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Deformed Chickadees in Alaska

Date Posted: December 16, 2008

Since January 1998,  more than 2,000 Black-capped Chickadees with abnormal beaks have been identified in south-central Alaska. This is the highest concentration of such abnormalities ever recorded in a wild bird population anywhere! More recently, rapidly increasing numbers of other species, including Downy Woodpeckers, Northwestern Crows, Steller’s Jays, and Black-billed Magpies have also been reported with beak deformities by biologists and local residents throughout the state. Sightings often involve 2-3 deformed individuals together, but up to 20 abnormal individuals have occurred at a single location. The birds have difficulty feeding normally and are living largely on suet and peanut butter at residential bird feeders. An investigation to determine the cause of these abnormal chickadee bills has been funded cooperatively by the Service and the U.S. Geological Survey (USGS) - Biological Resources Division. Diagnostic tests were conducted to look for any evidence of disease, physical injury, parasites, or exposure to contaminants. Genetic analysis is also being performed to determine whether groups of affected individuals are siblings that were exposed to the same harmful variable, or whether the deformities are genetically linked. No evidence of disease, parasites or fractures of the bone underlying the sheath of the bill have been found. Nearly all of the species affected are year-round residents, and it is suspected that factors responsible for this cluster of deformities may be unique to Alaska and the Pacific Northwest. The Service and USGS are currently pursuing additional studies to determine where these deformities are occurring and why. Studies of deformities in Northwestern Crows began in 2007.


Kim Trust of the U.S. Fish and Wildlife Service at (907)271-2883

Or, if you see a bird with a deformed beak, you can report it online at
or, contact:
USGS - Alaska Biological Science Center
1011 E. Tudor Rd.
Anchorage, AK 99503
(907) 786-3418

USGS Alaska Science Resource Center: Beak Deformities


Handel, C. M., L. M. Pajot, S. M. Matsuoka, C. Van Hemert, J. Terenzi, S. L. Talbot, D. M. Mulcahy, C. U. Meteyer, and K. A. Trust. 2010. Epizootic of beak deformities among wild birds in Alaska: An emerging disease in North America? Auk 127(4):882-898. (11.9mb PDF high resolution) or (719kb PDF lower resolution)

Van Hemert, C., and C. M. Handel. 2010. Beak deformities in Northwestern Crows: Evidence of a multispecies epizootic. Auk 127(4):746-751. (976kb PDF) Online Supplement. (134kb PDF)

Van Hemert, C. 2007. Alaskan birds at Risk: Widespread beak deformities in resident species. American Birding. 39(5):48-55. (977kb PDF)

Potential Role of Environmental Contaminants in the Pathology of Beak Deformities among Black-capped Chickadees in South-central Alaska. Unpublished final report. Project ID: 1130-7F22. U. S. Geological Survey, Alaska Science Center, Anchorage, Alaska.
Written Report [PDF - 5 MB]
Tables [PDF - 2 MB]
Figures [PDF - 9.5 MB]
Appendices [PDF - 632 KB]
or, Complete Document !!![PDF - 15 MB]!!!

Use of buccal swabs for sampling DNA from nestling and adult birds. Wildlife Society Bulletin 34(4):1094-1100. [PDF - 701KB]

Last updated: June 12, 2015