Not actually a finch, but now classified as a tanager (Thraupidae). The name "diuca" comes from the Mapuche name for the bird. These birds forage by walking on the ground rather than hopping. Four subspecies are recognized. This is the nominate race, smaller and smaller-billed than D. d. crassirostris. Canon PowerShot SX50 HS.
References:
Common Diuca-Finch (Diuca diuca), In Neotropical Birds Online (T. S. Schulenberg, editor). Cornell Lab of Ornithology, Ithaca, New York, USA. retrieved from Neotropical Birds Online: https://neotropical.birds.cornell.edu/Species-Account/nb/species/codfin1
Jaramillo, A. & de Juana, E. (2018). Common Diuca-finch (Diuca diuca). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/62050 on 11 February 2018).