LUND, Sweden, April 26 (UPI) -- Call someone a birdbrain and they're liable to be offended. Despite their diminutive noggins, many bird species are quite intelligent.
In fact, new research suggests ravens and crows are just as clever as chimpanzees.
"Absolute brain size is not the whole story. We found that corvid birds performed as well as great apes, despite having much smaller brains," Can Kabadayi, a researcher at Lund University in Sweden, said in a news release.
Measuring intelligence is a tricky task, but measuring inhibitory control, an important aspect of cleverness, is more straightforward. In 2014, Duke researchers tested the inhibition of several mammal species -- mostly apes, monkeys and other primates -- using the so-called cylinder test, whereby food is placed in a transparent tube with side openings.
Instead of reaching for the food through the tube's end openings, more clever test-takers used the side openings. Their success relied on the ability to control the urge to reach directly for the food and use a less obvious but more efficient strategy.
The findings suggested brain size predicted cleverness. The primate species who passed the cylinder test were more likely to boast big brains.
But the study didn't test corvids, birds in the crow family. Corvids are well known for their intelligent use of tools.
When researchers at Lund replicated the test for corvid species, they found jackdaws and common ravens passed at a rate close to 100 percent. Their performance was comparable to bonobos, gorillas and chimps.
"This shows that bird brains are quite efficient, despite having a smaller absolute brain size," Kabadayi said. "As indicated by the study, there might be other factors apart from absolute brain size that are important for intelligence, such as neuronal density."
Kabadayi and his colleagues published their latest findings in the journal Royal Society Open Science.
"There is still so much we need to understand and learn about the relationship between intelligence and brain size, as well as the structure of a bird's brain, but this study clearly shows that bird brains are not simply birdbrains after all!"