Category Archives: Graduate Research

Putting the “crow” in necrophilia

It’s early April 2015, and John Marzluff and I are standing with a film crew attempting to capture some footage of a crow funeral to compliment a story they are working on about Gabi Mann.  I’ve already set the dead crow on the ground, it’s placed just out from a cherry tree resplendent in springtime blossoms.  After only a few moments of waiting, the first crow arrives and alights on the tree, its head cocking around to get a better look at the lifeless black feathers beneath it.  I hold my breath for the first alarm call, ready for the explosion of sound and the swarm of birds that will follow it.  But it doesn’t come.  Instead, the bird descends to the ground and approaches the dead body.  My brow knits together in surprise but, ah well, I think, the shots of it getting so close and then alarm calling will make good footage.   The audience will have no questions about what it is responding to.  To my continued surprise, however, the silence persists; only now the crow has drooped its wings, erected its tail, and is approaching in full strut. No, no, this can’t be, I think.  But then it happens.  A quick hop, and the live crow mounts our dead one, thrashing in that unmistakable manner.  “Is it giving it CPR?” someone asks earnestly.  Still in disbelief, John and I exchange glances before shaking our heads and leaving the word “copulation” to hang awkwardly in the air.  After a few seconds another bird arrives to the cherry tree and explodes in alarm calls, sending our first bird into its own fit of alarm, followed by a more typical mobbing scene.  The details of what I’ve just witnessed as still washing over me when I hear John lean over to me…”You need to start your field season tomorrow.”

***

What crows do around dead crows is something I’ve dedicated much of my academic life to understanding.  In the course of my first study, my findings made for a nice clear narrative: crows alarm call and gather around dead crows as a way of learning about dangerous places and new predators.  Although there are other hypotheses we can’t rule out, certainly danger avoidance is at least partially driving this behavior.  An important detail of that original study though, is that because of the way it was designed, with a dangerous entity always near the dead crow, our live crows were never in a position to ever get very close to our dead stimulus. So the possibility that they do other things around dead crows, like touching them, couldn’t be explored.

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It’s been 3 years since that day in April and during that time it has taken every ounce of my power to remain tight lipped when journalists would ask “what’s the most interesting thing you’ve learned from your studies?” Because until we were able to scientifically vet the prevalence of this behavior, I wasn’t willing to say much about it for fear of making necrophilia mountains out of mole hills. But with our findings now officially available in the journal Philosophical Transactions B, I am delighted to finally share what has been the most curious secret of my PhD: crows sometimes touch, attack, and even copulate with dead crows.

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Although this statement is jarring in its own right, what really gives it power is that we know this not just from that first fateful day with the film crew, but through an experimental study testing the response of hundreds of birds over several years.  That’s important because it allows us to say not just what they’re doing but possibly why they’re doing it (and at least why they’re not doing it).  So how did we conduct this experiment?

First, I dove into the literature to try and see if there was any precedent for this kind of behavior in other animals.  Although there have been no systematic studies, repeated observations of animals touching, harming, even copulating with their dead occur in dolphins, elephants, whales, and many kinds of primates, among some other animals.  Based on this, we hypothesized that this behavior may arise from: attempts to eat it, attempts to learn from it, or a misuse of an adaptive response (like territoriality, care taking, mate guarding, etc.). To test these ideas I searched the neighborhoods of Seattle until I found a breeding adult pair and (while they weren’t looking) presented one of four stimulus options: An unfamiliar dead adult crow, an unfamiliar dead juvenile crow, a dead pigeon or a dead squirrel.  The latter two stimuli being key in helping us determine if the behavior was food motivated, whereas the nature and prevalence of the interactions themselves (common, uncommon, exploratory, aggressive, sexual) helped us address the other hypotheses.  In all, I tested 309 individual pairs of crows; or in other words, once again I freaked out a lot of Seattle residents wondering why there was a woman with a camera, binoculars, and some dead animals loitering in front of their house for long periods of time.

Our main findings are that crows touched the animals we would expect them to eat (pigeons and squirrels) more than the dead crows, and although crows sometimes make contact with dead crows, it’s not a characteristic way they respond.  Because this behavior is risky, this seems to back up previous studies in crows that suggest that they are primarily interested in dead crows as a way of self preservation and avoiding danger.

