The dark streak of feathers beneath a falcon's eye. The biological theory for this is that, much like athletes putting blacking under their eyes to prevent glare, this also prevents glare from reflecting off their feathers. The picture here shows a Lanner with the dark streak. Also called the facial stripe or eye stripe.
A distinctively colored stripe in the malar region of birds; also called a mustache stripe or whisker stripe.
Line from base of bill down sides of throat, often forming distinctive stripe in birds.