Category Archives: Crow curiosities

Australian magpies are not corvids

Ah the Australian magpie.  With its glossy tuxedo plumage, heavy bill, and charismatic reputation it’s no wonder it’s a favorite among corvid lovers.  Why then, do scientists keep insisting that it’s not, in fact, a corvid?  This insistence of ours can feel arbitrary, even perhaps insulting, to a bird that superficially looks and acts like the corvids we know.

magpie

A still frame from the infamously cute video of an Aussie magpie and a puppy play-wrestling together.  

To address this question, corvid expert and my colleague, Jennifer Campbell-Smith, recently penned a terrific piece to lay the confusion to rest.  I recommend everyone take the time to read it in full.

If you do not have time, the short version of the story is that physiologically, Australian magpies, like the other butcherbirds they are classified with, lack the nasal bristles indicative of corvids.  Genetically, DNA work done in the late 80’s also showed that, while they share a common ancestor, are are phylogentically  distinct from other corvids.  There has been some back and forth since then on the details, but there’s no scientific evidence that we should be lumping them in with corvids.

comparison

The nasal feathers are those thin, wire like feathers covering the base of the bill on the crow to the right, but conspicuously absent on the Aussie magpie to the left.  Australian magpie photo: Guy Poisson

Why this bums so many corvids lovers out is a curious mystery to me.  Personally, I find the convergent evolution with respect to both appearance and behavior much more interesting than if we simply made a taxonomic mistake.  As for whether corvid lovers should continue to find joy and fascination in observing these birds well, I’ll direct you to this video and let you be the judge.

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Filed under Being a scientist, Birding, Crow curiosities, Crow life history, Taxonomy

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

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.

trial

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

Crow curiosities: Causes and consequences of bill deformities

If you live in the Pacific Northwest, chances are you’ve come across a crow that’s made you do a double take. No, not for an unusual behavior or vocalization, but for what might be described as an overgrown, monstrous even grotesque looking bill.  Bills like the one belonging to a bird in south Seattle I recently came across during one of my field experiments.  It is, at best, unsettling to see something like this.  So what exactly is going on here?

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A “crossbill” crow living in a south Seattle neighborhood

First, it’s helpful to understand the different layers of a bird’s beak.  The beak is comprised of bone overlaid with a horny structure made of keratin (for you Scrabble people out there it’s called the rhamphotheca).  Keratin is the same stuff that makes up our hair and fingernails and, just like our nails, the rhamphotheca is always growing and wearing away.  For most birds, this growth is very slow which means that keeping bills nicely manicured takes no special effort.  For birds suffering from what’s now termed Avain Keratin Disorder, however, the growth can be as much as 2x as fast as normal, making it impossible to keep things in check.  This growth results in bills that are extra long, decurved on the top, bottom, or both, or overgrown and crisscrossed like my friend in Seattle.  Even if the bill is clipped or broken, it grows right back.

Across most of the country, incidences of AKD in crows are other birds are rare.   Which means that, unless you’re the afflicted individual, there’s no real cause for alarm.  If you live in the PNW, especially Alaska, however, it’s not only increasing common, it’s spreading.

Data taken between 2006-2008, indicates that 17% of Northwestern crows in Alaska have AKD, the highest rate of deformities ever recorded in a wild population1.   Needless to say, the alarm bells, gongs and vuvuzelas are going off within the scientific community.

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So what causes AKD?

~In 10/2016 I published a new post with the most current information on causes.  For now though, I will leave the ’causes’ content in this post as-is, so readers have access to the history of scientific thinking and progress on AKD research.~

Well, lots of things can.  Heat stress, diet, genetic disorders, environmental contaminates, parasites, or bacterial infections have all been linked to the disorder in individual cases.  Given that it affects residential, adult birds, environmental contaminants seem a likely suspect.  But tests on afflicted birds (mostly chickadees) show no consistent correlation with the top suspects like heavy metals and trace elements, organic pesticides, and toxic environmental pollutants like PCBs, PCDDs, and PCDFs.  Future studies will look at compounds like PCDD-Fs, polycyclic aromatic hydrocarbons, and emerging contaminants such as brominated compounds (stuff found in flame retardants which were used for wildfire suppression)2.  For now though, there’s no clear culprit for the disorder’s spread across Alaska and the PNW.

