What crucial activity defines the purpose of stopover sites along the Appalachian spine during the southbound migration?

Answer

Refueling efficiently with high-calorie insect resources

Successful migration relies heavily on efficient refueling at stopover sites to gather the energy needed for the long flight across the Gulf of Mexico or Central America.

What crucial activity defines the purpose of stopover sites along the Appalachian spine during the southbound migration?
speciesbirdornithologyanimalwarbler