The greylag goose (Anser anser) is a large and sturdy bird from the waterfowl family. From the tip of the bill to the end of the tail it measures 74 to 84 cm, and the wingspan is 149 to 168 cm. It is the most common goose living in Europe. It is the ancestor of the domestic goose, which has lived with humans for many centuries ... among other things, geese alerted the Romans to an attack by Gallic conquerors who besieged Rome, and thus saved the city from total catastrophe. The greylag goose is a bird of subdued colors, dressed in gray plumage. We recognise it by its long, but sturdy neck and a large light head. The strong beak is entirely pale, pale orange. On the light gray neck and body there is a narrow dark stripe, the back and wings are darker, and the lower part of the body behind the legs is white. The greylag goose is characterized by its relatively dull pinkish-colored legs. Like other geese, it flies in V-shaped flocks, as this reduces air resistance toward the end of the formation, which the birds use to conserve energy. In flight it is revealed by a relatively contrasting color on the upper and lower sides of the wings – the front part of the wing is very light gray, the rear part is dark. When taking off, its back is revealed as relatively contrasting – the front part is dark (gray-brown), the tail is light (gray).
It is a diurnal bird, which feeds mainly at dawn and dusk. At night and around noon it gathers in flocks and rests on open water surfaces, where it feels safe from predators. The greylag goose is a herbivorous animal. It feeds mainly on grasses and plant buds, with leaves, shoots, fruits and seeds of marsh and aquatic plants; it also likes to visit agricultural fields, where in fields it searches for cereal grain or rummages for potatoes in fields.
Nests in a variety of habitats, but most often on wetlands. It prefers shallow lakes with extensive and sufficiently dense reed beds and small islands on large lakes or along the coast. It builds a shallow nest from plant material and hides it on the ground. In smaller groups it nests from April to May. After nesting, the social nature of this species becomes evident, as greylag geese begin to gather into enormous flocks, sometimes tens of thousands strong, as winter approaches. The greylag goose is a migratory bird that moves according to weather conditions. Some populations do not migrate at all, while most migrate regularly south before the harsh frost. In Slovenia it is a very rare breeder, but it can be observed here year-round – also during passage and wintering.
The greylag goose is strongly threatened by the disappearance of its habitat due to drying up and conversion to agricultural land and peat extraction. On nesting areas it is threatened especially by burning and excessive mowing of reed. It is threatened by hunting, and in addition it is sensitive to poisoning from lead shot, which it ingests with its food. Because of its habit of foraging on agricultural fields, it is also driven away by farmers.
