I love capturing birds and reptiles utilizing their nictitating membranes. Though I have lots of different shots of birds/reptiles with their nictitating membranes, these shots of an emu at High Park Zoo are my favourite.
For those not familiar with the term, "A nictitating membrane is a third eyelid that is translucent or clear. It is used as an extra level of safety for the eye and allows the creature that has it to still see while affording its eyes an additional amount of protection. Some birds, reptiles, and sharks have nictitating membranes as well as a few mammals. (Though many mammals have a vestigial nictitating membrane that does not cover the whole eye.) Unlike the first and second eyelids, which open and close vertically and meet in the middle of the eye, the nictitating membrane moves across the entire eye horizontally.
Nikon 55-200mm VR AF-S f/4-5.6G ED
ISO - 400