From May onwards, you will no doubt have seen the dance of the common terns on Lake Geneva as they return from the Gulf of Guinea for their breeding season, after their winter in the warmth... Easily recognisable with their streamlined wings and black cap, their refined and slender silhouette makes their flight particularly lively and elegant, earning them their nickname: "sea swallow".
Historically, Lake Geneva has been a welcoming place for terns. The species' natural habitats are the natural shores consisting of sandbanks and alluvial rivers. However, various human pressures and shoreline artificialisation works have led to the loss of many nesting sites, resulting in a drastic fall in the number of breeding pairs up until the 1950s.
Since the 1970s, the installation of nesting rafts on various critical bodies of water (Lake Geneva, Lake Neuchâtel, Lake Zurich, etc.) has reversed the trend: they are replacing these disappearing environments, which are essential to its reproduction. Today, the Common Tern in Switzerland is dependent on these artificial structures. If they are well maintained and placed away from disturbance, they reduce competition for nesting sites and reduce the pressure of predation on eggs.
Various natural sites on Lake Geneva offer these nesting rafts, mainly reserved for terns. At Préverenges, for example, the îIe aux oiseaux platform welcomes around thirty nesting pairs every year!
Photo: © Gaetan Mineau / Flickr
