Let me try to persuade you (if persuasion is required) to join me in admiring the American Crow (Corvus brachyrhynchos). My early interest in these birds was nourished years ago when as a bookstore owner, I hosted an author presentation by Jean Craighead George about her middle grade book, The Tarantula in My Purse. (I know, great title!) The book chronicled Jean’s many adventures with various animals, including a crow she rescued as a fledgling that her children named Crowbar. Crowbar’s exploits with the George family were hilarious and brilliantly portrayed the bird’s ingenuity. An example: when Jean’s daughter complained that the crow was taking toys from her sandbox, her mother suggested she play on the slide, since the crow with its large, taloned feet couldn’t do that. Crowbar observed the child gaily swooping down the slide a few times, then flew to the sandbox, plucked up a plastic coffee can lid, flew to the top of the slide, stepped onto the lid and sailed down the slide! Another example: Jean once placed candy party favors under upside-down paper cups to keep Crowbar from bothering them. Crowbar waited until Jean was in the kitchen, then carefully tapped the little cups to the side of the table until the candy fell out, ate it, and then neatly tapped the cups back in place to hide his misdeed.
So imagine my delight when the Bird Academy at Cornell Lab of Ornithology offered a 3-hour online course on crows taught by Dr. Kevin McGowan who’s studied these birds for 30 years! I signed up at once for “Anything but Common: The Hidden Life of the American Crow.” Since winter walks don’t offer much birdsong – but do frequently feature crow calls – I thought I’d take this opportunity to share some of what I’ve learned and my general enthusiasm for the American Crow.
First, the Bad Rap on Crows
Let’s get the complaints about crows out of the way first. I know some friends who are frightened of crows or at least “creeped out” by them. The main reason seems to be that part of their diet is carrion. But consider, cleaning up carcasses is actually a service to both us and the ecosystem, since it reprocesses lots of nasty stuff that we don’t have to deal with! Crows eat just about anything – sumac berries, wild cherries, seeds, fish, discarded pizza – whatever! They are often disliked because they do occasionally consume baby birds. But guess what! The most lethal predator of baby birds in our area is this guy!
Yes, the chief wild predator of nestlings in the northern United States is chipmunks – and their relatives the squirrels! They’re omnivores and excellent, quick tree climbers. In the southern U.S., the main predators of baby birds are snakes:
Dr. McGowan cites a meta-analysis study done in 2007 (“Factors Affecting Nest Predation on Forest Songbirds in North America“, F.R. Thomson). Out of 245 predation events on nestlings by wild animals, only 2 were caused by crows. Chipmunks, squirrels and snakes consumed half of the nestlings in the study. Outdoor cats kill a lot more baby birds than crows and among wild creatures, raptors, insects, cowbirds, jays, and mice are all more likely to kill or dine on baby birds than crows. Birds eggs are most often eaten by raccoons and opossums. So I think we can dispense with the notion that crows are killing lots of songbirds.
But you don’t want to park your car under trees in which large groups of crows roost on a winter night – very messy! And they can tear things apart trying to get at garbage or any kind of available food. Early morning is a noisy time to be around a family of crows, too, especially in the spring when young crows are hungry and insistent that they be fed right now! Crows are also loud and boisterous in flocks and a flock can consume large amounts of seed, which doesn’t endear them to farmers, of course!
Now On to the Positives!
So yes, like all animals, crows can cause problems. But crows also provide a variety of services within a habitat. They keep insect and rodent populations under control, as well as some agricultural pests like Japanese beetles and corn borers. Their nests are often acquired by some owls and merlins who don’t make their own. And crows are superlative sentinels, warning other creatures about predators on a regular basis, as you’ve probably noticed when they start cawing whenever you’re around.
And of course, they become prey for higher predators; the Great Horned Owl (Bubo virginianus) is the most dangerous predator for adult crows.
Raccoons (Procyon lotor) eat crow eggs and nestlings too, and occasionally add insult to injury by sleeping in the nest once they’ve finished! The birding group may have seen one of these culprits at Cranberry Lake Park a few years ago. The nest was made of sticks like crow’s nest are, and this raccoon looked quite content to be there early in the morning – after a late night snack perhaps?
Crows will also “mob” hawks in their territory since raptors take a fair number of crow eggs.
