I wonder how birds can see so far. Especialy eagles spot their prays form very large height and land on exact point? What is the principle

 

Thanks

A smaller pupil (vs human) means the diffraction limit is smaller, so there is better resolution. (It would not surprise me if the vision sensitivity was weighted toward the shorter-wavelength end of the spectrum as a result.) Basically, adjacent spots can be closer together without blurring into each other.

http://hyperphysics.phy-astr.gsu.edu/hbase/vision/rodcone.html