Breeding season is often a hard time for the tender hearted among us. The joy of watching an animal construct a nest just to see their efforts cut short by predation is painful. Likewise, finding a dead chick is tough, and prompts many to ask how they could have prevented such loss and better protected them.
I appreciate the people that bring me these questions so much. That care so deeply they would put in the effort to seek out these answers from a scientist and spend their time doing what I suggest. These are good people.
But whether you’re asking how to protect birds from crows, or crows from other animals, my answer is always the same. As hard as it is to watch animals get eaten, it’s vital to remember that predation is what keeps wildlife wild. It’s what keeps ecosystems complex & beautiful.
When we get into the business of deciding that (native, natural) predators are bad, and attempt to take action against them, we are denying the very wildlife we want to thrive from facets of their identity that make them who they are. Prey communities are shaped by the predators that have historically hunted them, and vice versa. Whether it’s how cryptic the chick’s color pattern is, how many eggs the female lays, where they build their nests…not one corner goes untouched. It’s this very process that has made something so beautiful that we can’t stand to see it harmed. But for communities to function that death is essential.
Predation is the transfer of life and that life is a gift. It’s a gift that ensures the survival of another, and even if we don’t know that individual as well as the one we watched perish, it’s not for us to assert that it, or its offspring, deserves that gift any less.
On the other hand, finding a dead, otherwise unharmed, chick can feel less…purposeful. “Why was it out of the nest so early?” “I read to leave it alone and it died anyway…should I have stepped in?” “I feel so bad I couldn’t save it!”…These are common responses.
But while it’s true that baby birds do sometimes (rarely) accidentally get kicked out of the nest, it’s also true that it’s not always an accident.
Sometimes parents simply reject offspring for reasons that are not for us to know. And that is okay. Part of honoring their wildness is accepting that they know more than us about their own lives, and that if they choose to not to support a chick they have a reason. There are exceptions of course in cases of conservation concerns, but for most backyard circumstances it is okay to accept their choice without interfering. Even if it hurts.
So please, rather than shutting down those deep feeling you have for wildlife by intervening, lean into them. Teach your friends and neighbors and children to feel those deep feelings. Because it’s from that space that we can do best by wildlife, even if it’s the kind red in tooth and talon.
It’s from there that we can grow a culture of care and empathy that shows us that nature is a community and by thinking first of community and not of the individual, can we have the broadest reach. That planting native vegetation, and keeping cats indoors, and fighting to protect land and water, is the way to love wildlife. Not by choosing who deserves to eat and who does not.
I had imagined it like a beckoning flood. A small sputter of water followed with increasing force until a great river finally makes its way. Rather than water though, the flood I was trying to envision was the ascent of 12-15,000 crows to their nightly roost in Bothell, Washington.
Witnessing it in person, I found that my water analogy was not entirely accurate. Rather than being a steady stream with a predictable course, their arrival ebbed and flowed, sometimes leaving the sky lonely with only its fading grey light while other times exploding into seemingly endless black clouds. They arrived from all cardinal directions, colliding into a mass that could be deafening at close range. Although the movement of the flock as a whole was more restrained, individually they showed off with spontaneous dives and barrel-rolls. Soon the light receded completely, and all I could sense was the cacophony of so many crows settling into the willow trees they would call their beds for the evening.
Time lapse of Bothell crow roost I took with my GoPro in December of 2016. Music by Andy McKeen.
Since that first experience, I have visited the Bothell roost many times, each as awe inspiring as the time before. This behavior isn’t unique to my region, however. Cities and rural areas all over the world call themselves home to the upwards of thousands, even hundreds of thousands of crows that may seek their refuge when darkness falls. Even in the greater Seattle area, Bothell is only one of two roughly equally sized roosts. This kind of mass sleepover, known as communal roosting, isn’t unique to crows, but it certainly captures our attention in ways most other birds don’t. So what exactly are the characteristics and functions of roosts?
