Climate change influences the behavior of migratory birds

Migratory birds are hardly deterred from their flight schedule by the prolonged warm and dry weather. However, there are indications that climate change is causing them problems in the long term.

Birds are actually well prepared for heat and drought, as biologist Livio Rey, spokesperson for the Swiss Ornithological Institute in Sempach, explains. With a body temperature of around 42 degrees and an exceptionally low water requirement, they are perfectly equipped for weather conditions such as those that prevailed this summer.

To Spain in three days

In general, the weather does have an influence. However, it is less of a problem for so-called short-distance migrants, which fly to their winter quarters within Europe. Red kites fitted with transmitters by the Swiss Ornithological Institute in Sempach, for example, flew from Switzerland to Spain within three days.

As winters become warmer, they also find more food in Switzerland and can remain here for longer. This can be observed in species such as white wagtails, starlings, wood pigeons, white storks, and indeed red kites: “They can react relatively quickly — if it suddenly turns cold, they are soon in Spain,” says Rey.

Arriving at the destination at the wrong time

The situation is more problematic, however, for so-called long-distance migrants, which spend the winter south of the Sahara. “They have no idea what the weather is like here,” says Rey. Their “genetic programme” tells them when they need to set off. Nature has arranged it so that this coincides with the time when food is most abundant. Climate warming could change this: a so-called “mistiming” is a looming threat.

The consequences of this can include poor breeding success, or the birds' fitness is not at its best. “When they then fly to Africa for the winter, more individuals die because they are in poorer condition for the flight,” says the bird specialist, “and over a longer period of time, this can become problematic for a bird species.”

Study revealed initial impacts

A 2003 study by the Swiss Ornithological Institute in Sempach showed that long-distance migrants begin their migration considerably earlier than short-distance migrants, in whom a delayed migration was observed. The long-distance migrants apparently attempted to cross the Sahel zone before the dry season began there.

To gain these insights, 65 bird species were recorded over a period of 42 years at the Swiss Ornithological Institute's ringing station at Col de Bretolet in the Valais Alps. Each year, between 10’000 and 20’000 birds from more than 100 species are ringed there. More on wildlife and on biodiversity.