Category Archives: Crows and humans

Saving the rarest crow

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.

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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.

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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.

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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 

Literature cited

  1. https://www.fws.gov/pacificislands/fauna/alala.html
  2. Faike, E. 2006. Wild voices in captivity: the date of the ‘Alala. Birding 38: 64-67.
  3. Banko, P. C.; Burgett, J.; Conry, P. J.; David, R.; Derrickson, S.; Fitzpatrick, J.;
  4. 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/
  5. 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

  6. Maxfield, B. 1998. Wild ‘Alala population suffers major setback. ‘Elepaio 58: 51.
  7. 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.
  8. 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.
  9. Valutis LL, and Marzluff JM. (1999).  The appropriateness of puppet-rearing birds for reintroduction.  Conservation Biology 13: 584-591

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Filed under Conservation, Corvid diversity, Corvid health, crow conflicts, Crows and humans, Ecosystem

5 reasons to leave baby crows alone 

Those blue eyes, that awkward gate, their seemingly constant precariousness, they’re all calling to you to intervene. Here are 5 reasons second guessing that instinct might be in the bird’s best interest.

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1) The vast majority don’t need your help. It’s totally normal for baby crows to be on the ground and flightless as long as they’re covered with feathers and appear otherwise alert and mobile. Even nestling crows are usually on the ground on purpose. Not because they are ready, but because their parents have intentionally rejected them for one reason or another. They will die and that’s ok. Part of coexisting with wildlife is giving them the agency to be wild. The story is different of course for species where the survival of individuals may mean the difference between population survival and extinction, especially because these situation are almost always driven by human activity.

2) It’s hard to tell when they’re stressed.  Recently, I saw a video on Facebook of a Steller’s jay fledgling in the care of a very well intentioned good samaritan.  She was giving it gentle strokes with her fingertips, each touch resulting in the young bird turning its head towards its back and opening its mouth.  The comment thread filled with ooo’s and awww’s and general comments of encouragement or gratitude for her actions.  For me it was like watching an alien attempt to care for a human child, the child recoiling and screaming while its caretakers congratulated themselves on how kind they were being.  Having handled baby corvids before, I know what that kind of posturing means, it means “I’m scared and stressed.”  To an untrained eye though, it may not look much different than the kind of gaping that means ‘feed me.’  Being stressed to death is a reality for young, or even adult animals, so any handling best be done by experts whenever possible.

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3) It’s illegal to rehab crows without a license. You can provide temporary care until you can get them to a licensed facility, but do not attempt to rehab them on your own.  Mistakes like the one I just described are a prime example of why the law seeks to protect animals by ensuring they are only raised or rehabilitated by experts.  For more information on how to handle them until you can get them to a facility visit my previous post.

4) Imprinted crows do not survive well in the wild.  Even if baby crows are receptive to being treated like a pet, doing so is both a legal violation and I would argue a violation of their right to be a wild animal with a healthy fear of people.  Of all my daydreams, at the top of the list is having a wild but imprinted crow that follows me around.  I even have a name picked out.  This fantasy of mine will forever remain just that, however, because it’s too dangerous to allow a crow to become that comfortable with people.  All it would take is one cranky neighbor with a pellet gun and it would be over.  Not to mention being imprinted on people, instead of crows, denies them access to skills and relationships with other crows that will help them survive into adulthood.

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Killing them with kindness is a real risk.

5) It may do more harm than good.  The conventional wisdom suggests “well, worse case scenario is I try and rehab this baby crow and it dies, which it would have done anyway so really, nothing’s been lost.”  The more we study death in social animals the more we are beginning to realize there may be a cost to prematurely removing ailing or dead animals from their groupmates, however.  Being able to interact with their dead may serve an important role for social animals, and denying them this opportunity may have serious implications in their ability to process that death.  So be thoughtful about how slim the chance of survival is.  It might be that the kindest, most responsible action is no action at all.

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Filed under Corvid health, Crow behavior, Crow curiosities, Crow life history, Crows and humans, Uncategorized

Everything you want to know about crow nests

Spring marks one of my favorite times of year.  Cherry blossoms abound, the rain smell sweet and the birds get busy putting their carpentry skills to good use. Starting early March, the silhouettes of crows with bill loads of timber or wads of soft material dot the skies as they shuttle back and forth to their nest tree. Like a townhouse development, these construction projects are over in the blink of an eye and soon, their bill loads of twigs will be replaced by food for their mate and, eventually, their insatiable young. Spotting these nests is both a great way to observe and engage with your local crow family and avoid unpleasant conflicts with protective crow parents.  With a little knowledge and a bit of practice, tracking down your resident crow nest will become one of your favorite spring traditions in no time.