For all species of corvid, roosts are places where anywhere from a small handful to hundreds of thousands of individuals may converge to spend the night together. Though roosting occurs year round, it peaks in winter, when territorial pairs are free from the eggs or nestlings that demand all-night attention. They may occur in wildlands, but more typically occur in cities, where sequestration of heat is higher than in surrounding areas. Here in Bothell, the roost converges in a wetland outside of the University of Washington’s Bothell campus, but in other areas they may take over the rafters of abandoned buildings or trees dotted within a business district.
Historically Danville, IL hosted North America’s largest roost, a whopping 325,000 birds but I do not know if they remain the contemporary record holder. The midwest is particularly primed to host such large numbers because many thousands of crows head there during winter from their too cold territories in Canada and because appropriate roosting locations are few and far between.
Prior, or just after roosting crows attend “staging” or “pre/post-roost” areas where they gather in the trees or on the ground by the hundreds or thousands. Since these staging areas often occur on asphalt or turf where there’s little food or water, their function continues to elude scientists though social or anti-predator implications seem likely.1 A new UW research study is attempting to parse why crows are so vocal during the staging period and what they might be trying to communicate. Perhaps their findings will shed some much needed light on these events.
Corvids get different things out of roost itself depending on the species or possibly even the region they live. For example, for ravens roosts act, in part, as mobile information centers.2 A raven knowledgeable of a food bonanza such as a moose carcass will display to other ravens at first light, and recruit others to the food. Rather than being a sign of food altruism, this kind of recruitment is often the only way a lone raven can gain access to a large carcass. Finding and gaining access to an animal carcass is challenging both because its arrival is unpredictable but also because it’s intensely guarded by the pair whose territory happened to claim the animal’s life. Overpowering a pair takes a small army, so by recruiting other birds, rather than giving up food in the name of helping others, the lone raven actually gains access to a resource it would have otherwise been boxed out of.
American crows on the other hand do not have this need because urban waste and invertebrate filled yards are so easy to come by. For crows, roosts act in large part as predator protection. The odds of successfully fleeing an incoming owl are much better when there are thousands of you, rather than just you and your mate. They may serve other purposes as well though including socialization, mate finding, and thermoregulation. Lastly, while there isn’t strong evidence of information sharing among crows it would be arrogant to claim we know it doesn’t occur.
How roosts are organized remains largely mysterious. For example some evidence shows that ravens that come from the same food bonanzas also sleep near each other in a roost,2 whereas other work done on crows suggested that group cohesion is low at roosts.3 Still, other research suggests that while group cohesion from the territory is low, it’s high leaving the staging area. So perhaps there is deep rhyme and reason for who they sleep with, it just hasn’t been captured by the questions we’ve so far asked. One thing is for certain though; the one place you don’t want to be is low in the trees with others above you. There would be no escaping the white shower raining down throughout the night.
Even the people who share the UW’s campus are sensitive to this reality. In perfect synchrony with the incoming cloud of birds, the umbrellas bloom like moonflowers. Here in Seattle, people seem willing to take such measures to coexist with the birds (though I’m sure there are many who only do so only by rule of law). In other areas though the cultural attitude or resulting damage makes such cohabitation difficult, even deadly. In the most extreme case, 328,000 crows were killed in 1940 when the city of Rockford, IL elected to dispose of a local roost with dynamite.4 Today, crows are protected under the migratory bird treaty act and cities are usually required to take more creative, non-lethal approaches including noise and light deterrents.
City living doesn’t always lend itself to witnessing the kind of mass animal movements we fawn over when they appear in Planet Earth footage, but that doesn’t mean they are devoid of such spectacles. The mass micro-migration of thousands of crows is an awe inspiring event, grand in both scale and the mysteries it contains. Any corvid or birdwatcher would be remiss to ignore such an opportunity and I encourage everyone to get outside, head to your roost, and watch the magic unfold.
Literature cited
Moore JE, and Switzer PV. (1998). Preroost aggregations in the American crow, corvus brachyrhyncos. Canadian Journal or Zoology. 76: 508-512.
