A look into the details of a bird's facial anatomy, their eye rings.

A bird's anatomy can be highly variable, from the broadest being body shape, color, bill, wings and feet. Down in more minute features that can often get overlooked. 

When drawing, we are always told the eye is the most important feature that you want to stand out. But how often do you notice the intricate feathers or bare skin that are around that eye. What color they are, do they form a shape or particular pattern?

Bare skin surrounding a bird's eye is called an orbital ring. This can be of various thickness, from a thin ring like the killdeer to excessive like a white-eye, a group of birds named after this large orbital ring they have.

If a bird has a particular colored feathers around their eye, it is often referred to as an eye ring, generally, a different color than the rest of the face or head. This difference can be subtle or bold, broken or complete.

The bare skin or feathers can be of various thickness, each variety of this part of a bird's anatomy can help add to its overall appearance.

Birds such as killdeer can have a red orbital ring around their eyes, or a stunning blue like on a Double-crested cormorant. They can even change as a bird ages, if you look closely at a fledgling tufted titmouse, you may notice that the flesh around their eye is actually a bright yellow, which will fade eventually to a pale gray that we are more often familiar with this common backyard bird. Orbital rings are believed to help indicate to other birds that they are sexually mature and healthy.

Other birds, feathers may make up this eye ring. From there, this group of feathers may have different colors as it encircles the eye. If all these feathers are the same color, they are referred to as a complete eye ring, if it is broken up with a different color, it's an incomplete or broken eye ring. One form of a broken eye ring is called an eye arc, generally seen as a partial eye ring directly above and directly below the eye. This characteristic can be seen in species such as the Northern Parula. 

How bold or subtle an eye ring can also vary, a good comparison is the very subtle eye ring on the Orange-crowned Warbler and the bold white eye ring of the Connecticut Warbler.

It's interesting to note that the appearance of an eye ring can also be affected by other parts of a bird's facial anatomy such as eye lines, lores, and eyebrow/ supercilium.