The Short Version
"Parliament" is indeed a widely recognized collective noun for a group of owls, confirmed across multiple reference sources including HowStuffWorks, Birdfact, and Grammar Monster. The phrase "is called" does not imply it is the only term — alternatives like "stare" and "wisdom" also exist — but "parliament" is the most commonly cited. The term's exact historical origin is debated, but its current usage in English is well established and uncontested.