Interesting study on Honey Buzzard migration:

Vansteelant, W.M.G. ; Shamoun-Baranes, J. ; van Manen, W. ; van Diermen, J. & Bouten, W. 2016. Seasonal detours by soaring migrants shaped by wind regimes along the East Atlantic Flyway. Journal of Animal Ecology . [We tracked 62 migratory journeys of 12 adult European Honey Buzzards with GPS loggers.… Honey Buzzards cross western Africa using different routes in autumn and spring. In autumn, they overcompensated for westward winds to circumvent the Atlas Mountains on the eastern side and then overdrifted with south-westward winds while crossing the Sahara. In spring, however, they frequently overcompensated for eastward winds to initiate a westward detour at the start of their journey. They later overdrifted with side winds north-westward over the Sahel and north-eastward over the Sahara, avoiding adverse winds over the central Sahara. We conclude that Honey Buzzards make seasonal detours to utilize more supportive winds further en route and thereby expend less energy while crossing the desert]