Getting really close to Forster's Terns at Chincoteague during the spring led to me being able to finish this head study shown here - at this distance, they are quite spectacular! You don't often see a highlight in the eye of a tern as they either have hooded brows or eyes that are deeper into the skull (I'm not sure which) so unless the angle of the sun is lower in the sky (as is in this case) the eye simply looks black. And it is only close up that you can see the very dark brown iris.
And here is the same species showing the head in winter (I actually painted this study first). The bill looses its bright orange-red color and becomes dull red and black - some even darker than shown here. Just a faint highlight in the eye as the sunlight is weaker. Both watercolor on Grumbacher paper. Sizes are 6" x 9".