Is it fatal?  That really depends on the nature of the growth.  The main problem is that it can affect eating and preening, both of which are critical to survival, especially in cold climates.   But animals (including people of course) are amazingly adaptable, and according to the USGS, a surprising number of individuals find mates and breed (though reproductive success is lower3).  Indeed, even my friend in Seattle was followed by the “wah! wah!” of its relentlessly begging juvenile.

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The good feather condition and successful fledgling of at least one offspring suggest that this bird is, for now, managing just fine.

Is there anything I can do?  Yes, report your sightings!  Help scientists track the spread and proliferation of this disorder by documenting and reporting whenever you encounter it.  You can do so at the USGS site here.  As far as the individual bird is concerned, you can make feeding easier by supplementing with easy to ingest foods, like this Birdie corn “bread” recipe.  And as always, make your yard safer to vulnerable birds by providing lots of cover and keeping unattended pets indoors.

Make feeding easier by providing meals which can be easily ingested and offer big nutritional value.

Make feeding easier by providing meals which can be easily ingested and offer big nutritional value.

Literature cited:

1.  Van Hemert, C., & Handel, C.M. 2010.  Beak deformities in Northwestern crows: Evidence of a multispecies epizootic.  The Auk 127: 746-751.  doi: http://dx.doi.org/10.1525/auk.2010.10132

2. http://alaska.usgs.gov/science/biology/landbirds/beak_deformity/contaminants.html

3. http://alaska.usgs.gov/science/biology/landbirds/beak_deformity/effects.html#reproduction

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Filed under Crow curiosities, Crow disease

Crow curiosities: who is begging in April?

Right now, in early spring, you may have noticed a crow or two fluttering their wings and making the classic “waaah, waaahhh” sound that roughly translates to “feed me, feed me”!  Although it’s tempting to think these are young crows, it’s far too early in the breeding season for fledglings to be on the loose.  So who are these juvie doppelgangers? Adult female crows.

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Begging juveniles like this one won’t be roaming around the PNW until mid June and later.

During the nest building stage you may hear females making these sounds just while on the ground foraging with their mate or while perched near the nest like this female was.  Why do they do it?  It’s essentially a way to prime the pump and remind their mate that they’re going to need to be fed once they’re saddled to the nest and can’t forage as much for themselves.  Once they are actively incubating, they’ll continue to beg only now it’s really a demand for the food they need and can’t get for themselves without risking their eggs getting too cool.  Although males will take a turn on the nest, they do not have a formal brood patch and can’t do much more than temporarily keep the eggs insulated.

Although it’s tempting, hopefully now you won’t be fooled by this April trick!

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A male returns to the nest with a bill-load of peanuts for his hungry mate.

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Filed under Crow behavior, Crow curiosities

Best books for corvid lovers

This post was prompted by someone on my twitter feed who asked that I put together a reading list for people who want to learn more about corvids; a totally kick-ass idea if I say so myself.  The following are all the books I have read and can speak personally to, however, I’m sure there are others and I encourage folks to add them in the comments section.  As a preface, I’ll remind readers that John Marzluff is my graduate adviser, nevertheless, I assure you that I genuinely believe he is a fantastic writer and my review of his books are not inflated in the hopes of getting approval on my dissertation. 🙂  So without much further adieu, here’s a list of all the corvid books I’ve read with a brief synopsis of the material and my recommendation.

index

In the Company of Crows and Ravens by John Marzluff and Tony Angell
If watching, feeding or rehabilitating corvids is something you do in your free time, consider this your crow bible.  Curious how long crows live?  What they do as juveniles?  The sounds they make?  The ways the interact with people?  It’s all in there.  This book remains my go-to guide for general crow knowledge.  Yet, despite the fact its backbone is rigorous science, it’s written in a way that feels very easy to digest.  John and Tony wrote it with the intent that it would be for a wide audience and I think they achieved that beautifully.  After reading this book, I have no doubt you’ll have a deeper understanding for these birds, not to mention a new admiration for Tony’s artwork.  I even used one of his drawings for the book on the invitations for my wedding (with permission, of course).

