Category Archives: Crow behavior

Why crows sunbathe

With its bill agape, I watch as the crow fans out awkwardly across the cedar shingles. Pressing the camera to my face I snap a couple photos, pleased to finally capture on film a moment I so often encounter in the field.  Unlike the crow, who’s keeping a watchful eye on the sky, I’m completely taken with my admittedly creepy behavior.  Until, of course, I hear the stiff “Excuse me, can I ask what you’re doing?” from the driver’s window as the homeowner’s minivan pulls up behind me.

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Fortunately for me, crow curiosity isn’t hard to come by and quickly the homeowner is as taken with watching this bird as I am.  “So, what is it doing up there?  I see them like this on my roof all the time” he asks after I give him my credentials.  It is a rather odd sight.  It’s nearly 90˚ and the crows is sitting in direct sunlight, mouth open, head cocked and wings outstretched like it’s injured.  Rather than escaping to shade, it’s joined by its fledgling and together they bake their bodies in the hot sun for a few minutes before gathering themselves and carrying on down to the grass to forage.

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Although the specifics can vary slightly, this general kind of posture can be observed across hundreds of bird species, even those you might not expect to have much opportunity for it like owls.  Often it’s used to dry wet feathers or warm up on a crisp winter morning but, given that they do it even when it modestly heat stresses them, it must have some other physiological benefits beside thermoregulation.

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There are a handful of other reasons that birds may sunbathe, but the big picture is that applying intense heat to feathers is critical to maintaining them in good condition.  For example, sunlight exposure has been shown to suppress feather degradation caused by the bacteria Bacillus licheniformis 1.  Heat also helps control ectopatasites, possibly by making them more mobile and easier for birds to remove2.  Lastly, sunning may relieve discomfort caused by molting and promote vitamin synthesis3.

So, far from being a signal of distress or heat exhaustion, observing this posture in crows is like watching them ruffle around in a puddle. It’s a routine, and important part of their self care regimen. Plus, everyone knows a few minutes in the sun just plain feels nice.

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Photo c/o Kathy Brown.  Find more of her great photos on Instagram @kat2brown

Literature cited

1. Saranathan, V., and Burtt, E.H. Jr. (2007).  Sunlight on feathers inhibits feather-degrading bacteria.  The Wilson Journal of Ornithology 119: 239-245

2. Blem, C.R., and Blem, L.B. (1993).  Do Swallows sunbathe to control ectoparasites? An experimental test.  The Condor 95: 728-730

3. Potter, E.F., and Hauser, D.C. (1974) Relationship of anting and sunbathing to molting in wild birds.  The Auk 91: 537-563

 

 

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Filed under Crow behavior, Crow curiosities, Crow disease

5 reasons to leave baby crows alone 

Those blue eyes, that awkward gate, their seemingly constant precariousness, they’re all calling to you to intervene. Here are 5 reasons second guessing that instinct might be in the bird’s best interest.

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1) The vast majority don’t need your help. It’s totally normal for baby crows to be on the ground and flightless as long as they’re covered with feathers and appear otherwise alert and mobile. Even nestling crows are usually on the ground on purpose. Not because they are ready, but because their parents have intentionally rejected them for one reason or another. They will die and that’s ok. Part of coexisting with wildlife is giving them the agency to be wild. The story is different of course for species where the survival of individuals may mean the difference between population survival and extinction, especially because these situation are almost always driven by human activity.

2) It’s hard to tell when they’re stressed.  Recently, I saw a video on Facebook of a Steller’s jay fledgling in the care of a very well intentioned person.  She was giving it gentle strokes with her fingertips, each touch resulting in the young bird turning its head towards its back and opening its mouth.  The comment thread filled with ooo’s and awww’s and general comments of encouragement or gratitude for her actions.  For me it was like watching an alien attempt to care for a human child, the child recoiling and screaming while its caretakers congratulated themselves on how kind they were being.  Having handled baby corvids before, I know what that kind of posturing means, it means “I’m scared and stressed.”  To an untrained eye though, it may not look much different than the kind of gaping that means ‘feed me.’  Being stressed to death is a reality for young, or even adult animals, so any handling best be done by experts whenever possible.

