Grooming

Striker (green) grooms Belle (blue)
Striker (green) grooms Belle (blue)

Parakeets are highly social birds; they travel in enormous flocks sometimes in their native land of Australia; and in homes they are likely to form close bonds with one another, and often the humans in the house as well.
Grooming is often thought to be a social behavior; it not only helps clean those hard to reach places and feels good, but also conveys affection and status to the bird being groomed.