Stone Age Bird?

Often, scientific advances are the result of long years of toil in the lab or the field, but every now and then they fall into the researcher’s lap — especially if that researcher is willing to take a long, hard look at a mirror.

On a sunny June morning two years ago in the northeastern corner of Great Smoky Mountains National Park, Jason Love and his two companions were sorting out their gear for a multi-day backpacking trip. The trio of scientists was there to set up recording devices to capture bat sounds near shelters on the Appalachian Trail.

Love was done packing before the others and was absent-mindedly looking around the parking lot of the Big Creek Ranger Station when he spotted, some 35 feet away, a male northern cardinal repeatedly pecking at the side mirror of a white Ford Escape SUV. Cardinals are known to attack their likeness in windows and mirrors, which ornithologists interpret as the birds’ way of defending their territory against an imaginary — but particularly persistent — intruder.

Love, who is a birder, was familiar with the behavior and found the display “amusing,” but something stood out: After each peck, which produced an audible “clack,” the cardinal dove to the ground before flying back up to the mirror.

“When I took a closer look through binoculars, I saw that it was picking up pieces of gravel and attacking its reflection with that,” Love said. “I knew that was special.”

Love, the associate director of Highlands Biological Station, a research and environmental education facility affiliated with Western Carolina University, beckoned to his colleagues, Rom Stanek, an undergraduate student at North Carolina State University, and Reagan Jarrett, a research assistant at Highlands. The cardinal was too far away for them to film him with a smartphone, but Stanek happened to have a high-quality camera with him, and the team was able to capture several minutes of the bird’s shenanigans. (Love thought about protecting the car from the winged vandal, but none of them had anything on hand to cover the mirror, and he reasoned that shooing the cardinal away would have been futile. “It probably just would have come back,” he said.)

After witnessing the cardinal’s hammering for some 25 minutes, the three had to leave to meet the driver who would take them to their trailhead, but Love was already thinking that the description of this incident could make for an interesting academic paper. As they departed, the cardinal was still pounding away. Who knows how long the bright-red passerine had been at it before Love noticed and how long he continued afterward, but Friedrich Nietzsche could well have been describing a frustrated cardinal when he declared that the worst enemy you can meet will always be yourself.

For a long time, the use of tools was considered a distinctly human ability, said Robert Shumaker, the lead author of a revised edition of the book “Animal Tool Behavior.” “There was the assumption that no animals used tools,” Shumaker said. “And, you know, chimpanzees shattered that myth.” Primates use tools more frequently and in more diverse ways than any other group of animals, but Shumaker and his co-authors cataloged examples of tool use by an incredible variety of creatures, from female digger wasps using a pebble to compact soil around their burrow’s entrance to veined octopuses assembling a shelter out of two halves of a coconut shell. “Most people assume that to use tools you have to have hands, and that is certainly not true,” Shumaker said. “We see tool use in all kinds of species that don’t have hands, and birds are probably the most dramatic example.”

Among avian tool users, crows have received much attention from researchers, who documented behaviors such as New Caledonian crows fashioning small hooks at the end of twigs or stems to extract prey from their hiding places. It’s easy to assume that the use of a tool by an animal is a sign of higher cognitive abilities, but Shumaker said the link is not always there. There is no evidence, for example, that a hermit crab exhibits sophisticated thinking when it picks up a shell to protect itself. “You can never, ever directly examine thinking or intelligence,” he said. “It’s invisible.”

Love pored over the relevant scientific literature to find out if what he had witnessed was indeed novel behavior. He found no other example involving a cardinal using a tool, with the exception of a 1940s paper documenting “anting” where birds rub ants on their feathers — the ants being the “tools” in this case — possibly using the insects’ formic acid as protection against parasites.

After Love submitted a draft of his paper, a reviewer suggested that he extend his research to include relevant behaviors posted on social media. So Love, Stanek and Jarrett spent “many hours” on YouTube and Google looking for videos of cardinals and other birds fighting or attacking mirrors. “You can go down a rabbit hole pretty quick,” Love said.

After weeding out false positives involving the occasional St. Louis Cardinals mascot and videos that were too grainy, the three found just two videos of a cardinal carrying an object during an encounter with a rival or a mirror, but the object (a flimsy twig in one case and something that looked like a sunflower seed in the other) wasn’t used to strike anything. The team also found a few videos of other bird species using a tool while being aggressive, including one of a raven dropping a stone near a dog. Based on what is known, “it turned out to be pretty rare behavior for any bird,” Love said.

The final version of the paper, which Love, Stanek and Jarrett co-authored and published recently in The Wilson Journal of Ornithology, also made the point that content from trail, security or smartphone cameras posted online — and evaluated with scientific rigor — could prove useful in figuring out how widespread certain animal behaviors are. “Scientists are giddy about all the data that are out there,” he said.

It’s unclear how the Great Smoky cardinal’s epic battle with itself ended. Maybe the car owner drove away, taking the bird’s pesky rival out of the picture, or the cardinal finally cracked the mirror, either eliminating the reflection or creating “two of it, getting more mad,” as Love conjectured. In any case, when he and the others came back to the ranger station parking lot three days later, both the car and the cardinal were gone.

Shumaker said Love’s paper may prompt behavior ecologists to take a closer look at a common species that they might have neglected. “It will not surprise me if there are more behaviors in cardinals and similar birds that just haven’t been documented yet,” he said.

For his part, Love said the cardinal discovery has inspired him to pay attention to what birds do in addition to checking off species he’s spotted on birding apps. “I’ll watch birds a little longer, just to see what they’re up to,” he said. And just maybe, he might spot academic paper-worthy behavior once more.

“We’re planning on hitting the trail again this summer,” he said. “So I’ll keep my eyes out.”