Wright J, Stone RE, and Brown N. (2003). Communal roosts as structured information centers in the raven, Corvus corax. Animal Ecology 72: 1003-1014. DOI: 10.1046/j.1365-2656.2003.00771.x
Donald F. Caccamise, Lisa M. Reed, Jerzy Romanowski and Philip C. Stouffer
(1997). Roosting Behavior and Group Territoriality in American Crows. The Auk 114: 628-637
Marzluff, J.M. and Angel, T. 2005. In the company of crows and ravens. Yale University Press
It can be hard to imagine crows as anything but ubiquitous. During winter across the country, dusk marks the time where some cities see their skies turn black with thousands, even hundreds of thousands of American crows converging to roost. These crows have taken nearly all that people have thrown at them: deforestation, mass waste, and the urban sprawl that simplifies previously complex ecosystems, and uses it to their advantage. Not all species of crow have thrived in the Anthropocene, however.
Thousands of gather accumulate in the skies above UW’s Bothell campus in the winter
Far from being icons of the ultimate adapters some species of crow represent some of the most endangered animals in the world. Among those, the ‘Alalā or Hawaiian crow, is arguably one of the rarest birds on earth. Once locally abundant in the forests and woodlands of Hawaii’s Big Island, their decline began in the 1890’s following persecution by coffee and fruit farmers1. Back in September, 2015 there remained only 114, all living exclusively in captivity giving them the unenviable title of ‘extinct in the wild’. How can one species thrive with such zeal while another holds on by a thread?
Island species are generally more specialized and therefore more sensitive to human induced changes. In fact proportionally, islands host a higher number of endangered or extinct species than continental areas2. In Hawaii alone, 77 different species of endemic birds have gone extinct since the arrival of the Polynesians 2,000 years ago4, all largely for similar reasons: habitat destruction and invasive species.
Unlike their generalist, continental counterparts, the ‘Alalā is more specialized to feed on understory fruits and nuts and in fact were key seed distributors for many of Hawaii’s native plants. Island living also fostered a similar behavior seen in only one other species of crow: tool use. Like the New Caledonian crow, the ‘Alalā is a dexterous tool user, though the two species are only distantly related. Scientists believe this example of convergent evolution is fostered by aspects typical of islands, namely low predation and low competition for embedded food5.
Unfortunately, limited distributions and higher specialization also meant their population was more fragile than that of continental crows. Logging, agricultural development, loss of native pollinators, and alterations by non-native ungulates challenged both food acquisition and breeding habitat. Introduced diseases such as avian pox, malaria and the Toxoplasma gondii parasite carried by cats further weakened an already ailing population6,7. Invasive predators including rats, mongoose and cats consumed eggs, nestlings and fledglings. Finally, humans continued their tradition of persecution, particularly feral pig hunters who would shoot the birds before they could alarm call and scare off their prey2.
Together, these threats set into motion a decline in population we failed to recover despite some increases in research and management starting in the 1970’s. The last known wild egg was laid in 1996, and the last wild pair was seen in 20022,3. Some people did recognize the urgency of their decline prior to 2002, however, and a captive breeding population was started successfully rearing over 90 birds8. Although such a small number of breeders may raise red flags with respect to inbreeding and genetic depression, this is rarely as big of an issue as is commonly perceived. Unfortunately, light management and depredation by the also endangered Hawaiian hawk (‘io), decimated the released population and reintroduction efforts were halted in 1999 until a larger captive population and better management strategy could be devised.
Since that time, the ‘Alalā Restoration Project (collaboration between the State of Hawaii, the U.S. Fish and Wildlife Service, and San Diego Zoo Global) has spearheaded captive breeding programs on Maui and the Big Island culminating in a population of over 100 birds. An important part of these captive breeding programs is the use of puppets, which help prevent habituation to humans9. In addition, intensive management operations have taken place to ready their prospective home at the Pu‘u Maka‘ala Natural Area Reserve including the removal of invasive/feral animals, erecting exclosure fencing, and constructing a sort of half-way house to help ease the birds into life in the wild. These efforts have not been without setbacks, however. Back in June, 2015 two miles of protective fencing was cut down by vandals, though their motivations remain unknown.
