Incidence of beak deformities in austral thrushes (Turdus falcklandii) increases with urbanization and flocking behavior

GOROSITO, C.A.; JAHN, A.E.; CUETO, V.R.

Integrative Zoology

John Wiley and Sons Inc

Año: 2023

Beak deformation, known as avian keratin disorder (AKD), can impair feeding and preening of birds, reducingtheir survival. This disorder is apparently caused by Poecivirus infection, although to date, the viral origin has beencorroborated in only a few North American bird species. Considering that fruit-eating birds can track spatiotemporal variations in fruit abundance and that AKD may have a viral origin, the incidence of this disease can be expectedto increase with flocking by birds. Therefore, we evaluated if austral thrushes (Turdus falcklandii) were attractedto urban areas when exotic plants offered fruits and if flocking of thrushes in urban areas increased the spread ofAKD in this species in a Patagonian town. We fitted GPS loggers on some individuals with normal beaks in ruralareas and found that they visit the town in fall. Through point count censuses, we recorded greater abundances ofthrushes with normal and deformed beaks during fall–winter in urban sites than in rural sites. However, the abundance of birds with AKD declined more (78–87%) than that of individuals with normal beaks (44–52%) duringthe transition from fall–winter to spring–summer. In urban zones in our study area, fruits of exotic species ripenduring fall, attracting austral thrushes from rural sites. Nevertheless, such an attraction for food resources may bean ecological trap for this species, as the increase in incidence of AKD in urban areas may drastically reduce thesurvival of birds during the most unfavorable period of the year.