I was once threatened by a sun bittern in the Blackburn Pavilion at London Zoo. It stood with wings outstretched in front of me. Each time I tried to get past the bird blocked my way, eventually losing interest when other visitors entered the building. I assume it was defending a nest.
@bongorobi have only seen them display once and it was so briefly and it was the chester zoo male, he was trying to shoo off one of the victoria crowned pigeons, they have such wonderful marking under those wings,