In Alaska during the mid-1990s, bird experts noticed an uptick in overgrown, warped beaks among black-capped chickadees. Now, using high-throughput RNA sequencing, researchers at the University of California, San Francisco, and their colleagues have identified a candidate culprit: a new picornavirus, the authors reported last month (July 26) in mBio.
Avian keratin disorder can cause the top and bottom of misshapen beaks to swoop in opposite directions. The deformity, which affects the fibrous protein layer above the bone, impedes normal feeding and grooming. For the fist-sized chickadees that endure Alaskan winters, these can be fatal liabilities, National Geographic reported.
“It’s a gut-wrenching experience when we see these small birds with gross beak deformities,” study coauthor Colleen Handel, a wildlife biologist with the US Geological Survey in Anchorage, told National Geographic.
To search for the potential cause of the condition, the researchers sequenced RNA collected from eight misshapen chickadee beaks. They found that 0.04 percent of reads belonged resembled sequences of picornaviruses, a family that includes turkey hepatitis virus and chicken picornaviruses 4 and 5. The team dubbed this virus poecivirus (after the black-capped chickadees’ Linnaean name, Poecile atricapillus). Of 19 other chickadees with avian keratin disorder the researchers screened, all were infected with the new virus. Of nine control chickadees without symptoms, two had poecivirus, suggesting the birds may have only recently acquired it, National Geographic reported.
Scientists have observed avian keratin disorder in 24 bird species in North America and 36 species in the U.K., the authors wrote in their study.
“The birds most commonly with beak deformities seem to be social animals. Chickadees come to bird feeders. Crows congregate along coastlines. It’s a lot like human sanitation,” Handel told National Geographic. “We have to let people know to keep bird feeders clean.”