This is a flycatcher of the genus Empidonax in the tyrant flycatcher family (Tyrannidae), which all look remarkably similar.
Identification of empidonax flycatchers should be based on a combination of characteristics including, most important, voice.

Biological Station Las Guacamayas, Parque Naturel Laguna del Tigre, Petén, Guatemala, 21 January 2020