird flaps its wings to generate lift and speed to overcome gravity and drag. Depending on the species, birds either flap their wings in bursts or continually, interspersed with moments of gliding or bounding. The frigatebird, the pelican, the gull, and the tern perform gliding flight. The red-headed woodpecker that lives in the palm outside my house performs bounding flight. It flaps, then holds its wings perfectly still next to its torso for a moment, falling like a little cylinder before it flaps again. In this sense, both birds and surfers share an appreciation for appendages held still at the side.

The mechanics of a seabird’s flight has an equivalent to the bottom turn and to the high-line. Their wing-beat is divided into an up-stroke and a down-stroke. The down-stroke is when the bird pushes its wings downwards to generate lift. The wings raise on the up-stroke and the bird pauses and falls, sometimes holding the up-stroke as a way to adjust force generation at medium and high speeds. Thus, the high-line correlates to the up-stroke and the bottom turn to the down-stroke.

There are many parallels between the carving that seabirds do through the air and the lines that surfers draw across the water. Seabirds see and read different pockets of wind like we read different waves and different sections of a wave.

“As the crow flies” implies directness, efficiency. But neither crow nor seabird fly only straight. Why do seabirds and surfers draw carving lines instead of going straight? The surfer’s immediate answer to this question is instinctual, reactive. Because it feels good. Because that’s what the wave presented. Do birds choose what lines they draw through the sky? 

The albatross uses an S-shaped flight pattern called “dynamic soaring” to ride the airflows up and down along the face of open-ocean swells. Using this soaring pattern, the lower wind shear at the ocean’s surface, and the airflow on the face of each rise in the swell, an albatross can glide for days while barely flapping its wings. The albatross’ flight pattern looks exactly like a smooth bottom turn and high-line linked together, and it can fly around the earth in about 60 days by carving in this way.

Art historians have done plenty of work trying to figure out why humans draw different lines. Rudolph Arnheim, a twentieth-century art historian and psychologist, writes that thinking “takes place in the realm of images,” and that since these thought-images are “highly abstract…to get at them is not easy.” Arnheim explains in his book Visual Thinking that the subconscious image, which is “hard to describe and easily disturbed,” is best consciously explained in drawings. This possibly explains why we refer to the line that a surfer draws across a wave. It is an attempt to explain what we understand subconsciously by using sketchbook vocabulary. Our vocabulary is always linked to the tools we are using.

William Hogarth, an English painter and writer from the eighteenth century, analyzes the value of different lines in his book The Analysis of Beauty. He writes that, “Straight lines vary only in length and are least ornamental.” For Hogarth, the perfect line is an S-shaped carving line, which he calls the “line of beauty” or the “serpentine line.” Hogarth believes that the serpentine line is superior to others because its curves lead the eye “in a pleasing manner” in “different ways,” though it is just one line. In addition, he writes that “the hand takes a lively movement in making it with pen or pencil.” The S-shaped line is best because it is fun for the artist to draw and it takes the viewer to different places, despite being one motion from the artist’s hand.

Drawing the S-shaped line is one of the things that queues us into the natural flow that we crave and find in the act of surfing. And maybe birds crave and get some physiological benefit from their air-surfing, too? We share a lot with them. The shape of the line we draw across our element of choice. Our migratory tendencies. And the same space in the lineup, which also happens to be a wonderfully complex place for their dynamic flight.

Watching from the lineup, I frame the sooty tern’s flight pattern into clips in my mind, each their own little ride. A set looms. The birds repeat their flight patterns. We repeat ours.

With thanks to David George Haskell for reviewing the ornithological material in this essay. 

Illustration by Kate Copeland.