|
Résumé :
|
Les espèces spécialistes des milieux agricoles ont fortement décliné au cours des 20 dernières années (1978-2000), en particulier en-dessous de 1000m d'altitude.
Capsule: During the past 20 years, farmland specialist birds have declined in the Alps, especially below 1000 m asl. Aims: To investigate whether the altitudinal distribution of birds in the northern French Alps has changed over the last 20 years in relation to farming intensity and/or climate change. Methods: Two point-count surveys carried out in 1978-80 and 2001-02, at the same 316 spots along an elevational gradient of decreasing farming intensity, were compared. Account was taken of potential changes in species detectability over time. Potential differences between observers were also taken into account. Results: Most farmland specialist bird species decreased from the late 1970s onwards, but the decline was much stronger below 1000 m asl (70%) than above (20%). Such a pattern was not found in farmland generalists or woodland bird species. Conclusion: Specialist species probably suffered from changes in farming practices at low elevation following mechanization, rather than from climate change. Lowland farmland species are particularly threatened. Therefore, the Alps should no longer be considered as refuges for farmland species.
|
