The Intelligence of Corvids

For hundreds of years humans thought that tool making was a uniquely human trait. In 1960, Jane Goodall observed chimpanzees using tools in the wild, a discovery to which Goodall’s mentor Louis Leakey famously responded, “We must redefine tool, redefine man, or accept chimpanzees as human.” It is now commonly accepted that various primates engage in tool making, and there is a growing body of evidence that many corvids, a group of bird species that includes crowsjaysrooksravens, and magpies, are also tool makers, and that they show many other signs of possessing high intelligence.

Scientists have observed wild New Caledonian crows making hooks out of twigs to pull grubs from tree holes that are too deep for their beaks. New Caledonian crows also sometimes use their beaks to create small spears from leaves for collecting insects. Because New Caledonian crows are highly social and because tool design varies from area to area, most researchers assume the birds’ tool use is cultural; that is, the tool use is learned from other crows.

In 2002, however, three researchers at Oxford University reported in Science a startling new twist to tool making in corvids: A New Caledonian crow that had been captured in 2000 as a juvenile had invented a new tool from materials not found in her natural habitat without observing the behavior in other crows. The crow, named Betty, shared space with a male crow named Abel. The researchers had set up an experiment in which both crows were presented with a straight wire and a hooked wire and food that could most easily be retrieved with a hooked wire. When Abel flew away with the hooked wire, Betty bent the straight wire and successfully lifted the bucket of food with her hook. The researchers then set out to see whether they could get Betty to replicate the behavior. Ten times, they set out a single straight wire and food to be retrieved. Betty retrieved the food nine times by bending the wire; once she managed to retrieve the food with the straight wire. Alex Kacelnik, one of the researchers who worked with the crows, noted that she had solved a new problem by doing something she had never done before.

Professor John Marzloff, at the University of Washington in Seattle, demonstrated another interesting ability in American crows: recognizing faces of individual humans. In 2005, he and other researchers each wore a caveman mask when they capturedtagged, and then released crows on campus

. Then Marzloff and other researchers took turns wearing the mask and walking around campus. Over time, increasing numbers of crows flocked together and cawed at anyone wearing the caveman mask, regardless of the size, gender, and skin color of the mask wearer or whether the wearer was one of the researchers who had originally captured crows. When the same people did not wear the mask, they got no reaction from the crows. This showed that it was clearly the face that was identified as a threat to the flock. Crows that had not originally been captured were joining the harassment of the perceived threat. When Marzloff suggested that researchers try wearing the caveman mask upside down, some crows actually turned their heads upside down to better identify the face of the “enemy.”

In their studies of western scrub jays published in Science in May 2006, Johann Dally, Nathan Emery, and Nicola Clayton showed that jays have the ability to remember whether a specific other jay saw then hide food for later use. When it became clear that a jay that observed the hiding might have access to the cache, the hiders retrieved their food and re-hid it when given the opportunity to do so without observation. They did not re-hide food when other jays were introduced to the situation. Similarly, ravens in the wild have been observed misleading other ravens by pretending to hide food in one location then flying off to hide it elsewhere when the other raven goes to investigate the false cache.

Corvids are also capable of fooling humans. Marzloff tells the story of a pair of crows that buildfake nest that they always flew to when researchers were in their area. The crows’ actual nest with their young was nearby, but the humans never saw the crows actually fly to it.

In an experiment to test social cooperation in rooks, University of Cambridge researchers found that pairs of rooks quickly figured out how to pull on ropes at the same time to bring food that could not be gained through the individual effort of one rook.

Otto Koehler tested the ability of captive jackdaws to count, a skill apparently related to their communication often being based on the number of calls. First, Koehler trained jackdaws to expect five food rewards. Then the jackdaws were given a number of boxes, some of which contained food. They proceeded to open the boxes until they had found five pieces of food, at which point they stopped opening boxes because they knew they had reached five. In another experiment Koehler also trained jackdaws to choose a box with the same number of dots on the lid as the number of dots on a cue card.

Tool makers, tricksterscooperatorsmathematicians – the corvids are far from “bird brains.” In fact, their intelligence, in many cases, appears to equal or even surpass that of many on our primate “cousins.”


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