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3) It’s illegal to rehab crows without a license. You can provide temporary care until you can get them to a licensed facility, but do not attempt to rehab them on your own.  Mistakes like the one I just described are a prime example of why the law seeks to protect animals by ensuring they are only raised or rehabilitated by experts.  For more information on how to handle them until you can get them to a facility visit my previous post.

4) Imprinted crows do not survive well in the wild.  Even if baby crows are receptive to being treated like a pet, doing so is both a legal violation and I would argue a violation of their right to be a wild animal with a healthy fear of people.  Of all my daydreams, at the top of the list is having a wild but imprinted crow that follows me around.  I even have a name picked out.  This fantasy of mine will forever remain just that, however, because it’s too dangerous to allow a crow to become that comfortable with people.  All it would take is one cranky neighbor with a pellet gun and it would be over.  Not to mention being imprinted on people, instead of crows, denies them access to skills and relationships with other crows that will help them survive into adulthood. 

5) It may do more harm than good.  The conventional wisdom suggests “well, worse case scenario is I try and rehab this baby crow and it dies, which it would have done anyway so really, nothing’s been lost.”  The more we study death in social animals the more we are beginning to realize there may be a cost to prematurely removing ailing or dead animals from their groupmates.  Being able to interact with their dead may serve an important role for social animals, and denying them this opportunity may have serious implications in their ability to process that death.  So be thoughtful about how slim the chance of survival is.  It might be that the kindest, most responsible action is no action at all.

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Filed under Corvid health, Crow behavior, Crow curiosities, Crow life history, Crows and humans, Uncategorized

American crow nesting ecology 101

*This article was updated and renamed from Everything you want to know about crow nests on April 14th, 2020.

Spring marks one of my favorite times of year. Cherry blossoms abound, the rain smells sweet and the birds get busy putting their carpentry skills to good use. In fact for me, there’s nothing more iconically spring than watching the silhouettes of crows with bill loads of timber or soft material dot the skies as they shuttle back and forth to their nest trees. Like a townhouse development, these construction projects are over in the blink of an eye and soon, their bill loads of twigs will be replaced by food for their mate and, eventually, their insatiable young. Watching your local nest is both a great way to learn more about your neighborhood crow family, and avoid unpleasant conflicts with protective crow parents.  Whether you’re years into this tradition or just getting started, there’s always more to learn and enjoy!

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Nest site selection, construction, and reuse

Nest construction is initiated anytime from early February to late April, depending on the region.  In Washington, nest construction generally kicks of by the second week of March. Crows will nest in an astounding array of places, depending on where they live and what’s available.  In Seattle, I see them nest anywhere from the eaves of skyscrapers, to the crooks of well concealed tree limbs, to within reach in saplings that are struggling to support their weight. In areas where appropriate trees are unavailable they may even nest right on the ground!¹ How crows make their precise nest site selection is unknown, but most commonly in the PNW, nests are placed close to the trunk in a fork or on a horizontal branch in the top third of a conifer.

Both the male and female participate in building the nest. In areas where auxiliary helpers are present, helpers may also contribute to gathering nesting materials and may add these materials themselves, or leave for the female to work in.

If trees are abundant, the nest exterior is constructed mainly from twigs pulled from live trees.  In areas where such materials are in short supply, nests may be composed of as much as 50% grass and other plant stems.² After the bulk of construction is complete, they’ll line the cup of the nest with soft materials like grass, bark, moss, flowers, mud, cow dung, roots, paper, fabric, fur, etc. Fur may be found or collected from live animals, as this large-billed crow (Corvus macrorhynchos) demonstrated on a panda at the Beijing Zoo in 2015.  Contrary to the news anchor’s fears, this would not have been painful for the panda. 

It takes 1-2.5 weeks to finish a nest, though second attempts can take as little as 5 days in areas where helpers are present.  A new nest is usually about 1.5 ft across and 8-10 in deep. The life of a typical nest is only about 10 weeks (1-2.5 weeks of building, 6 days of laying, 20 days of incubating and 4 weeks of nestlings) though they are hardy structures and can remain intact for years. After the young fledge, the crows will not return to the nest. Generally speaking, crows will only use a nest once, though the occasional observation of a pair repairing and reusing an old nest have been reported across the country. More often it appears that if they are going to reuse a nest site, they will build on top of an old nest, particularly in areas where nest trees are especially sparse like downtown Seattle. This also appears to be more common in the Midwest.

