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Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	Population trend, time of arrival and altitudinal distribution of the Corncrake Crex crex in Switzerland - the results of 20 years of conservation (2016)
Auteurs :	Eva Inderwildi, Auteur
Type de document :	Article
Dans :	Vogelwelt (Die) (136(2-3, Sp. Iss.) 2016)
Article en page(s) :	107-112
Résumé :	The Corncrake once was a widespread breeding bird in Switzerland which occurred mainly on the Swiss Plateau (the lowlands of Switzerland). By the end of the 19th century and in particular during the first half of the 20th century, the population declined markedly and disappeared nearly entirely from the Swiss Plateau. Between 1970 and 1995, the species occurred sporadically, but was no longer breeding regularly. Being on the verge of extinction, measures were urgent. In 1996, SVS/BirdLife Switzerland started a conservation programme for the Corncrake which debuted in 1996-1998 with a pilot project and has been conducted as conservation programme each year since 1999. The main measure consists in the negotiation of 1-year contracts with the farmers of meadows where stationary calling males have been registered. The mowing of around 1 ha of meadow around the calling place is generally delayed until 15th August. The grants for the farmers are paid by the cantonal administration.Since the beginning of the conservation programme of SVS/BirdLife Switzerland in 1996, the number of Corncrakes observed in Switzerland has increased considerably. One part of the increase is probably due to the more intensive search. However, our results show that Corncrakes not only occur in greater numbers but also have much more possibilities to breed in Switzerland since the beginning of the conservation programme. In the last 20 years, the number of Corn crakes found each year in Switzerland varied between 12 and 87 calling males. Altogether, 715 Corncrakes could be found, 659 during the breeding season (April-July) and 56 during migration in autumn. 55.1 % of these birds were stationary, i.e. they remained at the same place for at least five nights. Most of the Corncrakes (76.3 %) arrived in Switzerland in June or July (second half of the breeding season) and were found mainly in meadows at altitudes between 1,000 and 2,000 m a. s.l. (75.6 % of the observations made during the breeding season). This is very different from the situation in the beginning of the 20th century. At that time, Corncrakes mainly arrived in May and were essentially found in meadows of the lowlands. The present agricultural management explains the late arrival and the shift to higher altitudes: At the beginning of the breeding season in May, only the meadows in the lowlands offer a tallness of vegetation corresponding to the needs of the Corncrake. But these meadows are managed very intensively, are probably too dense for the Corncrake and are often mown before the arrival of the species. At higher altitudes, the meadows are more extensively managed and more suitable for Corncrakes, but the vegetation grows high enough only in the course of June.

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