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A crow tentatively pokes at one of our dead crows

That said, in nearly a quarter of cases, crows did make some kind of contact with dead crows.  Like with mammals, we saw that these behavior could be exploratory, aggressive and in rare cases even sexual (about 4% of crow presentations resulted in attempted copulations), with the latter two behaviors being biased towards the beginning of the breeding season.  Importantly, the latter two categories of interactions were rarely expressed independently, and it was often a mixture of the first two; in rare cases, all three.  In the most dramatic examples, a crow would approach the dead crow while alarm calling, copulate with it, be joined in the sexual frenzy by its presumed mate, and then rip it into absolute shreds.  I must have gone through a dozen dead crows over the course of the study, with some specimens only lasting through a single trial. It was an issue that may have been insurmountable if not for the donations of dead crows by local rehab facilities and the hard work of my long time crow tech turned taxidermist, Joel Williams.

It’s hard to witness this behavior without wondering if maybe the crows somehow don’t recognize that it’s dead and are instead responding like they might to a living intruder or to a potential mate.  So we tested that idea too, by conducting a second experiment where we presented either a dead crow or a life-like crow mount.  The differences in their response was clear.  They dive bombed the “live” crows and less often formed mobs, just like we would expect them to do for an intruder.  They also attempted to mate with the “live” birds but in these cases it was never paired with alarm calling or aggression.  So the issue doesn’t seem to be that they think it’s alive.

The fact that this behavior was rare, and often a mix of contradictory behaviors like aggression and sex, seems to suggest that none of those hypotheses I outlined earlier are a good fit for this behavior.  Instead, what we think happens is that during the breeding season, some birds simply can’t mediate a stimulus (the dead crow) that triggers different behaviors, so instead they respond with all of them. This may be because the crow is less experienced, or more aggressive, or has some neurological issue with suppressing inappropriate responses.  Only more experiments will help us determine what makes this minority of birds unique, and whether expressing these seemingly dangerous behaviors are the mark of the bird that is more, or less reproductively successful in the long haul.

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So while there’s still much more left to be explore here, I can finally say that this is without a doubt some of the most interesting behavior in crows I’ve ever witnessed.  I hope you will check out the publication here, and seek out all the other amazing work being reported in this special thanatology (death science) themed issue.

***

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Filed under Being a scientist, Breeding, Crow life history, Field work, Graduate Research, New Research, Science

#FieldworkFail

Recently, scientists have been taking to social media to share their stories of field work bloopers under the tag #fieldworkfail.  Things like dropping fecal samples on themselves, falling sleep while waiting for a turtle to arrive, only to be woken up by the curious turtle crawling over them, or darting a zebra and having it pass out in a precarious position.  Needless to say I have plenty of stories of my own so I thought I would share my top three favorite, or at least most memorable, field moments.

1) What’s crackin? 

At one point during my first field season I found myself spending a week’s worth of my mornings in Seattle’s International District between the hours of 5 and 7am.  Looking back, this was a bad idea.  So much so that at one point a cab driver pulled over to ask what I was doing and urge me, for the sake of my safety, to leave immediately.  But there were crows there and after months of time on the streets of Seattle I had developed an inflated sense of my safety and bad assery and decided to stick it out.  On one of my last mornings at this particular site, a women who I had previously encountered pan handeling took a seat on the bench next to mine, and proceeded to pull out what was unmistakably a crack pipe.  Unwilling to give up my data, I politely asked her to move but, much to my dismay, she didn’t seem very interested in listening.  High on crack, she then proceeded to do cartwheels over my peanuts and dance pants-less around my field site.  After a while she tuckered out and left me alone to do my work.  Looking back, I’m not sure if this was more a #FieldworkFail or a #KaeliLifeDecisionFail but it’s certainly not a field experience I wish to relive!

My unwelcome field participant spicing up my morning with some drug induced cartwheels

My unwelcome field participant spicing up my morning with some drug induced cartwheels

2) Sorry kids

During some of our experiments looking at the funeral behaviors, we would have volunteers stand around holding dead crows.  To protect their identity should the crows decide to hold a grudge, I had the volunteers wear rubber makes that covered their whole head.  One of my best volunteers was a fellow UW student, a mountain of a man who had a proclivity for wearing black and camo.  One of these field experiments was in Magnuson park which, if you live in Seattle, you know is one of our most curious parks.  It’s got all the features of a park you might expect like a play ground, soccer fields, trails that wander through peaceful restoration areas, but it’s also got some more curious features.  Old, WWII era airplane hangers, a block of abandoned school building and a few miscellaneous businesses just to name a few.  So when selecting a field site I picked a spot that seemed far from the potentially curious glances of parents or kids coming to enjoy a day at the park and instead nestled against one of the many buildings which appeared to have no foot traffic.  I was surprised then, when moments after starting our experiment a police car rolled up with its lights flashing.  Turns out the building I thought was rarely used was actually a pediatric dental office and I had planted my 6’6”, black and camo clad, dead bird holding, creepy mask wearing volunteer right under the side window.   Whoops!

