We like ravens. The raven who frequents the woodlot comes and sees us every day when we are doing fieldwork, and has a great deal to say. He or she also does an excellent crow imitation, rather black humour for a raven, as they do not generally think well of crows. For our part, we certainly plan to repect the ravens' needs for many large trees for nesting and perching habitat.
Bird Brains
Pesky, oft-reviled ravens and other corvids are turning out to be one of the animal kingdom's cleverest of creatures. Studies suggest they're veritable feathered Einsteins
Two months ago, in response to ratepayer complaints, Chatham, Ont., posted a bounty on an estimated 30,000 crows that haunted the city's uncovered refuse dumps. First an amateur free-for-all was organized, with a prize for the biggest crow shot. When this was unsuccessful, the city decided to hire professional hunters.
Chatham's response to its noisy, scavenging birds is not unique. Last year, the Alberta government allowed ranchers to shoot ravens on private land, while in New Mexico, peanut farmers rent special propane cannons for discouraging crows during harvest season. No doubt about it, the corvids -- crows, ravens, rooks, magpies, jays, nutcrackers, jackdaws and rooks -- can be a pesky bunch.
Humanity seems evenly divided into those who find corvids intelligent and fascinating, and those who consider them vermin. Detractors hate their guttural croaking. Admirers love their amazing variety of sounds.
Not only can crows hum, sing and utter human words, they have been recorded duplicating the sound of counteravalanche explosions, down to the "three . . . two . . . one" of the human technician counting down to detonation. These talents of mimicry reflect the general braininess of corvids -- which is so high that, by most standards of animal assessment, it's off the scale.
It's astonishing how many people cherish a story to this effect. Ravens who pull eagles' tails, then evade their enraged victims by doing cheeky barrel rolls; ravens working as a tag-team to swipe food from an intellectually outclassed dog; ravens that deliberately cover streetlight switches on cold days, keeping the lights on to warm their feet; the ravens of Whitehorse that extend their foraging range by hopping on the backs of the city's ubiquitous pickup trucks; crows that hop tantalizingly within 10 centimetres of a tethered dog's teeth, knowing exactly the length of the leash, to playfully snatch up a piece of kibble.
Lay people have long known how smart the corvids are; science has arrived at the same conclusion more slowly. One sympathizes with the scientists, for their training drums into them that things are not always as they seem. A raven apparently engaged in horseplay -- sliding down snowbanks, buzzing deer -- may have a functional motive: scraping off parasites, or finding food. But surely no species other than our own can possess such premeditation? Such deceit? Such in-your-eye sassiness? Corvids can't be as smart as they seem . . . except that they are. Scientist or lay person, everyone who watches ravens realizes that these birds seem brilliant, because they are brilliant. They're feathered Einsteins.
There's another reason for the tardiness of science in the area of corvid intelligence. The observations that support raven braininess are mostly anecdotes -- that is, one-of-a-kind stories. And for 300 years, science has treated anecdotes as optional illustrations, mere flourishes. Science, after all, is based on reproducible statistics; anecdotes by themselves are nothing more than icing on the scholastic cake.
Increasingly, however, scientists are basing papers on unique observations, without parallel control situations and with more than the usual lone independent variable. Well-chosen anecdotes may now comprise a paper's main content, and be its main theoretical vehicle. The change extends to disciplines other than ethology. When elegant equations in hydraulics have proven insufficient to restore a river system, geotechnical engineers have found the facts they need in the tales of old-timers who grew up along the river banks. Science is realizing there's a place for anecdotes.
That's certainly true in corvid research. When researchers present ravens with situations the birds have never encountered, the birds usually assess the circumstance and solve it before the scientists' eyes. Ravens have deduced how to transport two doughnuts to a food cache in one trip: Reach through one doughnut hole and grasp other doughnut, or balance first doughnut on top of second.
Orthodox ethology struggles in vain to reduce such anecdotes to footnotes by overwhelming them with observational statistics. ("10:03:30 a.m. Three Corvus corvax visit wolf kill, stay 11 min. 22 sec. Made four flights, presumably caching food. Lacking banding, birds may not be identical. 10:08:05 a.m., no activity.") The ethologists' conversion to raven storytellers is amusing to human bird-watcher-watchers. It must make corvids roll, laughing, on the floor.
The scientist who has done more than any other to study the raven is Bernd Heinrich of the University of Vermont. Despite years spent observing corvids both captive and in the field, Dr. Heinrich often resorts to anecdote to explain his birds' behaviour. In 1998 he designed an anecdotal experiment to demonstrate that ravens really were intelligent: specifically, that they could devise new behaviour to solve a problem they had never before encountered.
