Ecologist Joshua Tewksbury and his team from the University of Washington in Seattle were rumbling along a road in southern Bolivia one night last spring with a truck full of plant samples, when a pair of yellow eyes materialized in the middle of the track. It was a Nyctidromus albicollis, also known as a nightjar, a medium-sized nocturnal bird with long wings, short legs, and a squat head. In Tewksbury's experience, nightjars are wise enough to fly away from approaching vehicles. But this one refused to budge. The truck made no attempt to stop, and the bird vanished underneath. That was that. Like Schrödinger's cat, it was unclear whether the bird was alive or dead, but judging by the engine's giggles and gasps, the team assumed the worst.
According to one dubious extrapolation by Merritt Clifton, editor of the Animal People Newspaper, 41 million skunks, 26 million cats, and millions of other species are killed by cars each year in the United States. Clifton's estimate is based on the Roadkill Project, a survey conducted by schoolchildren in New England, so it is unclear whether their limited counts are representative of the entire country. Still, had Charles Darwin known about roadkill, he might have wondered why these critters are not adapting.
That spring night in Bolivia, Tewksbury (who was slightly delirious from the day's botanical fieldwork, studying wild chili peppers), realized that if any animal has evolved a roadside manner, so to speak, it would be the nightjar. For most of their evolutionary history, nightjars lay in wait for flying insects where they emerge from dense forests, typically at the edge of clearings. In modern times, they have taken to the roads. "The general hypothesis is that nightjars on main roads know how to deal with cars," says Tewksbury. "Nightjars on back roads don't, simply because there are so few cars; there's no selection for dealing with cars."
Thus, an experiment was born. Or, at least, a pilot study. After all, what else can a team of data-hungry biologists do when they're cooped up in a car six hours a day, shuffling between remote research sites? Tewksbury could watch for yellow eyes. Carlos Manchego, a field assistant, could hang outside the vehicle and estimate the survival rate. The task of data recording is delegated to me, a journalist and the only member of the expedition who still has a field notebook out at midnight. Tewksbury preps me: Nightjars that did not easily get out of the way were considered to fly "inappropriately."
After the methodology is worked out, complications arise. "How many nightjars have we had so far?" Tewksbury asks.
"I have to check the notes," I say. "We're at four: one flier, three nonfliers."
"The first one flew, other three didn't," Tewksbury says.
"Second one, we may have killed," says graduate student Noelle Machnicki.
"So that wasn't appropriate," he responds, in reference to the bird's faulty attempt to avoid the truck.
"Third one, we may have killed. No, no, Carlos saw it," she says.
"Still, wasn't appropriate," Tewksbury says.
"And the last one we had to brake for," she says.
"That's a good one, too," he says, because it lent further support to his theory.
"We should tell Uco [the driver] to maintain his speed," says Machnicki.
"No, we'd kill too many nightjars," says Tewksbury.
"If he has to brake, then that's a nonflier: inappropriate," she says.
"Let's do 'fly,' 'not-fly,' and 'edge,' 'center.' That's all we really need to do," instructs Tewksbury.
Thirty-five kilometers later, the team still sorely lacks in the data department, but they are already musing over publication. "We'll submit it to Science," says Machnicki. Tewksbury chuckles and says that probably wouldn't fly, "but it still might be a note to The Auk or something."