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Dog Days Raven Nights by John and Colleen Marzluff
This is the book I most often recommend to my own friends and family.  Not because it offers superior or more easily read  information on corvids, but because this book gives you the best insight into what it really means to do fieldwork.  Nearly the entirety of the book focuses on the period of time after John and Colleen had finished their graduate work in Arizona, and were conducting a post-doctoral study on ravens with Bernd Heinrich in remote Maine.  It’s organized as a back and forth between John and Colleen, which means you get two perspectives on the raven work and Colleen’s development as a dog sledder and trainer.  As a reader, you experience what it means to completely dedicate every moment, piece of sanity, and dime you have on conducting a field experiment and you walk away with a much deeper appreciation for how difficult it is to answer questions of animal behavior.  If the human dimension of science isn’t your interest, however, fear not.  The book is still loaded with fascinating information on ravens including, in my opinion, one of John’s most important contributions which is information sharing among ravens.  An excellent read for sure.

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Gifts of the Crow by John Marzluff and Tony Angell
For those looking for a more scientifically dense reading on crow behavior and neurology this is the book for you.  It doesn’t make for the lighthearted Sunday reading that ITCOCR does, but it still satisfies the trademark Marzluff style of mixing rigorous science with the anecdotal stories of crow behavior that makes us love them.  If you’ve been fascinated by the story of Gabi Mann, the little girl who feeds and gets gifts from crows, then this is the scientific background you need to see the whole picture.

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Mind of the Raven by Bernd Heinrich
Long before John Marzluff started writing books, his post-doc adviser, Bernd Heinrich, was already an expert at the game.  Heinrich has a reputation for being one of the most eloquent and engrossing natural history writers and it’s a reputation that’s been well earned.  Mind of the Raven is actually what initially peaked my interest in corvids, so in many ways I have this book to thank for the work I am doing now.  For anyone who lives with ravens, or simply has a fascination for them, I can’t recommend it enough.  Bernd’s writing will nurture your passion and give you the science to back up what you already know: ravens are badass, awesome animals.

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Crow Planet by Lyanda Lynn Haupt
Crow Planet it a book best characterized by Haupt’s journey to find curiosity and loveliness in an increasingly urban landscape where the natural world can feel further and further away.  Crows therefore, offered the perfect vehicle for looking at and appreciating what remains when the forests retreat and box stores and neighborhoods take their place.   By the author’s own admission her journey through writing Crow Planet made Haupt appreciate, “but not quite love”, crows.   Despite this, she manages to write about them with grace, and her stories will make even the biggest skeptic take another look at these animals.  Although Haupt’s background is not in science, she doesn’t omit the scientific facts, though she does take more artistic liberty when describing their antics than John or Heinrich do.  All that being said, this is an excellent book for the urban naturalist or crow watcher.

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Crow by Boria Sax
If you’re interested in crow mythology this is the book for you.  Sax takes you through time and space to explore the role of corvids in human myth, religion and art.    His thoroughness is without compare, but if anthropology is not your interest this book will prove taxing.  It’s one I happily keep on hand, but not one that I’ve ever had the patience to read all the way through.  Nevertheless, I probably should, since it’s chalk full of information and historical context that I would be better off knowing.

Bird brain

Bird Brain: An exploration of avian intelligence by Nathan Emery
Although not exclusively dedicated to corvids, Bird Brain, written by corvid cognition expert Dr. Nathan Emery, offers an incredible look at the minds of your favorite birds.  Although his book tackles some of the more difficult concepts of avian cognition, it feels and reads more like a coffee table book, complete with beautiful artwork, some of which was done by Emery himself.  Each chapter is themed around a particular aspect of cognition (communication, spatial memory, etc.) and walks the reader through the fundamental biological principals and samples the most interesting studies that have been done on the topic.  The book is rich with the kinds of analogies and descriptions that break through the barriers of dry scientific writing.  Perfect for the budding young scientist or the long time corvid fan.

