The barnacle goose is a medium sized, black and white goose. Barnacle geese occur in three separate populations that breed in northeast Greenland, in Svalbard and in northwest Russia and the Baltic region.
The sexes are identical in appearance. They are 58–70 cm in length and weigh 1.5–2 kg. They have a yellow-white head that has a black crown. The neck and breast are black; the belly is white with grey mottling along the sides. The upper-parts of the bird are blue-grey with black and white stripes across the wings. The bill and legs are black.
The juveniles resemble the adults, but are somewhat duller in colouration and have brown instead of black bars across the wings.
Their call is a repeated single-tone barking.
Barnacle geese occur in three separate populations that breed in northeast Greenland, in Svalbard and in northwest Russia and the Baltic region. The birds from Greenland winter in Ireland and in the western parts of Scotland, whereas the Svalbard birds spend the winter in the Solway Firth between England and Scotland. The eastern population winters along the western coasts of Germany and the Netherlands.
The Svalbard barnacle goose is indistinguishable morphologically from birds in the other populations, but is geographically isolated. In Svalbard, the barnacle goose breeds on the western coast of Spitsbergen and within Tusenøyane south of Edgeøya.
Most barnacle geese breed in colonies on small islands, but some pairs also breed on cliffs on Spitsbergen.
The spring migration starts in April or early May, when the geese leave Solway Firth and head for Helgeland on the western coast of mainland Norway. In the second half of May they move on to the southern part of Spitsbergen before reaching the nesting areas toward the end of May.
In late August or early September the autumn migration starts. Bjørnøya is an important stop-over site where the birds can spend up to three weeks waiting for favourable winds to initiate migration to the wintering grounds in northern Britain. Some birds probably migrate directly from Spitsbergen to the Solway Firth.
Barnacle geese breed on rocky ledges on cliffs, on skerries and on small rocks surrounded by water, as well as on grassy islets near the sea, but occasionally they can be found nesting several kilometres inland.
After hatching, the families leave the nesting islands and swim to the mainland to forage on the lush vegetation near tundra ponds. In Svalbard the breeding and brood-rearing sites are normally 5–25 kilometres apart.
The adults moult after nesting. At this time they cannot fly so they seek protection from predators on tundra lakes and at sea.
After the moulting period, the families assemble at gathering areas, which are often near bird cliffs, where they feed before starting the migration to the wintering grounds. The gathering sites are located in the southern part of the archipelago in Svalbard.
Barnacle geese eat a wide variety of plants. When they reach the breeding sites they forage on snow-free patches, where the birds eat roots and mosses. Later in the summer grasses and sedges dominate the diet, together with a variety of herbs and horsetails. During the autumn, when they stage-up on Bjørnøya, grassy habitats are used.
In their wintering areas they forage within salt-marshes, but also feed on agricultural pasture land.
Life history and reproduction
Barnacle geese nest in quite closely packed colonies, often sharing the areas with the common eider. The timing of nest establishment and egg laying varies from year to year according to snow conditions. In years with late snow melting reproduction can be poor.
The nest is a shallow depression that is lined with plant material and down, the outer rim of the nest is elevated. Nest-sites are reused year after year.
The four or five eggs that make up a clutch are white, though they often become a dirty yellow during the course of incubation, which lasts 24–25 days. Only the female incubates. But, the male always remains nearby and he actively protects the nest when the female leaves to graze. The families leave their nests immediately after the eggs hatch.
The young are self-feeding, eating lush vegetation in damp areas near freshwater pools. They are fledged after 40–45 days. The families remain together through the winter and until the spring migration. Barnacle geese are normally sexually mature at three years of age. The highest age recorded in Norway (including Svalbard) is 24 years.
Management status and monitoring
The Svalbard population of barnacle geese has increased dramatically since the end of the 1940s, when it was estimated that there were only a few hundred individuals left. Many new colonies have been established, and the colonies that survived the earlier hunting pressure at both ends of their migration route have all increased dramatically.
The barnacle goose colonized Kongsfjorden in the 1980s. In 2004–2005 counts in the wintering area gave a total estimate of 26,500 individuals.
The Svalbard barnacle goose population is one of the most studied populations of migratory geese in the world. Some research programmes working with these geese have been on-going for more than three decades. Population dynamics have been studied via an extensive ringing programme, which has employed large plastic leg-rings with individual identification numbers that are visible at great range.
In spite of the population increase in all three populations, the barnacle goose remains vulnerable to human impacts because of it habit of aggregating in very few specific geographic areas during breeding, staging and wintering.