Julie Feinstein writes male and female mourning doves "have a small dark comma-shaped mark on both sides of the head below and behind the eyes. Their eyes are dark brown and ringed about with pastel blue skin. Their eyelids are blue, too -- one of my favorite things is to find a mourning dove asleep with its powder blue eyelids showing." And I feel the same way way when I see mourning doves do this, it is peaceful sight.
By the way, mourning doves have many fascinating aspects; and a number of their traits, along with beautiful photographs, are included in both the digital version (iBooks and ePub) as well as the hard-copy (soft-cover) version of the book Words In Our Beak Volume One.
Either version makes to give if you happen to celebrate Easter or Passover, which are approaching soon! However, these books are a great thing to have, or to give to someone during anytime of year.
ADENMENDUM: The versions (digital and softcover) of volume one within the Words In Our Beak book series that are mentioned in this entry may only remain available for a limited time, but a hardcover version of volume one can be found wherever books are sold.
Moreover, Volume Two of the book series is now available! Both volumes one and two are in hardcover format (as seen below) and can be purchased any place where books are sold.