Eggs and nestlings

Egg laying may begin immediately, or up to a week after the nest is complete.  Crows, like nearly all birds, have a single ovary and oviduct and can only lay one egg a day.  In some cases they may even skip a day or two between laying. Crows generally lay a clutch of 4-5 eggs, but nests with up to 9 eggs have been observed, though it’s possible this was the result of a second female laying in the same nest.³  Females will usually start incubating the nest once the third egg is laid. To aid with incubation, females develop a patch of featherless skin on their underside called a brood patch.  Brood patches are common in birds, and generally only occur on females but observations of male crows with brood patches have been reported. Only female crows incubate, though eggs may be briefly “incubated” by helpers.

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Common raven eggs left | American crow eggs right

For a couple of days before the full clutch is laid, the female will sit next to the nest and give begging calls.  This behavior continues even after she starts incubating, which in Seattle is most often the explanation for begging calls emanating from nests during April. Both her partner and helpers will bring her food, usually 2-4 times an hour. She may hop off the nest to help chase away threats, feed, preen, or stretch, but generally doesn’t leave for more than a few minutes.

The eggs will start hatching after about 15-20 days of incubation.  Since the female starts incubating before the full clutch is laid, crows exhibit asynchronous hatching, where not all the young hatch on the same day. In other species of birds like mallards, even though the eggs were laid days apart, the young all hatch within a few hours of each other because the female waited to start incubating until only after all the eggs were laid.

Like other songbirds, crow chicks are altricial and nidicolous, meaning they hatch blind and helpless, and will remain in the nest for many days after hatching.  Ducks, chickens, quails, etc. all produce precocial, nidifugous young which hatch sighted, covered in downy feathers, and ready to follow their parent(s) away from the nest within a few hours.

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Once the eggs start to hatch the female will continue to brood the nestlings continuously for the next couple of weeks.  Once the nestlings are more developed and covered in feathers, she will brood less and less often and transition mostly to food provisioning.  Nestlings appear to be fed primarily invertebrates, but their diets vary depending on local resources.  For the first couple of weeks after hatching, nestlings are fed about every 30min by parents and helpers, if they are present. After about 4 weeks the young will fledge (leave the nest permanently). Prior to fledging you may see the nestlings sitting on the rim of the nest and flapping around awkwardly.  Not all fledglings are flighted at the time of leaving the nest, so take care not to assume young have simply fallen out. After the chicks fledge, they remain in the care of their parents for the duration of summer, and will continue to be fed for about 4 months.

Differences among corvids

Crow, jay and raven nests are similar in shape and choice of materials and mostly differ in overall size. The main standout are magpies,  which build incredible domed-shaped nests the size of a large beach ball.  The nests require so much material that they can take as much as 40 days to build.  Japanese jungle crows are another species of note, as they have a (relatively) new and problematic habit of building nests out of wire hangers and causing massive blackouts.

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A Jungle crow nest in urban Japan. Photo: Götz

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The magpie’s nest is the big clump in the middle of the tree.

Avoiding conflicts

Most breeding related dive bombs occur as the result of a person being too close to a fledgling, but some crows get feisty around their nest too. Physical contact between birds and people during these altercations are rare, but can happen and might hurt. In areas where crows are less persecuted (like cities) they tend to be more aggressive than their rural counterparts. If you know where a nest is and can avoid it, do so and save everyone the aggravation. Otherwise a good strategy is to invest in an umbrella you don’t care about.  It’s a simple and inexpensive solution that protects both yourself and the legacy of recognizing that outdoor spaces are shared space between ourselves and wildlife.

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Crows build their worlds on our backs.  We might as well lean in and appreciate the joys of watching nesting birds!

Have more questions? Let me know in the comments!

 

  1. Gross, A. O. (1946b). “Eastern Crow.” In Life histories of North American jays, crows, and titmice., edited by A. C. Bent, 226-259. U.S. Natl. Mus. Bull. 191
  2. Good EE. (1952). The life history of the American Crow Corvus brachyrhynchos Brehm. Phd Thesis, Ohio State Univ., Columbus.
  3. Peck, G. K., and R. D. James (1987). Breeding Birds of Ontario: Nidiology and Distribution. Volume 2: Passerines. Miscellaneous Publications of the Royal Ontario Museum, Toronto, ON, Canada.

