Effects of Water Barriers on the Migration of Soaring Birds
The migration of wild animals has been historically conditioned by ecological barriers such as seas, deserts, mountains, rivers, and more recently by human-derived landscapes and structures. Those features may block the course of migration, or generate of migratory divides, but they can also act as ecological filters, pushing individuals to the limits of their physiological capacities, and reducing the survival chances of those less well adapted. Despite the wide interest of this topic in evolutionary biology, there have been obvious methodological difficulties in determining how exactly animals overcome great ecological barriers. This scenario has changed in the recent years with the emergence of global-tracking techniques.
Using a novel remote tracking method we have been following the movement and flight behaviour of black kites migrating across the Strait of Gibraltar in great detail. For soaring birds, large water bodies represent major obstacles, because thermal uplift does not occur over water. We expect to identify the proximate and ultimate consequences of this natural barrier for migrating soaring birds.