What characteristics of living things best explains why some north american birds fly south for the winter?

They need to migrate and gather food to stay alive during winter

This is what i found on google “phytoplankton, tiny organisms that live in the ocean, are autotrophs. some types of bacteria are autotrophs. most autotrophs use a process called photosynthesis to make their food.” i hope this you for what your looking for

Where are the following choices