A curious honking noise can currently be heard coming from the duck pond at Basel Zoo. The noise is coming from the male common eider ducks, who are trying to impress the females with their calls.

The warm, sunny weather we have been experiencing recently has stirred up some spring fever among the common eider ducks, and the males are making this known to the females using their unique honking calls. The drakes (the proper name for the males) put on a real swimming show to impress the females: they stretch themselves out, throw their heads back and then turn them back and forth.

Common eider ducks also have an impressive diving technique: at the edge of the pond, the ducks dive all the way down to the bottom so that, much like in a hot tub, only the spirals of air bubbles can still be seen.

The mussel crackers of the sea

Common eider ducks primarily live along the Arctic coast of the Atlantic and the Pacific. They are very common in northern Europe, but have only been more frequently found in Switzerland since the second half of the twentieth century. Since 1970, there have been numerous sightings of flocks of common eider ducks flying into the country. The birds were able to find enough food thanks to the increasing number of zebra mussels and even stayed here even during the summer. They have now become one of Switzerland’s breeding bird species. Common eider ducks are perfectly suited to the sea: in addition to snails and crabs, these birds predominantly feed on mussels and also eat fish, unlike other species of duck. They swallow the mussels whole and are able to crack their shells with their strong gizzards.

Fine plumage

Common eider ducks are larger in size than the more well-known mallard ducks. On land, they look quite plump, but in the water, they are very agile. It is easy to tell them apart from other ducks because of their wedge-shaped bills. Many people are more familiar with the ducks’ plumage – eiderdown – than the ducks themselves. The ducks pad their nests with this down, protecting their clutch from the freezing temperatures of the northern climate. Eiderdown’s natural use also means it possesses the ideal properties for making bedding for humans. Eiderdown is brown in colour and is made up of larger, finer and denser feathers than other downs. Thanks to their cohesive structure, the downy feathers stick to each other and form bundles.