Epizootic of Beak Deformities Among Wild Birds in Alaska : An Emerging Disease in North America
Kimberley A. Trust Carol U. Meteyer Colleen M. Handel Lisa M. Pajot Steven M. Matsuoka Caroline Van Hemert John Terenzi Sandra L. Talbot Daniel M. Mulcahy
882 - 898
The sudden appearance of a large cluster of animals with gross abnormalities may signal a significant change in
an ecosystem. We describe an unusual concentration of beak deformities that appear to have arisen rapidly within Alaska and now
extend southward along the Pacific Coast. In Alaska we have documented 2,160 Black-capped Chickadees (Poecile atricapillus) and 435
individuals of 29 other species of birds, primarily during the past decade, with grossly overgrown and often crossed beaks. The annual
prevalence of beak abnormalities among adult Black-capped Chickadees in south-central Alaska varied from 3.6% to 9.7% and averaged
6.5 ± 0.5% between 1999 and 2008. Only 0.05 ± 0.05% of nestlings and 0.3 ± 0.2% of juveniles <6 months old had abnormal beaks, which
suggests that this is either a latent developmental or an acquired condition. We documented 80 cases in which a Black-capped Chickadee
captured with an apparently normal beak was subsequently recaptured with a beak abnormality and 8 cases in which a beak deformity was
no longer detectable upon recapture. Necropsy and histopathology of a sample of affected individuals provided no conclusive evidence
of the etiology of this condition. Deformities appear to affect primarily the keratin layer of the beak and may result from abnormally
rapid growth of the rhamphotheca. Some affected birds also exhibited lesions in other keratinized tissues of the skin, legs, feet, claws,
and feathers, which may represent a systemic disorder or secondary conditions. Additional studies are currently underway to determine
diagnostic signs and the underlying cause of this avian keratin disorder.
The American Ornithologists’ Union
http://alaska.usgs.gov/science/biology/landbirds/beak_deformity/pdfs/Auk_Handel_beak_deformities2.pdf, 720 KB
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USGS Alaska Science Resource Center: Beak Deformities
University of California press