This video from the USA says about itself:
22 September 2017
Close up of a stunning Green Heron hunting in the trees over flooded swamp behind the Backyard. Dense heavy vegetation in or near water is the preferred place to spot these elusive and beautiful herons. This heron was attacked by the Backyard Blue Jays at the end of this film – to see the mobbing and attack that follows check out here.
Along quiet streams or shaded riverbanks, a lone Green Heron may flush ahead of the observer, crying “kyow” as it flies up the creek. This small heron is solitary at most seasons and often somewhat secretive, living around small bodies of water or densely vegetated areas. Seen in the open, it often flicks its tail nervously, raises and lowers its crest. The “green” on this bird’s back is an iridescent color, and often looks dull bluish or simply dark.