Mike McGrann has a good ear. He can identify a bird just by listening to it sing. He also can tell from its song if it’s bragging about its territory, about to migrate, or seeking a mate. McGrann shrugs off his skill — he can recognize the sounds of more than 200 species — saying other ornithologists can do it, too. “It’s like learning a language,” he said. Recently the birds’ songs have sent him a disturbing message: climate change is hurting them.
On mountains, temperature and precipitation interact in complex ways, making them especially sensitive to climate change, a fact that has avian researchers worried. The fear is that rising temperatures already are prompting birds to migrate and breed earlier, a change that could make it difficult for them to find food for their babies. If, when spring arrives, they head north too soon, there may not be enough insects available to nourish their young.
That’s why McGrann, who chairs the environmental science department at William Jessup University, and his collaborators — including Brett Furnas of the California Department of Fish and Wildlife — have enlisted tools beyond their ears to gauge the damage of global warming on songbirds. This includes placing hundreds of automated voice recorders to capture birdsong at sites across California’s Klamath Mountains and the southern Cascades. They also are using computer programs to visualize the recordings, and to create statistical models of peak vocal singing activity.
As part of the experiments, most of them between 2009 and 2011, McGrann and his team hiked the rugged mountain trails, first listening, then recording. They dispatched more than 500 recorders programmed to turn on and off at specific times. Later, after retrieving the devices, they fed the data into a computer, which visualized the songs. McGrann listened — and watched. “With the software, I could see the songs of the birds as I was listening to the recordings,” he explained.
The timing and intensity of the singing lets scientists know whether songs are “peaking” earlier than in the past, causing birds to migrate and breed, and whether they are moving to higher elevations to escape the heat. “We expect that more birds will be singing more often near the peak of the breeding season,” Furnas said. “In this way, we can use the amount of singing we hear during a survey as a measure of how close to the peak of the breeding season we are in a particular place on a particular date.”
For this experiment, the goal only was to test their method to determine if it is an effective technique to track birds’ vocal activity over the coming decades. They regard their preliminary observations as anecdotal, and caution that more time is needed to be conclusive. Still, the early results are troubling.
“They suggest that migrants may be at greater risk,” Furnas said, as rising temperatures lead birds to head to their summer homes before the landscape has thawed. “If they are prompted by increasing temperatures to migrate earlier, birds may arrive to find that there aren’t enough insects ready yet for them to eat.
“[They] have to compress a lot of activities into a shorter time period with less margin for error,” he added. “Think of it like if you schedule a short holiday somewhere nice — but when you show up, a few days of bad weather cancel out a lot of your itinerary.” They described their work in a recent studypublished in The Condor: Ornithological Applications.
The scientists placed the tiny recorders — small enough to fit in the palm of one’s hand — on the ground, hidden at locations ten to 20 feet off the trails, and away from trees, large rocks and shrubs, which could interfere with recording. The scientists put them in plastic containers to protect them from rain and condensation, but they poked holes in them so the recorders could “breathe.”
The containers didn’t protect them from everything though. A few had tooth marks in the plastic and on the devices when the scientists came back to collect them, a sure sign of bear curiosity, they said. “A few times I had bears chew up the recorders and spit the batteries out,” Furnas said. “I had one recording I am pretty sure was a bear smelling or licking the microphone while it was recording a bird.”
Furnas compares their work to the caged canaries miners used to carry into tunnels to signal the presence of poisonous gases, like carbon monoxide. Toxic fumes would kill the canaries first, giving the miners advance warning — and time to flee.
“In our case, when the birds start singing earlier in the season, they are warning us that climate change is starting to disrupt complex ecological cycles that developed slowly, over millions of years of evolution,” Furnas said. “It behooves us to listen.”