Why an eagle always look so angry?

A bald eagle.

What is the angry-looking eye of a eagle all about ?

Actually, the raised “eyebrow,” which we interpret as a sign of boldness, is a bony protrusion above the eye socket that serves as a protection for the eye.

It has nothing to do with attitude, and the eagle cannot change its looks even if it wants to.

Most birds close their upper and lower lids only to sleep.

Blinking is done by sweeping the eye with a semitransparent membrane (its third eyelid)—so it won’t lose sight of its prey in the process.