Though not a scene from the Hitchcock classic, “The Birds”, it very well could be during the morning fly around by these mourning doves.
They fly in large groups, in a sweeping, circular fashion, from Point A to Point B. They do so to avoid falling prey to a raptor, like hawks that normally fly and hunt this same patch of sky. When they land to warm their feathers in the morning sun, they can seem imposing by their numbers.
Then again, they could be plotting their takeover.