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  • Thomas Grohmann

Arjuzanx

Aktualisiert: 5. Dez. 2023

Where the cranes go (1)



Who is not familiar with the crane flocks, accompanied by loud trumpets, cries and squeaks, when they migrate over Hesse and the Taunus ranges in autumn and spring? And how often have you thought during the autumn migration of these birds to their wintering grounds: I would like to join them and spend the winter in pleasant surroundings. Reason enough to take a look at where exactly the migratory species fly from their breeding grounds in Northern Europe, their homeland, what drives and controls them, where they rest and where they spend the winter.


The great migratory bird questions of "when, how and where" have long been subject of research, the basic principles are now known, but much remains to be studied in detail. For their temporal and spatial orientation, migratory birds possess a whole arsenal of innate and learned skills that help them to safely master the often long migratory distances. Today, we can assume that an internal annual clock ("migratory restlessness") as well as innate directional information and a learned map in the brain, together with the ability to use the sun, stars and the earth's magnetic field as compasses, guide them to their destination areas at the right time.



Cranes breeding in Scandinavia (Norway, Sweden, partly Finland), Central Europe (Germany, Poland, Czech Republic) as well as in the Baltic States (Lithuania, Latvia, western Estonia) use the western European migration route, which leads them to the wintering grounds in France and Spain after stopovers in Germany. In south-western France, the Parc Naturel Régional des Landes de Gascogne, and in particular the Arjuzanx nature reserve, serves as a resting or wintering site. We took a closer look at the area around Arjuzanx for a few days in February 2023.



The region of Les Landes de Gascogne, located in the extreme southwest of France, has always been a popular destination for cranes, as it is ideally situated on the relatively narrow corridor of the aforementioned western European migration route. This route and wintering site were used by at least 476,197 cranes in the winter of 2021/2022, of which 279,237 were in transit to the Iberian Peninsula (figures from the European Crane Working Group, Crane Network France). Actually, the crane disappeared completely from the area 150 years ago after the draining of the marshes and wet heaths. Only in the 1960s it did return with the expansion of corn cultivation in agriculture. Since then, a constantly growing wintering population has developed over the entire triangle of the Landes de Gascogne (Bordeaux - Dax - Mont-de-Marsan).



Today, Les Landes is an important crane region, where up to 20% of the Western European crane population winters in many places. In addition, Les Landes offer suitable resting places on the migration of the animals and thus also play a fundamental role in the conservation of this protected species. Cranes on migration or on their way home find rest and food here before continuing their exhausting journey, such as crossing the Pyrenees on their way south.


The Arjuzanx nature reserve is one of the most important wintering and resting areas in Les Landes. The area, which used to be characterised by open-cast coal mining, was renaturalised in 1980 and then the pits were flooded. Today it forms a 2,500 ha fenced nature reserve with lakes, meadows and corn fields. Since 1983, cranes have been wintering in the former pits again from mid-October to mid-March, finding favourable conditions there and in the surrounding area: Feeding grounds (cornfields) that allow daily feeding, as well as open wetlands that provide roosting sites and sufficient landing zones in the shallow areas.



In addition, scientific studies and intensive crane monitoring are ongoing at the Arjuzanx Nature Reserve to better understand wintering phenology and overall increase our knowledge of these special birds.




The nature enthusiast will find an information centre with tour offers in Arjuzanx, as well as a number of observation platforms that are accessible near the roosts only by reservation and a guide. From the platforms, the spectacular morning take-offs and evening fly-ins to and from the feeding grounds can be easily observed.






A worried outlook: Corn, available in the fields after harvest, is the preferred food of cranes in the Landes de Gascogne. The daily food ration of a crane on migration is estimated at 300g of corn. In the last ten years, however, cultivation methods have changed and the power of agricultural machinery is constantly increasing. The corn stubble is ploughed under in late summer, for example, and herbaceous winter sowing is intended to help improve the soil. In addition, farming is moving towards vegetable cultivation. Thus, foraging areas in harvested cornfields are being lost. This leads to the question of what food resources will still be available to the cranes here and elsewhere in the future, and whether we need to worry about the birds' wintering possibilities in this area in the long term.


During our stay, the nights also had a lot to offer. After the cries of the cranes slowly faded and darkness settled over the landscape, the bright planets Jupiter and Venus appeared in the west. They were to accompany us for quite a while in various constellations. And a visitor from the edge of our solar system now appeared in the sky of the northern hemisphere for almost the whole night: the long-period comet C/2022 E3 (ZTF) with an orbital period of about 50,000 years. Although it had already left its closest position to the Sun in mid-January, it reached its smallest distance to Earth at the beginning of February before disappearing into the depths of space. From our earthly perspective, it passed a number of exciting objects on its calculated celestial orbit, which promised beautiful wide-angle sky pictures. A part of the opportunities could be realised with a mobile setup. At the beginning, the bright full moon (5.2.) still interfered, so that only short time slots remained for taking pictures.



The image above shows comet C/2022 E3 (ZTF) in the constellation Auriga near the star Al Kab, taken on 8.2.2023. Its thin ion tail reached beyond the red emission nebula IC405. Even with binoculars, the close encounter was an optical delight. It was a crystal clear night with -3°C and very good seeing, approaching Namibia's exceptional winter nights in terms of perceived quality. "I can't remember ever seeing such clear structures in M42 (Great Orion Nebula) through the binoculars" was noted in the diary.


The entire picture gallery can be found here.




Sources

  • La Grue cendrée dans les Landes de Gascogne. Migration et hivernage Saison 2021-2022 - www.grueslandesdegascogne.com

  • Franz Bairlein, Das große Buch vom Vogelzug. Eine umfassende Gesamtdarstellung; Aula Verlag 2022

  • Kranichschutz Deutschland gGmbH - www.kraniche.de


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