Dr. Heinrich suspended a choice tidbit of dried salami from a branch by a 75-centimetre string. The string was strong and the food was dense and well above the ground, hence no raven could hop up to it or seize it in a flyby. To get the food, a raven would have to deduce six steps ab initio, then perform them in sequence:
As the scientist expected, ravens feeding at an animal carcass in the wild were startled by the hanging food and gave it a wide berth. Ravens raised by Dr. Heinrich in an aviary inspected the setup, tried and failed to rip off the bait, and seemed to lose interest. But just as Dr. Heinrich was concluding that no bird could exhibit intentional behaviour, a lone raven flew down to the branch, perched above the string, and performed the entire sequence perfectly in front of the dumbfounded scientist on the first try.
- Perch on the branch above the string;
- Reach down and grasp the string in its beak;
- Pull one loop of the string up and over the perch;
- Lift one foot and step on the loop to prevent string slippage;
- Shift the bill-grip to the hanging portion of the string;
- Repeat the above steps until the whole string is taken up
"I conclude," writes Dr. Heinrich in Mind of the Raven, "that [the ravens] experience some level of consciousness, and use it for insights to make decisions." (Incidentally, when Dr. Heinrich submitted these groundbreaking observations to scientific journals, they were rejected five times -- presumably as too anecdotal.)
The real reason ravens fascinate us may be a hunting partnership that goes back to the Old Stone Age. Dr. Heinrich has propounded a new theory, supported by anecdotal and statistical observations. Over millions of years, he thinks, corvids developed a symbiotic link with large mammalian pack-hunters. The birds learned to act as aerial observers, spotting prey and revealing it to the hunter species; the birds then shared the kill. At first the hunter was likely Canis lupus, the wolf. But when the highly effective human hunter emerged, the ravens' high intelligence let them transfer their attachment.
Dr. Heinrich cites a striking anecdote to support his theory. In 1998, a woman in Colorado noticed the wild activity of a raven directly over her head. Disturbed by this, she glanced around -- and looked directly into the face of a cougar about to spring on her. Being religious, she believes heaven sent the bird to warn her. Being a corvid ethologist, Dr. Heinrich believes the raven led a symbiotic predator to an easy kill in order to share the meat.
Dr. Peter Sherrington, an avian ethologist who lives east of the Rockies on the high plains of Alberta, agrees with Dr. Heinrich's thesis "without question. . . . I often see a crowd of ravens out on the plain, following wolf packs. I have observed a pack of 12 wolves accompanying an overhead armada of ravens and magpies. In this area, ravens are even shifting their attention to coyotes."
Dr. Heinrich is not alone, however. A New Zealand researcher who studies the giant ravens of New Caledonia reported conclusively in 1996 that the birds have learned to both make and use tools. Gavin Hunt of Massey University says ravens daily fashion leaves and twigs into hunting tools that resemble the stone tools of early humans. The crows produce two different types of tools -- a hooked twig that they strip of its bark and vegetation, and a tapered, barbed leaf -- to patiently tease grubs out of rotting logs.
The tools possess three distinctive features, says Dr. Hunt. "They're standardized to a high degree, the two types are distinctly different and they involve the use of hooks."
By contrast, early humans didn't come up with anything quite like that until late in their evolution. Early man had, until millions of years before then, banged about only with stone and bone.
Closer to home on Mittlenatch Island, B.C., Simon Fraser University researchers report that crows there methodically collect shellfish at low tide, cache them and crack them open later in the day when water covers their food source. It's a classy, businesslike operation that confounds their audience of dimwitted gulls.
Other scientists, too, are weighing in with evidence that crows and cousins are all tool users. Florida scrub jays, for example, have been reported selecting forked branches as vises for tough nuts. And crows have a special technique for pulling up ice-fishing lines and stealing either the bait or the catch. And they don't try to fly away with it -- crows know all about hooks, it seems.
Such research goes far to explaining why corvids inspire love and hate in humanity in equal quantities. Hunting cultures revere ravens. Farming cultures are more likely to find them pests. In this, the PR profile of corvids may parallel that of their allies, the wolves. Throughout history, they have been regarded alternately with awe and hostility. Dr. Heinrich calls ravens "wolf-birds." In how we view them, they may be exactly like the wolf.
Whatever the attitude toward corvid species, there's little chance that the genus is endangered. What's happened in Alberta and Chatham doesn't worry the experts at all.
"I don't think Corvus corvax is threatened by this latest Act revision," says Gordon Court, an Alberta wildlife biologist. "I've seen only one piece of land where anyone actually shot a raven. They're pretty darned hard to hit."
Adds Dr. Sherrington: "Magpies were persecuted for years in Alberta, with no real effect on their population numbers. They're corvids, after all. Most corvids are simply too smart."
BY: WILLIAM ILLSEY ATKINSON Special to The Globe and Mail Thursday, February 17, 2000 William Illsey Atkinson is a science and technology writer who lives in North Vancouver, B.C. E-mail: billatki@axion.net