Arquivo da tag: Corvos

Friend or Foe? Crows Never Forget a Face, It Seems (New York Times)

nytimes.com

Michelle Nijhuis


Aug. 25, 2008

Crows and their relatives — among them ravens, magpies and jays — are renowned for their intelligence and for their ability to flourish in human-dominated landscapes. That ability may have to do with cross-species social skills. In the Seattle area, where rapid suburban growth has attracted a thriving crow population, researchers have found that the birds can recognize individual human faces.

John M. Marzluff, a wildlife biologist at the University of Washington, has studied crows and ravens for more than 20 years and has long wondered if the birds could identify individual researchers. Previously trapped birds seemed more wary of particular scientists, and often were harder to catch. “I thought, ‘Well, it’s an annoyance, but it’s not really hampering our work,’ ” Dr. Marzluff said. “But then I thought we should test it directly.”

To test the birds’ recognition of faces separately from that of clothing, gait and other individual human characteristics, Dr. Marzluff and two students wore rubber masks. He designated a caveman mask as “dangerous” and, in a deliberate gesture of civic generosity, a Dick Cheney mask as “neutral.” Researchers in the dangerous mask then trapped and banded seven crows on the university’s campus in Seattle.

In the months that followed, the researchers and volunteers donned the masks on campus, this time walking prescribed routes and not bothering crows.

The crows had not forgotten. They scolded people in the dangerous mask significantly more than they did before they were trapped, even when the mask was disguised with a hat or worn upside down. The neutral mask provoked little reaction. The effect has not only persisted, but also multiplied over the past two years. Wearing the dangerous mask on one recent walk through campus, Dr. Marzluff said, he was scolded by 47 of the 53 crows he encountered, many more than had experienced or witnessed the initial trapping. The researchers hypothesize that crows learn to recognize threatening humans from both parents and others in their flock.

After their experiments on campus, Dr. Marzluff and his students tested the effect with more realistic masks. Using a half-dozen students as models, they enlisted a professional mask maker, then wore the new masks while trapping crows at several sites in and around Seattle. The researchers then gave a mix of neutral and dangerous masks to volunteer observers who, unaware of the masks’ histories, wore them at the trapping sites and recorded the crows’ responses.

The reaction to one of the dangerous masks was “quite spectacular,” said one volunteer, Bill Pochmerski, a retired telephone company manager who lives near Snohomish, Wash. “The birds were really raucous, screaming persistently,” he said, “and it was clear they weren’t upset about something in general. They were upset with me.”

Again, crows were significantly more likely to scold observers who wore a dangerous mask, and when confronted simultaneously by observers in dangerous and neutral masks, the birds almost unerringly chose to persecute the dangerous face. In downtown Seattle, where most passersby ignore crows, angry birds nearly touched their human foes. In rural areas, where crows are more likely to be viewed as noisy “flying rats” and shot, the birds expressed their displeasure from a distance.

Though Dr. Marzluff’s is the first formal study of human face recognition in wild birds, his preliminary findings confirm the suspicions of many other researchers who have observed similar abilities in crows, ravens, gulls and other species. The pioneering animal behaviorist Konrad Lorenz was so convinced of the perceptive capacities of crows and their relatives that he wore a devil costume when handling jackdaws. Stacia Backensto, a master’s student at the University of Alaska Fairbanks who studies ravens in the oil fields on Alaska’s North Slope, has assembled an elaborate costume — including a fake beard and a potbelly made of pillows — because she believes her face and body are familiar to previously captured birds.

Kevin J. McGowan, an ornithologist at the Cornell Laboratory of Ornithology who has trapped and banded crows in upstate New York for 20 years, said he was regularly followed by birds who have benefited from his handouts of peanuts — and harassed by others he has trapped in the past.

Why crows and similar species are so closely attuned to humans is a matter of debate. Bernd Heinrich, a professor emeritus at the University of Vermont known for his books on raven behavior, suggested that crows’ apparent ability to distinguish among human faces is a “byproduct of their acuity,” an outgrowth of their unusually keen ability to recognize one another, even after many months of separation.

Dr. McGowan and Dr. Marzluff believe that this ability gives crows and their brethren an evolutionary edge. “If you can learn who to avoid and who to seek out, that’s a lot easier than continually getting hurt,” Dr. Marzluff said. “I think it allows these animals to survive with us — and take advantage of us — in a much safer, more effective way.”