Most of the general information was sourced from:

  1. Verbeek, N. A. and C. Caffrey (2020). American Crow (Corvus brachyrhynchos), version 1.0. In Birds of the World (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi-org.offcampus.lib.washington.edu/10.2173/bow.amecro.01

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Filed under Birding, Breeding, Crow behavior, Crow life history, Crows and humans

Why the crow smiles

There’s hardly a corvid species that doesn’t strike me as beautiful but there’s only one that’s always struck me as particularly gleeful.  Looking at the New Caledonian crow it’s evident there’s something different about the shape and proportions of its bill. It’s a bit shorter and more blunt, and it lacks the obvious downward curve of a typical crow bill, with lower mandible actually curving slightly up. Put together, these features appear to give it the perpetual grin that trademarks this species.  I’ve joked that this must be because they’re always feeling very pleased with themselves for being so smart, and thanks to new research, I’ve come to learn my joke had it backwards.

By using tomography scans, Hiroshi Matsui and his team were able to compare the shape and structure of the NC crow’s bill with that of its close relatives. Their conclusion, which they report in the March issue of Scientific Reports, is that this shape makes the handling and manufacturing of tools easier. Looking at photos of the birds in action, it feels intuitive that the more exaggerated curve of a raven or American crow bill would have a hard time achieving the dexterity that NC crows need to use their stick and hook tools.

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Given this new research it’s time to amend my joke. It’s not that NC crows grin because they’re smart, they’re smart because they grin.

Literature cited

  1.  Matsui, H., Hunt, G., Oberhofer, K., Ogihara, N., McGowen, K., Mithraratne, K., Yamasaki, T., Grey, R., and Izawa, E. 2016.  Adaptive bill morphology for enhanced tool manipulation in New Caledonian crows.  Scientific Reports 6. doi:10.1038/srep22776

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Filed under Crow behavior, crow intelligence, Crow life history, New Research

I spy with my raven eye…

…someone trying to steal my lunch.  Turns out, humans are not the only ones wary of peeping Toms; new research shows raven can imagine being spied on by a competitor.

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***

The other day my friend and I were having a very merry time at the thrift store when, without cause or provocation, this women decides to up and ruin our trip.  Well really, she simply spotted the same gorgeous caste iron dutch oven that my friend wanted and reached it first, but the consequence was the same (it was a tragically beautiful dutch oven). This dynamic-my friend having her own intentions (to obtain and own that dutch oven for herself) and recognizing that this other women had her own intentions (to obtain and own that dutch oven for herself) is something so second nature to being human we rarely give it any thought.  But the ability to attribute mental states to those around us is an incredibly profound and complex cognitive task.  Understanding if this ability, called Theory of Mind, exists in other animals has been among our top interest as ethologists.

Like other corvids, ravens cache food and, as a consequence, run the risk of their caches being stolen by others.  It has long been known that if ravens can see that they are being watched, they behave differently when it comes to caching than if they are alone.  This is interesting, but doesn’t necessarily speak to whether they posses theory of mind because of the confounding effect of “gaze cues”.   Basically, the correlation between head cues and competitor behavior make skeptics doubtful about non-human animals having the ability to know what others might be seeing.  So raven master Thomas Bugnyar and his colleagues Reber & Bruckner recently published an elegant study to address just this issue.

By training captive ravens to look through a peephole, and then allowing them to cache food with the peephole opened or closed, the researchers were able to show that ravens behaved as if they were being watched when they could hear ravens and the hole was open, but not when they could hear ravens but the peephole was closed.  What this suggests is that ravens are capable of remembering their own experience of looking through a peephole to see into another room, and can imagine that another bird might be doing the same thing even if they cannot see this bird.

