Migratory routes, climate change: what bird ringing has revealed

In the 18th century, we began to identify birds by passing them the wire to the leg, precisely colored woolen threads. It was then a question of “raising an enigma” which occupied the scholars of the time. Namely: but what do swallows do in winter? Seeing these birds in black and white livery disappear from the edges of ponds, lakes and marshes at the end of fine weather, we thought they were sinking into the mud to spend the cold season there.

Scholars like the Italian monk Lazzaro Spallanzani came up with the idea for these rudimentary means of identification. This is how we gradually understood that these graceful birds weighing some 20 g crossed 10,000 km to bask in the African sun. In France, Henri Auguste Ménégaux, vice-director of the National Museum of Natural History, institutionalized ringing before the First World War. It is generalized a little after the conflict.

The warmer the years, the bigger the birds would be

While the migration routes are now well known, ringing data are used to better understand the functioning of the birds. How they benefit or not from the global rise in the global thermostat. This is how, for example, a thesis was able to demonstrate that warm years made larger birds. On YouTube, you can find the summary of this painstaking work in the form of a hilarious humorous rap. “But if the climate changes over time / Will the animals change in size? / To find out, I use a huge data set / Volunteers who measure birds throughout France”, greets the ecological rapper Nicolas Dubos.

Thanks to these data, it was also discovered that certain Siberian passerines known to migrate to Southeast Asia had passed west, and had recently taken up their winter quarters in the south of France. At the Bird Population Biology Research Center (CRBPO), a researcher is currently wondering if tits are able to adjust their reproduction in a program called “Mommy knows best”. This “plasticity” is a major issue since it is almost the only option for living organisms to adapt to a change as rapid as the current climate change.

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