Hummingbirds are loners.  They do not flock like other birds and they do not fly together in groups during migration.  These birds have incredible memories for the location of flowers and feeders and they will return to these same places looking for their food source year after year.  Once they have established a food source, they will aggressively protect it from other hummingbirds.  

The males protect their food source and the females protect their nesting sites.  Once a male and female have mated and the female has laid her eggs, she will not even let the male near the nest.  The female will raise her chicks by herself.