A few days ago I was in the cemetery near my father's mother's mother's grave and found it surrounded by birds. There were a score or more of Canada geese (Branta canadensis) wandering among the headstones and eating off the ground.
"Birds of a feather flock together."
Intermixed with the geese were about 4 sandhill cranes (Antigone canadensis) wandering among the gravestones and eating off the ground. Just up the lane were 7 wild turkey (Meleagris gallopavo) wandering among the graves and eating off the ground.
Birds of the same feather will flock to the same place but other feathers gather there too. So is the proverb true? Of course it is. But if you presume the proverb tells the whole truth you are wrong.
In actual reality I think there was more truth in standing among the birds than in talking about them. This puts me in mind of another commonplace, if not quite a proverb. As phrased by William Naumann [on November 19, 1970]:
"Every time we talk about something we kill it ... because we say something instead of everything."
But the proverb didn't become a proverb because it said something about birds. In actual reality this and every proverb is quoted with reference to human beings. That the saying is proverbial is a recognition that many people have found a workable analogy between the behavior of birds and that of humans. There is something like the flocking of birds in the way we form human communities. The turkeys walk the cemetery together even in the peaceful company of 2 other species and we tend to walk most closely with people who are more similar to ourselves.
That's something true but it isn't everything. That's the proverb alive and walking.
Also true is the wonder and exhilaration of being surrounded by birds of a very different feather from myself, actual birds in the cemetery but by analogy people of different attributes.
That's another bit of truth. It isn't in the proverb. And like the proverb it too isn't everything.