Alaska chickadees linked to virus causing beak deformities

Biologists have identified a likely cause for a widespread beak deformity in Alaska’s black-capped chickadees. Since 1991, reports of avian keratin disorder—where beaks grow excessively long, curved, or crisscrossed—have increased significantly. The U.S. Geological Survey’s Alaska Science Center has cataloged over 3,000 reports of the condition across the state, marking what researchers call the highest concentration of visible deformities ever recorded in a wild bird population.

The disorder is characterized by the unregulated accumulation of keratin, a protein found in feathers, nails, and skin. Affected beaks can reach up to 1.5 inches in length, nearly six times their normal size, making it difficult for the birds to feed. While early theories suggested chemical exposure or contaminated birdseed, research has pointed toward a novel virus named poecivirus. A 2016 study found that 100% of birds with the disorder carried the virus, compared to only 20% of birds with normal beaks.