Context: The control of migration, its timing and response are genetically controlled and appear to be a primitive trait that is present even in non-migratory species of birds. The ability to navigate and orient themselves during migration is a much more complex phenomenon that may include both endogenous programs as well as learning.

Question: What controls a birds migration?
Answer: a primitive trait

Question: How do birds navigate and orient themselves during migration?
Answer: endogenous programs as well as learning

Question: What is a primitive trait present even in non migrating birds?
Answer: migration

Question: What is a complex phenomenon in regards to migration?
Answer: The ability to navigate