During the fall semester of my sophomore year at college, I learned a valuable lesson that has remained with me over the intervening two decades: don’t try to study wild animals that are smarter than you. You might think I was endeavoring to work with some great ape or dolphin, but the animal that humbled me back then is familiar to most everyone in North America: the American crow. Crows are in the family Corvidae, which includes about 120 species of crows, jays, magpies, ravens, rooks, and jackdaws worldwide.
As part of a Field Biology class at Cornell, I was attempting to conduct a research project examining the responses of crows to different types of predators; would they treat a terrestrial predator like a cat or a fox differently than an aerial predator like an owl or hawk, and would they treat a great horned owl differently than a sharp-shinned hawk? Great horned owls generally represent the most extreme threats to adult crows and their offspring, and should elicit an animated and prolonged mobbing response, whereas the smaller sharp-shinned hawk and the terrestrial predators like the fox and cat should evoke a more restrained response. Or so I hypothesized.
Right off the bat, things went askew. I had managed to acquire a captive great horned owl from a raptor rehabilitation center to use in my study, and I planned to unveil the owl (protected in a cage) in an area frequented by crows. I covered the owl cage in a sheet which had a long trailing line, and once I had positioned the cage in a conspicuous location and hidden myself for 5 minutes in the bushes a little ways away, I pulled the string and revealed the owl. I expected that once one crow had found the owl, it would recruit others and the mobbing would begin.
In my first few owl reveals, one or two crows did show up, but their response was not what I expected. After a few initial caws, they appeared to transition into what I deemed was an “evaluation stage,” during which they would fly around the cage, seemingly inspecting it. After this assessment, they would take off, and that was it. No recruiting, no angry mobbing, nothing to suggest that their most feared predator was in the area. I’ve seen crows mobbing wild great horned owls, and it is a raucous, wild affair. I thus had an idea of what should be happening. So why wasn’t it? After a half dozen failed attempts at eliciting a response, I decided that the crows were correctly gauging that my owl was not a threat. Could they tell that the owl was unable to fly? Did they know what a cage was? I’m not sure, but they were clearly making a determination that this particular owl was not a risk to them or their families and returning to more pressing matters.
In order to salvage my project, I shifted gears and opted to work with birds of less advanced cognitive abilities. I focused on birds like chickadees, robins and nuthatches, and I’ve mostly stuck with the “less sophisticated” members of the avian group since. I know that lots of people study primates and cetaceans, and they have gleaned valuable information from these geniuses of the animal world. But in most cases, they can only do this with captive animals that have “agreed” to cooperate with the researchers. Studying the behavior of wild animal Einsteins is often an exercise in futility, as I discovered long ago.
There are some persistent researchers, however, who have successfully worked with corvids over the past few decades, and we’ve learned an incredible amount about this family of high achievers. In fact, recent work has placed some corvids at the level of seven-year-old children when it comes to problem-solving, easily equaling or even outpacing the most advanced primates and cetaceans. Check out the video of a New Caledonian crow working through an 8-step puzzle. This crow had seen the individual steps before but had never encountered the multistage puzzle prior to this trial.
Moreover, these crows have been shown to not just use tools, but make tools, and even keep them for future use.
In addition to the puzzle-solving example above, corvids are savvy problem-solvers in an everyday context. Anyone who has attempted to keep crows, magpies or jays from eating their bird food has experience with this. In the Pacific Northwest, northwestern crows have learned how to crack open hard-shelled bivalves by taking them into the air and dropping them onto hard rocks. This behavior is widely exhibited by their gull neighbors, but it is unclear if the crows adopted this behavior on their own, or from watching the gulls.
Even more impressive than the clam-dropping is the walnut-cracking behavior shown by the Japanese carrion crow. These birds have learned how to utilize both cars and crosswalks in order to get at their walnut prizes. The crows drop their hard-shelled walnuts onto the road at crosswalks and wait for passing cars to crush them open. Then, they wait for the crosswalk light to change, which allows them to recover their food without the risk of getting squashed. The following clip from the Life of Birds shows how they go about doing this.
