When birds flew on the moon in winter
Published: Sunday, Oct 6th 2024, 11:20
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The latest technologies can be used to precisely track the flight routes of migratory birds. However, the realization that some birds fly south in winter is surprisingly new. For a long time, there was great confusion about the sudden disappearance of birds in winter.
BIRDS TRANSFORM
Even the ancient Greeks noticed that the bird species around them changed with the seasons. Aristotle concluded from this that redstarts turn into robins at the onset of winter. Aristotle believed that storks and swallows sleep in hiding all winter and only wake up again in spring.
BIRDS HIBERNATE UNDER WATER
Theories remained similarly adventurous until well after the Middle Ages. In the 16th century, the Swedish bishop Olaus Magnus assumed that birds would sink to the bottom of lakes in winter. This theory persisted until the 1800s.
BIRDS FLY TO THE MOON
However, some scholars rejected the widely accepted hibernation theory. For example, the English scientist Charles Morton. For him it was clear: birds fly to the moon in winter. In an essay published in 1703, Morton argued that no one had ever seen a migratory bird during the winter months and that it was therefore likely that the birds moved away from the earth completely during this time. Furthermore, the returning birds would suddenly appear over the ships on their return in spring as if they were falling from the sky.
FIRST HYPOTHESES
However, the fact that no one has ever seen a migratory bird in winter is not entirely true. As early as the 15th century, travelers reported the presence of storks in Africa, while they were no longer to be seen in Europe. Gradually, the early fanciful explanations gave way to the realization that birds fly south.
THE ARROW STORK
One of the first physical proofs of bird migration is the "arrow stork" of 1822, when a white stork was discovered in Mecklenburg-Western Pomerania, on the Baltic Sea, pierced by an African spear.
RINGING THE BIRDS
A decisive breakthrough in bird migration research was achieved by ringing. In 1899, the Danish ornithologist Hans Christian Cornelius Mortensen began systematically marking birds with aluminum rings. This revolutionized research into bird migration. This made it possible to find out exactly where birds migrate to. Today, the areas of origin and destination as well as the migration routes of most species are known.
Birds have been ringed in Switzerland for exactly 100 years. In 1924, the Sempach Ornithological Institute was founded as a bird ringing center in the home of an enthusiastic ornithologist. Today, the Swiss Ornithological Institute still rings over 100,000 birds in Switzerland every year.
GPS TRANSMITTER
However, bird migration research is making great progress thanks to new technical instruments. GPS transmitters are strapped to the backs of large birds such as storks and eagles, allowing them to be tracked precisely along their migration routes. However, this is not possible for smaller birds as the trackers and batteries are relatively heavy.
GEOLOKATOREN
It is only in the last few years that there has been a solution for lightweight birds: so-called geolocators, which weigh less than a gram. These record when the sun rises and sets and when it is at its highest point. These three values can be used to determine approximately where birds are located. Geolocators were used in Switzerland for the first time in 2008.
Unlike GPS, such geolocators store the data without transmitting it and therefore only require a small, lightweight battery. However, the birds have to be found again after their migration in order to read out the data. The locators were developed by the Bern University of Applied Sciences.
In addition to light, the latest geolocator models also record bird activity and air jerks. This is currently providing researchers at the Sempach Ornithological Institute with many new insights. For example, they recently discovered that, contrary to previous assumptions, hoopoes mainly migrate at night.
©Keystone/SDA
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