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Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	Future prospects for the Black-tailed Godwit Limosa limosa in the Hetter: land acquisition as a prerequisite for grassland and water management for stabilizing population size
Auteurs :	Andreas Barkow, Auteur
Type de document :	Article
Dans :	Vogelwelt (Die) (135(1) 2014)
Article en page(s) :	3-17
Résumé :	In Europe, and in particular in the core areas of its distribution in The Netherlands and northern Germany, the Black-tailed Godwit nominate population has decreased for decades and partly dramatically. In the Hetter, located in the SPA Lower Rhine area in North Rhine-Westphalia, a local population of 25-50 territorial pairs can be maintained since the mid-1990s. The nature reserve holds up to a quarter of the North Rhine-Westphalian breeding population. Since 2009, hatching success is monitored and breeding success is assessed by the number of alarming adult birds. The daily survival rate is 0.966. The hatching success estimated with the Mayfield method is about 45%. The breeding success is subject to large annual fluctuations. A careful estimate of the fledging success, assuming one young bird for each successful breeding pair only, results to an average reproduction rate of 0.42 fledglings per breeding pair and year. In favourable years such as 2010 and 2011 values of 0.53 and 0.55 are achieved. When looking at successive years, those with an increase in the number of breeding pairs show more pairs indicating success compared to years with less pairs present than in the preceding year. Only under the assumption of two fledged chicks per successful breeding pair, Black-tailed Godwits in the Hetter raise more than one chick per territorial pair on average.In the Hetter, land acquisition has consistently been part of the management since 1992. Purchased land was managed extensively. By taking into account for the habitat requirements of grassland birds i) suspended management during the breeding season, ii) extensive management with waiver of pesticides, mineral fertilizers and manure under moderate conservation fertilization with solid farmyard manure and grazing with a reduced number of cattle, and iii) improvement of the grassland by a system of ponds (so-called Blanken) was achieved. The land acquired by the NABU or especially the NRW-Stiftung (a foundation) was leased to local farmers for cultivation under the above-mentioned standards.After another 20 ha of land was bought in the frame of a LIFE+ project, a total of c. 90 ha of continuous land is now property of nature conservation. The purchase of land was the precondition for sustainable effects and area-wide measures, which enabled a variable retention of water in the area through the installation of weirs. First congestion measures proved to be successful with respect to bird density. The removal of perennial herbaceous plants and bushes along existing waterbodies also showed positive effects, because Black-tailed Godwit as the target species populated a larger continuous area in the study area. However, a permanent increase of local population could not be found. Effects of increasing loss rates to clutches and chicks due to a rising predation pressure are discussed.

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