Tag Archives: sick crows

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

Crow curiosities: Causes and consequences of bill deformities

If you live in the Pacific Northwest, chances are you’ve come across a crow that’s made you do a double take. No, not for an unusual behavior or vocalization, but for what might be described as an overgrown, monstrous even grotesque looking bill.  Bills like the one belonging to a bird in south Seattle I recently came across during one of my field experiments.  It is, at best, unsettling to see something like this.  So what exactly is going on here?

DSC_1648

A “crossbill” crow living in a south Seattle neighborhood

First, it’s helpful to understand the different layers of a bird’s beak.  The beak is comprised of bone overlaid with a horny structure made of keratin (for you Scrabble people out there it’s called the rhamphotheca).  Keratin is the same stuff that makes up our hair and fingernails and, just like our nails, the rhamphotheca is always growing and wearing away.  For most birds, this growth is very slow which means that keeping bills nicely manicured takes no special effort.  For birds suffering from what’s now termed Avain Keratin Disorder, however, the growth can be as much as 2x as fast as normal, making it impossible to keep things in check.  This growth results in bills that are extra long, decurved on the top, bottom, or both, or overgrown and crisscrossed like my friend in Seattle.  Even if the bill is clipped or broken, it grows right back.

Across most of the country, incidences of AKD in crows are other birds are rare.   Which means that, unless you’re the afflicted individual, there’s no real cause for alarm.  If you live in the PNW, especially Alaska, however, it’s not only increasing common, it’s spreading.

Data taken between 2006-2008, indicates that 17% of Northwestern crows in Alaska have AKD, the highest rate of deformities ever recorded in a wild population1.   Needless to say, the alarm bells, gongs and vuvuzelas are going off within the scientific community.

DSC_1650

So what causes AKD?

~In 10/2016 I published a new post with the most current information on causes.  For now though, I will leave the ’causes’ content in this post as-is, so readers have access to the history of scientific thinking and progress on AKD research.~

Well, lots of things can.  Heat stress, diet, genetic disorders, environmental contaminates, parasites, or bacterial infections have all been linked to the disorder in individual cases.  Given that it affects residential, adult birds, environmental contaminants seem a likely suspect.  But tests on afflicted birds (mostly chickadees) show no consistent correlation with the top suspects like heavy metals and trace elements, organic pesticides, and toxic environmental pollutants like PCBs, PCDDs, and PCDFs.  Future studies will look at compounds like PCDD-Fs, polycyclic aromatic hydrocarbons, and emerging contaminants such as brominated compounds (stuff found in flame retardants which were used for wildfire suppression)2.  For now though, there’s no clear culprit for the disorder’s spread across Alaska and the PNW.

Is it fatal?  That really depends on the nature of the growth.  The main problem is that it can affect eating and preening, both of which are critical to survival, especially in cold climates.   But animals (including people of course) are amazingly adaptable, and according to the USGS, a surprising number of individuals find mates and breed (though reproductive success is lower3).  Indeed, even my friend in Seattle was followed by the “wah! wah!” of its relentlessly begging juvenile.

DSC_1617

The good feather condition and successful fledgling of at least one offspring suggest that this bird is, for now, managing just fine.

Is there anything I can do?  Yes, report your sightings!  Help scientists track the spread and proliferation of this disorder by documenting and reporting whenever you encounter it.  You can do so at the USGS site here.  As far as the individual bird is concerned, you can make feeding easier by supplementing with easy to ingest foods, like this Birdie corn “bread” recipe.  And as always, make your yard safer to vulnerable birds by providing lots of cover and keeping unattended pets indoors.

Make feeding easier by providing meals which can be easily ingested and offer big nutritional value.

Make feeding easier by providing meals which can be easily ingested and offer big nutritional value.

Literature cited:

1.  Van Hemert, C., & Handel, C.M. 2010.  Beak deformities in Northwestern crows: Evidence of a multispecies epizootic.  The Auk 127: 746-751.  doi: http://dx.doi.org/10.1525/auk.2010.10132

2. http://alaska.usgs.gov/science/biology/landbirds/beak_deformity/contaminants.html

3. http://alaska.usgs.gov/science/biology/landbirds/beak_deformity/effects.html#reproduction

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Filed under Crow curiosities, Crow disease

Identifying crow dieases: Avian pox

Recently, I received an email from someone in distress over an obviously sick crow in their yard. They sent some photos and were wondering about the cause of the crusty areas around the bill and eyes. Although I am by no means an expert in avian diseases, there’s one that’s easy to identify and by far the most common I see in the field so I feel it’s appropriate to provide a brief description of it here.

Bird with a likely avian pox infection as identified by the whitish/pink lesions around the exposed skin.  Photo c/o D. Wright

Bird with a likely avian pox infection as identified by the whitish/pink lesions around the exposed skin. Photo c/o D. Wright

Avian pox is a common disease affecting birds across many different orders including songbirds, raptors and game birds. It’s caused by the avipoxvirus of which there are at least 3 different strains. There’s multiple modes of transmission but it’s most often spread by mosquitoes which is why it’s observed more commonly in the spring and summer months. It can also be spread via direct transmission or indirectly through inhalation of dander, feather debris or sharing contaminated food or water sources (a good reminder to regularly clean feeders and bird baths).

There are two types of avian pox: wet and dry. Wet pox affects the mouth, throat, trachea and lungs and is most likely to be fatal because it can eventually cause suffocation. Dry pox infections are easy to identify because they result in visible lesions and scarring on the non feathered areas of the bird. In the early stages small yellow, white or pink blisters form which become large raised areas that eventually burst. This results in the formation of crusty scabs that, on crows, will appear brown or black. As long as the the bird’s ability to feed isn’t influenced by the location of the scabbing the lesions will generally heal in 2-4 weeks. The general health of the bird before the infection, and the presence of any secondary infections that result from the open lesions will influence the bird’s likelihood of survival.

The pox covered feet of a crow fatally weakened by this disease.

The pox covered feet of a crow fatally weakened by this disease. c/o Sarah Ramirez

If you notice pox infected birds at your feeder(s) the best way to protect your visitors is to stop feeding them. This may seem cruel or counterproductive since sick birds need access to consist food sources to fight the infection, but providing food bonanzas concentrate birds and increases the risk of transmission to healthy individuals. Depending on your situation you may be able to provide food to the individual without worry of creating contact between multiple birds.

Please leave a message in the comments if you have high quality photos of your infected birds and would be willing to let me use them in this post.  Thank you!

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Filed under Crow disease, Crow life history