Chickadee Bill Deformities: An Update


A few weeks ago, when WC was doing the blog posts on bill deformities, a reader emailed asking whether researchers had tracked down the cause of the beak deformities that plague species like Black-capped Chickadees.

Black-capped Chickadee with Deformed Bill

Black-capped Chickadee with Deformed Bill

WC wrote about the problem back in 2012. As this photo – taken in WC’s Fairbanks’ front yard – shows, the bills are seriously overlength. It’s called Avian Keratin Disorder – AKD – because birds’ bills and beaks are composed of keratin. The disorder, the abnormal growth of the bill, inteferes with the bird’s ability to feed and to groom itself. Starvation or exposure from loss of body insulation follows.

Recent research published July 2016 suggests that a newly discovered virus – poecivirus – may be the cause of the bizarre beak deformities in chickadees, crows, and other species. Percivirus is a member of the picornavirus family. They’ve found this new and divergent picornavirus in 19 of 19 AKD-affected Black-capped Chickadees that they examined but in only 2 of 9 control cases. The researchers also found this virus in 4 individuals of 2 other songbird species that had symptoms of AKD. The researchers conclude that the data suggest that this novel picornavirus warrants further investigation as the causative agent of AKD.

They can’t be certain that this poecivirus is the cause without a much larger sample of birds. That effort is under way now. But if the cause of AKD is an infectious agent, it’s very concerning. The geographic range of AKD is expanding, and the species affected are likewise expanding. Currently, epidemiological studies of AKD suggest 6.5% of adult Alaskan BCCH are affected by AKD, a rate of beak deformities far greater than any previously known from wild birds, which typically exhibit frequencies of beak deformities of less than 1%.

Kudos to Dr. Colleen Handel and her team who may have solved a 20-year-old mystery.

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