This is a male. Females are overall green above and yellow below. This species is distinguished by its whitish undertail coverts. Two subspecies are recognized, but the differences are so slight that their validity has been questioned. Based on range, this is the nominate race in which the yellow forehead is supposed to be smaller. Euphonias were formerly classified in the Tanager family, but have since been moved to the Finches (Fringillidae) based on recommendations by Zuccon et al. (2012). Canon PowerShot SX60 HS.
References:
Hilty, S. (2019). White-vented Euphonia (Euphonia minuta). 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/61800 on 4 August 2019).
Schulenberg, T. S. & Stotz, D. F. & Lane, D. F. & O'Neill, J. P. & III, T. A. P. & Egg, A. B. (2010). Birds of Peru: Revised and Updated Edition. Princeton: Princeton University Press.
White-vented Euphonia (Euphonia minuta), In Neotropical Birds Online (T. S. Schulenberg, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. retrieved from Neotropical Birds Online: https://neotropical.birds.cornell.edu/Species-Account/nb/species/whveup1
Zuccon, Dario; Prys-Jones, Robert; Rasmussen, Pamela C.; Ericson, Per G.P. (2012). "The phylogenetic relationships and generic limits of finches (Fringillidae)" (PDF). Molecular Phylogenetics and Evolution. 62 (2): 581–596. doi:10.1016/j.ympev.2011.10.002. PMID 22023825.