A hawk's eyesight is eight times better than ours, even though its eyes are much smaller than ours. What lets them see so well?
It is easy to find sites that tell you that a hawk's vision is eight times better than ours, but it is much harder to find details on why they see better. Often they give the impression that somehow the hawk's eyes are telescopic, acting like a zoom lens. Instead, we need to look at the hawk's retinas for the answer. The retina contains light sensitive cells called rods and cones. These cells are stimulated by light, sending messages to your brain to tell you what you are seeing. The hawk's retina has many more of these light sensitive cells than our eyes do. More cells is much like having more pixels in a photograph. Both add more detail to the image. Think of our eyes as one megapixel digital cameras, while the hawk's eyes are eight megapixel digital cameras. If both images are the same size, the hawk will be able to see much smaller details, letting it spot a mouse at a distance where our eyes would cause it to blur into the background.
The hawk in this photo is a Red Shouldered Hawk.