Tag Archives: Crow facts

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

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

5 corvid facts that will surprise you

With all the online crow trivia listicles that are already floating around it can be hard to come up with tidbits that are both factual and interesting.   I was up the the challenge though and am hoping I found at least one thing every reader didn’t know.  Let me know how I did in the comments section!

 1.   Avocados are toxic to crows.1

Well, really avocados are toxic to most birds, and many other kinds of domestic animals.  Avocados contain a molecule called persin, which the plant produces as a fungicide.  In birds, it can cause damage to the heart tissues, difficulty breathing, lethargy or even death.  The resplendent quetzal is a rare exception in that it can not only tolerate avocados, but is considered a crucial seed distributor of the plant.  So next time you’re considering sharing your Chipotle leftovers, make sure you didn’t order extra guac.

2.   Scavenging accounts for very little of a crow’s diet2

Scavenging, meaning the consumption of dead plant or animals material, is a crucial part of our ecosystem that is commonly the recipient of unfair prejudice. American crows often get thrown in with this lot, and while there wouldn’t be anything gross or insulting about this if it were true, it simply isn’t.  Whether you’re in the city or the wildlands, scavenging and active predation account for only a minority of a crow’s diet.  The bulk of their daily meal is made of human refuse, invertebrates and worms.  In the cities, about 85% of their diet is human refuse, whereas in exurban and wildland areas human refuse and invertebrates account for roughly equal proportions of their daily food (about 35% each).

Photo: W. Perry Conway/CORBIS

This scene is not as common as many people think! Photo: W. Perry Conway/CORBIS

3.  There’s only three places with no native corvids3

New Zealand, the southern part of South America and the poles (ok so I guess technically 4 if you want to be a stickler about it).  Why this is remains largely mysterious, but it probably has to do with where and how these birds radiated out from their ancestral origins.

Global corvid distribution. They'll be our avian overlords soon enough I'm sure.

Global corvid distribution. They’ll be our avian overlords soon enough I’m sure.

4.  They have some of the best spatial memory of any animal4

Every year Clark’s nutcrackers and pinyon jays store tens of thousands of seeds to sustain them through the lean winter months.  If they fail to retrieve enough they’ll perish, so a good spatial memory can literally be the difference between life and death.  To deal with this mental load, these two species (and other food caching birds) have a huge hippocampus relative to the rest of their brain.  With the spatial memory part of their brain super charged they’re able to retrieve 20,000-30,000 seeds with 90% accuracy or better.  I can’t usually retrieve my cell phone what that kind of accuracy so I certainly tip my hat to them!

Photo: Minnesota Birder

Clark’s nutcracker.  Photo: Minnesota Birder

5.  They account for the largest songbird in the world.5

The common raven is marginally the largest songbird of the world with a 4.9ft wing span and weighing in at up to 4.5lbs.   An extremely close second is the thick-billed raven, which is native Ethiopia and has limited range in some surrounding countries.  In fact, the two are so close in size that there are conflicting reports of which is bigger depending which publication you look at3,5.  Scientists finally resolved this dispute, however, and came to the consensus that the common raven is larger for the 2009 publication of the Handbook of the Birds of the World.*

Photo: Ignacio Yufera

Thick billed raven.  Photo: Ignacio Yufera

*This section has been updated from a pervious version which incorrectly stated that the thick-billed raven was larger.

Literature cited

  1.  http://www.aspca.org/pet-care/animal-poison-control/toxic-and-non-toxic-plants/avocado
  2. 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.
  3. Madge, S. and Burn, H. 1999.  Crows and jays.  Princeton, New Jersey: Princeton University Press 1999.
  4. Marzluff, J.M. and Angell, T.  2005.  In the company of crows and ravens.  Yale University Press.
  5. dos Anjos, L., Debus, S., Madge, S., & Marzluff, J. (2009). Family Corvidae (crows). In J. del Hoyo, A. Elliot, & D. A. Christie (Eds.), Handbook of the birds of the world (Vol. 14, pp. 494e641). Barcelona, Spain: Lynx Edicions.

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Filed under Corvid trivia, Just for fun

Baby crow detective work

By now, most of us have come across these images of  “baby crows” so often it induces more of a yawn than a fit of aggravation.
Image-1If, somehow, these images are new to you feel free to check out my post fully debunking them, as I will not dedicate any further time to them here.   But there’s a new photo circulating social media, and it makes for a much more compelling crow doppelganger;

baby crow
You’ve got three, black, altricial baby birds in a nest and really, they’re not terribly un-crow like.   It doesn’t make you a complete crow rookie to make this mistake, but there are some key things wrong here.  And this is the moment where, as a scientist, these photos elevate from being simply another source of annoying misinformation (which, they are) to the kind detective work that childhood doctor visits fostered a deep love for.  Because, not unlike my favorite activity in the Highlights magazines I anxiously parsed through in those waiting rooms, there are 4 things that are different between these two photos and it’s up to you to find them.  So take a minute and see what jumps out at you….

