Small and rather scarce flycatcher of montane cloud forest. Look for a combination of gray crown, yellow wingbars, white eyebrow, and stubby bill with a pale base. Breast is slightly striated in some populations. Voice may be the best way to confirm ID since it is usually heard before being seen. It often gives a sharp, rather piercing whistle, either alone or in a steady series. Now considered a separate species from Rough-legged Tyrannulet, which ranges mostly in southern and eastern South America. The area of overlap is not well known. White-fronted Tyrannulet has a grayer, less olive head that contrasts more with the rest of its body. Usually stays high in the forest, and tends to be less active and perch more vertically than most other tyrannulets.