A human dressed as an ‘Alala feeds captive reared nestlings. Photo c/o San Diego Zoo Global
Finally, after so much work, the end of 2016 marked the first time researchers and managers agreed the elements were in place for a reintroduction effort. On December 14th, five male birds were released onto the reserve, marking the first time the ‘Alalā set claw into the wild since 2002. Sadly, within weeks all but two had died. Two were killed by the native Hawaiian hawk or ‘lo, and the third was killed by “natural circumstances” which, I’m guessing, is related to a heavy storm that occurred shortly after their release. As a protective measure, the remaining two were recaptured until the results from the necropsies are obtained.
While clearly disheartening, early hiccups in a release effort like this are not unusual and conservationists and biologists are not losing hope that success is still possible. Part of ensuring such success, however, is undoubtedly public support particularly with respect to maintaining the strength of the Endangered Species Act and support of the ‘Alalā Restoration Project. The perception that all crows are alike or that generous populations of American crows means protections for other corvus species is unwarranted or redundant will be a disaster for these rare birds. So make your voice heard when funding for conversations efforts come under fire, and share your passion for endangered corvus species with friends and family. The fate of the world’s rarest crow quite literally depends on it.
Two newly released ‘Alalas peer around their new surrounding in the Pu’u Maka’ala Natural Area Reserve. Photo c/o the San Diego Zoo Global
Faike, E. 2006. Wild voices in captivity: the date of the ‘Alala. Birding 38: 64-67.
Banko, P. C.; Burgett, J.; Conry, P. J.; David, R.; Derrickson, S.; Fitzpatrick, J.;
National Research Council (US) Committee on Scientific Issues in the Endangered Species Act. Science and the Endangered Species Act. Washington (DC): National Academies Press (US); 1995. 2, Species Extinctions. Available from: https://www.ncbi.nlm.nih.gov/books/NBK232371/
Rutz C, Klump BC, Komarczyk L, Leighton R, Kramer J, Wischnewski S, Sugasawa S, Morrissey MB, James R, St Clair JJH, Switzer RA, and Masuda BM. (2016).
Discovery of species-wide tool use in the Hawaiian crow. Nature 537: 403-407 doi:10.1038/nature19103
Maxfield, B. 1998. Wild ‘Alala population suffers major setback. ‘Elepaio 58: 51.
Liebermann, A.; Nelson, J. T.; Simmons, P.; Unger, K.; Vitousek, P. M. 2003. Draft revised recovery plan for the Alala (Corvus Hawaiiensis. US Fish and Wildlife Service, Portland, OR, USA.
Lieberman, A. C., Kuehler, C. M. 2009. Captive propagation. In: Pratt, T. K.; Atkinson, C. T.; Banko, P. C.; Jacobi, J. D.; Woodworth, B. L. (ed.), Conservation Biology of Hawaiian Forest Birds: Implications for Island Avifauna, pp. 448-469. Yale University Press, New Haven.
Valutis LL, and Marzluff JM. (1999). The appropriateness of puppet-rearing birds for reintroduction. Conservation Biology 13: 584-591
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.
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.
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.
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.
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
Ah fall, the changing colors, the arrival of mushrooming season, and the gratuitous consumption of hot drinks makes this season a favorite of mine. But if you live in a temperate zone like the PNW, there’s one drawback to fall; West Nile virus (WNV). Make no mistake, since its first appearance in the US in 1999, cases of WNV have been documented year round. Outbreaks, however, typically peak in late summer and early fall which is why you often start to see increasing media attention directed towards the discovery of crow corpses. Such is the case with a recent die-off in Spokane which inspired a fleet of recent articles. My favorite was a post from an otherwise predominately car-focused site called The News Wheel which included the following passage:
“In either case, authorities are telling residents that, should they find a dead or dying crow in the street, that they should under no circumstances handle them…In the mean time, it may be a good idea to replace your car’s windshield cleaning fluid with holy water (just in case).”
