I came across this article about a photographer by the name .Phoo Chan, that captured a crow hitching a ride on the back of a Bald Eagle. You can read full article at this link; Crow Rides On The Back Of An Eagle Enjoy the read and pictures of this amazing photographer.
I have heard of hunters finding hummingbirds on the backs of ducks they have shot from the air but a crow on an Eagle is definitely a once in a lifetime shot, no doubt about that.
If you are interested in finding out more about birds, here is a link to Cornell Lab of Ornithology (the study of birds). This will guide you in the right direction or give you all the information to get started.