Look closely at this Kestrel. At any of the Kestrels. Look at any of the Falcons. They all have something in common. There’s a sooty smudge under their eye, a black stripe on their cheek, a wide patch of darker feathers giving their faces a distinctive mascara-in-the-rain look. What’s all that about?
The likely evolutionary advantage is that the dark patch reduces the glare reaching the eye which helps hunting in bright conditions. Stopping stray reflections which confuse the image is clearly important, given that the inside of the lens I used to take this photograph has a black anti-reflective coating. Most of the things we invent have an equivalent which has been developed naturally by nature in the last 3 and a half billion years.
Nature got there first.