DThe loud clatter drowns out the sounds of the nearby motorway. A pair of storks have settled at the exit of the Rivas-Vaciamadrid metro. The birds built their nests on all high masts along the station on the railway line to Madrid, 20 kilometers away. There is no space left on the roof of the old brick church. The area southeast of the Spanish capital is one of the most popular winter quarters on the Iberian Peninsula. Thousands of storks from Spain and Central Europe can not be disturbed by the nearby metropolis. Fewer and fewer of them continue across the Strait of Gibraltar to West Africa.
“There are two river valleys nearby, small lakes and rubbish dumps,” says Ana Bermejo of the Spanish bird protection organization SEO / Bird Life. She is one of the coordinators of the “Migra” program and has worked on a study that was recently launched. For seven years, researchers have studied the routes of the white storks that hibernate or fly on in Spain.
Conclusion: More and more white storks choose the short distance. Instead of traveling more than 5,000 kilometers to the Sahel region, they only fly around 1,500 kilometers from Central Europe to Spain. Together with other scientists, including from the German Max Planck Institute for Ornithology, the researchers equipped 79 storks with GPS transmitters. It turned out that the older Spanish storks hardly left their home country. Four fifths of them stay in Spain; only a lot of young storks are still far away.
Garbage dumps and rice fields offer plenty of food
People have created an important reason for this development. “Every stork we monitored has stopped at a dump at least once,” says Ana Bermejo. There the birds find so much to eat that they no longer move very far. Climate change with shorter winters also plays a role here. However, Ana Bermejo prefers to speak of “global change” for which people are responsible. This applies to the huge amounts of waste and the growing areas that irrigate farmers: in addition to the landfills, the storks in Spain also love the moist rice fields. There, as on other shores and estuaries, they prefer an intruder that is multiplying in Spain – the red American swamp crab, which, as the name suggests, comes from the United States.
But many Spanish white storks don’t even reach the rice fields in the Ebro Delta and Andalusia. The stork “Blas”, for example, comes from Sierra above Madrid and usually spends half a year in Rivas-Vaciamadrid, less than 100 kilometers away. These days he is going home again. Others are drawn to the Doñana National Park on the Atlantic coast, Extremadura, the Rioja region or Galicia. Storks from Central and Northern European countries join them. While there were a good 33,000 breeding pairs in Spain at the last count in 2014, it is assumed that their number has increased significantly since then.
Storks also hibernate in Germany
Only the younger animals from Spain and around 14 percent of their Central European peers go on the long, arduous journey to West Africa. The Spanish birds are on the move for two months, already leaving in July, the remaining animals then cross the Strait of Gibraltar at the end of August and in September. “They are genetically programmed to fly into the Sahel region. But they learn from their parents and only cover shorter distances later, ”says Ana Bermejo. The older they get, the more of them stay in their breeding area. Only a fifth of the older white storks take a winter break in nearby Morocco. They like to settle there near cities with landfills. According to the study, a third of the young storks from Central Europe join them. Even for them, this is no comparison to the east route, on which birds from Russia to Africa still travel more than 15,000 kilometers.
Despite the risk of injury and poisoning on the garbage dumps, the search for food is not as complex as in West Africa, where there are more competitors and the journey is further and more dangerous. As a result, the population of storks that migrate westward has grown in Europe – if they move so far at all: In France, too, more and more birds stay at home or at most fly to neighboring northern Spain. In Germany, where the winters have become shorter and milder, the first couples are also overwintering. White storks from Uzbekistan and Armenia, who prefer the proximity of the nest thanks to the increased local food supply, have become just as tired of traveling.
In Europe, however, the abundant food supply is not guaranteed. Waste separation and recycling are making progress. In 15 years, open dumps in the European Union are said to be the exception. Then the white storks have to look for new sources of food – or go back on the long haul.