The saying is "Birds of a feather, flock together."
I don't know who wrote it but it implies that people that have the same interests or likes, or feelings will gather together just as birds do.
Birds will flock with their own kind.
Mean people tend to hang out with other mean people.
Intellects tend to hang out with other intellects.
Crows fly with other crows. Sparrows gather with other sparrows.
Criminals tend to stay near other criminals.
And so on......
The related link below will explain it better than I can.
Horse Isle answer: featherSossie, Brown Server
A flock of birds is a group of birds flying or gathered together. Birds often form flocks for protection, to find food more easily, or to migrate together. The size of a flock can vary greatly depending on the species of bird.
"Flock" can refer to a group of birds or sheep. It can also mean a group of people gathered together for a common purpose. In computing, flock can also be a term used to describe a synchronization mechanism.
A flock
A group of birds is called a flock. A group of bitterns is called a siege or sedge of bitterns.
Birds of a feather, flock together - meaning that birds of the same breed will more often than not do the same thing. If 1 migrates, chances are there's a flock doing the same.
Birds of a feather flock together, Meaning people of similar tastes congregate together. English proverb of the mid 16th Century
In the nursery rhyme "Birds of a Feather," the birds will flock together.
Birds of a feather flock together, but all birds cannot fly.
A Flock of Birds means a lot of bird flying together
A Flock.
Yes, "Birds of a feather flock together".
Birds of a feather are said to "flock together".
"Birds of a feather flock together."
A flock typically refers to a group of birds, particularly small birds like sparrows or pigeons, that move together in coordinated flight. However, the term "flock" can also be used more broadly to describe any group of animals that move or gather together, such as a flock of sheep or a flock of geese.
Horse Isle answer: featherSossie, Brown Server
The collective noun is a flock of birds.