by Sue Halpern
“Five hundred feet,” David shouted, a fact that I accepted ambivalently. Up was definitely better than down, but up meant we were moving farther away from the ground, from the world where gravity was as transparent and unthreatening as air. “Seven hundred feet!” I caught sight of the altimeter. It was inching up. But I didn’t need an instrument to tell me that. The fields and farms below were growing distant, flattening the third dimension till it looked as if, really, there were only two.
As we approached a thousand feet, David asked me to call out the readings. “You have to release the rope at two thousand feet,” he added.
“I do?” I yelled back. Apparently, I did. There was only one release knob, David explained, and it was by my knees. I put my hand on it and looked straight ahead at the rope, which was sending a wave in our direction. Bump.
“Fifteen hundred feet,” I called. The higher we went, the more the sun bore through the canopy and spread heat and light relentlessly. No wonder David was in short sleeves and a wide-brimmed floppy hat. There was no escaping the sun. Off to our right I could see another glider, off its tow, making tight circles.
“It’s in a thermal,” David shouted, seeing it, too. “Don’t worry. We won’t hit that plane for the same reason you don’t run into the car in front of you, or next to you, when you’re driving.”
Really? I knew plenty of people who had inadvertently rear-ended another vehicle. Didn’t they count? “Seventeen hundred feet.” The climb was steady, and the horizon stretched in front of us, and with no landmarks there was no way to distinguish eighteen hundred feet from nineteen hundred feet. But we had reached nineteen hundred feet and were pulling up to the invisible station. My hand tightened on the release knob, independent, it seemed, of my reluctance to separate from the motor that was carrying us aloft. Something about letting go felt suicidal, like pulling the switch on one’s own electric chair.
“Two thousand feet,” I sang out to David.
“Two thousand feet,” he confirmed. I pulled back on the knob, which resisted for a moment, then gave way with a jerk and a loud pop that startled me. The yellow cord snapped away, and all the noise did, too. Quiet rushed in around us, a whispering quiet, and the plane untensed like a hand gone from fist to open palm, and for the first time since taking to the air we were flying, really flying, and it was, much to my surprise, glorious: serene, buoyant, unlikely, glorious. The air, which until then I think I had not seriously taken into account as a force in my life, was holding us up. I could feel it, as if it had especially large fingers that pressed into my flesh. Air was a fluid, David had told me earlier, and now, buoyed by it in a tangible way, I felt what he meant. He pushed gently on the right rudder pedal and we turned slightly, then rushed forward in a graceful swoop.
“The clouds are pretty fragmented,” David said, referring to the thermal updrafts we were seeking. David’s voice was calm and measured. He was a seasoned pilot. I figured if he was untroubled by the fragmentation, I should be, too. I leaned back in my seat and looked out the window. I could no longer say that I didn’t like to fly.
A MONARCH TRAVELING to Mexico from where we were in southern Ontario would have to fly about two thousand miles to reach one of the overwintering sites, and it would take it ten or eight or six or fewer weeks to get there. Powered flight—flapping—would propel the bug forward, but at a cost in terms of both fuel consumption and time, since powered flight, despite its name, is relatively slow. When most people think of monarch butterflies’ migrating to Mexico, though, and then going back to the United States and Canada, that’s the image they have in their heads—a small and fragile and vulnerable creature flapping like mad in a determined and enervating manner.
Up in the cockpit of his Grob 103, David Gibo understood in an intimate and practical way that a butterfly could not possibly flap its way to Mexico. Gibo could travel on the wind for hours in his fixed-wing airplane, soaring and gliding across the sky using thermal updrafts, or rising columns of warm air. The butterflies, he reasoned, must do the same thing. Gliding (nonpowered flight in still air) and soaring (nonpowered flight in moving air, such as a thermal) were the methods that enabled both him, in his Grob, and a monarch, with its aerodynamic constraints, to travel long distances with little wear and tear and even less fuel consumption.
