Birds of a feather flock together.
People of similar character naturally seek out one another's company.
What They Mean
Like finds like. Shared habits, shared opinions, and shared grievances form flocks faster than any introduction could.
Are They Right?
Broadly. Similarity is comfortable, and comfort is how most groups are assembled. The observation is zoologically sound and socially well documented.
What They Left Out
The flock is also how nobody's opinion is ever disturbed.
They Also Say
Read the ruling: Birds of a Feather Flock Together vs. Opposites Attract