Volunteers were required to wear signs after this incident...

Volunteers were required to wear signs after this incident…

3) Off with their heads!

During one of my preliminary field experiments we were looking at how crows respond to a mounted stuffed hawk.  We didn’t want them to see it before it was in position, so we would cover the bird with a piece of mesh camo fabric until moments before we were ready when a volunteer would run over and pull the cloth off.  Although the holes in the mesh were very small, as it turned out they were exactly the right size for the tip of the hawk’s bill to fit through.  One fateful day, my volunteer got more than she bargained for when the hawk’s bill caught on the mesh and the head ripped right off along with the cloth.  Unsure of what to do she balanced the head on the hawk’s shoulders and proceeded with the experiment.  All was well until right at the end, when one of the aggressively diving crows actually hit the hawk and knocked the head to the ground.   We’ll never know what was going through his or her mind at the achievement or what followed, but I like to imagine that on the block of 8th and Madison in downtown Seattle to this day juvie crows share in uncertain but excited whispers about the legend of the crow so powerful, it took the head of the a hawk in one fell swoop.

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Big Red is a little worse for the wear but she still gets the job done!

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Filed under Field work, Graduate Research, Just for fun

Corvid of the Month: How abundant food may be killing the Mariana crow

For most of us, it’s hard to imagine crows being anything but ubiquitous.  Here in Seattle, American crows can nest so densely, I once found myself within 50 m of three different active nests.  Such is the case for many other parts of the world too, where house crows, jungle crows, or hooded crows are an almost inescapable part of the landscape.  Given these species’ success, it might be tempting to assume that all crows welcome human presence and habitat modification.  Rules don’t exist without exceptions however, (especially in nature!) as our Corvid of the Month, the Mariana crow, tragically illustrates.

A female Aga and fledgling do some exploring. Photo: Matt Henschen

A female Aga and fledgling do some exploring. Photo: Matt Henschen

The Mariana crow, or Aga, is endemic to Guam and Rota and is the only corvid native to Micronesia1.  In appearance, they bear a striking resemblance to the American crow, only they’re 40% smaller (cue adoring sound effects).  Across their range they’re considered critically endangered and as of today, all of Guam’s birds have been extirpated by the invasive brown tree snake, and only about 46 breeding pairs remain on Rota.  If that wasn’t alarming enough, their numbers continue to dwindle and researchers at the University of Washington project they could be extinct within the next 75 years2.  Unlike Guam, however, there are no brown tree snakes on Rota.  So what is causing the drastic decline of this island crow?   As my colleague and Mariana crow researcher, Sarah Faegre, is beginning to tease out, the answer may lie in the delicate nature of island food webs, and the unanticipated butterfly effect that started with a few errant snails.

Like our American crows, Mariana crows are generalists and eat a wide variety of foods from insects, to geckos, to fruits and seeds.  But adult Mariana crows have one other food source they’ve come to specialize on: the humble hermit crab. Despite the presence of hermit crabs near other species of corvus, the Mariana crow’s frequent predation on them is unique, especially when you look at how they extract them.  Unlike most coastal or inland living crows that drop tough objects like clams or nuts onto hard surfaces to open them, the Mariana crow actually uses its bill to peck and break the shell at the seams to extract the vulnerable crab, a process that takes place entirely on the ground and is only shared by two other known bird species in the world (one of which is now extinct).  So what does this have to do with wanderlusting snails?  As it turns out, everything.

What's crackin' crabby? Photo: C. Brevimanus

What’s crackin’ crabby? Photo: Sarah Faegre

Rota is home to several species of native land and sea snail, though hermit crabs only utilize the larger shell of the sea snail.  Critically, these shells are extra hard and apparently impenetrable to even the most determined crow.  In the late 1930’s, however, humans introduced the Giant African Land snail which quickly invaded the island.  Two major differences between the native and invasive snails are 1) that the invasive snails have thinner shells, and 2) people were anxious to get rid of them.  So, naturally, we introduced  yet another invasive species (a predatory flatworm) and…it actually worked.  By the 1970’s the island was brimming with large, thin, empty shells, ready and waiting to be filled with hermit crabs.  Gradually, the crows learned that these shells were possible to peck open and now hermit crabs are an important staple for Rota’s crows.

Photo: Matt Henschen

Photo: Phil Hannon

On its surface, this seems like the making of an ecological disaster turned into a conservation blessing.  After all, we successfully controlled an invasive species while simultaneously creating a new food source for a threatened bird.  But in our tangled web of introduced species and ecological fallout we must considering the one remaining player: cats.  Although further study is needed, Sarah’s work3 suggests that all that extra time adult crows now spend on the ground cracking open hermit crabs may be making them more susceptible to predation by cats.