“Typical gliding and soaring flight, with the wings outstretched, [does] not generally require any effort from the insect,” noted the German zoologist Werner Nachtigall in his book Insects in Flight. “No energy is expended, either because the wings themselves automatically take up the gliding position as soon as the flight muscles are relaxed … or else [because] there is a ‘click mechanism’ which puts the wings into the right altitude mechanically. This latter method is how butterflies assume a gliding mechanism.”
It was in the same book that, shortly before heading up to Toronto to meet David Gibo, I had read this: “[A glider pilot] climbs steeply in one thermal, then leaves this and glides obliquely downwards towards the nearest thermal, in which he soars again, and so on. By this means he can make long, cross-country flights without having any engine. The only snag is that each time he must find another thermal before his downward glide has taken him to ground level. If he does not he must land.”
Up above the farms of Wellington County we drifted with lazy purpose, circling laconically and moving in a direction that felt like up. I knew that some gliders could course the sky all day, and that some had reached altitudes that required supplemental oxygen. Our goal was to stay aloft as long as possible, which meant at best twenty or twenty-five minutes. I also knew that sometimes the thermals were so prevalent that it was hard to come down, though this was rare, and that most of the time pilots crossed the sky as if the thermals were stones in a stream—upwardly mobile stones that moved them both up and over at the same time. Lose the thermals, and you were on your way down.
“We’re in sink!” David said from the backseat. His voice was steady, uninflected. My eyes fixed on the horizon, trying to see what he meant.
“What is ‘sink’?” I asked, seeing nothing but wispy clouds and another glider, far enough away to look smaller than it was. David adjusted the rudder and the aileron. The nose of the plane, which was pointing downward, wiggled up.
“It means that we’ve lost the thermal and we’re losing altitude,” he said, but sounding calm and businesslike. Sink. It was a delightfully descriptive word. I knew I should feel scared, but I didn’t. I checked the altimeter: we had dropped five hundred feet within a matter of seconds. Even so, we were already on our way to another thermal, banking sharply as we aimed for a destination in the sky that only David Gibo could make out. In less than a minute we had caught the updraft as if it were the 1:17 commuter train pulling out of the station.
“Usually what you do is fly a pattern in order to fly into a thermal,” Gibo was saying. “Now, with the butterfly, it goes in the direction it wants to go, finds the thermal, and then behaves appropriately.”
I can’t say I was listening attentively when Professor Gibo explained this, or when he mentioned that meteorologists had picked up migrating monarchs on radar, flying at five thousand feet. Instead I was thinking about the words We are in sink, and the fact that we had been falling from the sky and that the sky—invisible and elusive—had held us up.
ON CLEAR DAYS, days without rain or significant cloud cover, monarchs start dropping out of the sky at around three in the afternoon. There’s plenty of sunlight left then for flying, but sun, for navigational purposes, and warmth, for thermoregulation, are only two of the factors that keep a monarch in the air. Another is wind—which way it’s blowing, if it’s blowing, and whether it’s moving horizontally or vertically in a reliable, exploitable way. In the late afternoon, as the earth cools and the thermals break up, monarchs lose their free ride. They drift down to the ground, flapping as they need to and adjusting their glide angles, sinking yet held aloft by their thin, rigid wings.
Our airplane, despite
its superior aerodynamic design, had the disadvantage of weight. It, and we in it, were far heavier than the wind. Gravity was always a factor. We caught a small thermal, gained a few hundred feet, lost it again, dropped a few hundred feet, found another updraft, gained fewer feet than we had lost, found another thermal. From the moment we came off the tow and for the whole time we were flying, we were in the process of landing, moving closer and closer to the ground until David said we were getting to the point where we’d have to put down. From the air we could see the gliderport with its stable of aircraft and its tin-roofed hangar reflecting the midafternoon sun. David said we had to fly a left circuit, over and behind it, then approach from the southeast. The trick would be in catapulting the power lines, since the wind, as we got closer to the ground, was gusting unpredictably in a southwesterly direction. We could see it now, combing the trees, which were swaying. “Not ideal circumstances for your first glider landing,” David said flatly, plying the rudder.
