Once they arrive at the humid savanna , they turn southeast to arrive at their winter feeding grounds .
The western group of swifts mostly follow the Atlantic coastline of Africa -- otherwise they would have to cross the Sahara .
Once swifts arrive at the humid savanna , swifts turn southeast to arrive at swifts ' winter feeding grounds .
The western group of swifts mostly follow the Atlantic coastline of Africa -- otherwise they would have to cross the Sahara .