night owl, n.All

The early bird gets the wormBut so does the bird that stayed up all night

Night owls have more psychopathic tendencies than those who sleep early.

Night owl is redundant considering that owls are nocturnal. Wouldn’t it be sufficient just to say someone is an “owl” instead of a “night owl”?

A Night owl is a man who doesn't give a hoot how late he gets home.