Curious to read my popular science take on our recent publication on how crows behave around their dead? Check out my latest article for Biosphere. Then check out all the other awesome authors and contributors to my favorite popular science publication. You won’t regret it. (And congrats to GO for making the article cover! She’s such a gorgeous bird…)
Filed under Crow behavior, Kaeli in the media, New Research, women in science
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
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: 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: 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:
Sunny the captive Aga on an ambassadorial trip to a local classroom with Luta Bird Conservation Inc.
Literature cited:
This year, my field sites range through the east side from Mercer Island to Kirkland. My first field season, however, took place throughout downtown Seattle and included the ID, First Hill, the Central Business District, SODO, Belltown, and South Lake Union. I went to high school on Mercer Island and, while certainly a victim of the “MI bubble” as we called it, generally felt pretty familiar with the west side. I went into my field season last year anticipating to learn a lot about birds, which I did, but what I had not expected was to learn as much as I did about the city and the people it harbors. In fact, I doubt there’s anyway to become more intimately familiar with the real identity of a city than to spend from dusk to dawn on its streets, just watching.
Watching from the same spot on the sidewalk for 2 or 4 hours, invites the attention of all kinds of people. Lots of these are people who, come nightfall, remain on the sidewalk. Partly what I learned from these interactions is that they too watch the crows, and delight in sharing their stories. My favorite was someone who told me that the reason crows can be seen methodically wiping their bills on branches is because that’s how they mark their landing spot for next time. I suggested that it’s likely a way for them to keep their bills clean and well manicured (like fingernails, bird beaks never stop growing), but he couldn’t be dissuaded. It was such an ingeniously creative idea, I didn’t blame him for being so stubborn. The other was a man who informed me that if it were up to him, we would be wiping out the crows. “They attack the eagles and I just can’t stand for that, it’s unpatriotic”, he explained while wearing a sweatshirt emblazoned with an American flag and a proud eagle head.
It wasn’t all positive, of course. There was the woman at six in the morning in the ID who causally sat down next to me and started smoking crack. Or the guy who sits on the walking bridge to the ferries who threw a stroller onto the street below where it landed about 3 ft away from me. But mostly it was just unintentional conflict. Arriving to an experiment site with a desperate amount of limited time only to find someone sleeping the location I had established as the feeding/experiment site. Or people eating the food I had set out. That was tough. How do you ask a hungry human being to not eat food off the ground because it’s for birds? In some places I just started bringing snacks. In others, folks with whom I had previously bonded with over the crows could address these folks by name and explain the situation for me. That was easier but it still felt…bad.
On the other side of the spectrum were the people on their way to work or who were renting the pricy downtown apartments who “see you everyday and just can’t figure out, and now must know, what you’re doing”. They too were delighted to tell me about crows. Mostly they insisted I come to their house because “there are more crows at my house than anywhere else in Seattle.” But they could also problematic, and usually in ways that threatened the whole seven day experiment and not just a few minutes of it. I am now an expert at identifying the sometimes surprisingly subtle line in the sand between public and private property in a city. When you’re throwing food on the ground, or asking masked people to stand around, this distinction can mean the difference between a successful experiment, and security being called and days of wasted work. But even on public property, food on the ground is in a constant state of peril.
Something I don’t know if a lot of Seattlites are aware of are the omnipresent human street sweepers. I’ll never forget watching the 2013 LGBTQ pride parade (well, less watching than quickly walking by it between trial sites) and feeling such pride and joy that so much proactive passion has paid off in this state, only to return to Belltown at five the next morning to find the sidewalks covered in apathetic rainbow garbage. But, like clockwork, the street sweepers came out to erase the evidence of people so figuratively and literally intoxicated with activism they forgot about the other battles to care about (like the planet). The street sweepers themselves were always a roll of the dice. Some would not hear one word about leaving my pile of food for the experiment while others laughed and obligingly kept moving. Many grew to recognize me as I moved on from one site in the city to another and would happily use it as an opportunity to take a break from work and engage with someone who would give them the time of day.
Then there are all the stories of people who span the spectrum. I listened to two men emerging from the 5 Point at 5:00am, causally exchange a story of witnessing sexual assault (and doing nothing). There was the time I overheard a group of people talking about a friend on their way to jail over what, suffice it to say, was a graphic murder. They were not happy once they discovered I was filming during this conversation. Not on purpose, but their conversation was in the line of fire for filming my experiment site. This was maybe the most danger I was ever aware I was in during my field season. But some calm(ish) explanation of my research diffused the situation and led to, you guessed it, crow stories. Then there was the guy who, unaware that the woman he was talking about was standing near him concealed in one of the experimental masks I use, proceeded to annihilate me personally to a friend. He was certain that that woman who is usually always here “watching birds” was a lazy, entitled piece of shit who is wasting her parents money.
“Excuse me, I’m doing a research study, will you please wait here while I take of this mask? And watch my camera?” (Shortly after this photo was taken I had professional looking signs made)
But stories like those are less common. What really demonstrated the spirit of the city to me were the dozens of people who, after being approached by the muffled voice of a creepily masked person, agreed to watch my video camera while I ran to remove the mask. You see, the most important piece of data I collect is the time it takes the birds to return to the food site after the “dangerous” person leaves. If it consistently doesn’t take them long then I can surmise that the presence of this person isn’t resulting in a change of feeding behavior. If, on the other hand, I show that their feeding behavior dramatically does change then I can say that seeing people associated with dangerous things like dead crows or predators causes birds to avoid areas they hang out in, even if those areas are good food resources. Ideally, I had a volunteer be this person, and maintained my position a ways away as the friendly feeder person who innocently stands around watching the birds eat. But volunteers were in short supply, and sometimes I had to show up to an experiment site, throw out the food as myself, the friendly feeder person, and then run to a hiding spot and don the mask. At the end of the exposure period I needed to leave to remove the mask and collecting this key data point was contingent on finding a person willing to hear me out while I wore this crazy mask, wait for what, to them, was an unknown amount of time, and, critically, not steal my video camera. Over the course of my field season I asked dozens of people of all stars and stripes (I was on too critical of a timeline to be judgmental or picky) and not one of them ever bailed or took my camera. Like I said, I received an unexpected education of this city and the result was learning that the vast majority of people here are in fact extremely wonderful.
And bathroom codes. I know the code to every Starbucks bathroom from SODO to SLU.
Filed under Being a scientist, women in science
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