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Résumé :
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Plumage bacteria may play an important role in shaping the life histories of birds. However, to design suitable experiments to examine causal relationships between plumage bacteria and the fitness of host birds, natural variation in plumage bacterial communities needs to be better understood. We examined within-individual consistency of plumage bacterial contamination in Great Tits (Parus major), comparing different body regions (ventral vs. dorsal) and comparing contamination between years. Numbers of free-living and attached bacteria and the species richness of feather-degrading bacterial assemblages were studied using flow cytometry and ribosomal intergenic spacer analysis (RISA). Numbers of both types of bacteria were higher on dorsal than on ventral feathers. Numbers of free-living, but not attached, bacteria on the two body regions were highly positively correlated. There was also a strong within-individual correlation between numbers of attached bacteria during the same breeding stages in different years. These results suggest that, despite variation in absolute levels of feather bacterial loads between years and different body regions, sampling individual birds can provide reliable estimates of relative levels of bacterial contamination, as long as sampling time and body region are carefully standardized.
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