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Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	Decline of the Ortolan Bunting Emberiza hortulana population in southern Germany - are causes outside the breeding area responsible?
Auteurs :	Manfred Lang, Auteur
Type de document :	Article
Dans :	Vogelwelt (Die) (128(4) 2007)
Article en page(s) :	179-196
Résumé :	The last remaining breeding population of the Ortolan Bunting in southern Germany is located in northern Bavaria. Compared to 1988 (at least 840 territories), this Population has decreased by 60% to 2003 (333 territories) and by 72% to 2007 (235 territories), respectively. Declines were also observed in optimal habitats without detectable habitat deterioration. The changed distribution pattern of territories (shift towards forest edges and tree hedgerows) can only partially be explained by losses of woods within the agricultural landscape and increase of field lot sizes, but is more likely connected with increased forest insect infestations (Tortrididae, Geometridae) supported by climate change. In the recent Ortolan Bunting distribution there is still no preference for sandy soils compared to loamy (loess) soils. The occupation of a new habitat type on dry sites resembling the habitat types inhabited by Ortolan Buntings in southern Europe is described.Males do not show any tendency to arrive earlier at the breeding sites (17(th) to 27(th) April). Thus, it is assumed that a quicker and earlier vegetation development in spring supported by climate change could cause a deficiency of suitable nesting sites in future. A slight shift of breeding phenology towards earlier dates can be explained by local weather events. The share of males in the studied population is 56-57%. The annual breeding success in optimal habitats was 3.3 fledglings per breeding pair with a slightly increasing tendency towards the end of the study period, because adverse weather events became less frequent. Weather data especially for the sensible nestling period do not indicate an unfavourable tendency within the study period, despite exceptional disturbance years have been observed in 2001 and especially in 2007. The contradictory relation between long-lasting population decline and still existing good capacity of suitable habitats indicates severe disturbances outside the breeding range. A possible cause could be the autumn-hunting of Ortolan Buntings at an industrial scale in southwestern France.

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