File:Whistling Heron (52142980788).jpg

The whistling heron measures 53 to 64 cm in length and weighs 521 to 546 g. The southern subspecies is bigger but has a shorter bill in proportion to the body.

The overall impression of standing birds is gray, with flying birds showing conspicuous white rear parts (lower back, belly, and tail). In both subspecies, adults' upperparts except the lower back are blue-gray. The feathers of the sides of head, sides of the neck, breast, and scapular area are basically white but are stained gold to buff, perhaps by the powder down typical of herons or by secretions of the preen gland; the color varies from bird to bird. In the nominate subspecies, the crown and crest (separate plumes up to 4 cm long on the nape) are black and the upper wing coverts are cinnamon-colored; the crown and crest are slate-gray and the upper wing coverts are honey-colored (or "chamois") in fostersmithi. The bill is pink with blue to violet at the base and the distal third black, the legs are greenish and rather short, and there is a fairly big area of bare bluish skin around the eye.

Juveniles have the same overall pattern but are duller than adults, with the crown lighter, the breast light gray, and the throat and sides unstained white. Chicks are undescribed.[2]

The bird is named for its most common call, a "loud, flute-like whistled kleeer-er"[3] or "a high, reedy, complaining whistle, often doubled or uttered in a ser[ies], wueeee, wueeee,.…, easily imitated" [4] or "a distinctive, characteristic, far-carrying, melodious whistle" that "can be rendered 'kee, kee, kee.'" It may also give "a slow, drawn-out whistle" when taking off. The alarm call is a harsh quah-h-h.