BIRD MIGRATION
Bird migration is a seasonal large-scale movement of birds to and from their breeding grounds.
Every year volunteers count migrating birds at specific locations.
Scientists capture some of the birds and tag their legs with a combination of colored rings and flags.
The scientists use sightings of tagged birds together with volunteers' counts to determine the migratory routes of birds.
Most migratory birds gather in one area and then migrate in large groups rather than individually.
This behavior is a result of evolution.
Which of the following is the best scientific explanation for the evolution of this behavior in most migratory birds?
