Answer:

FLOCK

EXPLANATION:

HERD means a large group of animals, especially hoofed mammals, that live, feed, or migrate together or are kept together as livestock.

"a herd of elephants"

SWARM means a large group of animals, especially hoofed mammals, that live, feed, or migrate together or are kept together as livestock.

"a herd of elephants"

FLOCK means a number of birds of one kind feeding, resting, or traveling together.

"a flock of gulls"