I suspect some sarcasm was at work there but, in truth, people can get very worked up about WNV. So here are some FAQs about crows and WNV intended to keep you safe and informed.
What is WNV?
WNV is an arthropod-borne virus which can cause febrile illness, encephalitis (inflammation of the brain) or meningitis (inflammation of the lining of the brain and spinal cord). It was first documented in the US in 1999, and exists across most of the world (sigh; the costs of globalization)1.
Why are crows associated with WNV?
No, this isn’t unfair prejudice at work, corvids really do have it rough when it comes to this disease. In all the documented cases of WNV 80% of them have affected corvids, despite its presence in 300 other species of bird2. The connection between WNV and climate change means that corvids could be in big trouble which you can read about in a previous post here.
What does a bird sick with WNV look like?
Most birds who contract WNV will survive, but for the many crows and other corvids what won’t, symptoms include trouble with balance both at rest and while mobile, and lethargy. There won’t be any way to tell if a dead crow is infected simply by looking at it2.
Can I get WNV from touching a crow?
According to the CDC, there is no evidence that a person can be infected by direct contact with infected birds, dead or alive3. That being said, always use gloves when handling wildlife.
Can people get WNV? Yes, though keep in mind that the virus really doesn’t want to be in you. Humans and other mammals are considered ‘dead-end’ hosts meaning we generally don’t develop a big viral load and the virus cannot be transmitted from you to other humans via mosquitoes1.
How is it spread?
Mosquitoes, mosquitoes, mosquitoes. They bite the infected bird and then bite you. And very, very rarely through blood or organ transfusions, and from mother to baby during pregnancy or by breast feeding1.
How worried should I be?
I’m not a doctor so let’s let the numbers speak for themselves on this one. Here are the key stats you should know c/o the CDC1:
80% of infected humans will not develop any symptoms.
Of the 20% that show symptoms, most will look like the flu. It will suck, but you’ll recover just fine.
Only 1% of infected individuals develop life threatening symptoms.
As of September 22, 877 people have tested positive for WNV in 2015. Of those 43 have died. That’s about half the number that will probably be killed by bee stings and twice as many as will be killed by cows4.
For a look at the average annual WNV incidence by state from 1999-2014, check out this map from the CDC. Suffice it to say, in most states the incidence per every 100,000 people is less than 1. As a reference point, about 5-20% of the population gets the flu every year and about 36,000 die as a result5.
How can I protect myself?
The CDC recommends an integrated management plan that includes:
Mosquito surveillance (are there lots around, how often are you getting bitten, are illnesses being reported etc.).
Reduction of breeding sits (i.e eliminate standing water around your home).
The use of chemical and biological mosquito control.
And finally, education (which by reading this you’re already doing!).
So, does a dead crow in your yard mean it’s time to break out the hazmat suit? Definitely no, but do Fish and Wildlife a favor and report your crow carcasses. And if any of your neighbors start to panic, calmly and gently give them the facts. Or just send them this meme I made you:
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:
Luta Bird Conservation Inc. c/o Aron Faegre
520 SW Yamhill Street, Roofgarden 1
Portland, OR 97204
Sunny the captive Aga on an ambassadorial trip to a local classroom with Luta Bird Conservation Inc.
If there’s one corvid that’s most notorious for getting into trouble, it’s probably the large-billed crow (sp: Corvus macrorhynchos* ). A dubious reputation perhaps, but it’s one that’s been well earned through this corvid’s knack for exploiting humans and the opportunities we create.
Physical description: While large-billed crows aren’t much bigger than an American crow, their square head and heavy bill gives them a more raven-like appearance. To me, they look like what I might expect if a common raven tangoed with Rick Moranis’s contraption from Honey I Shrunk the Kids.