I’m sure there are many others I haven’t read which subsequently didn’t make this list.  Feel free to make recommendations in the comments section!

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Filed under Crow behavior, Crow curiosities, Crows and humans, Raven behavior, Raven intelligence

Crow curiosities: Do crows play and why?

A few years ago, on a mildly windy day, I watched a group of crows line up on the top of a building and then take turns flying off into the draft before letting it gently return them back to the rooftop to do it all over again.  This continued for at least ten minutes before I had to bid my feathered friends adieu and go to work.  Last summer, I watched two juveniles perch on a cable wire that ran from the power lines down to the ground at a steep incline.  While one of the kids was minding its own business the other snuck up and pecked and pulled its sibling’s tail until the sibling lost its balance on the crooked wire and was forced to fly to a higher perch.  Then the mischievous, ah hem, ‘pecker’ followed its sibling to the higher perch and started again. And every winter without fail, at least one person will send me the video of the snowboarding Russian hooded crow or the barrel rolling crow or the crows having a snowball fight.  Ok, so that last one isn’t real, but with all the other videos of crows at play it certainly seems like it’s only a matter of time before they start hocking little crow-sized snowballs at each other.  With all these videos and stories comes the inevitable question: Are corvids having as much fun as it looks like and, if not, what are they doing?

rolling
For scientists, this question is inherently difficult to answer.  There’s the obvious part where it still remains impossible to ask animals how they feel about their activities, but at an even more fundamental level is the question of:  how do we define play?  Play, as all things in science do, requires a very specific definition that may or may not depart from how we use the word in everyday language.  The most widely referred to definition is the following very dry and jargony sentence:  ‘…all motor activity performed postnatally that appears purposeless, in which motor patterns from other contexts may often be used in modified forms or altered sequencing’1.  And with that, what I can only imagine must be one of the most fun things on the planet to study suddenly becomes sleep-inducingly boring and the humor of the picture below is no longer confined to biologists.

wildlife bioFor now, let’s just focus on the part that said “…activities that appear purposeless.”  That leaves scientists with a different problem; how do we define ‘purposeless’ (i.e do you mean right now, or indefinitely? What if it has a purpose but I just don’t know what it is?), and therefore, how do we even identify when animals are playing and when they’re not.  Can you see the big circular rabbit hole we’ve gotten ourselves into?  Since I think most people use the catch-all definition from Potter Stewart and simply say that you know it when you see it, it can be difficult to empathize with why play has been such a difficult behavior for scientists to say a whole lot about.  Now that I hope I’ve given you some insight into why this is a difficult subject to study and thus, in many ways remains mysterious, let’s get to the fun part of talking about what we do know.

So far, observations of play in birds is limited to corvids, parrots, hornbills and babblers, reaching a grand total of about 25 species2.  To put that in perspective, there are ~10,500 species of birds in the world, making it an incredibly rare behavior among birds, and emphasizing the awesomeness of getting to observe it in our own backyards here in the PNW.

Although the snowboarding crow is probably the instance of crow play that gets the most attention, there’s actually 7 kinds of play that researchers have documented3.  Maybe I’ll try and publish my observation of the bickering crow kids, but for now, irritating-your-siblings-play is not one of them.  Here are the big 7:

  • Object play (manipulating things for no reason)
  • Play caching (hiding inedible objects)
  • Flight play (random aerial acrobatics)
  • Bath play (more activity in water than necessary to get clean)
  • Sliding down inclines (snowboarding, sledding, body sliding)
  • Hanging (hanging off branches but not to obtain food)
  • Vocal play (you know how kids go through that phase when they talk to themselves a lot? The crow version of that.)
A crow just hanging out

A crow just hanging out

So what are we to make of seeing ravens hanging, apparently joyfully, from the ends of buoyant branches in our yards or magpies playing tug of war with an otherwise ordinary twig or crows doing elaborate aerial maneuvers for no obvious reason?

