The Snowy, while not the biggest wading bird is still 2 feet (.6 meters) tall. That’s still a decent size.
However, when they get mixed into some of the large flocks during feeding they are suddenly not the ‘big shot’ out there.
Being aggressive is what keeps the Snowy safe in these crowds.
I think they bluff their way through any problems. The large Wood Storks and Spoonbills are the calm birds and a pushy Snowy is usually ignored.