Range: They are found throughout the northeastern Asian seaboard to Afghanistan and eastern Iran in the west, through South and Southeast Asia, to the Lesser Sundas and Cambodia in the southeast. Although in India the eastern jungle crow and large-billed crow behave has two distinct species, in northern parts of Asia their distinction is less clear and colloquially the two are often analogous.
Conservation status: Given their large range, it may come as no surprise that their populations are abundant and are considered a species of least concern by the IUCN. In fact, since the 1980’s the number of jungle crows in Tokyo has quadrupled1.
“Corvus macrohynchos map”. Licensed under CC BY-SA 3.0 via Wikimedia Commons
So what accounts for their bad reputation you ask? Where to begin…how about vandalizing cemeteries1. In Japan, food is left at the burial sites of loved ones as an offering. Although in some cultures these offerings are meant to be eaten by animals, that is not the case here, and the crows’ stealing of food interrupts the intention of the ritual. Historically, this probably wasn’t a conflict since jungle crow populations were much smaller than they are now.
As if that wasn’t enough to get people fired up, jungle crows also have a bad habit of, well, firing things up. People were stumped how field fires near the Fushimi-Inari shrine in Kyoto were starting until someone thought to watch the crows. There are 10,000 candle holders that line the walkways of the shrine and on busy days they may contain thousands of individual burning candles. With some diligent watching, researchers discovered that crows were eating the melted candle wax (which is often made with tallow) and in some cases taking the burning candles out of the holders and flying off with them. Although they never witnessed it, researchers suggested that crows’ attempts to cache burning candles may have been the cause of the mysterious fires.2 The crows appeared to show no fear of the flames according to the paper’s author. Photo: H. Higuchi
To top it all off, large-billed crows seem to be just as good at turning out the lights as there are at lighting them up! Unlike American crows, which predominately use sticks to build their nests, large-billed crows have developed a fascinating (and immensely frustrating for the Japanese government) habit of using clothes hangers to construct nests. Mixing wire hangers with power lines is a recipe for disaster and in the summer time large-billed crows are responsible for massive blackouts. The Tokyo government spends millions of yen, and employs full time crews, to search for and destroy hanger nests in an effort to prevent such black-outs.1 Maybe Joan Crawford had just spent too much time around jungle crows… Photo: Götz
It’s not all bad press for these resourceful crows, however. One of the more spectacular things they are known for is using cars to crack open otherwise inaccessible nuts. Not only that, but they also appear to be sensitive to crosswalk signals and know when it’s safe to collect the exposed nuts and when it’s not.3So while large-billed crows make their fair share of trouble stealing food, candles and hangers, there are still plenty of people who adore these animals for their cleverness and ingenuity. For those that don’t, well, some aren’t shy to take control measures into their own hands. Or should I say mouths…
*The jungle crow was formally Corvus macrorhynchos, but the species was split into the large-billed crow Corvus macrorhynchos, the eastern jungle crow Corvus levaillantii, and the Indian jungle crow, Corvid culminatus.
Literature cited:
1Marzluff, J.M. & Angell, T. 2005 In the company of crows and ravens. Yale University Press
2Higuchi, H. Crows causing fire. (2003). Manuscript from The University of Tokyo
3Marzluff J.M & Angell, T. 2012. Gifts of the crow. Free Press
Updated with data from a new review of studies looking at impacts of corvid removal on other birds.
A comment I occasionally hear, especially while conducting my research in neighborhoods is, “Ugh, I hate the crows. All of a sudden we have tons of crows and they’ve scared off all our songbirds!” This comment always pains me, but I understand that for most people it arises from a genuine concern for songbird abundance and conservation. First off, as a reminder crows are songbirds themselves; ravens are our biggest songbird. Semantics aside, I understand that there are many, many bird lovers who just can’t get on the crow bandwagon and when they talk about wanting songbirds at their feeders they mean chickadees, juncos, grosbeaks, etc. They feel that since the “arrival” of the crows their observations of these other birds have diminished. So is there anything to this? Do crows indeed drive down populations of small, “desirable” backyard birds?
