Most people know about a pride of lions, a flock of sheep, a herd of cattle, a school of fish, an army of ants, a bunch of flowers, a swarm of bees, and a coven of witches in describing a collective.
Logically, a bunch of roosting owls might be described as a school of owls but no, they are a parliament. Perhaps the school came from Harry Potter.
Collective nouns are now rarely used except for the most common. Lists of collective nouns can be found here and here.
If in doubt, just use the word bunch.