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Résumé :
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Altitudinal shifts in distribution were investigated in forest breeding birds, along two elevational gradients in the French northern and southern Alps, from counts repeated at exactly the same locations in the 1970s and the 2000s. Significant shifts were reported for eight of 24 species in the northern alpine site (five downwards, three upwards) and for two of the 17 species in the southern site (one downwards, one upwards). Apart from the Crested Tit Parus cristatus, which shifted significantly downwards at both sites, altitudinal shifts were not significantly correlated between sites. Bird communities did not shift their distribution upwards despite a 2.3°C increase in spring temperatures in the two study areas. These results suggest that bird distributions by altitude have not yet been affected by climatic warming, and that most specific elevational shifts are probably related to site-specific factors.
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