I came across this grizzly scene while conducting research in…
Officer cleaning up one of the many dead crows found in Portland’s Waterfront Park. Photo c/o KOIN 6 News
Normally when I talk about a murder of crows I’m using it as a noun to describe a large group, but in this case I’m talking about the likely deliberate killing of at least 30 birds in downtown Portland, OR. The Wednesday before thanksgiving, people started to notice dead and seizing crows in the sidewalks and parks and, quickly, the bodies started to pile up at an alarming rate. Several specimens were sent to a lab for autopsies and, while more definitive answers are yet to come, all signs point to poisoned corn. Since corn isn’t generally found in urban areas unless put there by people, the Portland Audubon Society fears that these crows may have been deliberately baited and killed.
This has prompted both warranted outrage and…confusion. Why is Fish and Wildlife treating this like a crime, but hunting crows is ok? Crows, like basically all non-invasive birds, are federally protected under both the Migratory Bird Treaty Act and various state laws which means you cannot “take (gov speak for kill, intentionally or otherwise), possess, import, export, transport, sell, purchase, barter, or offer for sale…the bird, or the parts, nests, or eggs of such a bird except under the terms of a valid permit issued pursuant to Federal regulations” (MBTA, 16 U.S.C. 703–712). It’s that last bit that’s key here. It means that, just like other game birds, you can shoot crows with a hunting license, though you need a different “validation” than you need for waterfowl or upland game birds and it varies from state to state. Now here’s the rub that some people will say if they get caught killing crows without a license. In many states, including Oregon, you can kill crows without a hunting license and outside of the hunting season if they are “found committing or about to commit depredations upon ornamental or shade trees, agricultural crops, livestock, wildlife, or when concentrated in such numbers and manner as to constitute a health hazard or other nuisance” (ODFW 2013 Bird Regulations). BUT and this is a big one, you must report these “takes” and there’s all kinds of federal laws that limit how you can kill the animals in these cases. The person who did this both did not report it and used illegal lethal means (poison is basically never ok because it’s too hard to limit it to your target species) hence the pending investigation. Whether or not that investigation actually happens is another matter. You can share your voice and enthusiasm for more legal action here.
My friend, Simone, and one of her crows, Jekyll. Through both educational outreach and storytelling on social media, people like Simone are reshaping our attitudes towards crows and other corvids.
Hopefully the person(s) responsible for this are found and made accountable for their actions because they broke the law plain and simple. Though, honestly, I don’t think our best chances of precluding another incident like this are through punishing one or two individuals. Rather, I think we should continue striving for a more compassionate culture through both science and story telling. These are two of our greatest tools whenever we’re trying to change hearts and minds (forgive the cliche). Information on how to non-lethally get rid of crows, and what isn’t effective (like randomly killing 30 birds!), gives us tools to have informed discussions on how to manage crows without useless killings. Data on how smart they are, what their family groups are like, their emotional intelligence etc., challenge the thinking that they’re mindless automatons and makes it harder to treat them as such. Stories from crow watchers and lovers, set the cultural tone that these are animals we value and make the lives of individual crows more meaningful through personal connections. These are the tools that will ultimately help us reshape the way people think of, and treat crows.
A comment I occasionally hear, especially while conducting my research in neighborhoods is, “Ugh, I hate the crows. All of a sudden we have tons of crows and they’ve scared off all our songbirds!” This comment always pains me, but I understand that for most people it arises from a genuine concern for songbird abundance and conservation. First off, as a reminder crows are songbirds themselves; ravens are our biggest songbird. Semantics aside, I understand that there are many, many bird lovers who just can’t get on the crow bandwagon and when they talk about wanting songbirds at their feeders they mean chickadees, juncos, grosbeaks, etc. They feel that since the “arrival” of the crows their observations of these other birds have diminished. So is there anything to this? Do crows indeed drive down populations of small, “desirable” backyard birds?
I came across this grizzly scene while conducting research in Bellevue. An adult robin calling frantically while a crow munched on one of its young. Later that same week I would watch of pair of adult crows chase hopelessly after a cooper’s hawk that had taken one of their offspring.
