Least Flycatcher
(Empidonax minimus)

Audubon Field Guide
Habitat, diet, feeding behavior, nesting, migration, and conservation status of this bird. Includes range map, photos, and songs and calls.

WhatBird.com
Description, range, habitat, songs and calls, identification tips, and behavior. Includes photos, illustration with field marks, and range map.

Wikipedia
Description, distribution, habitat, behavior, diet, reproduction, predators, lifespan, and conservation status. Includes photo and range map.