A road junction in Sendai, Japan, in the early 1990s. The traffic light turns red, a line of cars stops, and a crow appears on the road just in front of a front tire. He drops a nut, then flies back to the sidewalk and waits. The light turns green, a tire passes over the shell, and once the cars pass, the crow returns to eat the grain. This is pretty much what Yoshiaki Nihei saw happen over and over again, and wrote about in a 1995 paper titled “Behavioral Variations of Carrion Crows Corvus corone Using Cars as Nutcrackers.” The story is often told as “crows are geniuses.” What we find most interesting is the actual record: what one observer documented at a set of intersections, what he concluded, and why other researchers refused. The gap between anecdote and evidence is where good questions live. What Nihei actually recorded Nihei described the sequence clearly. He wrote that “a crow puts a nut in front of the car that stops at a traffic light; then the car runs over the nut and the crow eats the pieces of the nut” (typos are his). That’s all the behavior: place, wait, retrieve. What gives it weight is the frequency with which he saw it. Nihei reported that “this behavior was frequently observed during the 21-month observation period and 43 such cases were recorded in detail.” Forty-three documented events over almost two years are not an isolated case. It’s a pattern that someone stood by and observed, over and over again. Crows also crack nuts without cars. Dropping hard food from a height onto a hard surface is a common trick of crows, and Nihei watched crows drop nuts from more than 10 meters high. According to his interpretation, the car version was a variation on that old habit, useful for nuts too hard to break when dropped on their own. Systematic or a lucky byproduct? This is where interpretation comes in and where the story stops being simple. Nihei analyzed the details of each event and came to a firm conclusion. He argued that “the analyzes of these variables suggest that the behavior of crows in the use of automobiles is not accidental but rather systematic.” He went further and said he considered the behavior “intentional.” That word, intentional, is the one discussed. Saying that a behavior occurs reliably is one thing. Saying the bird is deliberately using a car as a tool and understanding what the tire will do is another. Nihei’s 43 events support his interpretation, but cannot establish exactly what the birds understood. Two years later, Daniel Cristol and his colleagues tested the idea on American crows in Davis, California, and were not convinced. The watching crows showed no clear change as the cars approached and often dropped nuts where no tires could reach them. In 200 vehicle-present observation periods, not a single nut was hit by a car. Their conclusion was that the apparent car-using behavior in Davis could be an incidental byproduct of dropping nuts on hard paved surfaces. In layman’s terms: the crows may have chosen paths because the roads are difficult, and cars occasionally help by accident. But Cristol’s team was careful. They did not claim that crows could never deliberately use cars. Their view was more limited: the behavior was not regularly demonstrated in the Davis birds they studied. That makes contrast useful. What seemed systematic in Sendai did not seem so in California. Different populations of crows may have been doing different things. A different version in Hakodate A later comparison sharpens the point. In observations in 2016, a team including Osamu Mikami studied carrion crows in Hakodate, Hokkaido, and compared them to Sendai birds. They didn’t find Sendai’s neat routine of placing nuts directly in front of stopped cars. Hakodate birds more frequently dropped nuts from power lines onto roads in a more loose manner. The authors considered the behavior “less sophisticated” than Sendai’s version. They suggested several possible reasons, including differences in local learning history, the environment, and the nuts themselves. Those were possibilities, not proven causes. What a smart crow can and can’t tell us Perhaps what’s most useful here is how little a single vivid observation can resolve on its own, and how much more interesting the picture becomes once you stop asking whether crows are “smart.” The car-breaking Sendai crows are real and well documented. Nihei recorded 43 detailed events. Whether any individual bird understood that a tire would be the one to crack is harder to answer, and Cristol’s results in Davis are a fair warning against reading intent into every nut that gets crushed by a car. What holds up best is the least mind-reading part of the story: the Sendai crows repeatedly used cars in a very structured way, while the crows studied in California did not show the same pattern, and the birds in Hakodate used a “less sophisticated” version. That doesn’t tell us exactly what each individual crow understands. It does show that the same general problem of cracking nuts can produce surprisingly different behaviors in different populations of crows. Standards Space Daily articles are edited and fact-checked before publication. We use artificial intelligence tools in the newsroom. See our editorial standards and masthead.