Young crows playing tug of war. Photo c/o Bob Armstrong

Young crows playing tug of war. Photo c/o Bob Armstrong. (The white eye of the bird on the left is not from disease or injury, but is the protective nicitating membrane that many animals have, in case you were wondering.)

Let’s start with the conventional wisdom that everyone grows up hearing: Animals play to practice skills they need to be successful later in life.  Cats play with strings to hone attack skills, dogs wrestle to practice fighting skills their wolf ancestors would have needed as adults, etc.  The problem with this wisdom is that despite all the intuitive sense it makes it turns out it’s not very…true. In mammals, it has been shown over and over again to be unsupported.  In birds it hasn’t been looked at as extensively, and there’s at least one exception I know of that showed  ravens play cache (hide things) to evaluate competitors so that they know who is most likely to steal their cache once the stakes are raised and they’re actually hiding food4.

Other then that, the vast majority of data across both birds and mammals have shown that animals who play most often or most fiercely are no better hunters or fighters later in life than their peers.  Same goes for the studies that have compared animals that are allowed to play with those who were not5.  No difference.  So is it as easy as saying crows play just because it’s fun?  Well the problem with that is that play can be risky. Playful, distracted kids are often snatched up by predators or accidentally killed by a miscalculation of their environment.  With the level of risk that’s involved it seems unlikely it’s not doing anything for them. To make matters more complicated, although animals don’t seem to be better at the skills they appeared to be practicing, some studies show that they do seem to be better off overall.  In mammals we’ve seen that they’re more successful parents and have longer life expectancies6.  So what might be the adaptive value of fun?

Although there’s still much to be learned as far as testing play in corvids, right now I’m inclined to agree with play researcher Lynda Sharpe, who wrote a piece on this topic for Scientific American which I encourage everyone to check out.  Stress is in no way unique to humans, and it can be as debilitating and deadly for animals as it is to us.  Play is a great way for animals to hone their stress response so they’re less high strung as adults7.  Not to mention the complex, stimulating nature of play helps the brain grow8.  So why do crows play?  Learning about their peers, gaining new experiences in a low risk way, honing their stress response, and growing their big brains all seem like a good excuse to have a bit of fun to me.

Literature cited

1. Bekoff, M. and Byers, J.A. (1981) A critical reanalysis of the ontogeny of mammalian social and locomotor play.  An ethological hornet’s nest.  Behavioral Development, The Bielefeld Interdisciplinary Project.  pp296-337.  Cambridge University Press.

2. Diamond, J, and Bond, A.B. (2003) A comparative analysis of social play in birds.  Behaviour 140: 1091-1115

3. Heinrich, B. and Smolker, R. Play in common raves.  In: Animal Play: Evolutionary, Comparative and Ecological Perspectives.  Ed: Bekoff, M and Byers, J.A. Cambridge University Press

4.  Bugnyar, T., Schwab, C., Schloegl, C., Kortschal, K., and Heinrich, B.  (2007).  Ravens judge competitors through experience with play caching.  Current Biology 17: 1804-1808.

5. Thomas, E. & Schaller, F. 1954. Das Spiel der optisch isolierten Kasper-Hauser-Katze. Naturwissenschaften, 41, 557-558. Reprinted and translated in: Evolution of play behaviour. 1978. (Ed. by D. Muller-Schwarze.) Stroudsburg, PA: Dowden, Hutchinson & Ross.

6. Cameron, E.Z., Linklater, W.L., Stafford, K.J. & Minot, E.O. 2008. Maternal investment results in better foal condition through increased play behaviour in horses. Animal Behaviour, 76, 1511-1518.

7. Meaney, M.J., Mitchell, J.B., Aitken, D.H. & Bhatnagar, S. 1991. The effects of neonatal handling on the development of the adrenocortical response to stress: implications for neuropathology and cognitive deficits in later life. Psychoneuroendocrinology, 16, 85-103.

