This is a male. Females are much paler overall with dingy gray-brown back and nape, pale underparts smudged with gray-brown across the chest. Although widespread in tropical South America, this species is absent from much of Amazonia except in the immediate vicinity of the Amazon River and tributaries where it penetrates into eastern Peru. Canon PowerShot SX60 HS.
References
Farnsworth, A. & Langham, G. (2019). White-headed Marsh-tyrant (Arundinicola leucocephala). 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/57414 on 2 July 2019).
White-headed Marsh Tyrant (Arundinicola leucocephala), 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/whmtyr1