Seagulls — Basel’s Winter Guests

Have you noticed the piercing bird calls in Basel along the Rhein in recent weeks? They’re a sign that Basel’s winged winter guests have returned—the black-headed seagulls! The sight of seagulls flying around the water’s edge, squawking loudly while gobbling up everything in sight, is normally a spectacle that we associate with summer vacations by the shore. In this part of the world, however, the presence of gulls is actually a winter phenomenon. It would hardly seem like a normal winter day in Basel without the noisy cacophony of a large colony of gulls acrobatically zipping through the air, snatching the bread that is being thrown at the ducks and swans by well-meaning passers-by. (While they love it, giving bread to ducks and swans is nutritionally equivalent to feeding cotton balls to humans!)

The most common gull visiting Switzerland is Larus ridibundus, known as black-headed gull in English or “Lachmöwe” in German; the German name is translated from its Latin name, which means “laughing gull” because of its chuckling or laughing calls. Most gulls start to arrive by mid-October to spend the winter around Swiss lakes, rivers, streams, and wetlands—mainly near the Rhein and the shores of Lake Constance, Lake Geneva, and Lake Neuchâtel—before leaving in mid-March to return to their more northern homes for breeding and summering. In this region, the Rhein in Basel, the Dreiländereck, the canal in Village-Neuf, and the two ponds in Park im Grünen are favorite wintering places for these migratory birds. They come because of the milder climate as well as the plentiful sources of food. Apart from the stolen bread, they feed on fish, insects, earthworms, fruit, and of course, garbage.

The black-headed gulls are so-called because of the dark brown to grayish-black plumage on the head that they sport during their breeding season in the summer, together with gray wings, red legs, and a red beak. By the time they arrive in Basel in late autumn, this dark plumage has disappeared almost entirely, leaving them with a nearly fully white head with only one small black dot on the side of the head behind the eye. Younger gulls that have not yet reached maturity will still have some brown in the wings and tail. The black-headed gull has a wingspan of up to 100 cm (nearly 40 inches) and a weight of about 225–350 g (½ to ¾ pound). They nest on the ground, usually on nests made of reeds on gravel or stones by lakes, and have one brood per year, usually with a clutch size of 2–3 eggs. They live surprisingly long lives; while their average lifespan is about 18 years, the oldest recorded black-headed gull in Switzerland was over 26 years old, and the oldest in Europe was nearly 33!

In the past 20 years, the black-headed gull population has declined throughout Europe, both inland and also partly along the marine coasts. While they are not under threat of extinction in Europe or around the world, the breeding population has decreased dramatically enough in Switzerland to put them on the endangered list here. There are only just over 500 breeding pairs left in this country, and studies are ongoing to understand what measures can be taken to ensure their success.

In many countries where these birds spend either their summer or their winter, including Switzerland, they are fitted with leg rings to track their movements and survival. The ring-coding systems varies based on the country of origin; some countries use easy-to-read colored rings and others use serial numbers. Using the European Colour-Ring Birding database, ornithologists and bird watchers use the various coding system to track the birds’ migration. A group of young Basel-based ornithologists, who call themselves the Bebbi Babblers, have spent a couple of winters studying, photographing, and recording the gulls on the Rhein in Basel and tracing their origins using their coded leg rings. Their study revealed that just over a third of the black-headed gulls that spend the winter in Basel came from Poland, while the others came from Croatia, the Czech Republic, Denmark, Germany, Hungary, Lithuania, Sweden, and even as far away as Finland, over 2,000 km from Basel!

So next time you walk through Basel in the winter time, head down to the Rhein and take a moment to admire the beauty and flying agility of these welcome winter visitors to our shores—after all, like us, they have made incredible efforts to get here!