This is an adult showing yellow eyes and lacking white eyebrow. This species is famous for duetting antiphonally, each member of a pair singing different parts of a combined song. Bare yellow skin on the sides of its neck form air sacs inflated during song. Similar inflatable air sacs are found in the completely unrelated Prairie Chicken. Formerly classified variously as a thrush, thrasher or wren, this unique bird is now placed in its own family, the Donacobiidae believed to be allied with certain Old World warblers. Four subspecies are usually recognized. This is D. a. nigrodorsalis found in eastern Peru. It is smaller, blacker above and has barring on its flanks as seen here. Canon PowerShot SX60 HS.
Reference:
Black-capped Donacobius (Donacobius atricapilla), 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/bkcdon
Kroodsma, D. & Brewer, D. (2019). Donacobius (Donacobius atricapilla). 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/58176 on 1 July 2019).