This is the subspecies G. b. ucayalae, named for the river we were on and where the type specimen was collected. Note very faint head streaking and tail banding, combined with fairly heavy and dense underpart streaking, all characters of this race. This species is polymorphic with both rufous and brown morphs. This is the more common rufous morph. This race differs vocally with distinctly more hollow "toots" and more staccato notes. It also differs genetically suggesting that it may be a separate species. Canon PowerShot SX60 HS.
References:
Holt, D.W., Berkley, R., Deppe, C., Enríquez Rocha, P., Petersen, J.L., Rangel Salazar, J.L., Segars, K.P., Wood, K.L., Christie, D.A. & Kirwan, G.M. (2019). Ferruginous Pygmy-owl (Glaucidium brasilianum). 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/55075 on 18 July 2019).
Larsen, R. (2012). Ferruginous Pygmy-Owl (Glaucidium brasilianum), version 1.0. In Neotropical Birds Online (T. S. Schulenberg, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/nb.fepowl.01
Proudfoot, G. A. and R. R. Johnson (2000). Ferruginous Pygmy-Owl (Glaucidium brasilianum), version 2.0. In The Birds of North America (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.498
Restall, R., C. Rodner, and M. Lentino. (2006) Birds of Northern South America. Yale University Press.