supported by the National Basic Research Program of China(2013CB430404);National Natural Science Foundation of China(31071939 and 31572280);the State Scholarship Fund of China(201206100060);supported by a Project Grant(621-2010-5584)from the Swedish Research Council;a Linnaeus grant to the Centre for Animal Movement Research(CAn Move)from the Swedish Research Council(349-2007-8690);Lund University
Background: The motivation of birds to proceed with migration is associated with both endogenous and exogenous factors. According to their migratory situation and to the characteristics of stopover sites, birds might ...