Beak deformities in north Patagonian birds

Abstract

Within the last decade, many individuals of several bird species with abnormal and strange beaks deformations<br />have been reported from Alaska, United States, and from United Kingdom and Ireland. Different forms of beak<br />deformities were observed, but the causes of these abnormalities are unknown. We report beak deformities in two<br />species of birds in northwestern Patagonia, Argentina: Austral Thrush (Turdus falcklandii) and Patagonian Mockingbird<br />(Mimus patagonicus). Between 2013 and 2016, we captured individuals of White‐crested Elaenia (Elaenia albiceps, N<br />= 305), Rufous‐collared Sparrow (Zonotrichia capensis, N = 119), Austral Thrush (N = 100), Black‐chinned Siskin (Spinus<br />barbata, N = 64), Patagonian Sierra‐Finch (Phrygilus patagonicus, N = 48) and Gray‐hooded Sierra‐Finch (Phrygilus<br />gayi, N = 40) in surroundings of Esquel city, located in western Patagonia, Chubut province, and quantified the prevalence<br />of beak deformities. Only adult Austral Thrushes (5 out of 78; 6.41%) showed abnormal beaks. Neither juvenile<br />thrushes (N = 22) nor the other five species showed beak deformations. Austral Thrushes with beak deformations<br />were also observed and photographed (but not captured) in other areas around the city. We also photographed one<br />Patagonian Mockingbird with an abnormal beak near Las Plumas Village, Chubut province. Beak deformities varied<br />from light to severe, and also in their form. Most of them were characterized by an elongated and often decurved<br />upper mandible, producing an overbite; in other individuals both mandibles were elongated and sometimes crossed<br />or had a pronounced gap. Most affected birds showed signs of improper preening, and one of them was malnourished.<br />All of these characteristics are similar to those described for birds affected by avian keratin disorder in North<br />America. Further research is needed to detect potential presence of other species with beak deformities in Patagonia,<br />to find out possible causes of such deformities, and to determine whether these anomalies are associated with natural<br />habitats or urban environments.