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Nest construction and site selection

Nest construction begins in early March and will continue (as nests fail) through about June. It takes 1-2 weeks to finish a nest after which the female will lay a clutch of 2-6 eggs. Unlike similarly sized squirrel nests (aka: dreys) which are made of leaves, crow nests are made mostly of pencil-width twigs. A new nest is usually about 1.5 ft across and 8-10 in deep.  After the bulk of construction is complete, they’ll line the cup of the nest with soft materials like grass, tree bark, moss, flowers, paper or fur. Once we saw a crow ripping out the hair of an outdoor manakin, no doubt to use as lining material.

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A crow gathers moss off the branches of a big leaf maple to use as lining material.  


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This bird toyed with this branch for a few minutes before rejecting it and letting it fall to the ground.  


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A sidewalk littered with twigs is good evidence that the nearby deciduous tree is a favorite among the local crows to pull branches from.  I’ve only once seen a crow try and retrieve a branch it dropped, so these are all rejects.  

 

Crows will nest in an astounding array of places, from the eaves of skyscrapers to the crooks of well concealed tree limbs. They can tower in the sky or be almost within reach. Most commonly, I see them built close to the trunk in the top third of Doug fir trees, but this is, of course, specific to the PNW.  Both partners participate in nest construction. Helpers will aid to some degree but most of the work is left to the parents.

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Differences among corvids

Crow, jay and raven nests are similar in shape and material but differ in overall size in accordance with the size of the bird. The main standout are magpies,  which build incredible domed-shaped nests the size of a large beach ball.  The nests require so much material, they can take as much as 40 days to build.  Japanese jungle crows are another species of note, as they have a (relatively) new and problematic habit of building nests out of wire hangers and causing massive blackouts.

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A Jungle crow nest in urban Japan. Photo: Götz


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The magpie’s nest is the big clump in the middle of the tree.

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The life of a typical nest is only about 9 weeks (1-2 weeks of building, 6 days of laying, 20 days of incubating and 4 weeks of nestlings) though they are hardy structures and can remain intact in a tree for years.  After the young fledge, the crows will not return to the nest.  Crows will only use a nest once, and generally only fledge one brood a year. They will, however, build on top of an old nest particularly in areas where nest trees are especially sparse like downtown Seattle. This also appears to be more common in the Midwest.

Avoiding conflicts

Most breeding related dive bombs occur as the result of a person being too close to a fledgling, but some crows get feisty around their nest too. Crows in areas where they are less persecuted (like cities) tend to be more aggressive than their rural counterparts. If you know where a nest is and can avoid it, do so and save everyone the aggravation. Otherwise carry an umbrella or paint eyes on the back of a hat. Crows rarely attack from the front so having eyes on the back of your head can be an effective deterrent!

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Putting all this together to actually find nests, is one of the most rewarding moments an urban naturalist or crow enthusiast can have.  Be warned though: crows are wary of potential predators (including people) spying on them and they have a few tricks for throwing you off, so don’t be surprised if a nest location you were certain of turns out to have been a ruse!

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Can you spot the nest? 

Have more questions? Let me know in the comments!

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Filed under Birding, Breeding, Crow behavior, Crow life history, Crows and humans

Crow curiosities: Do crows collect shiny objects?

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.

‘Crow Collects’ by Cori Lee Marvin.

For instance, one study1 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.  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.

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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 about crows.  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 smoothed2.  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.

  1.  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.
  2. 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

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Filed under Corvid mythology, Crow behavior, crow conflicts, Crow curiosities, Crow life history, Crows and humans, In the news

Why the crow is black and other mythology

Since humans began telling stories and writing them down, they’ve told stories about crows and other corvids.  This should come as no surprise considering corvids are found in nearly every corner of the world and are as connected to us now as they were centennials ago.  Whether they are sharing (or thieving) the food we grow, consuming the soft tissues of our dead, or delighting us with their company, corvids have infiltrated the most intimate parts of our lives. They walk the earth cloaked in black, and yet persist with the light of life even we perish through disease or famine.  It is this juxtaposition that I think made our human ancestors look upon those glossy feather and conclude they must have some greater tie to creation than their other avian kin.  Be it India, Rome, the Middle East or the New World, they’ve been written into the oldest stories explaining how the facts of the world came to fruition.  With that in mind, let’s break from answering questions with the rigors of science this week and embrace the explanations offered by our ancestors.

Photo: American Museum of Natural History

Photo: American Museum of Natural History


Why the crow is black (According the the Greeks/Romans)

Apollo, the son of the most powerful greek God Zeus, had an important, albeit tumultuous relationship with crows.  The greek word for crow, corone, comes from the name of Apollo’s mistress, Coronis.  According to the version of this story told by Appolodorus, although Coronis and Apollo had been lovers, she left him to marry a mortal, Ischys.  The crow, then white, brought news of the marriage to Apollo who became so incensed he burned the bird’s feathers and then burned Coronis to death.  In other versions Coronis is herself turned into the black crow and it’s possible the Greeks saw a mated pair of crows as a representation of the forbidden love between Coronis and Ischys.   This may be one of the earliest stories of a woman marrying below her class for love.