But what intrigues me about crows are some of their special qualities, ones that are unusual in nature.
Crows Enjoy Family Life (or what scientists call “cooperative breeding”)
In all seasons, crows hang out with their family, which usually includes a monogamous pair, this year’s young, plus young from previous years. None of the brownish yearlings breed. Some female crows can breed at 2 years old, but generally mature when the males do, at about 4 – 5 years of age. So during this long adolescence, they generally stay with their family and help out with nest building as well as caring for and feeding their younger siblings. According to Dr. McGowan, that’s a rare trait in birds.
They also stick close to home, defending their territory year ’round, but they feel free to go off territory to forage and roost. They move together, feeding or just hanging around – but one of the family members is always on guard, signaling when danger approaches. Both adults and young will groom each other occasionally, which is called “allopreening.” So Dr. McGowan admonishes us that if we see a group of 2-15 crows gathering consistently in one place, “it’s not a gang, it’s not a ‘murder.’ It’s a family.”
Crows are Social Creatures (or What Dr. McGowan Calls “Fun- loving Party Animals!”)
Dr. McGowan likes the fact that crows “never do anything quietly or alone.” Their families live within larger communities of crows. Foraging flocks can swell to 250 crows or more in January, and then drop off to 50 or so in April when breeding starts. As soon as the fledglings can fly, though, the numbers in flocks go right back up. A crow flock changes from day to day; an individual crow may spend time with different groups every day. Blackbirds and geese, I learned, are the same way.
In winter, crows gather into very large groups to spend the nights together in huge “slumber parties,” as McGowan calls them. They’re probably seeking safety in numbers from predators, since crows see no better at night then we do. These huge roosts can contain birds from areas farther north who are unfamiliar with the territory. They may be keeping an eye on the birds that look best fed, so they can follow them when they go out to forage in the morning.
Researchers think that these social groups serve several other functions. The younger crows may be testing themselves as they call, chase and hold mock fights. They may be trying to determine whether they’re going to breed soon or stay with their family for another year. Social groups provide a good opportunity for finding both your competition and your potential mate. In some cases, the young hang out in social groups during the day, but go home to their parents at night. Or they may spend part of the day being social and part of the day on their home territory.
Do Crows Have Empathy?
According to Dr. McGowan, the social nature of crows also shows up in some other interesting ways. He has seen crows “adopt” young from outside their family. A bird rehabilitator that my husband and I once knew received a crow with a broken wing, healed it and then put it in a big, open aviary in her back yard. A large group of crows gathered around the aviary and called to the bird inside for three days, until it finally flew out and joined them. An adoption? Or perhaps a family encouraging an injured member to rejoin them? Dr. McGowan, who tags each baby bird for identification, probably could have told us, but I’ll never know.
Dr. McGowan also documented on film a crow coming upon an unrelated crow that was seriously ill – weak, encrusted eyes, almost asleep out in the open during the day. Though the male was foraging for his mate, he stopped and put a seed in the sick female’s beak – and two other unrelated crows did the same shortly thereafter. I wondered if this behavior may have contributed to the huge die-off of crows from West Nile virus several years ago.
The Crows and Their Relatives (Corvidae) are Smart!
Because crows demonstrate so many unusual kinds of intelligence, they’re occasionally referred to as “feathered apes.” You may have seen the PBS Nova sequence on YouTube in which University of Washington researchers donned a variety of masks around campus, but one researcher wore a caveman mask when climbing to crow nests in order to weigh, measure, tag and band the young. Ten years later, the crows still reacted negatively to someone wearing that mask – gathering, calling and sometimes even attacking the person in the caveman mask! Evidently, the information from that mask is remembered and passed on within the crow community to birds not yet born when the mask was used!
The Cornell Bird Academy finds the same memory in a more positive sense. Crows recognize Dr. McGowan since he feeds crows peanuts to attract them for study; they even come up behind him, recognizing his walk. One crow who saw him leaving the Ornithology Lab, flew down to the far end of a parking lot and perched in front of his Subaru waiting for him to arrive with a peanut! It knew his car as well as his face, despite the fact that were many Subarus in the parking lot.
