What does it mean when wildlife biologists say that “an eagle can see a rabbit in a field from miles away”? Does this imply that their vision is automatically more zoomed in? Do they have better than 20/20 vision, or is their vision simply clearer?

Question

What does it mean when wildlife biologists say that “an eagle can see a rabbit in a field from miles away”? Does this imply that their vision is automatically more zoomed in? Do they have better than 20/20 vision, or is their vision simply clearer?

In: Biology

Answer 1

So, a memorable lecture in first year physics tackled this, and it turns out that yes, eagles do have more light receptor cells packed into their retinas, however they only have marginally better detailed vision than humans do.

Why? When light passes by a sharp threshold like a slit, or an iris, abberation happens. The smaller the aperture, the more abberation, and the less detailed the image can possibly be. Eagle eyes are only so big, so this abberation limits the maximum distance it is possible to see clearly.

Eagles are NOT seeing in 4K resolution, spotting crystal clear mice from miles away. This is physically impossible. What they ARE doing is being VERY sensitive to changes in the fovea, so a distant mouse crossing a field is a very obvious black dot moving around whereas we humans would not have the sensitivity to pick this motion up.