Couple the effect of cats with habitat destruction and persecution by people and the results project a bleak outlook for crow recovery.  But conservationists and researchers like Sarah are working tirelessly to better understand the threats facing this bird and how to solve them.  In fact Sarah and her husband, Phil Hannon, recently started a non-profit called Luta Bird Conservation to help raise awareness and conservation funds to better protect this unique crow.  At the top of their priorities is funding initiatives that would bring the science of crow conservation to the classrooms of local people, helping to raise both pride and awareness for the plight of this endemic species.

So the next time you look at a crow and experience a slight feeling of fatigue at such a ubiquitous bird remember; not all corvid species welcome the consequences of people and some have suffered greatly from them.  Aldo Leopold once said “to keep every cog and wheel is the first precaution of intelligent tinkering.” The lesson from Rota, and so many others, is that the same can be said of not adding any either.

If you wish to contribute directly to Mariana crow conservation, I encourage you to send Luta Bird Conservation Inc. a check at:

Luta Bird Conservation Inc. c/o Aron Faegre
520 SW Yamhill Street, Roofgarden 1
Portland, OR 97204
Sunny, Luta's educational Mariana crow captivates the students in a local school

Sunny the captive Aga on an ambassadorial trip to a local classroom with Luta Bird Conservation Inc.

Literature cited:

  1. http://www.fws.gov/pacificislands/fauna/marianacrow.html
  2. http://www.washington.edu/news/2010/12/20/without-intervention-mariana-crow-to-become-extinct-in-75-years-2/
  3. Faegre, S. (2014) Age-related differences in diet and foraging behavior of the critically endangered Mariana Crow (Corvus kubaryi) (Masters thesis; University of Washington).  https://digital.lib.washington.edu/researchworks/handle/1773/27571?show=full

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Filed under Corvid of the month, Crow behavior, crow conflicts, Crow life history, Crows and humans, Graduate Research, New Research, women in science

Notes from the field: That golden moment

I am a huge fan of podcastes of all kinds. Especially when I’m working a pair of very “avoidy” birds and I’m basically in for several hours of watching an unchanging pile of food on the ground, an earbud with a good story is the key to maintaining my focus on the sidewalk, rooftops and trees for any incoming birds. One of my favorite podcasts is The Story Collider which describes itself as “stories about how science touches people’s lives”. I highly recommend it for both science geeks and non-scientists alike, but I imagine it resonates deeper with those who feel engaged with science on a more regular basis. A common theme of these stories is “the golden moment”, and whatever that may mean for the storyteller. Which got me thinking: What’s my golden moment?

Conducting research in an urban environment, especially a study as conspicuous as mine, has it’s benefits and drawbacks. Drawbacks include: Confrontation over the study itself, people or pets unknowingly interfering with experiments, sometimes unpleasant or slightly risky work environments, etc. But the advantage is easily summarized: I get to engage with all kinds of people about my research. I derive and immense amount of joy from explaining my study to folks, especially in the company of children. There’s one particular moment in the course of the experiment, however, that stands out from the rest.

At a certain point in the study I have the masked person walking around instead of remaining stationary. Today I found myself conducting just such a trial and, frankly, these tests can be rather awkward. I can hear people whispering about the masked person, what they might be doing (often they don’t notice their “UW CROW RESEARCH” sign) and rarely are they emboldened enough to ask and, frankly, it’s probably for the best because I need my full attention on my birds during these tests (I’m working the camera while my volunteer walks around). As you can imagine, it can be a bit uncomfortable to cause such a stir and then just keep walking leaving people to scratch their heads (or think worse) about what they just saw. But occasionally the golden moment happens. That moment when they’ve noticed the mask, perhaps even read the sign and are eagerly discussing what a bizarre scene they’ve just witnessed with their companions when, boom, in comes the crow. Suddenly, without my needing to explain it, every onlooker can see precisely what’s happening: A crow knows that person and they don’t like them. An explosion of scolding, body language and flight patterns makes the target of their animosity well known. During these moments without any effort or intention, people are experiencing science. They’re watching crows and potentially learning something new about them. They will not know the full back-story to what’s going on of course, but there’s enough information laid right out there for them that conversations about crows and their intelligence and antics are inevitable. Suddenly the bird so many people ignore becomes the object of fascination and attention. These are the moments that I believe create changes in attitudes about crows and, more broadly, what science research looks like. These are my golden moments.

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Filed under Being a scientist, Graduate Research