New Caledonian Crows (Corvus moneduloides) in the South Pacific make tools to get at food – saw-toothed tools, curved ones and others. Here’s a video of a wild female crow in the lab of Russell Gray at the University of Auckland in New Zealand. She creates a hook by sticking a straight metal stick under the duct tape at the bottom of a tube and then carefully bending it around the tube. Her hook complete, she then uses it to pick up a small bucket of food from within the tube. Pretty creative for those creatures that we disparage as “bird-brained!”
A Common Raven (Corvus corax), the American Crow’s larger Northern relative, was documented in Scandinavia using its beak and foot to haul up an ice fisherman’s line to grab his catch. The PBS video on YouTube has clearly been staged for the camera, but demonstrates nicely what the raven learned to do when a camera wasn’t around.
And yet another favorite video comes from the science section of the New York Times. An American Crow, after being taught to pick up rocks, quickly figures out how to raise the water level in a tube to get at a piece of floating food. Aesop’s fable come to life! (Be patient – a short ad comes first.)
Seasons of a Crow’s Life
Winter: Huge flocks of dozens or hundreds or crows can gather at night. According to the Bird Academy class, the largest on record had as many as a thousand crows! Where many pines are available, hundreds of them will often disappear inside the branches for shelter. In areas where only deciduous trees are available, they will make do and sleep more exposed on bare branches.
In just the last 20-30 years, crows have begun to nest and roost at night in suburban and urban areas. Crows have always foraged in towns, but generally flew to fields outside of towns when darkness fell. Dr. McGowan attributes this change to several factors: loss of natural habitat due to development, safety from predators due to city lights, abundant food, simple curiosity and freedom from being hunted. The Federal Migratory Bird Treaty Act of 1970 allows crows to be shot but only in season; urban and suburban areas, though, generally forbid hunting – a plus for the crows.
March and April: Around the time of the first serious snow melt, watch for crows carrying sticks. They construct their nests high up in trees, usually just below the top or in the top quarter of a tree in a crotch or on horizontal branches. The outer surface is all sticks, but the inner lining may be made of pine needles or animal hair from dogs or deer. The whole crow family may help build a new nest each year.Dr. Ben VanderWeide, our township Stewardship Manager, spotted this nicely camouflaged nest filled with snow at Draper Twin Lake Park. From the location and its stick construction, I’m guessing it’s a crow nest.
April to May: Females make a new high-pitched crow sound that the Cornell staff calls “whining.” They think it may be a signal that the female is hungry since males and their family helpers often fly to her with food when they hear it. The female lays 3-9 bluish to olive green eggs with gray or brown splotches near the egg’s large end. The female incubates the eggs for 18 -19 days and broods the little nestlings for an unusually long time, 5-6 weeks! As a comparison, our Eastern Bluebirds brood their nestlings for only 16-18 days. Crows usually have 1-2 clutches per year.
June to July: Dr. McGownan describes the summer months as often the noisiest time of the year for crows. Fledglings mouths are bright red inside as they beg loudly to be fed. (Listen to the fledgling call at this link.) The nestlings and fledglings don’t venture far from the nest if they leave at all in this period.
September: By now, baby crows are practicing more of their sounds. The crows start to forage outside of their territory again. Gangs of fledglings and yearlings may gather together wherever they find a food source. The family feeds the fledglings for two months after they’re out of the nest, so it takes roughly 4 months of work to raise a family of crows – a long time in the bird world.
No Wonder I Like Crows!
Crows live relatively long lives for a bird, about 20 years – and their feathers start to turn white here and there about halfway through their long lives. (Hmm…sounds familiar.) They clearly pass on information from one generation to another. Some of them are tool makers. Though DNA tests done at Cornell show there is infidelity among crow pairs (what researchers call “extra-pair breeding”), the majority are monogamous and family-oriented. In his 30 years of research, Dr. McGowan has only found one crow killed by another crow; killing their own kind is extremely rare. They clearly remember both good experiences and bad ones for a long time. In other words, despite being wild, winged creatures with vastly different lives, they still have many things in common with us humans.
Let’s see…crows can be described as a species that is social, curious, mischievous, creative, birds that enjoy investigating new things. Generalists rather than specialists, their behavior and skills show lots of variety and they enjoy a palate that ranges from nuts, seeds and berries to meat, beer and pizza. It occurs to me that those are some of the qualities I enjoy in my friends and family! So no wonder crows fascinate me – and I hope that now, they intrigue you a bit, too.