Epizootic of beak deformities worldwide: A review of avian keratin disorder in wild birds

HANDEL, C. M.; BRUST, K.; SCHILLACI, J.; GOROSITO, C. A.; VAN HEMERT, C.; WALTERS, J.; VAN LANEN, A.; COTTRELL, S.; ZYLBERBERG, M.; GERIK, D. E.; RISELY, K.; PRINZ, A.; ANDERSON, C.; CUETO, V. R.

Congreso; American Ornithological Society (AOS) and the Society of Canadian Ornithologists?Société des ornithologistes du Canada (SCO-SOC) 2021 Meeting; 2021

AOS & SCO-SOC

An epizootic of debilitating beak deformities in wild birds has been documented in recent decades. Avian keratin disorder (AKD) is characterized by overgrowth of beak keratin and was first observed in clusters among Black-capped Chickadees (Poecile atricapillus) in Alaska. The prevalence of beak deformities is higher among Black-capped Chickadees and American Crows (Corvus brachyrhynchos) in Alaska than in any other population ever recorded. Reports of birds with similar beak deformities have recently emerged from across North America, in South America, and in Europe. We compiled reports from citizen-science programs, bird monitoring studies, and scientific literature to summarize the current geographic scope and bird species affected by AKD-like beak deformities. From 1979 to 2020, >3,300 citizen-science observers reported 290 species with beak deformities, comprising >4,000 birds in Alaska, 1,600 elsewhere in North America, and >900 from outside of North America. We also examined the occurrence of beak deformities in populations of Black-capped Chickadees in Alaska, Red-tailed Hawks (Buteo jamaicensis) in the Pacific Northwest, Red-cockaded Woodpeckers (Dryobates borealis) in North Carolina, and Austral Thrushes (Turdus falcklandii) in Patagonia. Clinical signs of AKD in Black-capped Chickadees have been strongly associated with the occurrence of a novel picornavirus, which has now been detected in multiple species exhibiting morphologically similar beak deformities. Our detailed compilation, including geographic occurrence of individuals and species apparently affected, will help identify research and conservation actions required to evaluate and mitigate impacts of beak deformities on wild birds.