The Greylag goose is a large waterfowl of the Old World and is the ancestor of the domestic goose, having been domesticated at least as early as 1360 BC. It has mottled and barred grey and white plumage and an orange beak and pink legs. Its distribution is widespread, with birds from the north of its range in Europe and Asia migrating southwards to spend the winter in warmer places.
Greylag geese breed in Iceland, Norway, Sweden, Finland, the Baltic States, northern Russia, Poland, eastern Hungary, and Romania. They also breed locally in the United Kingdom, Denmark, Germany, Austria, the Czech Republic, Slovakia, and North Macedonia. The eastern race extends eastwards across a broad swathe of Asia to China. European birds migrate southwards to the Mediterranean region and North Africa. Asian birds migrate to Azerbaijan, Iran, Pakistan, northern India, Bangladesh and eastward to China. In North America, there are both feral domestic geese, which are similar to greylags, and occasional vagrant greylags. Greylag geese seen in the wild in New Zealand probably originated from the escape of farmyard geese, same as in Australia, where feral birds are now established in the east and southeast of the country. Greylag geese breed on moors with scattered lochs, in marshes, fens, and peat-bogs, besides lakes and on little islands some way out to sea. They like the dense ground cover of reeds, rushes, heather, bushes and willow thickets. On their wintering grounds, they frequent salt marshes, estuaries, freshwater marshes, steppes, flooded fields, bogs and pasture near lakes, rivers, and streams. They also visit agricultural land where they feed on crops, moving at night to shoals and sand-banks on the coast, mud-banks in estuaries or secluded lakes.
Greylag geese are gregarious birds and form flocks. Pairs with young stay together as a family group, migrating southwards in autumn as part of a flock, and separating the following year. Greylag geese are diurnal and forage on the ground or in water. When on land these birds are able to run rapidly and escape predators without difficulty. Greylags have a loud cackling call similar to that of the domestic goose, "aahng-ung-ung", uttered on the ground or in flight. There are various subtle variations used under different circumstances, and individual geese seem to be able to identify other known geese by their voices. The sound made by a flock of geese resembles the baying of hounds. Goslings chirp or whistle lightly, and adults hiss if threatened or angered.
Greylag geese are largely herbivorous and feed chiefly on grasses. They also eat leaves, berries, water plants, glean grain on cereal stubbles and sometimes feed on growing crops such as oats, wheat, barley, buckwheat, lentils, peas, and root crops. These birds may also consume small fish, amphibians, crustaceans, mollusks, and insects.
Greylag geese are monogamous and mate for life. Breeding season usually occurs in April-May. Greylags nest on the ground among heather, rushes, dwarf shrubs or reeds, or on a raft of floating vegetation. The nest is built from pieces of reed, sprigs of heather, grasses, and moss, mixed with small feathers and down. Females lay 4 to 6 creamy-white eggs which soon become stained. The female does the incubation, which lasts about 28 days, while the male remains on guard somewhere near. The goslings are precocial and able to leave the nest soon after hatching. Both parents are involved in their care and they soon learn to peck at food and become fully-fledged at 8 or 9 weeks. Young Greylag geese become reproductively mature when they are 2-3 years old.
Main threats to Greylag geese include hunting, poisoning, and destruction and degradation of wetland habitats on which these birds are so dependent. Greylag geese are also persecuted by farmers as they cause serious crop damage and they also suffer from the outbreaks of avian influenza.
According to the IUCN Red List, the total Greylag goose population size is around 1,000,000-1,100,000 individuals. The European population consists of 259,000-427,000 pairs, which equates to 519,000-853,000 mature individuals. Currently, this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today are increasing.
The Greylag goose was one of the first animals to be domesticated; this happened at least 3000 years ago in Ancient Egypt; the domestic breed is known as A. a. domesticus. As the domestic goose is a subspecies of the Greylag goose they are able to interbreed, and the goslings share characteristics of both the wild and tame birds.