One day I watched as a young Cooper's hawk (Accipiter cooperii) flew in and perched in the same tree as one of the kingfishers. The kingfisher began to screech and dive-bombed the hawk several times. The hawk maintained it's post and it's equilibrium and the kingfisher eventually flew off, screaming her displeasure for all the world to hear. These are not shy and retiring birds!
Because I was drawing at a distance and my eyesight isn't quite what it once was, I thought that the kingfisher had yellow eyes. When I got home and began to research the species, I was surprised to find that their eyes are dark and blend into the dark teal of their head feathers very nicely. What I thought were yellow eyes are two white spots placed just in front of the eyes. The only reference I found that made any attempt to explain the purpose of the eye spots was in The American Midland Naturalist, University of Notre Dame, 1974:
...kingfishers, when about to dive, appear to be using the two white spots in front of the eyes as sighting devices along the line of the bill to fix their prey and, by doing so, possibly to correct for the refraction of water.Well, it's not the most satisfying explanation but will have to do for now.
For more about Belted kingfisher:
The American Midland Naturalist
All About Birds