From: http://www.bbc.co.uk/worldservice/learningenglish/language/2014/01/140116_todays_phrase_wise_old_owl.shtml

Wise old owl

A long-eared owl
A long-eared owl at a display of birds of prey in London. Photo: BBC

Today's Phrase

When you say someone is a wise old owl, you mean they are very experienced in life.
Examples:
My English teacher was a wise old owl. He told me that I shouldn't give up on things when they don't work the first time.
Mary saved 20% of her salary for her retirement. She was a wise old owl.

Take note

A night owl is someone who stays up late into the night.
Example:
Bob is a night owl. He never goes to bed before 3am.

Interesting fact

Long-eared owls spend most of the year as a solitary species. But in winter they stay together in groups of up to 200. The visible parts of their ears are merely decorative: they have no purpose.