Crows_v_no crows
Figured it out (or given up)?  The first thing to know is that all bird species are very specific in terms of both nest materials and nest construction.  Sure, some birds can happily use some ribbon in place of straw (like orioles) or build nests in old shoes just as easily as in gutters (like bewick’s wrens) but the basic style is always the same.  Robins will always use mud as a binder and bushtit nests will always look like cozy sleeping bags made of moss.  Knowing that, the material used in the nest on the right should jump out as a red flag.  Of course you’ll find crow nests with a bit of string, fabric or grass (especially for lining) but the bulk of the nest is always made of pinky-wide sticks.   Really, you need look no further at this point to know immediately that the photo on the right is an impostor but let’s keep going because it’s fun.

Next let’s look at the babies themselves, which is where the three remaining differences are.  Two of them are color-coded, did you catch them?  Ah yes, gape and eye color.  See that brightly colored area on the corner of the bird’s developing beak?  That’s called the gape, and the bright color that flashes when they open their mouths is a powerful signal that tells parents to “insert food here”.  Crows have bright pink gapes, whereas these other birds have yellow gapes.  Our other color coded giveaway is the eyes.  Granted the lighting is not great, but it’s clear that the crows on the left have light blue eyes whereas these other birds have dark eyes.  In some species of crow the babies are born with brown eyes that turn blue as they age, but such is not the case with our American crows and you can expect that nestlings will always have blue eyes.  The last clue, which takes more expert level knowledge to notice, is the bill shape.  The birds on the right have a slightly more embellished curve to the bill than a typical crow chick.

The final mystery, of course, is what the birds on the right actually are.  Unfortunately, I failed to track down the original poster, but as best I can tell they’re black drongo chicks.  Black drongos are members of the drongo family (Dicruridae) and are native to Southern and Eastern Asia.  Here’s another photo I found that looks consistent with the previous one.  If any drongo experts read this blog though and want to correct me, I’d love to hear from you!

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Filed under Birding, Crow life history

Corvid trivia quiz!

How much trivia do you know about our favorite family of birds?  Head on over to Buzzfeed where I’ve created a quiz to test your knowledge.  When you’re done, feel free to come back to this page and scroll past the corvid photos for more information, citations/links, and to post your score in the comments section.  Can anyone get 100%???

TAKE ME TO THE QUIZ

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ready crow
congrats

1.  Were you surprised to learn that they are songbirds?  Indeed, corvids have impressive vocal repertoires and are among the minority of songbirds that can learn new sounds throughout their lives1.

2.  I’ve railed (get it?!) about this in a previous post but until this image stops circulating my Facebook feed I’ll take every opportunity show folks what real baby crows look like.

3.  The life span of different crow species (Fish, American, Hawaiian and Northwestern) is similar and generally they top out at between 14-24 years.  Ravens on the other hand, usually only make it to 13, though in captivity they can live 40-80 years1.

4.  It’s a common misconception that humans can get WNV  from touching a crow, but there’s no evidence for it according to the CDC.  It’s an understandable rumor, however, considering that corvids are an ideal host for this virus, something I’ve talk about in a previous post.  Humans on the other hand, are considered dead-end hosts, meaning the virus can’t proliferate in our bodies (though that doesn’t preclude it from making some of us very sick).  The real transmission culprits are mosquitoes.

5.  Learn more about the ‘Alala at American Bird Conservancy.

6.  Currently there are actually 7, not 6, ravens at the Tower (you know how those Brits are about their spares!).  According to Historic Royal Palaces they eat 170 g of raw meat a day, plus bird biscuits soaked in blood.   Yum!

7.  Originally, I was going to make the whole quiz just a corvid ID quiz, but I decided that might get old quickly.  Still wanted to get at least one question in there!

8.  Again, ‘murder’ and ‘unkindness’ are not words you’ll typically see in scientific writing (apart from, perhaps, as a means to a pithy article title).  But they make good trivia questions nonetheless.  Fun fact: Company is the term for parrots and deceit is for lapwings.

9.  John Marzluff discusses nearly all these behaviors in his books, so I’ll make thing easy and simply refer you to In the Company of Crows and Ravens.

10. New Caledonian crows are well know for their puzzle solving prowess, but I’m sure ‘007’ completing this task had his researchers especially delighted.  To see footage of 007 at work check out this video.

11. Keeping crows, like hunting them, is regulated under both federal and state laws.  To learn more about the rules regulating crows read my previous post on the Portland crow poisoning.

12. I recently acquired Crows and Jays by Madge and Burn, and recommend it to anyone who wants to become more familiar with all 120 species.

13.  See above.

14.  Part of why I wanted to create a trivia quiz is because I thought it would be a fun excuse to go hunting for a thing or two I didn’t know myself.  Jimmy’s story was exactly the kind of discovery I was hoping for.  Perhaps I’ll do a bit more digging and dedicate a whole post to it.

15.  It’s with good reason that John’s motto about crows is that “they’re little flying monkeys”.  I love this study2 and sharing its findings never gets old!  This kind of equity perception is something that’s been rarely documented outside of primates and underscores the impressive convergent evolve that’s occurred between corvids and primates.

Literature cited

1. Marzluff, J.M. and Angell, T. 2005.  In the company of crows and ravens.  Yale University Press

2. Wascher, C. F.  and Bugnyar, T. 2013.  Behavioral responses to inequity in reward distribution and working effort in crows and ravens.  Plos One: DOI: 10.1371/journal.pone.0056885

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Filed under Corvid trivia, Just for fun

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.

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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