Eyestripe

Dama. [i.e., the dama gazelle] Horns hooked forward at the ends; body white; dorſal and eye-ſtripes tawny.

MALIMBA BEE-EATER. [...] Cinereo-violaceous Bee-Eater, sanguine rose-coloured beneath, with black eye-stripe, white throat, and two lengthened tail-feathers.

These two birds somewhat closely resemble each other, but the Sedge Warbler is russet-brown above, the feathers with dark centres, the pale buff eyestripe is very clearly defined, and the underparts are buffish white; the Reed Warbler is more olive on the upper parts, the feathers having no dark centres, the underparts are more inclined to buff, and the eyestripe is nearly obsolete.

The plumage pattern of the red-backed shrike male is conspicuous from a long distance. This pattern, not the feathering, is all-important since a plain plastic model is as effective as a stuffed mount in eliciting mobbing by pied flycatchers. Removal of the conspicuous eye stripe (including the equally dark eye) renders the model almost ineffective[…].

Once in a while a design feature shows up in animals that are not closely related. A good example is the eyestripe coloration pattern, which appears in sparrows, antelopes, and chipmunks. In all these creatures, a dark facial stripe runs from the snout to the eye. [...] Presumably eyestripes serve as protective coloration in all these prey animals, disguising their eyes from predators.

The eye-stripe is exactly that: a stripe through the eye. When present, this is a dark line that usually extends from the bill back through the eye. On some birds, it extends just from the eye back, leaving the lores (the area between the eye and the bill) pale and unmarked.