Which behavioral characteristic would help identify migrating birds?

Flock formations, particularly the characteristic V shapes, are a significant indicator of migrating birds. These formations help birds conserve energy during long migrations by taking advantage of the aerodynamic benefits created by the lead bird, allowing those that follow to glide more efficiently. Moreover, such formations are typically observed during migratory periods, as birds travel over long distances either towards warmer climates for winter or back to their breeding grounds.

The other characteristics, although they may be present, do not inherently indicate migration. Busy feeding habits can occur year-round and are not restricted to migratory periods. Color-coded patterns of feathers can help with species identification but do not reflect behavior tied to migration. Similarly, while the height of flight patterns can be an aspect of bird movement, it does not specifically indicate migration behavior, as different birds might fly at various altitudes for reasons other than migration. Therefore, flock formations remain an essential behavioral trait associated with the migration of birds.