Landing scared me in a way that flying hadn’t. I had gotten used to the notion that air was a fluid. I understood, in a visceral way, the metaphor of swimming that David liked to use. “A monarch swims through the air,” he said, an image that I both understood and found comforting. But landing required a different metaphor, and since none seemed to be on offer, the hard and solid reality of the ground seemed even more solid and harder. We passed over the hangar, then banked near the road, turning toward the field. David pressed on the rudder again and the nose of the airplane made a steep angle to the ground, one that my internal protractor found terrifying.
“Here we go,” David said, and the glider began to accelerate, heading directly for the power lines. Too frightened to close my eyes, I saw the cables slip under the belly of the plane with what looked to be about two feet to spare as the wind buffeted us this way and that. I had seen monarchs tossed about like that, fighting to fly southwest as the wind pushed them to the east, till their bodies were moving eastward but their heads were aiming in the direction of Mexico, as if will alone would get them there. David held hard to the controls, wrestling the wind with his intelligence. It needed only to be a draw, and it was, as we came in over the runway and leveled off. Twenty feet, ten feet, one foot above the rutted tarmac, dropping with a thud as a group of air cadets ran out to catch us, holding on to the wings of the plane to pin it down before the wind could do it damage. We were down. David congratulated me. I thanked him. We popped open the canopy and climbed out and for the first time all day caught sight of a monarch butterfly flying at knee height, flapping energetically. Although it was facing southwest, it was moving southeast. Professor Gibo and I paused to watch it struggle against the wind for a time, only to give up and park itself in the grass. “It was losing ground with respect to the overwintering sites,” he explained as we went into the airport office to sign up for another flight. “Natural selection has produced an insect that can detect that. So it went down to where it could control its flight. If you watch, you’ll see that happen a lot.”
AS A BIOLOGIST, David Gibo watched a lot. With his binoculars and his sailplane, he was an entomological voyeur. The problem was that watching, as an individual, wasn’t getting him the information he wanted. What he was getting on his own was too sketchy, too thin. Gibo was interested in the monarchs’ flight tactics—in how, specifically, they exploited the wind in order to find their way to Mexico and back. And he was interested in the vectors they used and the directions they flew in. He knew that though their general orientation as they moved overhead in Toronto was southwest, they did not fly in a straight line. Not that they wouldn’t if they could, but the wind did not offer such direct routes. And he knew that for them, flying was like sailing: it required tacks to be made to close the distance between where they were and where they wanted to be.
“You can only do certain things when moving through the air that will allow you to get to where you want to go,” he said the day after our excursion to Arthur, as we were walking from his office on the University of Toronto’s Erindale Campus out to the parking lot, which serves as his study site. “This is the limitation of physics, basically, because, as you know, you are in a fluid. And you are using your interaction with this fluid to keep aloft. And if you’re going to take advantage of things like thermals to get a free ride and increase your potential energy so you have something to play with, then that means you’re going to have to have pretty darn complex tactics, because the way to get up is to circle this rising air, which is drifting downwind and probably not going in the direction you want it to go. And now you have to compensate for the displacement due to circling in a thermal, gaining altitude. The fact that wind increases as you go up, the fact that you swing clockwise as you go up—you’ve got all those things going on, and you have to decide which direction you’re going to fly in when you leave that thermal. That is a fascinating problem—what the monarchs are doing in northeast winds, in east winds, in southeast winds—and something I’d like other people to get dragged into.”
