Owl sizes vary greatly. There are especially small owls up to 20 centimeters (passerine owls) and very large ones up to 75 centimeters in height and up to 4 kilograms (Eagle-owl).
The color differs according to the type of bird. Currently, 420 variants of the color of the owl are known.
The strongest owlets begin to adapt to the environment, the weakest go to feed for birds of prey.