8. Ferchmin, P. A. & Eterovic, V. A. 1982. Play stimulated by environmental complexity alters the brain and improves learning abilities in rodents, primates and possibly humans. Behavioral and Brain Sciences, 5, 164-165.

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Filed under Being a scientist, Crow behavior, Crow curiosities

How to troll a corvid lover

In general, I find that crow people are lovely, and easy to get along with folk.  There are, however, two widely shared images that have proven themselves an effective trigger to turn an otherwise gentle corvid lover into a foaming at the mouth fact checker.  I say that as someone who has found themselves on the foaming end of that equation over some social media perpetuated misinformation on many occasions.  In the wealth of silly nonsense posts  a person could manufacture on corvids, why these are the two images that have become so ubiquitous on social media is a mystery to me.  Maybe it’s because people genuinely enjoy the narratives they offer, or have no reason to be suspicious of the images because they’re just beginning to learn about crow biology.   Or maybe some people know exactly what they’re doing and are just trolling to, ahem, ruffle a few feathers.

Either way, consider the following two images debunked.  So rest easy fellow fact checkers, until of course you see them posted again.  Probably tomorrow.

Myth: The infamous “baby crow

These are not baby crows.

These are not baby crows.

I blame this one on BuzzFeed.  In what was trying to be a cool post on crows, but really turned out to be just riddled with terrible photo choices, they start off with one of these pictures as evidence for how cute baby crows are (despite photos of very obviously different looking actual baby crow further down the in the same post!).  Since BuzzFeed ranks one of the more trafficked sites on the internet, searching “baby crow” brings up the photo attached to the story.

Fact: Those cute fluffy babies are actually a variety of baby rails, including a corncrake.  Notice how feathery and soft they look, like a baby duck or chicken?  That’s because there are basically two strategies for how young are born.   They can be altricial, which means you’re born naked and blind (i.e helpless) or precocial, which means you’re born fully feathered or furred and are ready to go from day one.

Actual baby crow

Actual baby crow

Fun fact, most birds that are ground-nesters, so game birds, waterbirds, etc., are born feathered and adorable.  Whereas most birds born in arboreal nests are little naked jelly beans.  Crows, fall into the latter category as anyone who studies crows, rehabs crows, or curiously peeked into a crow nest can attest to.

 Myth: White ravens are cannibalized and are social pariahs

poor raven

I have no hypothesis as to where this came from or how it generated such momentum on social media, other than that it’s dramatic and offers a kind of ‘misery loves company’ on a crumby day.

Fact:  Leucism, which is what this is, is pretty common in crows and ravens (check out this post if you want to learn more about the causes).  Not to this degree, of course, but even a complete leucistic like this are not unheard of.  Although life is certainly a bit harder for them (they’re a little more conspicuous, leucism is often nested in other health problems, etc.) the suggestion that they’re eaten by their mothers is nonsense.  They are however, generally subordinate to regularly colored ravens which is maybe the kernel of truth that this originates from.

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Filed under Crow curiosities, Crow life history, Crows and humans

Crow curiosities: what causes white feathers?

ZB in flight.  Photo c/o Sarah Ramirez

ZB in flight. Photo c/o Sarah Ramirez

At a recent field site in Bellevue, one of my regular visitors was the most fantastically leucistic crow I had ever seen.  Naturally, I dubbed him or her “ZB” for Zebra Bird.  One or two white feathers is pretty common but this was something far more spectacular.  Something that, to the naive observer, may look like a whole different species of bird.  In response, I thought it might be helpful to talk about how and why crows have white feathers or other kinds of color aberrations.  First off, let’s put some definitions on the table since there are a few terms that often get mixed up, or have different definitions depending on your source.  The following definitions are based on those provided by Guay et al. 2012.

Albinism results from a complete lack of melanin in both the feathers and all the soft body tissues.  This causes red eyes and pink legs, making it very easy to spot.  Albinism is often associated with poor vision and hyper-activity which quickly removes it from the general population and why, when it is spotted, it’s usually only in young or captive birds.

