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ALL EAGLES HAVE THAT PERMANENT SCOWL LOOK, BUT EAGLE PHYSIOLOGY DIFFERS BETWEEN SPECIES
A frequent comment [many raptor rescues hear] is, "eagles always look so angry". It's true! Eagles, and many raptors, always appear to be scowling and it has to do with the structure of their skulls. They have a very prominent orbital ridge that appears as though they have furrowed their brow. However, this feature serves some very important purposes, and the structure is different among different eagle species. Let's explore!
First and foremost, the most important sense that eagles have is their vision. They are visual creatures and that means their eyes are critical to survival. Without that super eagle vision, hunting would be much harder for them. As such, they have extra protection for their eyes in the form of the "supraorbital ridge", a bony protrusion that sticks out over the eye socket.
There is also a second important function that the supraorbital ridge plays - it is a visor to shield their eyes from the sun that works with the same principle as the brim of a baseball cap. This helps reduce glare from the sun, again for hunting purposes. But as you can see from the image, the structure is noticeably different even between Bald and Golden Eagles. Why is this?
. . . Bald and Golden Eagles generally have different habitats and different primary prey items. While Bald Eagles are water birds and fish eaters, Golden Eagles are upland, terrestrial hunters that often look out to the horizon for potential prey. Bald Eagles tend to perch in trees right over the water sources holding the fish, so they aren't generally looking as high in the sky (smaller brim). But Goldens, scanning the horizon, need more shielding from the sun and thus have a much larger supraorbital ridge which you can clearly see with these replica skulls.
Article credit to the National Eagle Center
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