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Experimental set up.  Bugnyar et al. 2016.  Nature Communications

Theory of mind and imagination (which are not mutually exclusive) are the cornerstones of what makes for a powerful cognitive toolkit and have long been thought to be uniquely human.  As we continue to build on the body of work showing non-human primates, corvids and some other animals posses some of the same skills we do, many will be challenged to redefine what it means to be human.  Personally, framing the question that way doesn’t interest me.  To me the more interesting question is not how are humans different from ravens, but how are we the same and why? What is it about being human and being raven that make possessing imagination important?  Fortunately there is still loads more research to be done, and when it comes to teasing out this question I can only imagine the possibilities.

Literature cited:

Bugnyar, T., Reber, S.A., and Buckner, C.  (2016) Ravens attribute visual access to unseen competitors.  Nature Communications 7.  doi:10.1038/ncomms10506

 

 

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Filed under Crow behavior, crow intelligence, New Research, Raven behavior, Raven intelligence

Crow curiosities: What do crows eat?

Spoiler alert: They’re not, as so many people believe, true scavengers.  Meaning, they’re not mostly eating carrion.  I know what you’re thinking: MIND BLOWN.  Also you might be thinking PBS lied to you, and you’d technically be correct.  So why is this myth so pervasive that even PBS fell victim to its ubiquity?

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An American crow picks at the torn up belly of a rat in a Bellevue neighborhood.  After a few minutes, it had its fill and moved on to other feeding opportunities, leaving most of the rat untouched.  

Well, a huge part of the problem is that like so many words in science, their use in general discourse has parted from their scientific meaning.  Typically we use this word to describe say, grad students at the end of the party stuffing their pockets with the leftovers but, biologically speaking, scavengers are organisms who are specialized to consume, or obtain most of their food, from the decaying tissue of animals or herbaceous matter.  Now don’t get me wrong, the title of ‘scavenger’ can get a bit blurry as Bernd Heinrich argues in his book, Life Everlasting.  Ravens for instance, switch primarily to scavenging during lean winter months.  For most American crows, however, the identity of ‘scavenger’ simply will not do.

Which is really too bad, since the title of scavenger is bestowed with honor given how they make our living on planet earth possible.  I’m not being hyperbolic when I say thanking the undertakers of our ecosystem should be part of everyone’s pre-meal ritual, but perhaps that argument should be saved for another post.

As for crows, carrion makes up only a very small part of their diet.  In Seattle, roadkill accounts for <5% of crow food, and in wildland areas carrion accounts for even less1.  Crow beaks aren’t even strong enough to break through the skin of a grey squirrel, though they will usually give it a try.

So what are they eating?  Mostly human refuse (no surprise) and invertebrates.  In fact human garbage (meat, grain products and veggies) account for about 65% of their diet in urban areas, whereas in wildland areas it’s roughly split between garbage and inverts (35% and 35% respectively)1.

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Crows spend much of their time patrolling lawns looking for invertebrates

 

These data correct another common misconception about crows: they’re not mostly eating the eggs and nestlings of other birds.  In fact, crows only account for 1 of 20 observed nest predators in WA and have been found to have a nonsignificant, negative relationship between abundance and rate of predation in experiments using artificial ground nests, shrub nests, and canopy nests1.

So there you have it, American crows are neither true scavengers nor meaningful nest predators. They’re primarily omnivores with an emphasis on human refuse and invertebrates.  So the next time you see one patrolling your grassy lawn remember; they’re busy trying to bring home the bacon.  Er, bugs.  Well, probably bugs, but preferably bacon provided you were crazy enough to throw some out.

Literature cited

  1.  Marzluff, J.M., McGowen, K.J., Roarke, D. and Knight, R.L.  2001.  Causes and consequences of expanding American crow populations.  in Avian ecology and conservation in an urbanizing world (J.M. Marzluff, R. Bowmanm and R Donelly, eds).  Kluwer academic Press, norwell, Ma.

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Filed under Crow behavior, Crow curiosities, crow diet, Crow life history

Crows with broken beaks

It hurts to look at.  The physical pain incurred at the time of the injury, the likely chronic pain on the path to recovery, the dubious chance of survival, it all makes me reach for my mouth in horror when I see this bird.  To me, the idea of living on in spite of such a grotesque injury seems impossible.   Yet here this bird is, surviving, reminding me of what life is capable of.

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So now that I had my moment of sadness and awe, let’s get to what everyone wonders when they see a bird like this: Will a crow’s beak grow back if it’s broken and if not, can it survive?