A complete leucistic crow.  What makes it leucistic and not albino?  The colored irises.

Albino crow spotted in Franklin Park, Seattle*

Leucism is a complete lack of melanin in all or part of the plumage, but not necessarily the soft tissues.  It is sometimes referred to as ‘partial albanism’ but if you’re familiar with the definition of albanism (which hopefully you are now!) you know the term ‘partial albinism’ is oxymoronic.  Leusistic birds can have one or multiple white feathers, as is the case with my friend in Bellevue, or be completely white but with regularly colored eyes.  Their feet and bills may or may not appear pink like that of an albino bird’s.

Schizochrosim is a lack of a particular pigment.  So a bird lacking the phaeomelanin (brown) pigment, for example, would appear grey.

Melanism is exceptionally high deposits of melanin that make the animal appear darker overall.

Carotenism is a change in the amount, distribution or composition of caroteniod (red, yellow, orange) pigments.

Dilution is, as the name suggests, a muting of colors across all or part of a bird’s plumage.

How do these color abnormalities arise?  There are a couple of different pathways including genetics, diet and injury/disease.

Genetics

Albinism is genetic, specifically, it’s linked to a recessive autosomal gene.  If you’re reading this and thinking “autosomal recesisve…what?” remember that humans have 23 pairs of chromosomes. Twenty two of them are autosomal and the last pair are sex chromosomes (you’re either XX or XY, sound familiar?).  Recessive means you need two copies of the gene to express the trait.  What this mutation does is cause an absence of the enzyme tyrosinase, which is used by the body to create some of the colored pigments. Because albinism is heritable, it can be bred into an artificial population by a skilled breeder, which is why you may see things like white tigers and lions in the entertainment business.  Despite their dramatic color variation from their peers, they are not distinct species-an idea I occasionally see being perpetuated on social media.  Genetics also plays a role in leucism, though it’s often only part of a more complicated mechanism.

A leucistic dark-eyed junco spotted at my feeder.

A leucistic dark-eyed junco spotted at my feeder.

Diet

Diets low in protein may also contribute to leucism, as the amino acid lysine has been correlated with increased white feathers.  This is supported by the observation that urban birds (who presumably have a diet lower in meat and protein) typically have more color aberrations than their rural or forested peers.  Carotenism, on the other hand, is very strongly influenced by diet, since animals cannot produce this color on their own.  A very familiar example of this is seeing the white young of flamingos who, in this early stage of life, have not yet had enough time to begin producing mass quantities of their pink pigments.

Age/injury

Lastly, age and injury may also contribute to feathers which fail to correctly pigment though this is poorly understood.  Somatic genetic mutation (i.e mutations that occur after conception) are associated with increased age, and indeed, older crows are more often seen with white feathers.  Avian Pox is known to play a role in carotenism though not much is understood about this.

ZB's eye catching leucism in fligh

ZB’s eye catching leucism in flight.  Photo c/o Sarah Ramirez

*Updates* a previous version of this post contained a typo stating that humans have 24 pairs of chromosomes.
A previous version stated incorrectly that a complete leucitic juvenile could be identified by its correctly colored iris.  Since blue pigments occur irrelevant of melanin, this is not the case.

Lit cited

Guay, P.J., Potvin, D.A., and Robinson, R.W. 2012. Abberations in plumage coloration in birds. Australian Field Ornithology 29 23-30.

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Filed under Crow curiosities, Crow life history

My top 15 favorite crow facts

I, apparently like so many of my generation, are a sucker for insta-read lists.  Something I can crunch through in about 5min between classes.  My favorite proprietor of this content is Buzzfeed.  Although most of their lists are some kind of pop-culture reference, every once in a while I see something nature or science related and on two separate occasions have even seen posts related to crows.  Both were rather jejune.  So it seemed a perfect marriage to unite one of my favorite social media sites with some carefully selected and researched crow tidbits.   You can check out my post here on my top 15 favorite crow facts.

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Filed under Crow behavior, Crow curiosities, crow intelligence