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

DANIELLE E. GERIK; CAROLINE VAN HEMERT; COLLEEN M. HANDEL; KATE RISELY; JEFF WALTERS; KERRY BRUST; ANNA PRINZ; ANDY VAN LANEN; JESSIE SCHILLACI; CLIFFORD ANDERSON; SUSAN COTTRELL; GOROSITO, C.A.; CUETO, V.R.; MAXINE ZYLBERBERG

Congreso; American Ornithological Society and the Society of Canadian Ornithologists ? Société des ornithologistes du Canada 2021 Virtual Meeting; 2021

An epizootic of debilitating beak deformities in wild birds has been documented in recent decades. Avian keratindisorder (AKD) is characterized by overgrowth of beak keratin and was first observed in clusters among Black-cappedChickadees (Poecile atricapillus) in Alaska. The prevalence of beak deformities is higher among Black-cappedChickadees 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 literatureto summarize the current geographic scope and bird species affected by AKD-like beak deformities. From 1979 to2020, >3,300 citizen-science observers reported 290 species with beak deformities, comprising >4,000 birds inAlaska, 1,600 elsewhere in North America, and >900 from outside of North America. We also examined theoccurrence of beak deformities in populations of Black-capped Chickadees in Alaska, Red-tailed Hawks (Buteojamaicensis) in the Pacific Northwest, Red-cockaded Woodpeckers (Dryobates borealis) in North Carolina, andAustral Thrushes (Turdus falcklandii) in Patagonia. Clinical signs of AKD in Black-capped Chickadees have beenstrongly associated with the occurrence of a novel picornavirus, which has now been detected in multiple speciesexhibiting morphologically similar beak deformities. Our detailed compilation, including geographic occurrence ofindividuals and species apparently affected, will help identify research and conservation actions required to evaluateand mitigate impacts of beak deformities on wild birds