New research on the cause of the AKD outbreak

Since the nineties, Avian Keratin Disorder has been an increasingly common disorder among Alaskan and PNW crows, chickadees (~17% of northwest crows1, ~6% of black-capped chickadees2) and a handful of other species, that causes gross deformities of the beak such as elongation, curvature or crossing.  I’ve written previously about the details of this disease before, but at that time there was little progress in determining the underlying source of the outbreak.  While AKD can be caused by a variety of things, at the scale it’s being observed now scientists questioned if there was a more consistent underlying factor.  Since AKD can cause discomfort or even death (primarily through the inability to feed or preen) understanding what might be the source of this outbreak has clear management and conservation implications.

DSC_1648

An AKD-afflicted American crow in Seattle, WA.

Among the initial suspects were environmental contaminants such as heavy metals, organic pesticides, and toxic environmental pollutants like PCBs, PCDDs, and PCDFs.   Blood work done on afflicted Northwestern crows, however, showed no significant difference in the 30 blood elements tested compared to unaffected adults or juveniles3.  Fortunately, new research may finally be shedding light on what’s going on.

Disease can be an easy thing to rule out if you know what you’re looking for, but new to science pathogens can evade traditional diagnostic techniques.  To account for this, a team of USGS and university scientists conducted a sequencing study comparing pooled RNA of healthy and AKD positive chickadees, crows and nuthatches in attempt to identify a candidate pathogen2.  Their work appears to have paid off, revealing evidence for a new picornavirus (a family of viruses previously known to science) they are calling poecivirus.  Whereas 100% of AKD-affected birds (23 subjects) tested positive only 22% of the 9 control individuals did.

black-capped_chickadee_in_homer_alaska_c_martin_renner-768x432

Alaskan black-capped chickadee with severe AKD. Photo c/o Martin Renner

Given these small sample sizes, it’s too early to throw our hands up in complete relief of having identified the cause of the AKD outbreak, especially since there’s still much to be done in understanding the potential relationship of this new virus to the environment.  Nevertheless, these findings offer some insight and hope that scientists are on the right track.  With more dedicated work we may soon have a much better understanding of this novel pathogen, its link to AKD, and management options moving forward.

Literature cited

1.  Van Hemert C, & Handel CM. 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. Zylberberg M, Van Hemert C, Dumbacher JP, Handel CM, Tihan T, and DeRisi JL. 2016. Novel picornhttps://wordpress.com/post/corvidresearch.wordpress.com/3363avirus associated with Avian Keratin Disorder in Alaskan birds.  mBio 7 doi: 10.7589/2015-10-287

3. Van Hemert C, Handel C. 2016.  Elements in whole blood of Northwestern crows (Corvus caurinus) in Alaska USA: No evidence for an association with beak deformities.   Journal of Wildlife Diseases 52:713-718 doi: http://dx.doi.org/10.7589/2015-10-287

8 Comments

Filed under Birding, Corvid health, Crow curiosities, Crow disease, Crow life history, Ecosystem, Uncategorized

8 responses to “New research on the cause of the AKD outbreak

  1. Pingback: Crow curiosities: Causes and consequences of bill deformities | Corvid Research

  2. CR

    I so enjoy and appreciate your posts. Very informative and educational. I appreciate learning new things about corvids. So much better than the Facebook groups re corvids, who only seem to show photos (though beautiful) and rarely post anything like this. Thank you.

  3. Jamila

    This is really interesting stuff. Thanks so much for keeping us informed.

  4. Lin

    I have a question I was hoping you could answer. I have been feeding crows out my back as I live on the edge of a park for quite some time now, I have a regular group,than appear every day,when I leave my house be it in my car or on foot they follow me,for the past few months one in particular gets very close and has even taken peanuts from my hand,lately when I go on my walk with my dog this crow swoops very close to me and has touched my head very lightly with the tip of his wing,or he flys by close enough I feel the wind in my face from his body It freaks my neighbours out,they think he is being aggressive with me,but I don’t think so as I don’t feel threatened by him,my Crows aren’t even afraid of my Dog or even my Cat. what are your thoughts on this. Thank you very much Lin

    “If we could live happy and healthy lives without harming others….. Why wouldn’t we?

    >

    • Hi Lin, I can offer some help here. I had a similar experience with a bird I used to feed at my old apartment. Only, in Captain Hook’s case (named an account of its overgrown upper mandible) it wasn’t a gentle whoosh it was an aggressive whack to the head. Sometimes with the bill but most often with its talons. As in your case though it wasn’t trying to be aggressive it was just trying really, really hard to get noticed and fed. Your bird is doing the same. If it was being aggressive it would scold you as it flew away. So it’s nothing for you to worry about in terms of what it might mean between you and the bird. I do worry though that we might be doing more harm than good in these cases because these birds getting aggressive with other, less appreciative people could spell disaster. I would discourage this behavior as much as possible simply to protect the bird, especially if you’ve noticed that your neighbors aren’t very happy about it. Cheers,

      • Christian

        Kaeli, first thanks for all of your interesting blog articles – this one included.
        Never seen a crow with AKD here. I wonder what can be done about it.
        — digression —
        I ‘ve often been “attacked” by crows at my site in winter crows’ season.
        Almost all of these events were gentle contacts.
        Last November though, a crow gave me 3 memorable hits at the back of my head. One week later I tried to get a video I hoped to reveal what was going on, but all of the contacts documented were of the soft kind.
        These crows started from the bottom behind me and touched my shoulder/head.
        Finally I concluded that the starting point for the massive bumps was a near tree, from, say, 5 meters above. These birds weigh some 500g or more.
        I know of a woman who had been treated ” the soft way” – she had been feeding crows before. I think that’s natural crow behavior.

        Your proposal to discourage this behavior would virtually mean to stop feeding crows at once. Frankly, that’s depressing. No feeding, no close observations anymore.

  5. Pingback: Have you ever seen a caramel crow?  | Corvid Research

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