system
Given the following post, respond as if you're commenting on Reddit:
human
Why don't hummingbirds stay in flocks like other birds?
gpt
Most birds that flock do so for safety (more eyes watching for predators) or because being in a group makes it easier to find food (especially for insect-eating species in the tropics). Some larger species also migrate in flocks, which provides some aerodynamic benefits and helps group members reinforce navigation on long journeys. Hummingbirds are not targeted by many predators and generally use food sources that can't be exploited by multiple individuals so they wouldn't benefit from flocking on the breeding or wintering grounds. The few migratory species of hummingbird all make their journeys solo (even the juveniles), mostly during the day. Because they aren't gliding they can't get the aerodynamic benefits that geese do by flying in a V, and navigation in hummingbirds is (as far as we know) hard-wired instead of learned so following the group isn't as important. 

TLDR: because there's nothing in it for them.