Todirostrum are small insectivorous flycatchers with bills that are notably long and relatively broad and flattened (recalling a tody, Todus, of the West Indies). Tody-flycatchers forage as singles or in pairs, not with mixed-species flocks, and often hold the tail partially cocked. The dominant plumage colors of Yellow-browed Tody-Flycatcher are black, yellow and green. In all populations, the crown and sides of the head are black, with a broad yellow supercilium that extends from just behind the eye back to the nape. The back is green, and the underparts are bright yellow; in some subspecies, the breast also is narrowly streaked with black.
Yellow-browed Tody-Flycatcher is distinctive in appearance, and is unlikely to confused with any other species within its range. Common Tody-Flycatcher (Todirostrum cinereum) lacks the prominent yellow brow, has grayer upperparts and a longer tail, and does not have black streaking on the underparts. The underparts of Spotted Tody-Flycatcher (Todirostrum maculatum) are yellow, marked with black, but Spotted has a gray (not black) crown and lacks the prominent yellow brow. Golden-winged Tody-Flycatcher (Poecilotriccus calopterus) lacks the prominent yellow brow, has chestnut lesser wing coverts and a white throat, and occurs in dense understory (not in the canopy).
The following description is based on Walther (2004), and refers to nominate chrysocrotaphum; see also Geographic Variation.
Adult: Sexes similar. Crown and sides of head black, with broad yellow postocular supercilium and white supraloral spot. Back, scapulars, and rump olive. Wings black; wing coverts narrowly margined with, and broadly tipped with, yellow; remiges margined with yellow. Rectrices black. Underparts bright yellow, with narrow black streaks at side of throat and across breast.
Iris: dark brown
Tarsi and toes: black, dark gray
Bare parts color data from specimens in the Field Museum of Natural History.
Total length: 8.6 cm (Hilty and Brown 1986), 9 cm (Ridgely and Greenfield 2001b)
Linear measurements (Novaes and Lima 1998):
male (n = 1): wing length, 40.0 mm; tail length, 27.2 mm; bill length (culmen from base), 14.5 mm; tarsus length, 14.0 mm
female (n = 1): wing length, 40.0 mm; tail length, 26.0 mm; bill length (culmen from base), 14.4 mm; tarsus length, 15.3 mm
Mass: 7 g (n = ?; Terborgh et al. 1990)