The Barnacle Goose is a medium-sized black and white goose. Due to extensive hunting, both in their breeding grounds on Spitsbergen, as on their wintering grounds in Scotland and during their migration, the population in the second world war was lower as 100 individuals. With the geese getting protection in all these areas, the species now has fully recovered and has a population of many thousands. They are most often seen in the western parts of the archipelago and on the islands in the south-east.
Barnacle Goose – Branta leucopsis
Length: 58-70cm – Wingspan: 120-142cm
Medium-sized grey and black goose with a long black neck and white face.
They breed on small islands in the fjords or on cliffs to prevent predation by Arctic Foxes. They lay around 4 eggs, which hatch around the end of June, beginning of July. The first thing the new family does is head for green pastures, as they all need a lot of food. For the island-breeding birds, this means they have to swim with their tiny chicks, sometimes up to 10km before they can start to feed. The cliff-breeding birds usually have a much shorter distance to cover as there is often lush tundra directly underneath those cliffs. However, this means the chicks have to jump, well before they can fly.
Where the island-breeding strategy made a lot of sense to avoid predation against foxes, it doesn’t do any good to prevent predation by Polar Bears. For a bear, an egg is just a small snack, but with dozens of families breeding together on the same island, there is a lot of food available for them. In recent years, with the sea ice disappearing on the western shores, we see more and more Polar Bears vacuuming those breeding islands, causing a collapse in Barnacle Goose (and Eider) numbers.
When they reach their feeding grounds, something strange happens. Here there is intense competition for the best feeding places. Initially, the strongest birds would win the fights over those places and managed to chase away the weaker birds. However, those fights cost a lot of time and energy, and there is always the risk of getting injured. So a new system evolved where the birds just ‘look’ at the number of chicks in the other family. The stronger the birds, the more eggs they can produce and the more goslings they have. So we see larger families always win the fights (which are a lot less fierce usually), and the smaller families make way for the larger ones.
This means the larger families get better feeding grounds, get more food and have a higher chance of reaching their wintering grounds in Scotland. They even have a higher chance of returning to Spitsbergen the next year. They are also likely to produce more eggs the following year, having a larger family again. This way about 20% of the geese produce 80% of the young. So what happens if you’re born into a small family? Are you always in trouble? Well, we know sometimes they give away their goslings for adoption to a larger family. This way their gosling has a larger chance on survival and has a better start in life, while the accepting family gets a little larger, resulting in more fights won and thus better food. This way everybody is happy…