The short answer is: not usually. Now, let’s be clear, crows will absolutely kill and eat eggs, nestlings and even adult birds if they can get their hands on one. I once saw a crow take down an adult house sparrow in an attack so quick and dexterous I only realized what had happened after the crow had already started eating its meal. It’s important to keep in mind, however, that crows are one of many, many animals that are eating the young and adults of other bird species. Raccoons, squirrels, foxes, hawks, owls, bullfrogs, rats, mice, and of course cats will all gladly eat birds, especially eggs and nestlings. The vulnerability of young birds is in fact why the breeding strategy of many birds is to have multiple clutches over the course of the breeding season. Crows themselves are subject to these same predators and very few of their young will make it to adulthood.
Why do we think that crows aren’t responsible for the any observed decrease in feeder birds? Predator removal studies. These studies are straightforward and essentially create two populations, a control population that has been unmodified and a second where the predator in question has been actively removed. Prey abundance or productivity is monitored and compared at the end of the trial.
Recently, Madden et al. published a comprehensive literature review of 42 studies across 9 countries that looked at the impacts of corvid removal on a variety of avian groups including gamebirds, passerines, waders and other ground nesting birds. They found that in 81% of cases corvid removal made no impact on prey abundance or productivity. They also found that impacts of corvids on prey species was similar, and no one group was particularly more sensitive than any others. Of the corvids studied, magpies consistently had the smallest impact on prey productivity, but no difference was found if the study was looking at prey abundance. So if corvids are such conspicuous avian predators, why doesn’t their removal seem to matter in most cases?
This is explained by idea of compensatory mortality, which is essentially that removing one predator just means that the other predators will account for its absence by eating the prey it otherwise would have. Kevin McGowan provided a great description for this idea on his site“I like to use the analogy of handicapped parking spaces at the mall You drive up to the mall, looking for a parking space in a crowded lot. You can’t find a parking space, but there are four near the entrance that are reserved for handicapped permits only. You complain and think that if only those handicapped restrictions weren’t there, you could park in those spots (common sense). In truth, of course, if those spaces were not reserved they would have been taken long ago, just like all the other spaces in the lot.” Indeed, Madden et al. found this to be true. When they looked at studies that only conducted corvid removal, they found that only 16% of cases saw a difference in prey productivity. Whereas if all predators were removed the researchers reported that 60% of studies found a significant difference in prey productivity.
What this means for those of us trying to improve the bad reputations of crows and other corvids is that the data is on our side, crows are not usually the problem predators they’re often made out to be (though in a small number of instances they are, and it’s important to acknowledge when that’s the case). In fact, in 6% of cases the researchers found that corvid presence actually benefited other birds. So what I suspect is happening when residents ask me why they see fewer birds and if crows are to blame is that crows often follow urban development and it’s possible that what these residents are experiencing is a change in species diversity as habitats are disrupted and modified to make way for new human settlements. Though it’s also possible they simply don’t know where to look. It wouldn’t be the first time I’ve listened to folks complain about crows driving away their birds in the presence of yellow-rumped warblers, white crowned sparrows, juncos and chickadees. Indeed, suburbia is often a great place to enjoy both crows and other smaller songbirds.
John Marzluff’s newest book which describes the awesome power of suburbia to become a heaven for a huge diversity of birds. Illustrations by my friend and colleague, Jack DeLap.
John Marzluff’s new book Welcome to Subirdia, highlights that vast species diversity that can come with suburban development, showing that these types of habitat modifications aren’t doomed to be low diversity. With a bit of thought on our part, we can create habitats that attract a variety of birds. Namely, by limiting lawn space, increasing snags, native plants and bushes and keeping our cats indoors, we can expect to see a great variety of birds visiting our feeders, crows included!
Madden, C.F., Beatriz A., Amar, A. (2015) A review of the impacts of corvids on bird productivity and abundance. Ibis: 157, 1-16.
corvidresearch.blog 
