Goose parents lead migration V

Many migratory animals travel in large social groups. Large, avian migrants that fly in V-formations were proposed do so for energy saving by the use of up-wash by following individuals and regularly change leadership. As groups have been rather homogeneous in previous work, we aimed to explore leadership and its flight mechanics consequences in an extremely heterogeneous case of social migration, namely in spring migration of goose families. In families the experience of group members differs strongly and inclusive fitness may be important. We successfully collected overlapping spring migration tracking data of a complete family of greater white-fronted geese Anser a. albifrons and extracted leadership, flapping frequency and wind conditions in flight. Our data revealed V-formations where one parent was flying in front at all times. Although the father led the family group most of the time, he did not flap at higher frequency while doing so. In contrast, the mother flapped faster when leading, possibly because she experienced less supportive wind conditions than when the father led. We argue that in heterogeneous, social groups leadership might be fixed and not costly if supportive environmental conditions like wind can be used.