Grey heron on the bank of a stream in the gardens of Charlottenburg Palace, City of Berlin, Germany
Some background information:
Grey herons (Ardea cinerea) are long-legged wading birds of the heron family, Ardeidae, native throughout temperate Europe and Asia, and also parts of Africa. They are resident in much of their range, but some populations from the more northern parts migrate southwards in autumn. As birds of wetland areas they can be seen around lakes, rivers, ponds, marshes and on the sea coast. They feed mostly on aquatic creatures which they catch after standing stationary beside or in the water, or stalking their prey through the shallows.
Standing up to one metre (three feet three inch) tall, adults weigh from one to two kg. They have a white head and neck with a broad black stripe that extends from the eye to the black crest. The body and wings are grey above and the underparts are greyish-white, with some black on the flanks. The long, sharply pointed beak is pinkish-yellow and the legs are brown.
The birds breed colonially in spring in heronries, usually building their nests high in trees. A clutch of usually three to five bluish-green eggs is laid. Both birds incubate the eggs for around 25 days, and then both feed the chicks, which fledge when seven to eight weeks old. Many juveniles do not survive their first winter, but if they do, they can expect to live for about five years.
Grey herons are closely related and similar to the North American great blue herons (Ardea herodias), which differ in being larger, and having chestnut-brown flanks and thighs, and to the cocoi herons (Ardea cocoi) from South America, with which they form a superspecies. Their main call is a loud croaking "fraaank", but a variety of guttural and raucous noises are heard at the breeding colonies. Male grey herons use an advertisement call to encourage female ones to join them at the nest, and both sexes use various greeting calls after a pair bond has been established.
Grey herons have a slow flight, with their long necks retracted in an S-shape. This is characteristic of herons and bitterns, and distinguishes them from storks, cranes and spoonbills, which extend their necks. They fly with slow wing-beats and sometimes glide for short distances. They sometimes soar, circling to considerable heights, but not as often as storks. In spring, and occasionally in autumn, birds may soar high above the heronry and chase each other, undertake aerial manoeuvres or swoop down towards the ground. Grey herons often perch in trees, but spend much time on the ground, striding about or standing still for long periods with an upright stance, often on a single leg.
These birds are apex predators in their aquatic ecosystem. Fish, amphibians, crustaceans, and insects are caught in shallow water with the herons‘ long bills. They have also been observed catching and killing juvenile birds such as ducklings, and occasionally take birds up to the size of water rails or white-throated rails. Small mammals such as water voles, rats, stoats and young rabbits are additionally caught.
Grey herons breed in colonies known as heronries, usually in high trees close to lakes, the seashore, or other wetlands. The clutches of eggs usually number three to five, though as few as two and as many as seven eggs have been recorded. The eggs have a matt surface and are greenish-blue. Both parents bring food for the young. At first, the chicks seize the adult's bill from the side and extract regurgitated food from it. Later, the adult disgorges the food at the nest and the chicks squabble for possession. They fledge at seven to eight weeks. Usually, a single brood is raised each year, but also two broods have been recorded.
Grey herons have the ability to live in cities where habitats and nesting space are available. They hunt as usual, but also visit street markets and snack bars. Some individuals even make use of people feeding them at their homes or share the catch of recreational fishermen. In ancient Rome, grey herons were birds of divination that gave an augury (sign of a coming event) by their call, like ravens, storks and owls. In Britain, roast heron was once a specially prized dish for special occasions such as state banquets. For the appointment of George Neville as Archbishop of York in 1465, 400 herons were served to the guests.
