Year-round presence of Slaty Thrush (Turdus nigriceps nigriceps) in mountains of central Argentina

Abstract

The migration patterns of passerine species in the Neotropical region present several gaps of knowledge. The migratory behavior of the Slaty Thrush (Turdus nigriceps nigriceps) has been well characterized in their central and northern distribution along eastern slopes of the Andes from Argentina to Ecuador. The Slaty Thrush was historically considered a migrant breeder in the southern extreme of their distribution. In the present study, we show new evidence of the resident status of this species in its southernmost distribution on western slopes of Sierras Grandes and Sierras de Comechingones in Córdoba Province, Argentina. There, the Slaty Thrush has a year-round presence only at sites invaded by fleshy-fruited alien plants. The main invasive plants form dense patches of vegetation and offer an abundant fruit supply that is highly consumed by this bird species during autumn–winter, when there are no native fruits available. We suggest that the Slaty Thrush was a migrant species in past decades, but the recent invasion by fleshy-fruited species could explain its actual year-round presence by providing fruit in a period of the year of food shortage and new suitable habitats.