Uncommonly Intelligent – Ravens at the Top of the Class

Call a despicable person “pond scum” and I take offense on behalf of pond scum everywhere.  Scoop up a handful of pond scum and you might actually be looking at diminutive, individual aquatic plants or even blue-green algae such as spirulina, which some health food fans herald.  Think someone is, um, “bat-guano crazy?”  Bats the world around resent the insult.  While unprocessed bat poop can be harmful for humans, it can be turned into a rich fertilizer full of microbes that can help clean up toxic soils.  Consider a foolish person a “birdbrain?”  Recent science says you’re wrong, at least where Common Ravens are concerned.


The world’s largest passerine, the Common Raven is a permanent resident of San Diego County.  It occurs in all habitats, including beaches, the desert floor, and mountain­tops and anywhere in between.  At about two feet long, bill to tail tip, with wingspans greater than four feet, adults are solid, glossy black, with wedge-shaped tails and massive bills.  Males and females look alike and their plumage doesn’t change during breeding season.  Differentiating a Common Raven from its smaller cousin, the American Crow, can present a challenge.  Ravens tend to soar on thermal currents and glide more often than crows do, which instead flap their wings nearly continually in flight.  Because they can extend their long throat feathers to create a ruffled look, ravens often look a bit more disheveled than crows do.  You’ll most often find a raven alone or in a pair; crows, especially in the winter, tend to move around in large, noisy, social flocks.  Voice offers one of the best ways to distinguish these two species.  Most people know the American Crow’s typical caw, caw call, although their repertoire can be quite varied.  Common Ravens can also produce a vast array of sounds. But if you’re looking at a large black bird or two uttering deep, resonant, croaking rawck, rawck, rawck calls as they pass by high in the sky—you’re looking at ravens.  I’ve heard people say that crows are negatively affecting ravens in San Diego county by aggressively running them out of their territories.  But if you turn to the county-level data (the U.S.G.S. Breeding Bird Survey from 1966 – 2015), you’ll find that the population of Common Ravens county-wide has been holding steady over the past half-century.


The scientific name for Common Ravens—Corvus corax—basically means “raven,” since corvus means “raven” in Latin and corax, “raven” in Greek.  The word “raven” comes from the Anglo-Saxon hraefn, purported to be an onomatopoetic representation of its call.  (My Anglo-Saxon pronunciation skills leave a lot to be desired, so it’s rather challenging to imagine how “hraefn” might sound like a raven’s call.  Poetic—or maybe onomatopoetic—license, I suppose.)  And the “common” in the Common Raven’s name reflects the fact that they are the most likely raven species within their range.


An oft-cited hallmark of being human has been is the ability to plan for future events, such as saving for retirement or figuring out tomorrow’s breakfast. Scientists previously believed such behaviors were unique to hominids—humans and great apes—because no other animals appeared to possess such abstract thinking skills.


Put a lid on that smugness, humans.  Although corvids (the avian family containing ravens, crows, jays, magpies, and nutcrackers) have brains no larger than a walnut,  recent experiments with ravens showed some humbling results.  Researchers taught a number of ravens to place a special tool—a uniquely shaped rock—in a tube sticking out of a box.  The rock would release a piece of dog kibble (a favorite treat).  (Okay, so maybe their palates are not as sophisticated as ours.  Or perhaps they know something about dog kibble that we don’t.)  The researchers then took the box and the tool away.  An hour later, the team offered the ravens a choice of objects—one being that special tool. After 15 minutes, the ravens got the box back.  About 80 percent of the time, the ravens had selected the correct tool and performed the task to get their treat. The team repeated the same experiment with a 17-hour delay in returning the box to the ravens. In this case, the birds succeeded nearly 90 percent of the time.  Next, the researchers taught the ravens to select and save tokens to exchange for treats at a later time. Again, the birds passed these tests over 90 percent of the time.  Even when the ravens knew that trading would only happen the next day, they chose and stored these tokens as soon as they were offered to them.


One star (or subversive, depending on your point of view) may suggest we stand at the brink of the Dawn of the Planet of the Ravens.  Setting the researchers on their heels, a female Common Raven quickly learned how to operate the box and began teaching the other ravens.  (Females rule!)  She then invented her own way of opening the apparatus without the special tool—filling the tube with a layer of small twigs and pushing a larger stick into that layer to release the treat. This rebel had to be excused from the experiment before she could teach any other birds her novel approach.  The researchers nicknamed this clever hacker “the little engineer.”


Tool-using.  Planful.  Creative thinkers.  Skilled barterers.  All in all, ravens were at least as proficient at these tasks as tool-using apes.  They even performed better than four-year-old children in a comparable set-up.  So the next time you consider using the term “birdbrain” as a pejorative epithet, take a moment to reconsider.  Quoth the raven, “Nevermore.”


Photo Credit: Steve Brad

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