Although early nocturnal raptors were considered close to day raptors(eagles, hawks …), later studies have shown greater similarity with nightjars and other nocturnal birds (podargos, nictibios, egotelos, etc.).

Based on DNA studies, some authors have come to group these strange birds and nocturnal raptors in the order Strigiformes, although later studies advised to maintain the traditional separation between them.

The classification by the definitive moment, and therefore more commonly used is the following:

N. Comonn N. Scientific Order Family
Eagle owl Bubo bubo Strigidae Strigiforme
Tawny owl Strix aluco Strigidae Strigiforme
Long-eared owl Asio otus Strigidae Strigiforme
Short-eared owl Asio flammeus Strigidae Strigiforme
Llittle owl Athene noctua Strigidae Strigiforme
Scops owl Otus scops Strigidae Strigiforme
Boreal owl Aegolius funereus Strigidae Strigiforme
Barn owl Tyto alba Tytonidae (lechuzas) Strigiforme

The differences between the two families are clear and are based on morphological characters, such as the following:

Caracter Strigidae Tytonidae
Skull Rounded Elongated
Orbits Big Small
Beak Short, curvy and width Long, straight and stretch
Notches at the posterior border of sternum Two pairs of recesses Two recesses
Tarsus-metatarsus Short Long
Ears Symmetrical in shape and size, but left higher than right. Often asymmetrical in size / shape (right is larger)
Furcula Pneumatic Not Pneumatic
Sawing on the nail of the middle finger Smooth Sawed
2nd and 3rd finger 3rd larger 2nd Same size
Eggs Rounded Elongated

Taxonomic comparison of Owl Royal (left) and Barn Owl (right).