Crows are self-aware just like us, says new study (Big Think)

Neuropsych — September 29, 2020

Crows have their own version of the human cerebral cortex.
Credit: Amarnath Tade/ Unsplash

Robby Berman Share Crows are self-aware just like us, says new study on Facebook Share Crows are self-aware just like us, says new study on Twitter Share Crows are self-aware just like us, says new study on LinkedIn Crows and the rest of the corvid family keep turning out to be smarter and smarter. New research observes them thinking about what they’ve just seen and associating it with an appropriate response. A corvid’s pallium is packed with more neurons than a great ape’s.


It’s no surprise that corvids — the “crow family” of birds that also includes ravens, jays, magpies, and nutcrackers — are smart. They use tools, recognize faces, leave gifts for people they like, and there’s even a video on Facebook showing a crow nudging a stubborn little hedgehog out of traffic. Corvids will also drop rocks into water to push floating food their way.

What is perhaps surprising is what the authors of a new study published last week in the journal Science have found: Crows are capable of thinking about their own thoughts as they work out problems. This is a level of self-awareness previously believed to signify the kind of higher intelligence that only humans and possibly a few other mammals possess. A crow knows what a crow knows, and if this brings the word sentience to your mind, you may be right.

Credit: Neoplantski/Alexey Pushkin/Shutterstock/Big Think

It’s long been assumed that higher intellectual functioning is strictly the product of a layered cerebral cortex. But bird brains are different. The authors of the study found crows’ unlayered but neuron-dense pallium may play a similar role for the avians. Supporting this possibility, another study published last week in Science finds that the neuroanatomy of pigeons and barn owls may also support higher intelligence.

“It has been a good week for bird brains!” crow expert John Marzluff of the University of Washington tells Stat. (He was not involved in either study.)

Corvids are known to be as mentally capable as monkeys and great apes. However, bird neurons are so much smaller that their palliums actually contain more of them than would be found in an equivalent-sized primate cortex. This may constitute a clue regarding their expansive mental capabilities.

In any event, there appears to be a general correspondence between the number of neurons an animal has in its pallium and its intelligence, says Suzana Herculano-Houzel in her commentary on both new studies for Science. Humans, she says, sit “satisfyingly” atop this comparative chart, having even more neurons there than elephants, despite our much smaller body size. It’s estimated that crow brains have about 1.5 billion neurons.

Ozzie and Glenn not pictured. Credit: narubono/Unsplash

The kind of higher intelligence crows exhibited in the new research is similar to the way we solve problems. We catalog relevant knowledge and then explore different combinations of what we know to arrive at an action or solution.

The researchers, led by neurobiologist Andreas Nieder of the University of Tübingen in Germany, trained two carrion crows (Corvus corone), Ozzie and Glenn.

The crows were trained to watch for a flash — which didn’t always appear — and then peck at a red or blue target to register whether or not a flash of light was seen. Ozzie and Glenn were also taught to understand a changing “rule key” that specified whether red or blue signified the presence of a flash with the other color signifying that no flash occurred.

In each round of a test, after a flash did or didn’t appear, the crows were presented a rule key describing the current meaning of the red and blue targets, after which they pecked their response.

This sequence prevented the crows from simply rehearsing their response on auto-pilot, so to speak. In each test, they had to take the entire process from the top, seeing a flash or no flash, and then figuring out which target to peck.

As all this occurred, the researchers monitored their neuronal activity. When Ozzie or Glenn saw a flash, sensory neurons fired and then stopped as the bird worked out which target to peck. When there was no flash, no firing of the sensory neurons was observed before the crow paused to figure out the correct target.

Nieder’s interpretation of this sequence is that Ozzie or Glenn had to see or not see a flash, deliberately note that there had or hadn’t been a flash — exhibiting self-awareness of what had just been experienced — and then, in a few moments, connect that recollection to their knowledge of the current rule key before pecking the correct target.

During those few moments after the sensory neuron activity had died down, Nieder reported activity among a large population of neurons as the crows put the pieces together preparing to report what they’d seen. Among the busy areas in the crows’ brains during this phase of the sequence was, not surprisingly, the pallium.

Overall, the study may eliminate the layered cerebral cortex as a requirement for higher intelligence. As we learn more about the intelligence of crows, we can at least say with some certainty that it would be wise to avoid angering one.