For decades now, ecologists have been attaching radio transmitters to the bodies of large animals: whales, bears, elephants, condors and eagles for starters. What these scientists haven't done is stick the same devices onto animals like song birds and big insects, those migratory flying things that sometimes mow down crops and spread diseases.
Martin Wikelski, an ecologist at Princeton University, says it's time to fill what he describes as a dangerous research gap.
"It's important for our understanding of conservation, and for understanding diseases like the avian flu," Wikelski says. "When it comes to understanding how small migrants move around, we're just about as ignorant as Aristotle was 2,000 years ago."
Aristotle was the first to marvel at the wonders of migration. But that's not the same as collecting the data points that tell you migration works.
The Wild Habits of Migrating Birds
For eight years now, Wikelski's been the leader of a group of scientists who do collect those data points, with the help of radio transmitters no bigger than a baby's thumbnail. These scientists are known as "microtrackers" and for now they're few and far between.
But Wikelski's work is changing that by forcing ornithologists to change the way they think about migration. His first microtracking studies started nearly a decade ago when Wikelski captured groups of mid-Western thrush and glued extremely sophisticated radio transmitters to the bellies of these birds.
"The transmitters recorded heartbeat, breathing, wing beats and location," he said. "Once every second, they sent all this information out in concentrated bursts."
Wikelski tracked those bursts by following the birds inside a boat-sized beat-up Oldsmobile that had what looked like a great big TV antennae sticking through the roof. Inside the car, the microtracker twisted at the base of the antennae until the beep-beeping bursts of information came in loud and clear. That information told him where the birds were going and how quickly they were moving.
At the time, ecologists assumed that migratory birds like thrush used huge amounts of energy when they flew south for the winter. They also assumed that when these birds were not busy migrating, they would either be resting or sleeping, so that they could build up energy for the next big migration.
Wikelski's studies punched some giant holes in those ideas, in part by showing that these birds did not do lots of resting. Instead, for reasons no one understands, they strayed far and wide from their migratory pathways, and at least one thrush seemed get a kick out of flying into thunderstorms.
"That bird came down in Chicago late at night," Wikelski said while taking me for a drive in what his students call the "Batmobile."
"When we went in to recover [the bird] we ended up in a dark alley. When I got out of the car, a bunch of guys I hadn't seen came up and asked me who I was. I said I was an ornithologist. They said, 'Get out of here. Get out of here fast.'"
Wikelski reported on his early findings in the journal Nature. He reported on further bird travels in the journal Science. Ever since, proposals to track other kinds of migratory birds have popped up like so many mushrooms.
Little Bugs Go Far
But Wikelski has moved on, refocusing his work on flying insects. With the help of prominent entomologists like Mike May of Rutgers University, he's been attaching even smaller transmitters to the backs and bellies of insects captured in a grassy meadow near Princeton, N.J.
"Insects migrate around the world in incredible numbers," says migration expert David Wilcove of Princeton.
"For example, look at the locust in the Serengeti," he says. "When you add up all the weight or mass involved, it's equal to the weight of all the wildebeests. There's an incredible amount of living tissue on the move out there, and we know virtually nothing about it."
Wilcove helped Wikelski with a recent study of migrating dragonflies -- one that started when transmitters were glued to the insects captured in this field. When they were set free, Wikelski followed the dragonflies in a small plane for weeks on end, drawing up elaborate maps of where they went from day to day.
In a recent issue of Science, he reported these dragonflies often covered 100 miles a day, and that they appeared to migrate up and down the East Coast. Wikelski also noted what he called some "striking similarities" between the flight paths of dragonflies and thrush, suggesting that there might just be a universal set of migratory rules.
Wikelski took me out into this field to track another of these dragonflies, but then something unexpected happened -- a colleague captured a very large tiger swallowtail butterfly.
No one's ever tried to glue a transmitter to a butterfly before -- they're supposed to be too light carry much of anything. On the other hand, this is exactly how new fields of study are created, and so Wikelski and his colleague decided to give it a try.
Slowly and carefully, they glued a tiny transmitter to the back of the butterfly. When Wikelski threw it up into the wind, the insect flapped its wings and flew.
Wikelski and his colleagues jumped cheered like kids.
But only for a few seconds, at which point the butterfly appeared to give up and fall out of the sky.
The scientists ran out into the meadow toward the place where the butterfly had fallen. After flying several hundreds yards, it had apparently crashed into a plant that had knocked the beeper off its back and onto the ground. By the time we reached the spot, the swallowtail had flown away, apparently unharmed.
Wikelski found the beeper and returned it to its case.
Nobody looked discouraged.
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