Cracks or complete fractures like this can result from a number of things, though the list could be longer since these accidents are so rarely observed firsthand.  Perhaps it was traumatic run in with a window, or perhaps the upper or lower bill got trapped against a fulcrum point and an opposing surface.

As far as the prognosis is concerned, I asked birds experts, wildlife rehabilitators and veterinarians and the answer was always an equivocal ‘maybe’.  Maybe it would heal back to something resembling normal and maybe it would remain stunted. Maybe it would survive and maybe it wouldn’t.  To fully understand the reasoning behind this ambiguity you need to understand how a bird’s beak is actually formed.

Like mammals, birds have two jaws bones that form the upper and lower mandibles.  These bones are surrounded by the nerves and blood vessels that support the beak’s functionality and growth. Protecting these layers is the outer lightweight layer of keratin called the rhamphotheca.  Like our fingernails, this layer is always growing and being replaced.

Depending on where the fracture occurs, the rhamphotheca can grow back enough to abolish the injury.  Unfortunately though, there’s not much room to work with before you hit bone, and the bone cannot be regrown.  In these cases the rhampotheca may heal over the exposed bone, but it may not grow back to full size since the template for its shape (the bone) has been stunted.  Even if it does grow back, it may not do so correctly, leading to twisty shapes.

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A crow skull.  You can see that the jaws bones are almost the full length of a crow’s beak.  The black outer layer, the rhampotheca, adds only a little (think mm) extra length so there’s not much that can be removed from the tip of the bill without hitting bone.

So what’s the prognosis?  Well again, that depends.  Even if the bill does not grow back correctly, or at all, some crows can learn to compensate.  Fortunately, being a generalist helps their chances considerably.  Although some foods may now be out of reach, many crows lean how to scoop, poke, and jab their way to a full stomach everyday. The same cannot be said for many species of bird whose beaks are the cornerstone for consuming a specialized diet.

So while it’s fair to be heartbroken at such an injury, it’s not cause for hopelessness. Many crows will learn to compensate, and go on to remind us of the beautiful stubbornness of life.

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Filed under Corvid health, Crow behavior, Crow disease, Uncategorized

Crows caught play wrestling

I’ve posted before about the generals of crow play behaviors, and it’s something I’m routinely delighted with as the kids of late summer start testing the limits of their world and their peers.  Adult play (or what I’m fairy confident are adults) is something I’ve encountered far less often, however.  Even more rare is a camera on hand to capture what’s usually a rather fleeting behavior.

You can imagine my excitement then, when yesterday not only was I present to witness either two adults or one adult and one subadult play wrestling in the grass but I also had a camera already rolling.  Granted the footage isn’t great (it’s an old camera and they were far away) but you can make out enough to see what’s happening.

Here’s a play by play of them moments leading up to and during the event.

  • I had been following a family group of three, presumably composed of two territorial adults and one subadult based on mouth lining color and general behavior (allopreening).
  • Two of them were foraging when they joined together and began to roll in the grass.
  • No audible calls were given, which I would expect if it had been a malicious attack.
  • You can see moments where one crow appears to have the upperhand and then willingly falls to its side to allow a shift in power and continue the play.
  • The roughhousing only stopped after the third bird flew overhead and gave a short loud ‘caw’.
  • After they disentangled they continued foraging near each other rather then taking chase, another indication that is was mutual and fun rather than antagonistic.

Pretty cool right?!

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Filed under Crow behavior, Field work, Just for fun, Uncategorized

Crow curiosities: Do crows collect shiny objects?

The notion that corvids, especially magpies, have a special affinity for shiny object has been around for more than a century.  In fact to refer to someone as a magpie is to describe them as someone who ‘compulsively collects or hoards small objects’.   This idea is so old hat that it can feel a bit frivolous to even wonder if it’s true.  The trouble with this bit of corvid whimsy, however, is that when we do investigate it, and scientists have, we find there’s no empirical evidence to support it.

'Crow Collects' by Cori Lee Marvin.

‘Crow Collects’ by Cori Lee Marvin.

