Owls’ night vision

While diurnal rapacious birds have evolved towards greater image definition thanks to the presence of two foveae and the large concentration of cones in both, nocturnal birds of prey have developed an excellent night vision system.

In these birds, the eyes are enormous. In the eagle-owl for example, they are as large as those of humans.

They have a very high density of rods in their retinas, the cells responsible for detecting light, and can intensify the little ambient light thanks to a structure found in many other animals called tapetum lucidum.

They do, however, need an external light source, however faint, and therefore are unable to see in absolute darkness.

A nocturnal bird of prey can indeed see at night, but is not able to have a perfect view of the environment. Sight is therefore used for their flights, but it is not sufficient to ensure the perfect identification of prey as small as a rodent dozens of meters away in the dark: Strigiformes use their extraordinary hearing for this purpose.