Avian Keratin Disorder (AKD), Bill Deformities in Birds and Recent Breakthroughs

by Bryce W. Robinson


Photo 1. Female Black-capped Chickadee (Poecile atricapilla) with bill deformity.

I recently had the pleasure of spending a few days with my friend Rachel Richardson of USGS trapping birds in the Eagle River Valley of south-central Alaska. We captured a few species such as Black-capped and Boreal Chickadees (Poecile atricapilla and P. hudsonicus, respectively), and Red-breasted Nuthatch (Sitta canadensis). USGS has been trapping in these areas for years with the main focus of monitoring bill deformities, the prevalence of Avian Keratin Disorder, and the prevailing causes of a new found virus, Poecivirus.

The Alaska Science Center of USGS in Anchorage is part of a team of researchers, including the California Academy of Sciences, and the University of California San Francisco that have been investigating the causes of Avian Keratin Disorder for over ten years. Avian Keratin Disorder was first documented in Alaska in the 1990’s by Colleen Handel of USGS who leads the research team at the Alaska Science Center. In an article in Molecular Biology that came out in July 2016 (Zylberberg 2016), the team reports on the discovery of a new virus they termed Poecivirus, which may be responsible for the bill deformities.

Appropriately, the discovery is receiving a good deal of press. Below are a few links to national and international articles that detail the work and the discovery. All are worth a read (or a watch):

A new article by the Associated Press

Science Daily’s article

National Geographic article detailing the work effort

Alaska Daily News Article

An APN video on USA Today


Photo 2. Rachel Richardson of the USGS Alaska Science Center holding a female Black-capped Chickadee (Poecile atricapilla) with a bill deformity.

On the day I spent with Rachel in the field trapping birds, we only had one Black-capped Chickadee show up with a deformity. However, the one bird had an interesting story. This female (Photo 1) was first captured in 2015 and had no signs of any deformity. This year she obviously has a developing deformity. Her bill grew 5.1 mm in one year, a 70% increase in length. Whether or not this developing deformity will impact her ability to forage, preen, or even breed and provision young is yet to be determined. There are reports of deformed birds successfully rearing offspring, however it is without question that the deformities present a handicap that will ultimately reduce the individuals fitness.

It is important to track the rates and severity of deformities across the world. Because of this, the Alaska Science Center has developed a submission form for anyone to report their sightings of deformities. Please contribute to this effort and submit details of any sightings of elongated bills, including photos and location along with any other evidence for Avian Keratin Disorder at the following website:

Beak Deformity Observation Record Report


Photo 3. Female Black-capped Chickadee (Poecile atricapilla) with bill deformity.

Below are additional examples of AKD in Chickadees that have been captured as part of the Alaska Science Center’s efforts near Anchorage. These individuals unfortunately have more developed deformities than the chickadee we caught while I was tagging along.


Photo 4. Black-capped Chickadee (Poecile atricapillus) with bill deformity. Photo copyright Rachel M. Richardson.

Black-capped Chickadee2_Richardson.jpeg

Photo 5. Black-capped Chickadee (Poecile atricapillus) with bill deformity. Photo copyright Rachel M. Richardson.


Photo 6. Black-capped Chickadee (Poecile atricapilla) with bill deformity. Photo copyright Rachel M. Richardson.

It’s excellent to have a breakthrough and a step forward. However, the problem still remains as well as the daunting task of discovering the correlation between Poecivirus and bill deformities, the causes of both, and what role humanity plays in the prevalence and transmission of either. I’d like to tip my hat to those who have done so much great work on this issue thus far. Keep up the good work.

Referenced Literature
  1. Maxine Zylberberg, Caroline Van Hemert, John P. Dumbacher, Colleen M. Handel, Tarik Tihan and Joseph L. DeRisi. Novel Picornavirus Associated with Avian Keratin Disorder in Alaskan BirdsmBio, July 2016 DOI: 10.1128/mBio.00874-16