The grey heron is a large bird, standing up to 100 cm (40 in) tall and measuring 84–102 cm (33–40 in) long with a 155–195 cm (61–77 in) wingspan.The body weight can range from 1.02–2.08 kg (2 lb 4 oz – 4 lb 91⁄4 oz).
The plumage is largely ashy-grey above, and greyish-white below with some black on the flanks. Adults have the head and neck white with a broad black supercilium that terminates in the slender, dangling crest, and bluish-black streaks on the front of the neck. The scapular feathers are elongated and the feathers at the base of the neck are also somewhat elongated. Immature birds lack the dark stripe on the head and are generally duller in appearance than adults, with a grey head and neck, and a small, dark grey crest. The pinkish-yellow beak is long, straight and powerful, and is brighter in colour in breeding adults. The iris is yellow and the legs are brown and very long.
The main call is a loud croaking "fraaank", but a variety of guttural and raucous noises is heard at the breeding colony. The male uses an advertisement call to encourage a female to join him at the nest, and both sexes use various greeting calls after a pair bond has been established. A loud, harsh "schaah" is used by the male in driving other birds from the vicinity of the nest and a soft "gogogo" expresses anxiety, as when a predator is nearby or a human walks past the colony. The chicks utter loud chattering or ticking noises.
