The greylag goose (Anser anser) is a widespread waterfowl species found across Europe and Asia. Recognized by its mottled grey-brown plumage and robust build, it is the wild ancestor of most domestic goose breeds. These geese inhabit various aquatic and terrestrial environments throughout their range.
Identification and Habitat
The greylag goose is a large, bulky bird with a thick neck, substantial head, and stout legs. Its plumage is primarily grey-brown, mottled with paler fringes, and it has a white belly and undertail coverts. The bill is typically pinkish-orange, and its legs and feet are consistently pink. In flight, large, pale grey patches on its upperwings contrast with darker flight feathers. It can be differentiated from similar species like the bean goose by its larger size, bulkier body, and specific wing patterns.
Greylag geese inhabit a broad range of environments across their Palearctic distribution, from Iceland to northeastern China. They favor extensive wetlands, marshes, and lakes, often nesting in dense reedbeds or on small islands. These birds also utilize agricultural fields, grasslands, and pastures for foraging. Many northern populations are migratory, moving south for winter, while some populations have become resident year-round in certain regions, including parts of the United Kingdom.
Diet and Foraging Behavior
Greylag geese are primarily herbivorous, with their diet consisting of plant material. They graze extensively on land, consuming grasses, roots, stems, and leaves from marsh plants. In summer, they focus on fresh green vegetation, while in winter, their diet includes underground storage parts like roots and tubers.
In agricultural areas, they feed on cultivated crops such as barley, oats, wheat, potatoes, carrots, and sugar beets. When foraging in shallow water, greylags employ “upending” or “dabbling,” submerging their head and neck to reach submerged aquatic vegetation. These geese often forage in large flocks, particularly during the non-breeding season, which provides collective vigilance against predators.
Social Structure and Imprinting
Greylag geese often form large flocks outside the breeding season that can number in the thousands. Within these flocks, a dominance hierarchy is established, with family groups often dominating single individuals or pairs. The presence of a partner or family members provides social support, influencing an individual’s stress response and dominance in social interactions.
Greylag geese form strong, monogamous pair bonds that typically last for life. These pairs form when geese are around three or four years old and remain together, even migrating as family units with their young until the subsequent breeding season. Some pairs may separate, and homosexual pair bonds, particularly between males, are also observed, sometimes persisting for over 15 years.
The greylag goose is known in ethology due to Konrad Lorenz’s pioneering work on filial imprinting. Lorenz demonstrated that goslings, shortly after hatching, develop a strong social attachment to the first moving object they encounter. In his experiments, Lorenz divided clutches of eggs; one group hatched naturally with their mother, while the other group, incubated by him, imprinted on Lorenz, following him as if he were their parent. This process, occurring during a specific, brief “critical period” after hatching, forms a rapid and permanent bond that guides their subsequent social and sexual behaviors.
Reproduction and Goslings
Greylag geese begin their breeding cycle around March to April, reaching sexual maturity at two to three years of age. Nest site selection is a joint effort, with the female choosing a location close to water, often in dense vegetation like reedbeds, heather, or rushes, or on small islands for predator protection. Nests are constructed on the ground, sometimes on floating vegetation, and are built from twigs, grass, and other plant material, then lined with feathers and down.
Clutch size ranges from 4 to 6 creamy-white eggs, though up to 8 eggs may be laid. The female alone undertakes incubation, which lasts 27 to 28 days, while the male remains nearby, guarding the nest against intruders. Upon hatching, goslings are precocial, capable of walking, swimming, and feeding themselves almost immediately. Both parents protect the young and lead them to feeding areas. Goslings remain with their family group until they can fly at about 50-60 days old, and often until the following breeding season.