Apollo

 

Why the crow is black (According to Muslims)

Muhammad, born sometime around 570 CE, is considered to be the founder of Islam and the last profit sent to earth by God, according to the Islamic faith.   A popular legend depicts a time Muhammed was hiding from his enemies in a cave.  A crow, then white, spotted him and cried “Ghar, Ghar!” (cave, cave!) to his seekers.  They did not comprehend the crow’s cries, however, and Muhammad escaped.  He turned the crow black for the betrayal and cursed him to only utter one phrase for the rest of time;  “Ghar, Ghar!”


Why the crow is hoarse (According to Greek/Romans).  

Apollo sent a raven to gather water for a feast but the raven was distracted by an unripened fig tree.  Determined to obtain the figs, the raven waited until the tree ripened, ate his fill, and then captured a watersnake to bring back to Apollo.  The watersnake, the raven explained, was the reason he was late and unable to collect the requested water, but Apollo saw through the lie.  As punishment, Apollo declared the raven could never again drink from the stream until the figs ripened.  Since the raven must now wait, his voice is hoarse from thirst.


Why owls and crows fight  (According to Hindus)

According to the great animal epic, the Panchatantra, the birds had come together to elect a king and choose his earthly appearance.  They had elected the owl and were beginning to organize his lavish coronation, when the crow arrived.  The crow laughed at their decision, protesting that the owl was too ugly, his features without tenderness, and his nature without pity.  Furthermore, Garuda, the eagle mounted Vishnu was already their king and to take another was a sin that could result in severe punishment by the Gods.  The others, scared by the crow’s warning left in agreement.  Being nocturnal, the owl had slept through all this but now awoke to find his coronation canceled due to the crow’s persuasive words.  They have fought ever since.

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Why we die (According to the Haida Natives)  

Ravens have a significant role in the creations legends of many different Native American tribes.  According to the Haida tribe of the Queen Charlotte Islands, Greater Raven was the creator that first called earth into being on the endless sea.  He then made humans out of both rock and leaf.  The people of rock were (as I can well imagine) more difficult to shape and were never finished.  The people of leaf, on the other hand, were quickly completed and ready to roam the land.  The raven instructed them that, like the leaf, they must eventually fall and rot back into the earth and thus death entered the world.

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Why the sky is full of light (According to the Tsimshian Natives)

Greater Raven, as mentioned above, eventually gave dominion of the world to his sister’s son, Lesser Raven, who it was said was as robust as stone and would live forever.  Unlike Greater Raven, Lesser Raven was both a trickster and had a voracious appetite.  To satisfy his hunger, Lesser Raven filled the earth with food, but feared he would be unable to find it, as at that time the earth was still dark.  Seeking a solution, Raven flew through a hole in the sky where he found another world much like our own.  When he saw the daughter of the Chief of Heaven collecting water he transformed into a needle and floated into her vessel.  When she drank the water and the needle, Lesser Raven impregnated her and was later reborn as her son.  The infant charmed the Chief and his wife and was granted permission to play with the box containing the light of day.  Suddenly, Raven took his original form and flew back to earth through the hole in the sky, taking the box with him.  Later, he broke the box out of anger and filled the sky with the sun, moon and stars.

Map showing tribal delineations for NW coastal tribes including the Haida and the Tsimshian

Map showing tribal delineations for NW coastal tribes including the Haida and the Tsimshian

 

Why we bury our dead (According to Judaism)

According to the Yalkut Shimoni, an aggadic compilation of the Hebrew bible written in the 13th century, after Adam and Eve’s son Abel died, they did not know what to do with the body.  Seeing their distress, a raven killed one of his companions to show the grieving couple how to dig a hole and bury the body. To thank the raven for his kindness, God feeds baby ravens until their feathers turn black after which their parents take over.

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Thus, be it the color of ravens or the intimate mysteries of human death, crows have offered a canvas on which early peoples the world over painted their explanations of life.   My thanks to Borgia Sax and his terrific book, Crow, which was the factual source and inspiration for this post.

 

 

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Filed under Corvid mythology, Crows and humans

The facts about crows and West Nile virus

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.

transmission cycle

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:

IMG_2711(1)

Literature cited

  1. http://www.cdc.gov/westnile/faq/genquestions.html
  2. http://www.seattleaudubon.org/sas/LearnAboutBirds/SeasonalFacts/WestNileVirus.aspx
  3. http://www.cdc.gov/westnile/faq/deadbirds.html
  4. http://wnyyradio.com/news/25-shocking-things-more-likely-to-kill-you-than-a-shark/
  5. http://www.cdc.gov/flu/about/qa/disease.htm

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Filed under Crow behavior, crow conflicts, Crow disease, Crows and humans

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