1 Buteo...3 eyelids...& the power of Google...

 The Eyelids - birds have 3 eyelids; one upper and one lower eyelid, of which the lower is more moveable, and a nictitating membrane. This nictitating membrane is between the other two eyelids and the cornea and has its own lubricating duct equivalent to our tear duct. It is used in cleaning and protecting the eye. http://www.earthlife.net/