I believe that eight crows constitute a "murder of crows". It is an old English expression.
Angry
It means people with similar interests or shared characteristics group together.
People of the same sort are usually found together.
Birds with the same feather flock together means that like people tend to associate with each other. Those that like sports tend to hang together and those that like video games can be found together.
In the nursery rhyme "Birds of a Feather," the birds will flock together.
It means people and animals tend to stick to their own kind.
Your friends have attitudes similar to yours. It is a criticism.
Birds of a feather flock together, but all birds cannot fly.
A Flock of Birds means a lot of bird flying together
"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.
Travel together from one location to another. Like geese or some birds migrate south for the winter.
Birds of a feather are said to "flock together".