In Which Animal Population Would Migration Be Least Effective or Necessary

In which animal population would migration be least effective or necessary as an adaptation for maintaining a population throughout the year?

A) Salmon, which live in salt water, but breed in fresh water
B) Blackbirds, which easily adapt to new food sources, regardless of weather
C) Elephants on the African savanna, where there is a pronounced dry season
D) Hummingbirds, who cannot survive in cold weather and migrate south in the winter
E) Humpback whales in the Pacific Ocean, where seasonal food supplies vary by latitude