There is often more than one collective noun for a group. In this case,I opted for the less common: wisdom. They are often referred to as a parliament, but other less common terms can be a congress or a stare of owls. In flight, you could use a silence of owls.
This is also one of my most favourite illustrations.
My book Siege of Herons – Collective Nouns Alphabetically is available for pre-sale on my site.
If you love language and love words; this is the book for you.