Keen Sight. The swarm has advantage on Wisdom (Perception) checks that rely on sight.   Pack Tactics. The swarm has advantage on an attack roll against a creature if at least one of the swarm's allies is within 5 feet of the creature and the ally isn't incapacitated.   Swarm. The swarm can occupy another creature's space and vice versa, and the swarm can move through any opening large enough for a Small blood hawk. The swarm can't regain hit points or gain temporary hit points.