Heatwave, yet the storks are already thinking of setting off

While the thermometer in Switzerland currently shows over 30 degrees, some of the native white storks already have a very different programme: setting off for the south. The Swiss Ornithological Institute has been receiving numerous reports these days about large groups gathering in fields, an unmistakable sign of the impending departure.

Large gatherings in several places

Particularly striking was a colony of 250 birds observed on Tuesday in Chavornay (VD). On Wednesday, a gathering of 180 storks followed in the Geneva region. However, according to Livio Rey, spokesperson for the Ornithological Institute, such numbers are not unusual: these are not the largest groups ever recorded. The topic clearly preoccupies the public greatly, though, as shown by the rising number of enquiries.

The reason for the gatherings is unspectacular: after the breeding season, both adult and newly fledged young birds are out and about in large numbers. At the same time, the migration season has begun, so white storks from Germany and France are also appearing in Switzerland on their way south. Freshly ploughed fields and recently mown meadows are popular gathering places, because food such as grasshoppers, mice or earthworms can easily be found there. Sometimes the groups even spend the night on rooftops, which draws additional attention. The search for thermals also plays a role: storks use warm columns of air to gain height, and gather where the conditions for this are favourable. There can be no talk of genuine social behaviour, says Rey, especially as the groups disperse again just as quickly.

Western route via Spain, eastern route via the Bosphorus

Swiss white storks traditionally follow the western route towards Spain and Gibraltar, all the way to West Africa, with migration usually beginning from mid-July. A second, eastern route leads birds from eastern Germany and Eastern Europe over the Bosphorus and the Gulf of Suez to East Africa. According to Rey, Switzerland is currently experiencing the peak of the migration. The return of the adult birds for breeding only begins again from February.

Record number of overwintering storks

A second trend is remarkable: more and more storks are spending the winter on the Iberian Peninsula or staying entirely in Switzerland. Whereas 288 overwintering birds were counted in January 2017, by January 2026 there were already 1’770 individuals, an absolute record. Rey cites the food supply as the reason: milder winters with less snow and frost mean that the birds also find enough food here. The temperature itself was never decisive for the migratory urge; the plumage insulates well against the cold.

This development was only made possible by a successful reintroduction programme: in the 1950s, the white stork was considered extinct in Switzerland. Today, around 1’300 pairs are breeding in the country again, a finding that is also put into context in our earlier article on the changing overwintering behaviour of storks. There, the number of breeding pairs in 2025 still stood at 1’250, which underlines the ongoing growth of the population.

A signal of the changing migratory behaviour

The observations fit into a larger picture: the white stork is increasingly regarded as a symbol of adaptability in the face of climate change. Its former breeding grounds are increasingly becoming winter quarters too, a pattern that can also be observed in other native bird species such as blackbirds or starlings. Anyone wishing to learn more about the background of the reintroduction and the connection with the protection of non-human animals in Switzerland will find further articles in the category Wild animals.