Why do some mountains play host to more migratory birds, while others favour sedentary species?
A new study, published in Journal of Biogeography, reveals that The answer lies in the interaction between altitude, landscape structure and species richness.
By analysing breeding bird communities along an altitudinal gradient of 4,000 metres in south-eastern France, Charlotte Rault (receiving a doctoral grant from the Sud-PACA region), Yoann Le Bagousse-Pinguet, Agathe Leriche and Alexandre Millon (POPCO team-IMBE), in collaboration with Amine Flitti and Catherine Godefroid from the LPO PACA, show that the balance between migratory and sedentary birds is based on complex interactions between environmental and ecological factors.
- The regional community is made up of 225 breeding species, including 34% of long-distance migrants.
- At lower altitudes, less diverse landscapes favour the presence of migratory species.
- Forests play a contrasting role: they reduce the proportion of migrants on the plains, but increase it at higher altitudes.
- Interestingly, the most species-rich communities - above ~117 species, particularly at lower altitudes - host more migrants than expected. The phenological lag between migratory species and sedentary species could reduce competition for resources and thus lead to higher species richness.
These results highlight the complexity of the mechanisms that structure bird communities and underline the importance of considering altitude, landscapes and biodiversity together. They provide invaluable keys to better anticipating the effects of environmental change and guiding conservation strategies in a context of rapid territorial transformation.