Category Archives: Raven behavior

RAVENous for crow eggs 

Given their similarities, it might surprise folks to see crows occasionally harassing and chasing ravens. After all, birds of a feather right? Not in this case.  Rather than being in cahoots, the relationship between crows and ravens is most often competitive, though it can also be predatory.

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A raven barrel rolls to scold an attacking crow.

Such is the case in a recent video shared with me by a reader, Ty Lieberman.  To the dismay of him and his colleagues, a crow nest they had been observing outside their Los Angeles office window was partially dismantled, and at least one egg taken by what they believed was a pair of crows.   Concerned for the survival of the nest, Ty reached out for my interpretation.  Based on his initial description, I wondered if maybe he had witnessed egg transport, something I knew had been observed in black-billed magpies and pinon jays.1  Previous accounts of these species included descriptions of eggs being taken, and then returned to the nest, as well as eggs being deposited into the nests of neighbors, both of which are utterly fascinating behaviors and probably warrant their own post.

To date, however, there are no accounts of crows engaging in this behavior, though there is one documented observation of a nestling being deposited into a nest from which it did not originate.2  Again, utterly fascinating, but not helpful here.

Later, a more detailed account from Ty made mention of the size of the intruding birds, which quickly led me to the story’s true explanation.  Shortly after my ‘ah ha’ moment, to the dismay of he and his colleagues the nest raiders returned, and this time were caught on video by one of Ty’s colleagues (who you can follow on twitter, @namnam).  Rather than being crows, these literal homewreckers were common ravens.

Instead of being something out of the ordinary, Ty had witnessed a typical breeding season interaction between crows and ravens.  It’s no wonder then, that crows can be so hostilie when ravens enter their territory. 

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Crows (top) mobbing a raven (bottom) in Kent, WA

Eggs of all kinds are one of the most power-packed meals in the animal kingdom, so it’s no surprise ravens would take advantage of crow nests when they find them.  Around this same time back in 2015, a black bear made a similarly memorable meal out of a raven nest, reminding us that for corvids of all kinds, it’s a constant fight between being predator or prey.

Literature cited

  1.  Trost CH and CL Webb. 1986. Egg moving by two species of corvid. Animal Behaviour 34: 294-295.
  2. Schaefer JM and Dinsmore JJ.  1992.  Movement of a nestling between American crow nests.  The Wilson Bulletin 104: 185-187

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Filed under Birding, Breeding, Crow behavior, Raven behavior

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.

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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

Raven nest provides tasty meal for Alberta bear

I’ve talked before about how the claim that crows (and ravens) are “destroying the ecosystem and songbird populations” is mostly unsupported by science.  Breeding plovers and desert tortoises are among the handful of exceptions1,2.  Nevertheless I still see, even in the comment threads of this very blog, people claiming that corvids are out of control and have no predators.  If it wasn’t such a misguided and ultimately dangerous sentiment I might just ¯\_(ツ)_/¯ whenever folks claimed that crows and ravens have no natural predators because those of us who spend even a small amount of time observing them in the summer will know this is anything but true.

Eggs and baby birds are a key summer food source for lots of animals and, while seeing a downy little gosling in the mouth of an arctic fox makes me cringe a little, knowing a healthy population of breeding birds is helping to sustain a community of predators is the kind of ecological balance that, in the long run, makes my heart sing.

Stillframe from Planet Earth

Stillframe from Planet Earth

Corvids are part of this system too, which means their babies are also getting eaten.  Usually it’s by things like hawks, eagles, owl and racoons but a recent video taken in Alberta shows yet another predator we can bear in mind.  It’s never gonna be fun to see the birds I care about taking a hit like this, but knowing that corvid babies are helping to sustain top predators only deepens my love and appreciation for them.  Predators and prey make the world go round and corvids have the badass role of being both.

Photo: Linda Powell

Photo: Linda Powell

Literature cited:

1. Johnson, M. and Oring, L.W. 2002.  Are nest enclosures and effective tool in plover conservation? Waterbirds 25: 184-190

2. Kristin, W.B. and Boarman, W.I. 2003.  Spatial pattern of risk of common raven predation on desert tortoises.  Ecology 84:2432–2443

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Filed under Ecosystem, Raven behavior

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.

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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

The politics of ravens

With the (insert relevant election cycle) coming up, a 2014 publication from Massen et al. reminds us that we are not alone in our affection/affliction for/of political scheming. No, ravens don’t hold elections or engage in thinly veiled attempts at voter suppression, but they do build relationships and attempt to thwart the alliances of others.   Massen’s team observed the interactions of hundreds of individually marked birds and categorized their relationships as either (1) breeding pair with territory, (2) strongly bonded w/o territory, (3) loosely bonded w/o territory or (4) nonbonded.   Ravens build bonds by participating in affiliative behavior such as allopreening (mutual grooming), and interrupting these interactions can be risky if the pair fight back. Over six months they recorded affiliative interactions and found that 18.8% were

Photo credit: Jorg Massen

Photo credit: Jorg Massen

interrupted by a third bird, giving rise to their curiosity over the function of these interventions.  Given that ravens have been previously shown to track the dominance relationships of others, they wanted to know if there was a relationship between bonding status and the likelihood of being an intervener or being intervened.  In both cases they found that there was a significant relationship between the two.  Birds who were either pair or strongly bonded were most likely to intervene and those attempting to forge loose bonds were the most likely to be interrupted.  The researchers interpreted these results to show that strongly allied birds attempt to preclude the threat of competition by squashing the alliances of future coalitions.  Importantly, they were less likely to bother with nonbonded birds since, for now, their social ties are too weak to become threatening.  Conversely, they also stayed out of the interactions of other pair or strongly bonded birds since these interventions pose a greater physical risk to the third wheel.

I suspect these results will not be widely accepted since, critically, there is no immediate benefit to the intervener.   Embracing the results of this study requires accepting the idea that an animal, especially a bird, is capable of putting future rewards ahead of current risk or losses.  Loose bonds are too weak to act as a competitive threat, so this effort on behalf of the intervener is only useful if you assume that those loose bonds will become a threat if allowed to flourish and become stronger over the course of days, weeks or months. Risking a fight now to thwart a relationship that only may be problematic next month is a big temporal leap.  As humans, this kind of future planning is an ability we take for granted but it’s quite a cognitive feat.  Although the scales are beginning to shift, I imagine we have many more studies to go before results like this are considered representative of the temporal flexibility of ravens and other corvids.

  1. Jorg J.M. Massen, Georgine Szipl, Michela Spreafico, Thomas Bugnyar. Ravens Intervene in Others’ Bonding Attempts. Current Biology, 2014; DOI: 10.1016/j.cub.2014.09.073

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Filed under New Research, Raven behavior, Raven intelligence