The Erindale Campus, where Professor Gibo taught was a small branch of the university in Mississauga, a suburb about half an hour outside the city. It was pleasant if undistinguished, with the look of a large suburban high school. Because many of the students commuted, parking lots dominated the grounds, circling the main academic building with a broad band of blacktop. Gibo walked over to his car and laid out his instruments on the trunk, using it as his lab table—a habit, I’d come to notice, common among field biologists. “Any fool can do science,” he said, taking stock of his kit: field glasses, wind gauge, thermometer, compass, logbook. “That’s why it’s so powerful.”
Gibo was a proponent of laypeople doing the looking, the measuring, and the recording essential to empirical science. “Every single comet was discovered by an amateur,” he said. “You want to know why? Because they’re the only ones who have the time to stand out there, take pictures, and then go back a week later to see if anything has moved. People are smart. They can do this work.”
The work to which Gibo was referring was the campaign he had launched on the Internet to enlist people to collect data about the flight patterns of migratory butterflies. “However clever their flight tactics, however mysterious their method of navigation, everything has to resolve into a series of simple rules,” he told the volunteers. “Lots of rules, hierarchically arranged and nested sets of rules, but above all, simple rules. The tiny nervous systems of butterflies just aren’t capable of anything else.” The rules would be revealed, Gibo believed, if enough data could be collected and then analyzed.
To encourage this, Gibo had set up an extensive Web site that was part field-biology cram course and part public record book. Participants were asked to record, in a standardized format, the flight behavior of migrating butterflies, including their estimated altitude, the type of flight (flapping, gliding, soaring), the wind velocity, the ambient temperature, cloud type, and heading. They were also asked to note—that is, to interpret—the context of the observation. “Butterfly was apparently engaged in courting behavior with another D. plexippus,” Gibo himself observed from the parking lot on September 1, a day when half the sky was dotted with cumulus clouds and the ambient temperature rose in the half hour he was out there from 20 degrees celsius to 23.5. “The one being observed appeared to maneuver to keep in tandem to two hundred meters, then glided back down to disappear behind the South Building. Two more solitary D. plexippus were also seen. Butterfly started at three hundred meters and soared level before gliding down to two hundred meters. Its descent was gradual. A gull was also seen in field of view. Butterfly flapped upward. A second, lower D. plexippus flew past. Two more D. plexippus were seen. One glided down to a group of trees, one was flapping SW at five meters.”
Two weeks later a glider pilot in Worcester, Massachusetts, added his observations to the record, noting that during a routine flight at midday on September 16 he had encountered two monarchs at about forty-five hundred feet, soaring in
a thermal that was also host to some fifty hawks. Again, cumulus clouds were scattered across the sky—often a good indication of thermal activity—and the wind was moderate. The thing that most intrigued David Gibo about this report was a detail that he posted as an addendum: the butterflies had been about sixty miles inland, and with the wind drifting in a southeasterly direction, they’d been moving with some dispatch toward the Rhode Island Sound and the Atlantic Ocean. By simply circling in thermals, Gibo surmised, they’d reach the water in just over four hours. If they spent half their time circling and half moving straight ahead by flapping and soaring, they’d get there about an hour earlier. Once they got there, Gibo said, “they would probably continue roughly southwest, paralleling the coast, pass through Cape May, New Jersey, and [maybe] even be counted by [Lincoln Brower’s associate] Dick Walton at the Cape May Bird Observatory.”
This, of course, was speculation. There was no way for anyone to know where these particular butterflies were going to go, or where they were going to end up. Gibo was making an educated guess based on what he knew about wind speed and cloud formation and monarch butterfly navigation. To me it was a story, but a compelling one based on some real things, the way certain literary nonfiction both is and is not true. To David Gibo, though, the story was the essence of a certain kind of scientific enterprise, wherein the weight of reality—the mass of observed phenomena—allowed the creation of hypotheses (stories themselves) whose usefulness, if not their truthfulness, could be tested against the further accumulation of data.
“Most of science takes place in people’s heads, and then you present an argument to convince people and of course you arrange your argument in a way to make it maximally convincing,” he said. To me it sounded remarkably like plotting a novel.