For instance, one study presented both captive and free-living magpies piles of blue or shiny silver screws, rings, and pieces of tin foil near piles of food to which they had been previously habituated.1  They found that, rather than thieving and subsequently caching the gleaming objects, the birds were actually more nervous to take food than they had been previously.  In the 64 conducted tests, only two instances of contact between a bird and an object were recorded.

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Experimental set-up for magpie study.

Cornell crow expert Kevin McGowen, elaborates on this general conclusion, suggesting that perhaps the origin of this folklore is pet crows who are attracted to the objects of obvious value to their owner like coins, keys or jewelry.  Speaking personally as someone who has spent countless hours observing hundreds of individual crows in the field, I can also attest to the fact I have never witnessed anything resembling this behavior.  So there you have it, corvids do not, according to the best empirical evidence, show an attraction to, or are otherwise known to collect shiny objects.

And yet…

And yet I still hear anecdotes about this behavior that peak my curiosity.  For instance, once or twice a year I’ll see a headline about crows thieving shiny stones at the expense of bereft family members.  In Jewish culture, it’s tradition to leave a small stone atop a gravestone, as a way to honor the deceased and indicate that they’ve been visited.  For whatever reason, particularly across Ireland, these stones occasionally go for joy rides in the mouths of crows.  In Omagh, Patsy Kerlin who mounts headstones in his town’s graveyard recently told a local reporter that “It seems to be only the black shiny ones they take and a lot of them go missing.”  Even in my own neck of the woods at the University of Washington one of the gardeners at the Urban Horticulture Center regaled John Marzluff and I with his story of how the crows regularly steal the shiny metal placards that identify the center’s plants.

In science, we often like to say “the plural of anecdote is not data”.  This is unequivocally true.  But just because they’re not data doesn’t mean they’re meaningless either.  I’m inclined to believe there’s more to these stories than random chance and I think they are worth exploring.  Perhaps these stories emerge out of confirmation bias, meaning people tend to report theft with respect to shiny things more often because they’re looking to confirm a suspicion they already had.  If so, it would be yet another fascinating example of the extent to which corvids have infiltrated our culture.  Or perhaps this is the work of curious juveniles as has been suggested by my crow colleague Dr. Jennifer Cambell-Smith.  If so, teasing out any evidence of discrimination or bias juveniles are using when selecting objects to explore could give us insight into how they learn about the world, or how our garbage is modifying that behavior.  Or perhaps crows do like to carry off with glossy objects, but for textural, rather than visual reasons.  At least some corvid species swallow small stones to aid in digestion and these stones are most often partially smoothed.2  These ‘grit stones’, however, are considerably smaller (on average only 2.9 mm) than I imagine grave stones are, so perhaps this behavior is evidence of poor grit stone selection among naive birds.

Or maybe it’s none of the above, we simply cannot say.  Which, for me, is exactly why I find these anecdotes so interesting.  While we can rule out that this behavior isn’t a manifestation of corvids’ love for bling, we can’t exactly explain this behavior either.   It’s yet another item on the shelf along with thieving golf balls and wiper blades where we can’t do much more than offer an educated guess.  So while I’m quick to clarify that crows are not attracted to shiny objects, I’m not dismissive of these anecdotes either.  My friend and colleague David Craig likes to say that every bird has a story, and citizen science is part of sharing that story.  In my book, the story of corvids and their light fingered behavior seems an ideal project for the crow minded bird nerd.

  1.  Shepard, T. V, Lea, S. E. G., and Hempel de Ibarra, N.  2014.  Thieving magpie’?  No evidence for attraction to shiny objects.  Animal Cognition 18: 393-397.
  2. Gionfriddo, J.P., and Best, L. B. 1996.  Grit-use patterns in North American birds: The influence of diet, body size and gender.  The Wilson Bulletin 108: 685-696

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Filed under Corvid mythology, Crow behavior, crow conflicts, Crow curiosities, Crow life history, Crows and humans, In the news

The science of crows and death

Curious to read my popular science take on our recent publication on how crows behave around their dead?  Check out my latest article for Biosphere.  Then check out all the other awesome authors and contributors to my favorite popular science publication.  You won’t regret it.  (And congrats to GO for making the article cover!  She’s such a gorgeous bird…)

Read the full article here

Biosphere

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Filed under Crow behavior, Kaeli in the media, New Research, women in science