They don’t.
Owls, unlike other birds, have one structured foot and three toes on each foot. As a result, they can balance easily on both trees branches and your windshield wipers. So they only need two really long legs to get around their environment – no short ones needed!
You should know that owls are also highly adapted to nocturnal life – something many animals would not be able to do without some kind of adaptation like large eyes located in the front of their heads (in order for the other animal’s eyes not to reflect light back at them which would render them blind). Owls are pretty awesome little fowl with all sorts of quirks and adaptive traits!