A humorous but real list I give the students in my wild bird photograohy class: How do you know you are getting close enough to the wild birds? (My secret is to get very close and still use a long lens)
1 - Hey it's a bird.
2- I always did like Robins. (next might have been you can tell what sex it is but too many birds, both sexes look the same.)
3- You need to swith to vertical from horiz. to fit the bird into the frame.
4- You can tell me the color of their eyes. Many birds eyes are not black but a very dark red or brown, etc. I have a chart of the eye color change in the first 5 years of a Bald Eagles life. Great ID tip.
5- You can tell me the color of their tounge. If you ever have to guess - say orange.
6- You are using the clarity of the eye ring for editing images.
7- If you enlarge the eye, you can see your reflection in it.
How are you doing?