This all begs the question, why are corvids so intelligent? To answer this, I think we need to look at other intelligent groups of animals and see what links them together. (Note: I’m using a rough, classical definition of intelligence here. There are many ways to define intelligence, and this classical version is simply one that many people are familiar with). Why, for example, are humans so intelligent (in theory, that is)? What about dolphins? African gray parrots? Chimpanzees? In short, we don’t know for sure, but most of these organisms live in complex social groups that may favor the evolution of more advanced cognitive functioning. The next question that arises is why do complex social groups favor advanced cognitive functioning? Is it because cooperating with others requires advanced thinking and reasoning skills? Or is it because cheating members of your social network (and not getting caught) requires innovative intelligence? It may actually be some of both; learning how to cooperate successfully with others who have the ability to surreptitiously cheat requires a lot of mental gymnastics. Indeed, researchers have found that when faced with a choice between working with a cheater or a reliable cooperator (based on previous encounters), most crows choose to work with the reliable option. Not only can they identify when a particular individual is cheating them, but they will continue to avoid working with that individual for months or longer.
Whatever the root cause of their smarts, corvids express their intelligence in myriad ways. Not all corvids are capable of advanced problem-solving or tool making, but most corvids shine in some cognitive capacity. Some, such as the Clarke’s nutcracker and pinyon jay, have fantastic spatial memory abilities that help them recall the locations of tens of thousands of seeds they’ve cached. Blue jays and Steller’s jays will mimic a red-tailed hawk’s call when approaching a bird feeder to scare the other birds away.
One of the more common strategies that corvids use is the “distract the bully” technique. This usually involves a large predator at a food source and may include multiple individuals working together. Crows, ravens, and magpies have all mastered this technique, and they often employ it upon eagles who have claimed an animal carcass. The strategy is simple; one bird sneaks up behind the eagle, grabs a tail feather, and tugs. The eagle whirls around in an attempt to catch the offender, but the smaller and faster corvids can easily outmaneuver the eagle. While the eagle is distracted, other birds dart in for a quick bite of meat. This process can be repeated until the eagle flies away, or all the corvids have had their fill.
In a similar vein, Bernd Heinrich (scientist, naturalist, and ultramarathoner extraordinaire) discovered that young common ravens in Maine will work together to acquire meals that have been claimed by more dominant adult ravens. He details his work in the wonderful book Ravens in Winter, but in short (spoiler alert—if you plan to read his book, skip the rest of this paragraph), he found that when non-territorial (often young) ravens find an animal carcass in the territory of adult ravens, the non-territorial birds often begin vocalizing. These vocalizations attract other non-territorial birds, and once their numbers reach some critical mass, they descend upon the carcass. The resident, and typically much more dominant birds are unable to defend the carcass against the onslaught of young hooligans, who are all able to partake of a meal they would have been unable to procure by themselves.
Another telltale sign of their intelligence is their penchant for play. Ravens appear to thoroughly relish aerial acrobatics, and perform a variety of stunts, including barrel rolls, flips, and even prolonged flights upside-down. Ravens also enjoy sledding or rolling down snowy slopes. One of the most entertaining videos of presumed corvid play comes from Russia, and shows a hooded crow repeatedly snowboarding down a roof on a plastic lid. It’s hard to know for sure if this is an example of play, but it certainly appears to be.
Corvids are well known for their mobbing behavior, which is generally directed at larger birds of prey like hawks, eagles and owls. There’s good reason for this behavior; these raptors pose a possible threat to the adults and their young, and mobbing is thought to serve as both a forum for alerting the neighborhood to the whereabouts of a potential threat, as well as a teaching aid for young birds.
But many corvids seem to derive a degree of satisfaction from tormenting raptors that goes beyond strict utilitarian function. The PBS video below shows a raven having some fun with an immature bald eagle.
A number of corvids have undeservedly acquired reputations as thieves and tricksters, and their fondness for eating the young of other animals doesn’t help. But these birds possess an intellect and awareness that may approach that of ourselves, and in my opinion they should be viewed with the same level of respect afforded cetaceans, parrots, and primates.
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About the author:
Loren grew up in the wilds of Boston, Massachusetts, and honed his natural history skills in the urban backyard. He attended Cornell University for his undergraduate degree in Natural Resources, and received his PhD in Ecology from the University of California, Santa Barbara. He has traveled extensively, and in the past few years has developed an affliction for wildlife photography.