This is a male (top) showing all yellow head and solid black back. Females (bottom) have a smudgy head and back. Formerly lumped with similar Yellow Grosbeak (Pheucticus chrysopeplus) of Mexico and Middle America, this South American endemic sometimes goes by the names Golden-bellied Grosbeak or Southern Yellow Grosbeak. This is the widespread nominate race found in Peru in which the male has a solid black back. Another race where the male has yellow mantle streaks is found in isolated populations in northern Columbia and Venezuela. Canon PowerShot SX50 HS.
References:
Brewer, D. (2018). Golden Grosbeak (Pheucticus chrysogaster). 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/62182 on 26 January 2018).
Golden Grosbeak (Pheucticus chrysogaster), 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/gobgro1